Newsletters

Best wishes for a Merry Christmas and a Happy New Year from Council!

We are sorry that due to health and family reasons Jonquil Florentin has resigned as a member of Council. We thank her for her valuable contributions the last year, and long-standing support at the observatory.

News from the Observatory

Simon Lang

We were very kindly donated a 400mm Dobsonian telescope from Dougy Burgess and it's proving to be a hit, allowing us to see many much fainter objects than the Cooke. The new paved area has provided the perfect home for it. As the Cooke is best for the Moon, Planets and Double/Multiple Stars and not much else, the Dobsonian has increased our ability to show more when entertaining our visitors. Now if only the weather would cooperate, we have only been open on a handful of occasions since we reopened in September!

A note for your diary: Terry Pearce and Yours Truly will be in January's Sky at Night program talking telescopes. In theory on BBC Four, Sunday 12th January at 10pm.

Transit of Mercury: November 11th 2019

Simon Lang

We opened the Observatory for the Transit of Mercury although the weather forecast did not look promising with broken cloud for the start of it but predicted to thicken throughout. This prediction was spot on but we were very lucky to have many openings in the cloud, to allow us some extended glimpses of the tiny, black spot, that is Mercury, as it lazily made its way across the face of the Sun.

Bearing in mind Mercury is only a quarter again in size larger than our own Moon and that it is 90 million km from Earth during the Transit, it is no surprise how small it appears. To see it as a defined disc you need to see it at about 50x magnification but in order to see it properly it is better to see it at magnifications of over 100x.

For the transit we swapped between 175x and 215x which was allowable with the 'seeing' or steadiness of our atmosphere on the day.

Having calculated where on the Sun's disc Mercury would first appear and operating at 175x magnification, we stood poised to see the first contact at 12:35 & bang on queue, the first tiny nibble appeared on the edge of the Sun's Eastern limb. Then the cloud thickened, as if it had a naughty sense of humour, to hide the remainder of the ingress. When the cloud next cleared we saw Mercury fully on the Sun's disc.

Usually there are other features visible on the Sun during transits but with the Sun at minimum in its 11 year cycle, there was little to see. No Sunspots or faculae were evident and we could only see the 'Granulation' of the convection cells, that draw up hot gases from the lower Radiative Zone, to then cool, spread out and then descend back down. These pepper the entire surface, however with reasonable seeing (unusual with scudding clouds!) we could see the normally elusive granulation, albeit in blurred apparition.

We had an estimated 50 visitors, many coming and going as their busy lives dictated and all but one managed to see some of the Transit. It was due to play out from 12:35 until 18:04 but with the Sun setting at 16:22, from the UK, we missed a big chunk. This was made worse by the trees at the South East of the Observatory and as predicted, we lost the Sun to them shortly after 15:00 although the forshortening effect in the thicker cloud cover was in play by then anyway. If you want to join us next time you'll have to wait until November 2032!

SWIFT-TUTTLE - OUR REAL SWORD OF DAMOCLES?

Doug Daniels

During August each year, the night sky treats us to a display of celestial fireworks in the form of the Perseid meteors, so called because the radiant of this shower lies in the constellation of Perseus. The meteors are small particles of dust and grains which have been left in orbit around the Sun by the parent comet Swift-Tuttle. Each year, on about the 11th of August, the Earth intersects this stream of comet debris. Particles are drawn into the Earth's atmosphere where they are heated up by friction, become incandescent and result in a display of 'shooting stars'. While we admire this annual display we should be aware that the parent comet - Swift-Tuttle, is possibly the greatest threat to the continued existence of life on this planet! It is a threat that will remain with us for the next 10,000 - 20,000 years!

When it was first discovered in 1862, Swift-Tuttle must have been a wonderful sight with a tail extending some 30 degrees. At that time the comet came to within 50 million miles of the Earth. During that apparition, the comet was observed to deviate from its calculated orbit by about 10 secs. of arc. The deviation was caused by jets of gas emitted by the comet, acting like rocket thrusters altering its course. Because of this deviation, it was difficult to predict an accurate orbit and date for its return. The comet's orbit is also perturbed by the gravitational field of Jupiter. For every one orbit of the comet, Jupiter makes 11 orbits of the Sun and computations of the comet's orbit have to take the perturbations due to Jupiter's powerful gravitational field into account.

All these effects contrive to make the position of Swift-Tuttle very difficult to predict accurately. Using the orbital elements obtained in 1862, the comet was expected to return in 1981-2, but in the event, it was not recovered until 1992! Using data obtained during this last apparition, Swift-Tuttle is predicted to cross the Earth's orbit again on August 5th 2126. At this date it is calculated that it will miss the Earth by as little as 23 million kilometres or by 14 days, give or take a day or two! However, the last prediction was out by 10 years! In 1993 further material ejection was observed which could further change the predicted orbit. The comet was lost to view in 1998, when it became too distant and faint to observe.

Swift-Tuttle is truly our Sword of Damocles. It is a real threat to life on Earth. With an estimated size in excess of 20 kilometres, it is far bigger than the comet or asteroid thought by some scientists to have been responsible for, or at least contributed to, the extinction of the dinosaurs 65 million years ago. The discovery, by geologists, of enhanced levels of Iridium at the boundary of the cretaceous & tertiary sediments laid down at that time, and the subsequent discovery of the trace of a huge ancient impact crater in the Yucatan Peninsula, yield compelling evidence to support the theory that the Earth suffered a major impact in the geological past which coincided with a major extinction event. Not only the dinosaurs, but as much as two thirds of all living species on Earth became extinct at that time.

When Swift-Tuttle crosses Earth's orbit in 2126 it will be travelling at over 60 kilometres a second and if it were to collide with Earth it is estimated that the energy released by the impact would be equivalent to an explosion of about 5 billion megatons of TNT. The object believed to have struck the Earth 65 million years ago, was equivalent to just about 100 million megatons! Such a destructive impact could strip away the Earth's atmosphere completely and annihilate virtually all life, except perhaps for some hardy species of bacteria buried deep in solid rock.

Our message to the next generation must be: KEEP WATCHING THE SKIES - that's where the real danger lies.

Supernumerary Rainbows

Julie Atkinson

Late one afternoon some years ago, I was walking East and saw against a very dark cloud a brilliant rainbow ahead of me. It had a fainter secondary some way from the primary bow, with reversed colour order. But the primary rainbow itself seemed to have several bright repeats with the same colour order, abutting it and each other in series, beneath. I'd not seen or heard of such a thing before, but on enquiry, both Trevor Law and Philip Eden recognised it as the well-known phenomenon of supernumerary rainbows. It was in the days before everyone had cameras on their phones so the best I can do is point you at [1] for examples. What I saw is likely to have been because of small uniform raindrops in the cloud.

Supernumerary rainbows cannot be explained by purely geometric optics. Thomas Young, the man who had demonstrated the wave nature of light, attempted an explanation based on interference. Consider parallel rays of light from the sun hitting a spherical raindrop. They are refracted where they hit, reflected from the back of the drop, and refracted on emergence (ignoring rays that pass through or are reflected more than once). Incident angles will vary depending on how far the ray is from the raindrop's axis as shown in the diagram. The graph below gives the scatter angle for different incident angles. For each scatter angle there are two incident angles, or paths through the drop, with the paths getting closer as the scatter angle gets closer to the primary rainbow angle, close to 138°, where the paths co-incide, giving the bright rainbow. (The primary angle varies with wavelength, of course, giving the colour spread of the rainbow.) In general the paths have different lengths and so can interfere. Young therefore suggested that there would be brightening where the path difference was a whole number of wavelengths, to give the supernumeraries.

The astronomer Airy criticised Young for being too simplistic. The diagram below shows lights as rays but Airy considered the plane wave front incident on the raindrop, and how it is distorted by refraction, and further affected by interference at reflection. He performed the more complex integration of intensities over curves for different angles and derived a pattern of bright scatter angles which was closer to the actual phenomenon. More sophisticated models are now possible using computing power to take account of diffraction, polarisation, the size of the sun and non-spherical raindrops.

Recently, Laven[2] has looked again at Young's method, and says that his problem was not taking account of phase changes within the raindrop, and in particular phase changes of 90° when rays cross a focal line. When a plane wave is distorted by hitting a raindrop, each little section has its own centre of curvature, which is a focal point. All of these together are a focal line. I am not sure who realised there would be a phase change - Laven quotes van de Hulst [3]. When Laven used these results with Young's method, despite its simplicity he found it gave a very good approximation of the supernumerary angles pattern. He compares the modified Young's method results with Airy's in [2].

Since that experience near Queen's Park, I always look out for supernumeraries when an ordinary rainbow is about. I may have just seen a faint example since but will keep trying.

References

[1] https://www.atoptics.co.uk/rainbows/supers.htm
[2] Philip Laven, Applied Optics, 56, 19, G104-G111 (1 July 2017)
[3] H.C. van de Hulst, Light Scattering by Small Particles, Dover Publications Inc., 1957.

The annual General meeting took place on June 20th preceded by the traditional wine and cheese party. Our thanks to all those members who contributed food and drink to the feast.

At the Council meeting on April 4th Simon Lang was re-elected as President. The Secretary reported that she had received no new nominations for Council from the membership, and that this year David Markham was resigning. The following were elected to Council:

We thank David Markham for his help on Council and welcome Martin Williams back on the team.

At the AGM, Trevor Law announced that he was retiring as Meteorological Section secretary as he felt that the task was beyond him. Council thanked him for his efforts at researching new equipment, and we have included his report of the year's weather below. We have now received a donation of a weather station from Adrian Larkman and members who are interested in the weather are invited to contact the General Secretary.

We are all looking forward to the Observatory re-opening for regular sessions in September. Simon gives an update below and keep an eye on the Facebook page https://www.facebook.com/pages/Hampstead-Observatory/194954637264652.

New Lecture Programme 2019-20

Together with this Newsletter, you will find a programme card for the next session of lecture meetings. More cards can be obtained at meetings. Do take some if you can place them in suitable locations such as Libraries and/or Schools.

The first lecture of the session will take place on Thursday September 19th at 8:15 pm. at which Johnathan Napier of Rothamsted Research will talk on:

Making Fish Oils in Plants – a Sustainable Source of Healthy Fats

I hope to see you at the meeting.

London Weather 2018-19

Trevor Law

Immediately after the AGM of 2018 (on the day of the Solstice), an Anticyclonic North Easterly type developed, bringing us warm, dry and fairly sunny weather up to the 13th July. On the 14th, winds turned South Westerly, initially bringing cooler weather but it soon warmed up again towards the hottest day of the year, 26th July, when it reached 35°C - before a thundery breakdown and cooler weather. Again, it soon warmed up again for the first week of August – but thereafter conditions reverted to nearer normal, with average to cool temperatures and gradually more rain, culminating on the 26th August with a thoroughly wet day and temperatures of just 13°C, nearly 10C° below normal.

June and July were remarkably dry. Parts of South East England got less than 10% of normal rainfall in June. August had nearer to average rainfall. Summer 2018 will be remembered as a warm, glorious summer but what was notable were a lot of very warm days – but almost no really hot ones. 26th July has already been noted and was the only day when temperatures widely exceeded 32°C - 90°F in old money and the lower boundary for 'Phew, what a Scorcher!'. Honourable mention must go to 6th August, which missed 32°C by a whisker.

September started, as is quite common, with a dry period – warm days but some chilly nights. Mid-month a brief warm spell with very mild nights led into an unsettled and windy spell from the 18th-23rd. After this we had a predominantly cool spell and, as the Equinox had passed, decidedly chilly nights.

October bought us quiet and less cool weather – though the night of 3rd-4th gave us the first of the autumnal fogs. Very mild weather came from the 10th-13th, with the overnight min on the 12th-13th an astonishing – if windy – 19°C! The rest of the month was unremarkable but cooler weather towards the end bought us the first frost of the autumn overnight 28th-29th.

In November, the first couple of weeks were fairly mild – if not dry – but the period from the 19th-27th was chilly with some sharp overnight frosts.

Milder weather came right at the end of the month, leading into a sometimes very mild first week of December before it turned cooler. A very wet weekend on the 15th-16th led us into a milder but unsettled spell. However, quiet and fairly mild weather predominated over Christmas and the New Year.

January this year bought quite benign weather for the time of year – but it gradually turned cooler after mid-month, eventually leading to a cold snap that bought us the winter's only snow and most severe frost on the night of 30-31st, below -5°C.

February gave us a wet and windy spell from the 7th-9th but the most remarkable weather event was a mild and predominantly sunny spell from the 19th to the end of the month, culminating in an astonishing and record breaking 20°C on the 25th and 26th. The nights were cool, even cold during this period, as the air was dry.

March started with unsettled and windy weather but it settled down after the 18th. The month ended with dry, sunny weather – classical "March, black ram, come in like a lion, goes out like a lamb".

Early April was largely unremarkable, but nights from the 7th to the 9th bought mist with some fog patches. The period from 17th to the 23rd, over the Easter weekend bought gloriously warm and sunny weather, temperatures reaching 24°C on the 21st (Easter Sunday) and the 22nd. The following Saturday bought strong and gusty winds, with us on the edge of Storm Hannah.

Early May was cool, unsettled and showery. A milder spell came from the 15th to the 25th but this was otherwise an unremarkable month.

Then June so far, what a shocker and what a contrast to last year! The first two days though were very warm and sunny, temperatures reaching 27°C on the 1st but since the 4th it has been cool, unsettled and very wet – though luckily in our area we've missed the worst of it. Unusually strong winds for the time of year on the 8th.

Indications are for a sudden contrast starting over the week-end, as a plume of very warm air developing over the continent clips us. There is a danger of it becoming humid and thundery.

Finally, a word about Noctilucent Clouds. These form in the summer months at the Mesopause, at the top of the Stratosphere, about 50 miles or 80km altitude and are illuminated by the Sun when we at ground level are in relative darkness. A chap in WOLAS, and others saw a display on 9th June, unusually early for this far South – and I saw a modest display on the morning of the 16th. They seem to be anti-correlated to the sunspot cycle. In 2008, 09 and 10 there were widespread, vivid displays. We are once again entering solar minimum and spaceweather.com reckon this could be a bumper year for them. It is claimed they have already been seen as far south as Los Angeles, at 34°N, smashing the all-time record. It may be worth keeping an eye open for them from an hour after sunset to an hour before sunrise till early August.

Observatory Reopening This September

Simon Lang

The works at the Observatory are now in their final phase, and we are now tackling the new paved viewing area, dry rot in the annexe, final fixing of the steps' lighting and finishing off various other things. We have the good fortune of employing Peter Gould who is an expert carpenter and problem solver, to help us see out the remainder of the works especially as he's assisting us at cost. He helped us repair the Dome building back in 2010, replacing all the footings, some timberwork on the Dome and the cladding of the annexe.

We had a tremendous one off reopening to celebrate Apollo 11's 50th Anniversary on Sunday the 21st July. For the opening:

• We displayed many information posters on the less well known technical details of the mission, from the creation of the rocket motors to how the spacesuits were made.
• We turned the annexe into a mini cinema and had a looped video of the lunar module being steered down to Tranquillity Base with Neil Armstrong and Buzz Aldrin talking through their procedures with NASA's Mission Control Centre and the tension was palpable!
• I'd made a Saturn V Rocket model (Revell 1:144 scale, 75cm high). It came with the Command/Service and Descent/Ascent Modules, which were used to show people the way the whole Apollo Mission worked from lift off to parachuting back into the Pacific.
• We had three telescopes in operation but sadly the Sun remained hidden by cloud and, although often in a thin haze, it prevented us using the Hydrogen Alpha Telescope at all (that relies on the Sun being fully exposed to view it properly). The Cooke did manage to show some misty views but with the Sun currently in minimum phase, no detail could be discerned.

Brian Travers, who was one of the telescope makers when we were still CATS, discovered a telescope in good condition, just binned at a local recycling centre, and after an email from me, he was allowed to take it. He fixed it up, donated a tripod and we then put it in a 'raffle for all those who donate £10 or more'. This raised £380 and the raffle was won by Kate Sellars. I made a point of contacting all the donors to thank them for their generosity.

It was a very successful day and I'd estimate we had about 200 visitors between Noon and 10pm with many children. The event was well covered in advance by two sizeable and enthusiastic articles in the Ham & High and Camden New Journal to help boost numbers.

We're particularly grateful to Will Scott, Nick Maslov, Brian Travers and James Levi for helping to get this set up and for helping on the day and to all the other members who came to do a stint of assisting.

We'll reopen for our normal weekend sessions towards the end of September. Over the closure period some demonstrators and assistants have moved on and we'd like to thank them for their sterling service! We'll have numerous new volunteers starting with us as replacements, many of whom have pitched in with the works already, and we thank them for waiting patiently for the chance to help out with the public.

Things will be looking up again (weather permitting of course).

OBSERVING THE MOON: (1) REGION OF PLINIUS

Doug Daniels

After an unsettled showery day, which included hailstones, the sky cleared just after sunset to reveal a five day old Moon. After a quick look at Theophillus etc, which was hard against the terminator, my attention was drawn northwards to the region of the crater Plinius and more particularly to the area surrounding it. Here, Lunar dawn was just breaking and the whole region, still in deep gloom, was criss crossed with numerous flow ridges no doubt formed by the extensive basalt flows which produced the Mare Serenitatis and Tranquillitatis. Plinius is situated close to the junction of these two Maria and the whole area must have been subjected to considerable tectonic upheaval by the violent processes which created them.

These flow ridges are only seen to their greatest advantage when close to the terminator, under higher illumination the whole area looks deceptively flat.

To the west of Plinius, the smaller crater Dawes, still filled with shadow, sits on a roughly triangular shaped raised platform. Westwards of Dawes, the ghost rings of an older burried crater chain can be discerned within this platform roughly midway between Dawes and Vitruvius.

To the north of Plinius a series of intertwined sinuous ridges begins which continue well into the Mare Serenitatis, while to the south, many concentric ridges follow the curved “shoreline” of the Mare Tranquillitatis, resembling frozen breakers lapping a petrified beach.

December Talk

We are sorry to announce that Prof. Nick Lane of UCL is unable to come and give December's advertised talk – 'How Energy Flow Shapes the Evolution of Life' – due to an unavoidable clash with his professional duties.

However, our own Dr Kevin Devine has kindly stepped into the breach, and will talk about:

Modern terran life uses several essential biopolymers like nucleic acids, proteins and polysaccharides. The nucleic acids DNA and RNA are arguably life's most important, acting as the stores and translators of genetic information contained in their base sequences, which ultimately manifest themselves in the amino acid sequences of proteins. But just exactly what is it about their structures that enables them to carry out these functions with such high fidelity? In the past three decades, leading chemists have created in their laboratories synthetic analogues of nucleic acids which differ from their natural counterparts by replacing three key components. The talk will examine in detail the physical and chemical properties of these synthetic nucleic acid analogues, in particular on their abilities to serve as conveyors of genetic information. And if life exists elsewhere in the universe, will it also use DNA?

Subscription Service

Some of you will know that the Hampstead Scientific Society website has a 'Subscription service', where subscribers are notified by email whenever the website is updated. That means they have early notice of when there are, for instance, changes to the programme. Members are not automatically subscribed, as the service was developed some years ago when spam was prolific and filters were not as sophisticated as they are now, so some members were wary of yet more emails, even if from the Society. We try to distinguish them by prefixing the subject with HSS Web Update.

If you are interested, and are over 13, just send an email info@hampsteadscience.ac.uk with HSS Subscribe in the subject line and you will be added to the list. Non-members may subscribe as well.

Newsletters by Email

As the cost of postage increases, so does the cost of sending out this newsletter. Council has suggested that some members may be willing or even prefer to receive the newsletter by email instead.

So, if any member would like to have the newsletter by email only, please send an email, this time to secretary@hampsteadscience.ac.uk with HSS Newsletter in the subject line, and we will arrange it.

Richmond Scientific Society

Our web site has long hosted the programme of our sister scientific society in Richmond. They have now proudly launched their own at http://www,rssbtck.co.uk. Do have a look. We have redirected their pages on our site to their site, and will eventually just leave a link. In case you don't have internet access, their next talk will be at 8pm on Wednesday 19th December in the VESTRY HOUSE, 21 Paradise Rd TW9 1SA:

Beware The Ides of Membranes - An Update on the Observatory

Simon Lang

Thames Water re-covering the reservoir with a 'smart membrane' has caused us many a conundrum and some external works on the building were somewhat overdue as well. We got the keys back to re-enter the site in July '17 and could finally take stock of just how much the works had affected us.

As part of our obligations we had to remove the Met. Station and all the cables for our lighting and supply from the intake head by the front gate. This entailed gutting all the wiring to our split fuseboard in the dome building. During the year of works we removed the Cooke object glass for cleaning, all the other expensive equipment and stored everything else away in a sardine like manner.

On going back in, we first tackled the outside of the building, to make good a number of timbers which were subject to weathering with some damage caused by the works. The door to the dome had been forced open at some point and was already poorly, as well as its frame and so it's had to be repaired and with break-ins now more likely, it was decided to reinforce the door and its frame.

Another key draw back was they put the concrete path to the building back to 1910 specs and so we lost about 5sqm of viewing area that had been subsequently poured. I asked the contractor about paving some of the Met Station area, having checked with the Met. men that we wouldn't be upsetting their readings. I pointed out that our tripods could sink into the ground and potentially damage the new membrane (extremely unlikely but...) and paving would spread the load. He agreed and so I went and got 20sqm of paving. Oops. Should have checked with Thames Water. On seeing the slabs waiting to be laid they asked why we had them and we were told in no uncertain terms to leave them until permission was sought and granted. Well after chewing it over the engineers have agreed we can have it, so YAAAAY! We have to adhere to certain conditions on its installation but I've had experience of that, so it'll be no problem.

Our needing to get onto the top of the reservoir to do works now has to be passed and Thames Water need to install temporary barriers to demarcate any work zone, all to do with insurance I believe. We couldn't wait for them and our painters have had to put their arms through the railings to paint their far sides but of course you can't see what you're doing and so there was much walking around in between, to check the backs of them were covered. Julia Daniels came up with the great idea of Thames Water completely surrounding our building by extending the existing style railings, permanently, so that we could go all around, doing maintenance whenever we needed to, especially important if an urgent job were to come up and gaining permissions would hold it up. Again in principle this should meet approval, subject to the engineers being happy with it.

Volunteers ran in new armoured cables to replace the 45 year old pyro's which were past their use by date. Where we had bulkhead lights that rather dazzled one going up the steps and which needed replacing as they were now irreparable, it was decided they'd be replaced by a rope light that gives an even illumination along their whole length and at 9m long, would illuminate the steps right down to the gate where there had previously been a black hole which the bulkhead lights failed to show up and where the steps are at their most precarious.

They'd have to be housed such that light would be cast across the steps, not up into the eyes nor shining across to the Observatory either and so a bespoke housing to take them has been designed and made. The main electrical intake box, serving us and Thames Water's equipment needed repairing too. In all, 52 pieces of ply and pine have had to be cut to shape, sanded, resined for weatherproofing and then given 6 coats of paint to adequately seal them. All that remains is for them to be assembled & mounted in situ, along the railings, with gap filling and touching up.

It was realised that the railings they'd be attached to could do with painting first, as it would be much more difficult with them in place. Teams of volunteers and a heroic Trevor Law, who joined me for several afternoons each week for weeks on end, stripped the worst rust off and they sanded clean the sound paintwork. In some exposed metal areas, no fewer than 6 coats of paint were put on to ensure they'd be well protected.

Having got the dome door, railings, overall outside work done while we had good weather (and that dragged on which really helped!) it was time to now get on with the inside. This meant moving things around inside the annexe and at that point the dreaded dry rot was discovered. Soon it was realised the floor was no longer sound enough to walk across safely. It had to be replaced for new. So far I've lifted about a third of it but gently because the spores from it can cause illness so I've been spraying it with water to keep dust down. I've slowly bagged up the smaller sections and am making a pile of the bigger stuff. It'll all have to be burnt on site, once I've secured a brazier.

Sadly the rot is also in the wall timbers and their supports but that can be dealt with next spring. It requires jacking the building up, section by section and replacing the base timbers with treated hardwood. This has been done on the dome section already, some 10 years ago. Being a telescope maker and using a water level we got the building base sections to RMS 1mm, I kid you not! Most of summer '19 pencilled into my diary then.

We've a helper doing the electrical work but he's having to squeeze in odd half days between other pressing projects and so that is coming on bit by bit. We should have the electrics reconnected within 2 weeks.

The BBC are doing an 8 minute slot about the HSS and Amateur Telescope Makers of London and how we cross over, in a London Inside Out program, that's likely to be aired in January. So far they've filmed me ripping up flooring to emphasise our need for donations. The rest will be telescope making and an observing session where we'll attempt a live feed through the Cooke of Mars or the Moon. It's all happening!

Live long and paint it,

Simon Lang.

Maggots

Julie Atkinson

Introduction

My mother had a venous leg ulcer which wouldn't heal. Nasty open sores, painful dressing changes, vulnerable to infection. I'd heard about alternative treatments, such as use of maggots, though was more inclined to think of them as undesirable infestations, indicating neglect, and associated with rubbish and mess. Or, in the case of those omnipresent detective series on the telly, as indicators of the time of death of an infested corpse.

But Prof. Yamni Nigam from Swansea was so enthusiastic about the little larvae and their properties at the British Science Festival a couple of years ago that I decided to look more into the topic.

History

The traditional medicines in some cultures made use of maggots: Hill People in Northern Burma, the Ngema tribe in Australia, and in the past, the Maya, used maggots on wounds, applying them directly or attracting flies to blow. In the 1500's in the West, a French surgeon named Ambroise Parxc3xa9 observed the healing of a severe head wound in the presence of maggots, and thereafter allowed any infestations in patients to remain for a while in an attempt to aid recovery. I don't know if others followed the practice. A compatriot surgeon in the Napoleonic wars in Syria observed that blue fly larvae cleaned the dead flesh from a wound and had a beneficial effect on the living flesh. It was a Confederate surgeon during the American Civil War, John Zacharias, who actually applied maggots to gangrenous tissue, saying that, in a single day, they would clean a wound much better than any agents they had at their command, and he believed he saved many lives by their use.

However, it appears that 19^th century experiments introducing maggots into wounds were not always so successful. If maggots were cultivated and applied to a wound, they might still themselves harbour pathogens, and so could bring infection to the site. Common bacteria in the soil or on raw meat could cause tetanus or gas gangrene in the patient. So considering maggots as dirty, revolting, to be removed rather than encouraged, was a quite logical response.

In the First World War, deaths from open wounds were increasing, as the cases overtook the means of treatment, even reaching 70%. So, when another American, William Baer noticed that two soldiers with battlefield injuries a week old had no pus, fever or infection and appeared to be healing, he was interested. What they did have were swarms of maggots. Back in the US, at the Baltimore Children's Hospital he experimented with applying maggots to wounds, with some success until two patients died of tetanus. But that drove Baer to attempt to sterilize the maggots. He found he could easily sterilize the outside, but the gut would remain contaminated, so eventually devised a method involving washing the fly eggs with a solution containing mercurous oxide and acidified alcohol.

The availability of sterile maggots led to a boom in maggot therapy in the 1930's. However, alternatives such as sulphonamides were also produced in the 1930's and antibiotics became available in the 1940's, soon gaining almost total supremacy. Probably helped by patients' natural aversion to creepy crawlies on their person.

Why is there recent renewed interest in maggot therapy? It may be due to the increase in antibiotic resistant infections. The treatment had been regularly used and promoted by Dr Ronald Sherman, University of California, Irvine, in the 1990's, claiming it led to more rapid removal of debris than other non-surgical methods, and faster healing.

Also in the early 1990's, a member of the Surgical Materials Testing Laboratory (SMTL) in Bridgend became aware of efforts to stimulate interest in maggot therapy in the UK. Steve Turner persuaded his NHS trust to fund work in the area, resulting in a method of sterilizing maggots and successful treatment of a number of patients. That in turn led to sales of the sterile larvae and the eventual spin-off to a commercial entity in 2005, the year after maggot therapy was made available on prescription on the NHS and also recognised as a prescription only treatment by the US FDA.

Problems

So, what type of maggot is suitable for the treatment? Flesh eating insects come in various guises. The screwfly larva, for instance, eats living flesh and so can be dangerous, particularly to livestock. Other fly larvae may restrict their diet to dead flesh but still be detrimental to the wounds. The larva of the greenbottle blowfly, Lucilia sericata, causes damaging lesions on sheep, but it is the preferred candidate for maggot therapy, where it feeds on decomposing human tissue.

Prime Uses

The main use for maggots is for 'debriding' wounds, i.e. the medical removal of dead, damaged or infected tissue to give the remaining flesh a better chance of healing.

The maggots don't have teeth to chew the dead tissue. They secrete enzymes which selectively dissolve it, and then they can suck up the result. That means that the maggots don't actually need direct contact with the flesh. These days, they can be applied onto the wound in a little sealed sachet, rather like a tea-bag. Patients don't feel them, and there is no pain when applying or removing the bags.

The maggots need to grow from hatchlings 1-2mm in length to 8-10mm before pupating and emerging as flies, the rate of growth depending on temperature. A maggot therapy nurse from the SMTL, Mary Jones, recalled that the hatchlings were kept in a fridge to slow down metabolism until they were needed, and she would travel to the patient with maggot pots up her jumper to warm them for application. In order to grow rapidly, the grubs are voracious eaters, helping to clean up a wound quickly. The sachet will hold any excreta and their moultings as they grow. They are generally removed after 3 days.

But if maggots eat infected tissue, won't the bacteria just be excreted back into the wound? Maggot cleaning seems to include eradication of bacteria. A group in Oxford and Israel have found that the larva gut kills almost all Escherichia coli passing through.

Is this wound cleaning the only benefit of maggots? The earlier work implies that there are positive effect that are not just due to the clearing of dead matter.

Swansea Group Research

Prof. Yamni Nigam has a background in medical entomology, and set up the Swansea University Maggot Research Group in 2001. The group has carried out numerous investigations into the composition of maggot 'spit', at the molecular level.

Fans of maggot therapy had long believed that the secretions contained an antibiotic. The research group has found that there are several antibiotic molecules present, the most interesting of which is Seraticin. This is a relatively small molecule, but with apparently powerful effect, attacking various pathogens, including several strains of MRSA. The group is now trying to purify the extract.

In long term wounds, bacteria may form a biofilm, a slime comprising layers of the micro-organisms sticking to proteins on the wound edges, and covered by a sugary layer that protects them from antibiotics. The research group has found that maggot secretions can destroy these biofilms, or even prevent their formation.

Bacteria are just one type of potential pathogen. Another are fungi. Some fungi could indeed attack the maggots themselves. The research group have also found that maggot secretions contain antifungal agents.

And finally, during her talk, Prof. Nigam speculated on whether the healing observed in maggot therapy may in part be due to growth factors contained in the maggot secretions, reasoning that the larvae are of course the young of the greenbottle fly, and are feeding in order to grow to maturity, so are likely to be producing such hormones. But, would they act on humans as well to promote cell growth and hence healing?

In investigating this, the group have found that there are particular components of maggot secretions that can stimulate proliferation of some blood vessel cells, and so are potentially positive healing factors. The research continues.

In Practice

At the British Science Festival talk, Prof. Nigam showed some rather gruesome pictures of wounds which had been treated conventionally without success, and which as a last resort were cleaned and healed with the help of maggots. Now the use of maggots is becoming more routine. Mary Jones commented that they were particularly useful for diabetic foot ulcers, which could be cleaned by the larvae within days rather than months.

Given her revulsion at my mentioning maggots as a potential treatment, it is just as well that my mother's ulcer finally managed to heal over without their help!

References

I have consulted the following for this article:

1. Creepy, crawly maggots are actually a medical powerhouse, Yamni Nigam, The Conversation January 10, 2017
2. Larval therapy from antiquity to the present day: mechanisms of action, clinical applications and future potential, Iain S Whitaker, Christopher Twine, Michael J Whitaker, Mathew Welck, Charles S Brown, and Ahmed Shandall, Postgraduate Medical Journal, v83(980), Jun 2007
3. Myiasis: maggot infestation, Ian F Burgess, Nursing Times, v99 No 13, April 2003
4. Medicinal Maggots, Wilder Damian Smith, Modern Drug Discovery, Vol 4 No 10, Oct 2001
5. Wound healing--from poultices to maggots. (a short synopsis of wound healing throughout the ages), J Donnelly, Ulster Medical Journal, 67, suppl 1, June 1998
6. Destruction of Bacteria in the Digestive Tract of the Maggot of Lucilia sericata (Diptera: Calliphoridae) , Kosta Y Mumcuoglu, Jacqueline Miller, Michael Mumcuoglu, Michael Friger, Mark Tarshis, Journal of Medical Entomology, Volume 38, Issue 2, 1 March 2001
7. SMTL History, Steve Thomas, Surgical Materials Testing Laboratory website, 2010 and 2017
8. Have maggots, will travel: reflections on my career, Mary Jones, Wounds UK, Vol 4, No 1

Hon. Secretary: Dr. Julie Atkinson

Hon. Treasurer and Membership Secretary: John Tennant

Hon. Programme Secretary: Jim Brightwell

The following nominations were received for the 5 ordinary members of Council.

David Brant, Dr.Kevin Devine, Jonquil Florentine, David Markham, Anne Watson.

As there were no further nominations, these nominees were declared as elected to Council.

In his final report the President said that the last session of lectures were, as expected, of the usual high standard and he reported that all of the next session lectures were already booked. He thanked the Programme Secretary for his hard work and persistence contacting prospective lecturers and juggling dates. The President also paid tribute to all Council members for their continued support and he also thanked all those members who helped at meetings by putting out chairs, making coffee and providing refreshments etc.

In past reports, the President had been pleased to say that this was ‘another good year for the Society’ but last year certainly was not! In April we were saddened by the news of the untimely death of Brian Bond, a member from 1980. Brian was our solar observer and he was to be found up at the observatory on most sunny Sunday mornings demonstrating his hydrogen alpha telescope and showing visitors what the Sun really looks like. Then we received news that our meteorologist, Philip Eden has also passed away after a long illness. But to cap it all, we then received the sad news that Prof. Heinz Wolff had also died. Heinz was a member for over 60 years and was President from 1968-1987. His last lecture to the Society was delivered in September last year. The Society extends our deepest sympathy to all relatives and friends, they will be greatly missed by all their colleagues in the Society.

Enclosed with this Newsletter you will find the Programme Card for the next session. More cards are available at meetings, so do take some if you are able to put them in public places such as libraries, schools etc.

The First meeting of the new session will take place on Thursday Sept 20^th at which Dr. Joel Davis from the Natural History Museum will tell us ‘The Story of Water on Mars’. I look forward to seeing you there.

Subscriptions

The Hon. Treasurer reminds members that Annual subscriptions are due next month and it would be helpful if those paying by standing order would make sure that their orders have been changed to the new increased rate by October 1^st.

News from the Observatory

Those members who frequently visit our website will know that Thames Water which owns the reservoir on which the Observatory is situated, were engaged in lengthy building and engineering works at the site. The work required the removal of all the grass turf from the entire site and then to fit a waterproof membrane; and then replace the turf. In order to do this the path and railings from the gate to the observatory had to be removed temporarily and also the meteorological instruments and the rain gauges belonging to the Environment Agency. Work began at the end of July 2016 and was expected to be finished by January 2017. But large scale engineering works are renowned for overrunning completion dates and when Thames Water finished, there was still a lot of work for us to do, restoring the electrical supply for example and reinstating the Met. instruments.

We are grateful to Thames Water for involving us in all the negotiations and being mindful of our charitable status and our position as long term tennants. Thank goodness we were not required to remove the observatory building so soon after investing such a large sum on its restoration two years ago.

At present the solar telescope and its mounting have been removed for safe keeping, and we are taking the opportunity to remove and clean the Cooke object glass which is being looked after by Terry Pearce.

Of course, all this disruption means that the Astronomy Section was unable to open the Observatory to visitors as it normally does, in fact the observatory will probably not return to normal operations until the end of September 2018. This will be the longest period of forced closure since the Observatory was founded in 1910, and it has totally spoilt our record for uninterrupted daily meteorological readings from one site.

Obituary Professor Heinz Siegfried Wolff, 29 April 1928 - 15 December 2017:

Julia V. Daniels

When Heinz passed away last December, it was a very sad loss to the world and the many organisations and charities that had benefited from his inventive genius; it left a void in the lives of those who knew him personally and loved him for the man he was, and it was a special loss to the Hampstead Scientific Society and to those members who knew him in the fifties before he became one of the best known scientists in Britain.

Heinz joined our Society in the mid-fifties, I don’t know the exact year, but when I joined in Spring 1957 he was already a member. My earliest memory of him was in May ’57 when he was demonstrating a Geiger counter to illustrate a talk on Radioactive Fallout by Dr. Otto Edholm, who was our President at that time. Heinz worked for Edholm who led the Division of Human Physiology at the Medical Research Council Laboratories at Holly Hill, Hampstead (part of the National Institute for Medical Research). We had just started holding our lecture meetings at Holly Hill, where many of our members at that time were working, though a few like myself worked at the other NIMR establishment at Mill Hill.

In 1959 Heinz and I were elected to the HSS Council, and Heinz soon became a familiar face and voice at meetings, charming members with his ability to present science as great fun. One of the highlights of every year was the Conversazione in October, a social meeting at which members could exhibit anything of scientific interest. Heinz took a boyish delight in demonstrating some scientific phenomenon especially if he could surprise his audience.

Heinz took over from Dr. Edholm as President of the Society in 1968, and remained in office for nearly 20 years, until 1987. While President he gave a lecture every year. It was listed on the Programme as ‘The President’s Evening’, and would be entertaining and unorthodox, but no hint of the subject was leaked in advance. Sometimes it was about designing simple gadgets to make life easier for the elderly and disabled. We began to see his talent for invention and his desire to help the aged with the simple problems of everyday life. His wife Joan said that he invented things before people knew that they needed them. One year he talked about teddy bears and how we interpret their facial expressions, and when he repeated this talk to children at the Royal Institution the front row was entirely occupied by teddy bears! He sometimes introduced a little drama into his talks. At the Society’s diamond jubilee meeting in 1959 members were transported both into the past and the future, as Heinz posed as a spaceman transmitting live pictures of his futuristic trip to Mars in 1999. Later, at the Victorian evening in 1988 where everyone came in fancy dress, Heinz dressed up to lecture in the guise of Isambard Kingdom Brunel.

His professional career was impressive. After working for Dr. Edholm, in 1962 Heinz himself founded and became Director of the NIMR Division of Biomedical Engineering at Holly Hill. Then from 1970 to 1983 he was head of the Bioengineering Division of the MRC’s Clinical Research Centre at Northwick Park. While there, he led a Hampstead Scientific Society outing to Northwick Park Hospital to see the MRI scanner. He explained that by scanning the body from all around, it could produce a series of images of the body in cross section, and it did this by solving an enormous number of simultaneous equations. I gasped at the idea and wondered how long it would take a computer to do that, with the patient still lying under the scanner. In 1983 Heinz founded the Brunel Institute for Bioengineering at Brunel University, and he served as its director until 1995, then becoming an emeritus professor. He never stopped working. When he resigned as HSS President in 1987 Heinz and Joan moved away from Hampstead to be nearer Brunel, but he remained an HSS member until he died.

Heinz became one of Britain’s best known scientists as a result of his many appearances on television, first on Panorama in 1966 when he produced the radio pill that could respond to conditions in the gut, then presenting the Young Scientist of the Year awards, The Great egg Race and Great Experiments Which Changed the World. The Great Egg Race ran from 1977 to 1986, and contestants were challenged to see how far they could propel an egg using just the energy stored in an extended rubber band. Heinz wisely retained his German accent and his voice was instantly recognisable. He used to say he was an English gentleman with a German accent, but he was born in Berlin and came to England as a Jewish refugee just as war was breaking out in September 1939.

According to Heinz, his grandfather Siegfried Wolff was a tolerably rich business-man, until the business faltered due to inflation in the 1920s. When Heinz was a child, he had a nanny until he was one and a half, and a governess from when he was four or five, which was not unusual in Germany in those days. Heinz got the impression that the family was comfortably well off. His father had desperately wanted to train as a chemist while he was growing up but he was not allowed to do so, and eventually studied law and philosophy. However he did manage to accumulate a large quantity of dangerous chemicals and chemical glassware and had his own laboratory when he was 16. After he married he kept all these chemicals in his loft. When Heinz was only 3 he already imagined that he would either become a chemist or an engineer, and his father knew enough science and technology to be able to answer the questions of a four or five year old.

Heinz had an electric train, chemistry sets, the German equivalent of Meccano sets, and he built radios. Having parents who were sympathetic to his technical ambitions, he always had lots of wire, batteries, and access to grownup tools. Almost unimaginable now, his parents let him repair mains-powered appliances from the age of 5. This may be why in later years he would often say that children need an element of risk in their lives (he called it vitamin R) so that they can learn from experience.

Heinz vividly remembered looking out of the window of their fourth floor flat in January 1933 and watching the torchlight parade of the SA as Hitler came to power. By 1935 when Heinz was 7, anti-Semitism was growing in intensity. Jewish businesses had to be compulsorily sold to new Aryan owners, and people wanting to emigrate from Germany were not allowed to take any money with them, but Britain expected you to come with some capital to avoid being a burden on the state. Heinz’s father helped people to transfer their money abroad, which was totally illegal under the Nazi administration, and Heinz was often present while these matters were negotiated. By 1938 Heinz and his father were sleeping in a different place each night, which Heinz found very exciting, not at all frightening.

Heinz arrived in England in 1939 when he was 11, just as war was breaking out. He came with his father, his mother’s sister and her husband and daughter, who lived as a family of five, his mother having died when he was 10. Heinz never felt like a refugee, but felt immediately at home in this country, and started school a couple of weeks after arriving here. He said he became a true patriot and England was one of the few countries that he would be prepared to live in.

When the Blitz started the family moved from Golders Green to Oxford, and Heinz went to the City of Oxford School which was one of the best-equipped schools for science teaching anywhere in the country. Here he learnt chemistry and physics, and the lab.technician taught him practical skills such as glass-blowing and soldering. Heinz often waxed lyrical about the versatility of the human hand, with which we can use a sledgehammer, thread a needle or play a violin – why we are homo sapiens. While he was in the sixth form it became possible to buy ex-War Department electronic equipment for ‘a penny-a-pound’, so he persuaded the school to buy a crate of these bargains. When he opened it he was utterly thrilled by the contents which included a cathode-ray tube and thermionic valves. He was given a free hand to play with this inspiring junk.

Heinz won a place at Oxford University to read chemistry, but was asked to delay his degree course for a year so that ex-servicemen could resume their interrupted studies. So he went to work at the Radcliffe Infirmary, the teaching hospital in Oxford, under the wing of Dr. Robert Macfarlane, one of the foremost haemato-logists in the country. Heinz was given the project of devising a machine to count blood cells. At Harwell they were counting the blood cells of their staff because they were concerned about radiation damage to their employees, but they were counting them by eye which was very unreliable and time consuming. It needed to be automated. After teaching himself engineering and electronics Heinz solved the problem, and published his results in Nature in 1950. And it was in Nature that he saw the advertisement for his next job, at the Pneumoconiosis Research Unit at Cardiff, which was founded by the Medical Research Council to investigate diseases which coal miners get by breathing coal dust. He soon realised that counting dust particles was not the way to proceed, but to sort them by weight. While at Cardiff he met Joan Stephenson, a nurse, whom he married in 1953.

Heinz still wanted to go to university, and the MRC generously offered him the equivalent of a state scholarship if he would work in a different medical research unit during each long vacation. He was free to read whatever he liked at university, so instead of Chemistry he chose to read Physiology at University College London.

In his first long vacation he chose to work at King’s College, London. It was the year of the double helix. Maurice Wilkins and Rosalind Franklin, who were key members of the team that lost the race to find the structure of DNA, were working there, and Heinz said that he learnt a lot from these eminent scientists. In his second long vacation he worked at the Division of Human Physiology at the National Institute for Medical Research at Hampstead, and he returned there to work for Dr.Otto Edholm after completing his degree course.

Edholm introduced Heinz to the Hampstead Scientific Society, an organisation which aimed to explain the latest developments in science to the layman and specialist alike, by organising popular lectures. Heinz was always keen to encourage young people to take up science as a career, so the HSS was the perfect society for him to join, and he was the ideal person to become its next president.

Through his many appearances on television, Heinz became well known and popular with the public. He also became involved with many other projects; he was an advisor to the European Space Agency and the British National Space Centre, he served on the board of the Edinburgh international science festival, and he was vice-president of the Royal College of Occupational Therapists. He was also involved in the Juno Project to fund a British astronaut into space, though actually it was the Russians who paid for Helen Sharman to join the cosmonauts on the Russian space station Mir.

Heinz was strongly motivated to design aids for the elderly and disabled, such as a computer programme to contact a GP or organise the shopping, intelligent homes, and a car with a front-opening door to be parked facing the pavement. But his most recent project, which he described to the HSS in a lecture in 2016, was called ‘Give and Take Care’. Soon there will be so many elderly people needing daily care that there will never be enough money to pay for it. Instead he proposed that fit young people should invest their spare time in caring for older people, and that this could earn them credits which will entitle them to care when they need it. Heinz contributed financially to the scheme which has already started operating in some areas. Heinz gave his last lecture to the HSS in 2017. It was in fact a set of three spoof lectures so convincing that he challenged members to guess which one was true. Heinz was a genial workaholic, and listed his recreations as working, lecturing to children, and dignified practical joking.

Heinz was awarded honorary doctorates by the Open University, Middlesex University and Oxford Brookes. Sir Peter Medawar described Heinz as ‘something of a genius’, and he certainly was.

References: The Making of a Refugee Scientist by Heinz Wolff 2013

* * * * *

Retirement of President

At the Council meeting on April 5^th, Doug Daniels expressed his wish to resign as President, having held the position for 10 years. He pointed out that at 78, he was beginning to feel his age and that Council should look for a younger replacement. Fortunately Simon Lang FRAS was willing to take on the job. As the Secretary had received no other nominations or volunteers, Julia Daniels proposed Simon and this was agreed by all present. The retiring President wishes to thank all Council members for their support during the last decade and wishes Simon all the best for his presidency.

The AGM agenda will include reports from officers and section leaders and the election of officers and 5 ordinary members of Council. Council proposes the following:

Council invites further nominations for the above posts. Such nominees should be duly proposed and seconded and should have agreed to serve if elected.

Under the revised Constitution, Council will replace one ordinary member, from those who have served longest each year. At the Council meeting on April 5^th Martin Williams retired, being the longest serving ordinary member of Council. Council proposed Jonquil Florentin to replace Martin Williams. Jonquil was proposed by Simon Lang and seconded by Julia Daniels with all in favour.

Notification of a change to the Constitution

It has been pointed out that when it comes to the election of auditors for the Society's accounts we should not appoint candidates who are currently serving members of Council.

The current wording is: The Council shall present to each Annual General Meeting a report of the Society's activities during the preceding year, including a statement of accounts duly audited by two members of the Society, who shall be appointed at the previous AGM.

The proposed change will say: including a statement of accounts duly examined by one examiner chosen from two members of the Society but independent of the Society's governing Council, who shall be appointed at the previous Annual General Meeting.

The Council shall have the power to employ, if it thinks fit, the services of a professional auditor.

The proposed changes are underlined.

New Laws concerning Data Protection

New legislation will soon be in force in an attempt to protect against illegal distribution of personal data. This will affect societies like ours, who keep records of addresses, e-mail addresses, web sites etc. necessary for archival purposes and to contact speakers, members, publish lecture programmes and maintain a website.

For our part we confirm that no personal details concerning our members will be provided to any outside organisation without prior consent. We will remove any personal details such as telephone numbers or home addresses if requested by members. This means that they will no longer be able to receive newsletters or programme cards by post, but they could be obtained at lecture meetings. You may at some point, be asked to sign a document consenting to your contact details being kept by the Society.

Heinz Wolff Memorial Service

Members are invited to attend a Memorial Service to commemorate the life and work of Professor Heinz Wolff, our past President from 1968 – 1987.

The Service will be held at Brunel University of London, Uxbridge UB8 3PN, on Monday 30^th April 2018 from 14.45 – 16.00 BST. Admission is free, but in order to attend you must register using their web-site.

Once registered, you will be able to download tickets from their web-site. If you require any additional information, please contact the Office Manager.

Wishing you all A Merry Christmas and a Happy New Year December 2017

At last - a Mystery solved?

Doug Daniels

During the ‘cold war’ era, when the USA and the USSR competed to produce more and more destructive atomic weapons, surveillance satellites were put into orbit to monitor atomic weapon testing. These satellites scanned our planet looking for the tell-tale emission of gamma rays which would have been released by any clandestine nuclear explosions. It came as something of a shock when these satellites began to record very frequent random bursts of gamma rays coming, not from our planet, but from deep space. These bursts were of very short duration, typically a few milliseconds and vanished without a trace before a telescope could be trained on the possible source. They were given the name ‘Gamma Ray Bursters’.

Gamma rays occur at the far short wavelength end of the electromagnetic spectrum and they are the most energetic of all particles. As these gamma ray bursts seemed to be coming from immense cosmological distances, it was reasoned that whatever was causing them must be a colossal explosion of energy equivalent to the energy of trillions of Solar masses. It would be very useful if the ‘afterglow’ of such an event could be studied to see if other radiations, such as x-rays, or even visible light was emitted. Plotting the light curve for such an event could give astronomers valuable information as to the mechanism which might be responsible for it.

Birthday Honours

Peter R Wallis

The date of 17^th August is important to me personally because it happens to be the 93^rd anniversary of my birth. But it is of greater importance to astronomers as it was the gravity-wave detection of the merger of two neutron stars, GW 170817. You will recall the gravity wave detection in 2016 at the Laser Interferometer Gravity-wave Observatory (LIGO) in the US of the merger of two black holes that demonstrated the new technique for observing the universe. But black holes have event horizons which limit our ability to see them. Neutron stars have no event horizons and we can see their mergers using optical, infra-red and X-ray telescopes. Moreover, there is now a second gravity-wave observatory (Virgo) near Pisa in Italy and this has allowed a reduction in the location uncertainty from 600 square degrees to 30 square degrees.

The GW 170817 event was announced in Nature Vol 551 of 2^nd November 2017 by M Coleman Miller. The event was first observed by NASA s Fermi Gamma-Ray Space Telescope just 2 seconds after the time of merger. There are also five papers published in the same issue covering x-rays, optical and infra-red light. It has been possible to locate the source close to galaxy NGC 4993 at a distance of 40 million parsecs (130 million light-years). This is quite close in galactic terms and 10 times nearer than any previously measured gamma-ray bursts. The gamma-ray burst from this event is rather weak, but probably because the polar jet is seen only obliquely. Recent theoretical work has predicted that some of the neutron-rich matter would be ejected in the orbital plane and combine to form new elements, perhaps heavy ones, leaving a signature glow for a few days. Three of the papers report such a glow, called “kilonova”. There is a possibility that the mix could involve the manufacture of very heavy elements such as gold and platinum, but this is not yet generally agreed. However, it is now agreed that neutron star mergers are responsible for the mysterious Short Gamma-Ray Bursts.

Observatory Closure

Simon Lang

We’d been closed for a year from July 2016 as Thames Water had to re-cover the reservoir with an impervious ‘smart’ membrane that would sense future leaks and hence prevent contamination of the water supply. We managed to get in at the end of July this year and hoped to quickly restore the Observatory to be ready to re-open in September as usual but sadly found we needed to do far more than hoped.

On regaining access, we found the Observatory had been broken into, this was going to require replacing the lock and some door repair, it’s been decided that we are going to make the door thicker and much stronger than before, Demonstrators, don’t leave your keys inside in future! The risk of damage to the new membrane meant that our barrier separating the Met. Station could not be put back as before and the instruments themselves are proving difficult to re-locate; sadly there’s rumour that the Met Office may abandon the site if alternatives to their normal set ups can’t be found. This would be sad and I’m lobbying to press them into a technical solution. We had removed the mains power and lighting supply but tests on the old cable suggested replacement, and the old electrical intake to the site also needs attention. Thames Water and UK Power Networks need to track down and install a new supply to the reservoir, in the meanwhile we need to replace much of our electrical installation but at least we have an advisor in a volunteer from UK Power Networks to assist!

As part of the works we have looked into extending the viewing area outside the dome with paving slabs but discovered we need permission to do this. This is now pending. These issues are sadly taking a while to resolve and will continue to do so.

We got on with what we could manage with the building being rather weather beaten! We held about 10 Sunday sessions with volunteers where we concentrated on removing bad timbers and replacing them, sealing as many cracks to the base of the dome building and annexe and resealing the dome coverings. Most filling and painting has been completed.

With the weather turning cold and or, wet, we’re now in limbo to continue and with the Christmas season coming it is unlikely we’ll be open until well into the New Year now. One positive note is that we have no planets of interest we can see and so apart from the Moon we’re not missing much. When we have better weather the paving and electrical work will proceed.

During slightly better periods and when I have time, I’ll finish repairing the door, front gate lock and with luck start to reinstall our side of the power supplies to the building and step lighting. Unfortunately we have particularly complicated, time consuming things to deal with but only one skilled person whose health could be better and is very busy elsewhere. We’d quickly use up our funds to employ others to do this and so the wait continues.

BALLOON OVER HAMPSTEAD

Jim Brightwell

I became interested in balloons as a child watching them being released at a fete. They were using hydrogen then with lots of balloons in a bunch near children. No spoilsport health and safety then! I was fascinated to know where they went and what the view from the balloon would be.

In 1962 I was filling balloons with coal gas which was not only explosive but poisonous as well. It was not health and safety that put an end to this project but conversion to natural gas in 1971. Natural gas does not have enough lift and would no doubt get investigated if I used it now. The project restarted in 1985 when I was working with helium. It is now an ongoing project with cameras.

At the start of the project I was using different colour balloons and one colour had much better response than others – guess which? I found the best meteorological condition to get them in to the continent and received German letters, Dutch letters and letters from France. The rate of return using the best colour was about 1 in 25.

A return rate of 4% would be too expensive using cameras but camera balloons are larger and designed to come down in an area with better chance of a find which turned out to be about 1 in 8. I have two ways of bringing the balloon down. One is to attach a 2^nd balloon to provide the extra lift with a fuse to release it after about 2 minutes. The fuse is made of paper treated with potassium nitrate from ebay. I could have brought a large amount with no questions asked. It seems most people buying it on ebay have also brought flowers of sulpher, I wonder why? The 2^nd way is to have one balloon inside the other with a hole in the outer balloon, to leak helium

Now for some results if you search for HAMPSTEAD FLIGHT on youtube you will see it passes over Fitzjohns Avenue at 8.50, Finchley Road at 9.50, South Hampstead High School sports ground at 10.45 and lands in Hampstead cemetery at 13.30. The first 5 minutes of this video are very unstable. The release for this flight was one balloon inside the other. The video MOAT MOUNT FLIGHT used a 2^nd balloon with a fuse and the separation takes place at 2.00. It passes over the A41 at 5.15, M1 at 6.20 and Barnet Way at 10.40 Barnet Way has much more traffic.

The videos are shaky as I am using cheap cameras which have a very narrow angle of view, so why not use a better camera? Well the camera I use costs about £3 and the ideal camera costs £60! Add an SD card, balloons and helium and each launch costs about £10. With a better camera it would be about £100 per launch! A GPS tracker has been suggested which would also add weight and cost and just knowing where it has landed would not help much if it is in a river, smashed on a motorway or most likely stuck up a high tree.

I fly well within CAA regulations – which are a limit not a target! The reason is I use a toy balloon about 12” in diameter and the CAA regulation limit for a free balloon in civil air space is 6 foot diameter. My balloon is far less than the weight of a pigeon and aircraft engines are designed to cope with a small bird. I read a report of a pigeon that got into a jet engine and it did no harm, but you should have seen what the jet engine did to the pigeon! I also do not launch if the wind direction is towards Heathrow in the interests of discretion as questions could be asked if it landed there.

The Secretary reported that she had received no new nominations for Council from the membership, but reported that Alexander Menegas was resigning because he was off to Princeton University in the USA to study physics. We thank Alexander for his help on Council and wish him every success in his studies. His resignation means that we do not need to ask a long-standing member to stand down.

Council agreed the following nominations for the offices with no objections.

Council welcomes Anne Watson to its ranks and the return of David Brandt.

PRESIDENT'S REPORT

In his report, the President thanked all members of Council for their continued support and congratulated the Programme Secretary for completing next session’s lecture programme in good time. He then said that he was sad to report the death of Brian Bond who was for many years a demonstrator at the Observatory. In recent years Brian became interested in the Sun and observations of solar phenomena using his own Hydrogen Alpha telescope and he could be found up at the observatory on most sunny Sunday mornings entertaining visitors with views of our nearest star. He will be greatly missed by his many friends and colleagues in the Society.

The main topic for discussion at the AGM was the proposed increase in subscriptions. The Hon. Treasurer pointed out that the running costs were rising e.g. venue hire, postage & printing, insurance etc. Clearly this situation could not be allowed to continue as it meant the slow erosion of our reserves. He then proposed an increase in the ordinary subscription from £15 to £19 but leaving the junior sub. at £5, Country at £6, Family at £29 and Group at £45. After much discussion, it was decided to increase the ordinary sub. to £20 to save possibly having to revise rates again in a few years time. The new rates were approved by the membership and will come into effect on October 1^st.

Changing his hat to that of Astronomy Secretary, the President said that he was sometimes accused of reading too lengthy astronomy reports – this would not be the case this time. He then gave the Astronomy Section report in one short sentence :-

‘The Observatory has been closed for the whole year while Thames Water have been working on the reservoir and in consequence there were no public open nights and no astronomical observations were made.’

CURRENT PROGRESS AT THE OBSERVATORY

Thames Water finished their work on the reservoir at the end of July, exactly a year after they started. This left us with a lot of work to do ourselves, but first we had to liaise with the Met. Office and the Environment Agency about re-siting their instruments. It is a pity that our record century plus of continuous daily met. readings has been interrupted with the loss of a whole year’s recordings. However, Thames’s work has left us with a few benefits. By relaying the concrete pathway from the stairs to the rotunda they have saved us the annual struggle to remove rogue weeds and tree saplings growing in the cracks, and moving the met. instruments further south has given us a much larger outside area for portable telescopes. The cast concrete ‘flange’ encircling the observatory has improved its appearance and the slightly raised level has removed the high step in front of the observatory door which had always been a trip hazard in the dark.

We now have to re-commission the Observatory so that we can resume our public open nights, but it seems pretty clear that we will have to postpone opening, probably until the end of October. We still have to re-connect and upgrade the electricity supply to modern specifications, re-fit the step lights and re-fit and adjust the telescope objective – to name but a few jobs!

When Thames Water finally vacated the site at the end of July, Simon wasted no time and organized a working party on Sunday August 6th and a follow up on the 29th. A good number of members turned up on nice warm sunny days to help. The first activity was to remove the vast quantity of tree bark mulch that Thames Water had spread over 50% of the Met. site. We needed to remove this in order to lay paving stones. In the event, the area proved far from level and will need some more work before we can begin to lay the stones, so we turned our attention to painting the building instead. Our thanks to all those who turned up to help and to Simon for organising the work and buying the materials.

NEW LECTURE SESSION 2017 - 2018

Together with this Newsletter, you will find a programme card for the next session of lecture meetings. More cards can be obtained at meetings. Do take some if you can place them in suitable locations such as Libraries and/or Schools.

The first lecture of the session will take place on Thursday September 21^st at 8:15 pm. at which Emeritus professor of bio-engineering, Heinz Wolff, will entertain us with a trio of interesting talks entitled: YOU MAY NOT BELIEVE THIS BUT..... Heinz is an ex-President and has been an HSS member for 60 years.

I hope to see you at the meeting.

Doug Daniels HSS President

At the Council meeting on April 6^th, Doug Daniels was once more elected as President for the next session. He was pleased to accept once again but he pointed out that at 77, he was beginning to feel his age and that Council should perhaps begin to look for a replacement sooner rather than later. As we are all aging, we never know when we might be suddenly struck down as you will see on the next page.

The AGM agenda will include reports from officers and section leaders and the election of officers and 5 ordinary members of Council. Council proposes the following:

Council invites further nominations for the above posts. Such nominees should be duly proposed and seconded and should have agreed to serve if elected. Such nominees should be duly proposed and seconded by two members of the Society not less than four weeks before the AGM. Nominations should be sent to the Secretary at the address on the programme card or by e-mail : secretary@hampsteadscience.ac.uk by May 25^th.

Under the revised Constitution, Council will replace one ordinary member, from those who have served longest, each year. At the Council meeting on April 6^th Martin Williams was due to retire but Alexander Menegas announced that he would have to retire as he was off to Princeton University in the USA to study physics. We thank Alexander for his work for the Society and we wish him every success with his studies.

Shortly before this Newsletter went to the printer, we received the very sad news that Brian Bond had died suddenly after a short illness. At this time our thoughts are with his widow Gina and his family and a fuller obituary will be posted on the website in due course.

Doug Daniels writes:

Brian was a dedicated amateur astronomer who joined Terry Pearce’s telescope making class way back in the 1980’s. It was here that he learned about the HSS and the Observatory. He soon joined and became one of our most enthusiastic demonstrators. He acquired a 10-inch Schmidt-Cassegrain telescope and about twice a year he would seek out dark sky observing sites; he was a regular camper at the Kelling Heath Astro camp. Brian embraced the new-fangled digital electronic method of obtaining high resolution images, having acquired a Starlight Express digital camera when they first became available. Brian was interested in all aspects of astronomical observation and it wasn’t long before he obtained a Coronado H-alpha solar telescope to add to his rapidly expanding kit. If it was a sunny Sunday morning, Brian could be found up at the Observatory and he soon became our Solar expert. Disaster struck when his van was broken into and his big telescope and much of the imaging kit was stolen. Fortunately the Coronado was not in the van and the portable mounting was up at the observatory, so Brian was able to continue with his Solar observations. He was also a great help when the Society decided to purchase its own Solar telescope and he put us in touch with the right people to get the best deal.

Simon Lang writes:

Brian was a most energetic and enthusiastic man with a huge repertoire of interests. Martin Williams knew him from 1973 when Brian taught radio skills at the Grafton Radio Society. He was a keen contester trying to seek out other enthusiasts from around the globe.

Brian started out observing all aspects of astronomy, but became increasingly interested in Solar activity and ended up doing the bulk of the Sunday duties, often spending many more hours demonstrating the Sun to our visitors than those required, such was his passion for teaching. He was at the observatory for nearly every special event we held, helping to keep the crowds engaged in his noted jovial way.

Photograph: Brian Bond standing on right with the Coronado showing visitors the Sun in all its glory.

His cheerful passionate presence will be sorely missed by many of us and Sunday mornings will not be the same when we do eventually re-open. I’ll miss his Sunday morning calls, checking up on the weather conditions up here, always a laugh and a real pleasure.

Brian Bond R.I.P. 1944 – 2017

MORE ON ANTI-MATTER

Peter R Wallis

Referring back to my article in the April 2016 newsletter, I remain interested in the hypothesis that there is as much antimatter as matter in the universe. This is far from being the conventional view. Let me look first at the conventional view of what happened in the very early days after the “Big Bang”. This is summarised in a book “A Down-to-Earth Guide to the Cosmos” by Mark Thompson [1]. The initial universe was an extremely hot plasma; gravity was the first force to form, ahead of electromagnetism, the strong and then the weak nuclear forces. There is supposed to be an inflationary period, in which the size of the universe increases enormously, then quarks and electrons form and also antiparticles; he claims that the quarks and antiquarks would eliminate each other, leaving only the matter form. He does not explain why, but I assume it is to ensure that the universe finishes up to be matter only. At a thousandth of a second the strong force would form protons and neutrons, still at a temperature of a million million degrees. At 3 minutes the protons and neutrons would be able to form the nuclei of hydrogen and helium. Then at about 380,000 years the electrons would be able to attach to the nuclei and form atoms of hydrogen and helium. At this time, therefore, the universe would become transparent to light.

It is clear that this picture is essentially a postulation rather than a measurement. In fact the only measureable quantity available is the light from the 380,000 moment. And due to the 14 billion years of expansion, we have only recently recognised it as the microwave background. I suggest that the picture is not an accurate postulation and fails to appreciate that gravity could have led to the separation of quarks and antiquarks instead of the elimination of the latter. So where can we look at today’s universe to settle the question? Firstly, we need to study the microwave background more closely; perhaps we can find some indication there.

My next suggestion is to measure the expansion of the universe more exactly. If there is a preponderance of matter, then the attraction of matter to matter would cause the expansion to slow down. Astrophysicists have invented “dark energy” to explain why it hasn’t, as Dr Phillips said. Indeed, some have suggested that the expansion is increasing. If antimatter and matter are present in equal amounts, the opposing effects could be expected to cancel and leave the expansion to “coast”.

I have recently been reading a book “Gravity’s Engines – the other side of black holes” by Caleb Scharf [2]. His book is about black holes but has interesting descriptions of the large-scale structure of the universe. I quote: “In some places there are thousands of galaxies clustered together within a few tens of millions of light-years: great cathedrals of light, --- leading into these glowing monuments are what appear to be strands and sheets. Then there are huge zones of emptiness, voids like great open soap bubbles which can extend over 100 million light-years with barely a galaxy within.” Is it not possible that this dichotomy of density could have been a consequence of the attraction and repulsion of matter and antimatter? (I shouldn’t talk of gravity’s forces, of course, as it is rather the different effect of matter and antimatter on space-time.) Maybe the structure of the universe will provide us with an answer.

1: Corgi books 2013 , pages 282 to 289. [back]

2: Penguin books 2012, pages 54 and 55. [back]

News from the Observatory.

Some members may not be aware of what is happening at the observatory site, so the following is a short report. Towards the end of the last observing session, during last summer, Thames Water informed us that they were about to carry out extensive works on the reservoir on which the Observatory is situated.

Their intention was to totally remove the covering of grass and turf, cover the whole site with a waterproof membrane, then to replace the turf. It was estimated that the whole job should be completed by January 2017. We were required to remove the met. instruments and disconnect the power cable as the concrete pathway was to be temporarily removed. We breathed a sigh of relief when told that we did not have to remove the observatory this time, something we had to do back in the 1960’s. We were informed that once work was underway we would not be able to access the building until completion.

We had our last meeting at the summer picnic on July 17^th when Doug & Terry Pearce removed the 6-inch Cooke OG for safekeeping. Terry will look after it until it is time to reinstate it, after a good clean. On the following day Simon, and representatives from the Met. Office and the Environment Agency, removed the met. instruments and stored them in the observatory building.

The latest information is that the work will take longer than estimated to complete (predictable), and that we are now looking at a completion date towards the end of March 2017. We will then have to reinstate the power supply and re-fit the met.instruments. At present it looks as though there will be no public open nights during the current session and they will probably not resume until September 2017.

Sad Footnote

During all this upheaval we had tried in vain to contact the Hon. Meteorology Secretary Philip Eden, only to discover that he was in a nursing home suffering with Parkinson’s and Alzheimer’s disease. Simon and Julie Atkinson visited Philip’s brothers and conveyed to them our sadness to learn such unwelcome news and to retrieve some Society reports etc.

Philip served as Meteorology Secretary for 33 years, taking over after the death of Robert Tyssen-Gee in 1983. When he began, readings were taken manually twice daily, but we converted to a fully automated system in 2000. Philip oversaw this transition and obtained grants to offset the expense of the computer controlled equipment. The fully automated system was made operational at a celebration on September 10^th 2000. At our centenary celebrations on April 25^th 2010, Philip received an award from the Met. Office for the Society’s record of 100 years continuous meteorological readings from the same site. Philip also acted as editor of the Society History.

It is indeed very sad to learn of Philip’s current condition and to be totally powerless to do anything about it.

At the AGM the Secretary announced that she had received no new nominations from the membership but Council had made the nominations in the April newletter. The revised constitution requires that one ordinary member of Council should retire each year. David Brandt volunteered to stand down due to other commitments. We thank David for his help and hope that he will return to Council in the future.

Your Council elected at the AGM is as follows:

The first meeting of the new session is on Thursday September 15^th when Professor Heinz Wolff Emeritus Professor at Brunel University and past President of HSS (from 1968-1987), makes another welcome return to the HSS with a talk entitled: A PERSONAL HISTORY OF 62 YEARS OF BIO-ENGINEERING. Heinz pretty well invented the science of bio-engineering. The discipline identifies problems encountered in life, especially those related to age and disability, and seeks solutions by the application of engineering techniques. Heinz has spent a working life in this field so his talk is bound to be of great interest, especially to those of us already facing age related problems. I look forward to seeing you at the meeting.

Proposed visit to the Horniman Museum Forest Hill.

We are proposing to arrange a Society visit to the Horniman Museum in Forest Hill south London on Sunday July 10^th. The Horniman Museum is a very interesting place, typical of the ‘old style’ museums of Victorian times with many varied collections. As car parking is very difficult it is proposed to travel by public transport via tube to Oval station and from there by bus stopping right outside the museum. If you are interested in taking part, please send your contact details to David Markham: markham dot dj at gmail dot com who is coordinating this visit.

News from the Observatory

Those members who frequently visit our website will know that Thames Water which owns the reservoir on which the Observatory is situated, are presently engaged in lengthy building and engineering works at the site. It is their intention to totally remove the grass turf from the entire site and then to fit a waterproof membrane; they will then replace the turf. In order to do this the path and railings from the gate to the observatory door will have to be removed temporarily and also the meteorological instruments and the rain gauges belonging to the Environment Agency. Work began at the end of July and it is expected to be finished by January 2017. But large scale engineering works are renowned for overrunning completion dates and when Thames Water have finished, there will still be work for us to do, restoring the electrical supply for example and reinstating the Met. instruments.

We are grateful to Thames Water for involving us in all the negotiations and being mindful of our charitable status and our position as long term residents. Thank goodness we were not required to remove the observatory building so soon after investing such a large sum on its restoration two years ago.

At present the solar telescope and its mounting have been removed for safe keeping, and we are taking the opportunity to remove and clean the Cooke object glass which is being looked after by Terry Pearce.

Of course, all this disruption means that the Astronomy Section will not be able to open the Observatory to visitors in September as it normally does, in fact the observatory will probably not return to normal operations until March 2017. This will be the longest period of forced closure since the Observatory was founded in 1910, and it has totally spoilt our record for uninterrupted daily meteorological readings from one site.

In the meantime the observatory site remains ‘out of bounds’ to everyone. To keep in touch, visit the website occasionally, as this is where we will publish news of any further developments.

International Space Station

From 26 July to 8 August we had a good series of evening passes of the ISS. Every night was cloudy apart from the 5^th and 6^th of August and in Edgware the ISS almost occulted Vega.

The next evening series starts in October. The high passes are:

October 3,4, 5, 6, 7, 8, 9,10,11,12 and 14^th. December 5th then 7, 8, 9, 10, 11, 12, 13, 14, 15, 17^th.

Timings can be found on the Heavens Above website which also shows the path in the sky. Take the timings with a pinch of salt as I found ISS two minutes late on data downloaded two months before. Forecasts closer to the date should be more accurate.

Jim Brightwell.

The AGM agenda will include reports from officers and section leaders and the election of officers and 5 ordinary members of Council. Council proposes the following:

Council invites further nominations for the above posts. Such nominees should be duly proposed and seconded and should have agreed to serve if elected. Under the revised Constitution, Council will replace one ordinary member, from those who have served longest, each year. At the Council meeting on April 7^th Martin Williams was due to retire but David Brandt expressed the wish to resign instead. We thank David for his support and hope that he will return to Council in the future. This leaves a vacancy for one ordinary member of Council.

Proposed visit to the Horniman Museum Forest Hill.

We are proposing to arrange a Society visit to the Horniman Museum in Forest Hill south London on Sunday July 10^th. The Horniman Museum is a very interesting place, typical of the ‘old style’ museums of Victorian times with many varied collections. As car parking is very difficult it is proposed to travel by public transport via tube to Oval station and from there by bus stopping right outside the museum. If you are interested in taking part, please send your contact details to David Markham: markham dot dj at gmail dot com who is coordinating this visit.

ANTIMATTER

Peter R Wallis

Thomas J Phillips writes in Nature[1] about our lack of understanding of antimatter. It is generally understood that the Big Bang at the beginning of our Universe produced equal quantities of normal matter and antimatter. Also we believe that when the two types of matter come together they annihilate each other; we observe experimentally, for example, that positrons (antimatter electrons) emitted during radioactive decay are annihilated when they collide with ordinary matter. We also observe that when galaxies collide they do not annihilate, but merge, leading to our conclusion that all the galaxies are made of normal matter. So where is the missing antimatter?

Dr Phillips considers that we need to find out a lot more about antimatter, particularly its gravity. When we are dealing with charged antimatter particles such as positrons or antiprotons we can handle them using electric or magnetic fields. But we cannot do this so easily if they have a neutral electrical charge, as we think antihydrogen would have, by analogy with normal hydrogen. Another article in the same issue of Nature[2] reports confirmation that this is so, using the ALPHA apparatus at CERN that traps antihydrogen atoms. They have been able to measure their charge to an accuracy 20 times better than previously reported and find it less than one billionth of the charge on an electron – essentially neutral. This is important as it opens the possibility of measuring the gravity force of antihydrogen; such forces are so very much weaker than electromagnetic forces that we could not measure them if electrical forces were present.

Dr Phillips points out that, in addition to the missing antimatter, there are three other big mysteries in astrophysics: dark energy, dark matter and cosmic inflation. These three have all been invented as ad hoc solutions to cosmological problems that do not fit the predictions of general relativity. Dark energy is needed to explain why the cosmic expansion is not slowing down; dark matter to explain why galaxies are rotating too fast to be bound by the gravity of the visible matter; cosmic inflation is needed to explain how all parts of the universe are at the same temperature when the Big Bang occurred too quickly for such causal connection. He considers that these problems may well be explained by a single change to our theory of gravity that should be tested in antigravity experiments.

He points to the Dirac-Milne cosmological model[3], which is based on the assumption that the Universe has equal amounts of matter and antimatter that repel each other gravitationally, contrary to the predictions of General Relativity[4]. Currently all observed galaxies are thought to be formed of matter because they are seen to collide without annihilation. “But if matter and antimatter repel each other, they would never collide, so the missing antimatter could be hiding in plain sight” (Dr Phillips’ own words).

Furthermore, this model of the Universe would have zero net gravitational charge, so dark energy would not be needed to explain why the expansion is not slowing down. Such a “coasting” universe would not need inflation because its expansion would have been slow enough for the entire universe to have been causally connected. We clearly need a new General Theory – Any offers from Hampstead?

1: Phillips,T.J., ”Antimatter may matter”, Nature,529, 21 Jan 2016, p 294,295.[back]
2: Ahmadi, M.,and 48 others, “An Improved limit on the charge of antihydrogen from stochastic acceleration” Nature,529, 21 Jan 2016, p 373-376.[back]
3: Benoit-Levy, A,and Chardin, G., Astron Astrophysics 537 A 78 (2012).[back]
4: Nieto, M. M. and Goldman, T. Physics Rep 205, p 221-281 (1991).[back]

SOME FURTHER THOUGHTS: Perhaps I can add a personal speculation, I do not think it would be sensible to revert to Newton’s gravitational system since it is unable to provide the detailed explanation in our knowledge provided by Einstein’s General Theory based on the geometry of space-time; and Einstein’s prediction of the generation of gravity waves in 1916 has only now, 50 years later, been confirmed. I think myself that we can manage with a very minor variation of Einstein’s theory. You will remember that his theory was often explained to non-experts by the analogy that space-time was a thin rubber sheet which was depressed by matter such as stars and planets and thereby caused their motions to be changed as if there were a force of gravity. So the variation I propose is that anti-matter would cause an elevation in the rubber sheet analogy instead of a depression. An anti-matter galaxy would behave similarly to a matter galaxy and seem to be identical in our view from a distance. But the difference between depression and elevation would ensure that they would never collide. We need to analyse galactic motions to confirm this and show which is matter and which is antimatter.

P R Wallis

So Mars is NOT dry after all!

Doug Daniels

For years now we have been saying that there is overwhelming evidence that in the past water was abundant and flowed on Mars but although there might be a small residue left frozen in the polar caps and perhaps in the form of permafrost below the surface, it doesn’t flow today – well how wrong were we?

Images taken by Mars Reconnaissance Orbiter, (MRO) many months apart show clearly downward moving streaks called linae, on the walls of the craters Horowitz and Garni. These linae were first spotted 5 years ago but only recently seen for what they are. They are of course not just simple water but highly concentrated brine which reacts with the changing Martian seasons, freezing in the winter months and slowly flowing down hill as temperatures rise.

The MRO’s spectrometer indicates a high concentration of calcium perchlorate which seemingly acts like an anti-freeze allowing the brine solution to flow. Not nice fresh water perhaps, in fact decidedly brackish, but it could still be good enough for some hardy species of extremophiles to exist. Here on Earth, certain strains of bacteria have been found locked up in salt crystals from vast salt lakes awaiting water to release them, and they revive despite having been locked up for over 90,000 years!

There are two new spacecraft missions to Mars which lifted off in March 2016. On the 5^th a joint Russian and European project was successfully launched from Kazakhstan on its way to examine the methane plumes that seem to occur seasonally in some regions. These may indicate a biological origin suggesting the presence of actual living organisms, but they could also originate from geological processes – residual volcanism for example; although the received wisdom is that Mars is no longer ‘geologically’ active. The Trace Gas Orbiter, (TGO) will hopefully identify areas where methane is being generated and these regions will be visited later by the ExoMars rover due to follow in 2018. The TGO mission will also deliver the Schiaparelli lander to its landing site in Meridiani Planum where it will monitor dust levels in the atmosphere, atmospheric temperature and electrification.

With 6 missions currently in progress and others planned for the future, new discoveries are certain. The lure of the Red Planet continues.

Mars is in opposition this year – on May 22^nd. But it is an unfavourable opposition for northern hemisphere observers due to the low declination of the planet and its small size at around 18 arc/secs at best.

First of all an apology: Due to an editorial error, the last Newsletter contained an article that had been published previously, instead of a new one by the same author. I hope I have got it right this time, so here is Peter Wallis’s article ‘More Batteries’

More Batteries

Peter R Wallis

You may be getting bored by my articles on battery development, but a paper on “An ultrafast rechargeable aluminium-ion battery” published in Nature on 16^th April 2015 deserves some attention. It has been written by a group of chemists and chemical engineers based at university departments in Stanford (USA), Changsha (China) and Taipei (Taiwan). The authors [1] point out that aluminium has 3-electron redox properties which lead to high capacity. Research efforts over the last 30 years encountered numerous problems, such as cathode material disintegration, low cell discharge voltage and insufficient cycle life. They now present a new battery using an aluminium metal anode and a three-dimensional graphite cathode. The battery operates by electrochemical deposition and dissolution at the anode, and intercalation/de-intercalation of chloroaluminate anions in the graphite, with a non-flammable ionic liquid electrolyte. The cell exhibits a well-defined discharge plateau close to 2 volts and has a specific capacity of about 70ma h per gram.

They worked at first with a pyrolitic graphite cathode but found that this limited the charging rate. In view of the importance of high-rate and high-power for applications such as grid storage, they moved to a graphite foam cathode. This achieved a remarkably high charge/discharge rate of 5 Amps per gram, some 75 times that achieved with the previous design. This would allow a charging time as low as 1 minute; the cell could also be discharged at such a rate or over an extended period. The battery cell operates at room temperature and is mechanically bendable. They drilled through one in operation and observed no safety hazard, owing to the lack of flammability of the liquid electrolyte in air.

The authors report in summary that their new Al-ion battery has a stable cycling life of up to 7,500 charge/discharge cycles without decay at high current densities. The present design offers an energy density of 40 Wh per kilogram (comparable to lead-acid and with room for improvement) and a power density up to 3kW per kg.

Readers may have seen reports in the newspapers that the Californian firm Tesla will be selling batteries this summer, based on the Lithium-ion technology used in their electric cars, to house owners to increase the efficiency of solar power which is often intermittent and unmatched to power needs. The ”Powerwall” daily cycle battery of 7 kWh capacity is estimated to cost some $3,000. Maybe we shall hear about an Al-ion alternative soon.

Principally Meng-Chang Lin, Ming Gong, Bingan Lu and Yingpeng Wu, supported by several others.

Is this more evidence that the perceived wisdom on 'Global Warming' might not be entirely correct?

Doug Daniels

Whenever the contentious subject of ‘global warming’ is discussed, we are presented with the fact that we can watch this process actually going on by observing the melting of the Antarctic glaciers. We were warned that ultimately the melting would cause a dramatic rise in world-wide sea levels and a study by the UN’s Panel on Climate Change (2013), stated that the melting of the glaciers was causing a rise in sea level of some .27 mm annually. Recent research is casting doubt on this finding.

The Antarctic continent has been under regular surveillance by satellites from NASA and ESA since 1992 and the height of the ice sheet has been monitored by radar and laser sensors. Although it is generally accepted that the Antarctic glaciers in west Antarctica are indeed receding, new studies, reported in the Journal of Glaciology by its author Jay Zwally, indicate that in other areas, the ice sheet is thickening and moreover at a rate that exceeds the loss from the melting glaciers. Hitherto, scientists attributed gains in the Eastern ice sheet to enhanced snow fall, but using data obtained from ice cores from as long ago as 1979, the NASA team proved that the ice sheet in the area was in fact thickening.

Once again, continued research is showing that the causes and effects of enhanced ‘global warming’ may not be so sharply defined as previously thought. But at the same time, you will struggle to find this new data widely reported by the media; the exception being the Daily Telegraph (02/11/15). This is presumably because this evidence is in direct conflict with the generally accepted ‘standard model’ for a man-made enhanced global warming theory. Just last night (09/11/15) on TV news, much was being made of the fact that average global mean temperatures show a rise of 1 degree per century. The Meteorological Section of the HSS pointed this out some years ago. We have records from the same site now spanning 115 years that confirms this average temperature increase. However, we do not, as yet have any proof that this is caused by the industrial activities of mankind or due to naturally cyclic events over which we have no control or, for that matter, a combination of both.

We should also be aware of the fact that during the last half century, London’s size has greatly increased as has its population rising from about seven million in 1910 and now in excess of 8.5 million. These increases together with expanding manufacturing processes naturally produce more heat, leading to the phenomenon known as ‘the heat island effect’. This has to be taken into account when attempting to calculate an accurate mean temperature increase, particularly in the vicinity of large urban concentrations.

Assuming that the recorded rise in mean temperature of 1 degree/century is correct, then what we need to know is if this seemingly small increase is sufficient to cause all the adverse effects of enhanced global warming predicted to pose a threat to our continued existence by the purveyors of windmills. Incidentally, many of the windmills scattered around the country were forced to shut down during the recent strong winds that swept in from Atlantic storms – presumably the wrong sort of wind?

Reminder: The first lecture of the New Year will take place on Thursday January 21^st when Professor Martin Elliot of Great Ormond Street Hospital will deliver his talk entitled: The Artificial Heart: A New Ending? I hope to see you at the meeting.

Enclosed with this Newsletter you will find the Programme Card for the next session. More cards are available at meetings, so do take some if you are able to put them in public places such as libraries, schools etc

At the Council meeting held on April 9^th the Secretary announced that she had received no new nominations from the membership but Council had proposed Alexander Menegas and confirmed the election of David Markham who had been co-opted by Council since the previous AGM. The revised constitution requires that one ordinary member of Council should retire each year. Roger O’Brien volunteered to stand down due to other commitments. We thank Roger for his help and hope that he will return to Council in the future.

Your Council elected at the AGM is as follows:

The first meeting of the new session is on Thursday September 17^th when Professor Heinz Wolff from Brunel University and past President of HSS (from 1968-1987) makes a welcome return to the HSS with a talk entitled: YOUR HAND IS A MIRACLE. Concern about the loss of dexterity in a digital world and the need for many more hands for care of the elderly. I look forward to seeing you at the meeting.

Footnote to “Whither Batteries?”

This article by Peter R Wallis was repeated from the December 2014 Newsletter in error. The new article will be published in the December 2015 newsletter.

AN INVITATION to join a GUIDED WALK IN HAMPSTEAD. SUNDAY 20^TH SEPTEMBER

Members are invited to join a guided walk on Hampstead Heath led by Diana Clements. This is a three mile walk looking at the geology of the heath and how it effects the landscape and what grows (and doesn’t grow) there. We will also be looking at geology-related topics such as springs and water supply and industrial archaeology, and we will be using the vantage point afforded by the Heath’s elevated situation to look at the structure of the Thames Valley and how that has influenced the siting of London.

NO NEED TO BOOK – JUST TURN UP AT THE FLAGSTAFF, WHITESTONE POND BY 10:30 AM.

The current session will end with the ANNUAL GENERAL MEETING on Thursday June 25^th. As usual it will be preceded by wine & cheese for which there is a small charge of £3.00. Any contributions to the refreshments are always welcome.

This year, we are hoping that the scientific entertainment will consist of demonstrations of 3D printing.

The AGM agenda will include reports from officers and section leaders and the election of officers and 5 ordinary members of Council. Council proposes the following:

At the Council meeting on April 9^th, Roger O’Brien asked to stand down due to other commitments. We thank Roger for all his help in the past and hope that he may return to Council in the future.

Council invites further nominations for the above posts. Such nominees should be duly proposed and seconded and should have agreed to serve if elected.

Sad News: We have recently received the sad news that Dr. Jamie Nelson has passed away at the great age of 101. An obituary will appear on our web-site in due course. In the meantime we send our condolences to his family and many friends.

ASTEROIDS, WATER and the search for extra-terrestrial life.

Doug Daniels

Between the orbits of Mars and Jupiter, there is a wide region of space occupied by numerous Minor Planets or Asteroids. These bodies might be the result of a planetary collision way back during the early formative period of the Solar System, or they might be left over material which for some reason did not accrete to form a planet. They are mostly quite small bodies which are invisible to the naked eye so it is not surprising that they were not discovered until 1801. The way in which they were discovered is fascinating.

In 1766, a mathematician named Titius of Wittenburg found an interesting relationship between the distances of the planets and a series of numbers. However, he failed to publish his work. In 1772 Johann Bode did publish it and he took the credit for it as well, so it is now known as “Bode’s Law”.

If we take the numbers: 0, 3, 6, 12, 24, 48, 96, 192, 348, each of which, apart from 3, is double its predecessor, and then we add 4 to each number we get : 4, 7, 10, 16, 28, 52, 100, 196, 388. If we now divide by ten, we get 0.4, 0.7, 1.0, 1.6, 2.8, 5.2 etc. corresponding quite well to the distances of the planets from the Sun in Astronomical Units. (Earth = 1 AU). The planets Uranus, Neptune and Pluto were undiscovered at the time of Bode and Titius but when Uranus was discovered by Herschel in 1781, it fitted in nicely! There was, however, no planet corresponding to 2.8, which should lie between the orbits of Mars and Jupiter.

In 1800 a group of German astronomers decided to search for this ‘missing’ planet. The group was headed by Johann Schroter and they were nicknamed the ‘Celestial Police’. Success was soon to come and on new year’s day 1801, one of their number Guiseppi Piazzi, found an 8th magnitude object in Taurus which he did not recognise. This object showed movement when he observed it 24 hours later. The ‘new planet’ was named Ceres. However, Ceres turned out to be disappointingly small at just about 1000 km. in diameter, so the search continued. Then, in 1802 Heinrich Olbers found Pallas, but again it proved to be a small body. Discoveries continued with Juno in 1804 and Vesta in 1807, and discoveries continue to this day!

It has been estimated that the Asteroid belt could contain more than a billion small Planetisimals and we already know the orbits of over 25,000 of them! Most of the Asteroids are small irregular shaped chunks of rock most of which are less than 1 km across and the majority are far smaller than this. Ceres at just 1000 km. in diameter is by far the largest.

It was once thought that the Asteroids were the remains of a large planet which had been broken up in a cosmic collision with some unknown body such as a passing comet. Today the consensus of opinion is that the asteroids were actually material that was prevented from joining together to form a planet when the Solar System was being formed, the asteroids began to crash into one another at huge velocities, causing even greater fragmentation. The process continues to this day but at a much reduced rate. Collisions within the asteroid belt are responsible for producing many meteorites and the vast quantities of Cosmic Dust, which fall to Earth each year. Jupiter may have been responsible for disrupting the asteroid belt during its early development with tidal forces preventing the material from compacting, but the true origins of the asteroid belt remains uncertain.

Many of the asteroids have very eccentric orbits. Some have orbits outside the main belt and are associated with planets. The Trojan group for example, orbit the Sun every 12 years with Jupiter. There are over a thousand Trojans in two groups. One group is ahead of the planet and the other follows it. They lie in regions known as the Lagrangian points. Lagrangian points are areas in which small bodies can maintain a stable orbit even though they are under the influence of the gravitational field of both Jupiter and the Sun. In the case of the Trojans, these points are located 60 degrees ahead and 60 degrees following Jupiter.

Other groups such as the Amors, have orbits which cross that of Mars, while the Apollo group, which numbers in excess of 2000 objects, crosses the orbit of the Earth. These could represent great danger. It has been suggested that the various species extinctions on Earth, which occurred in geological times, including the extinction of the Dinosaurs, might have been the result of a sizeable asteroid collision with the Earth. This threat is being taken more seriously today and there are certain projects such as the LINEAR – Lincoln Near Earth Asteroid Research, project, which constantly monitors the sky, looking for objects which might pose a threat to our planet.

There have been a number of space missions into the asteroid belt. The Galileo probe passed close to Gaspra on its way out to Jupiter in 1991. It sent back close up pictures of an irregular shaped rock peppered with impact craters. Two years later, Galileo passed Ida. Then in 1997, the NEAR space probe was dispatched to actually land on the minor planet Eros, a mission which it successfully accomplished in 2001. On the way it passed and imaged Mathilde. Currently, NASA’s ‘Dawn’ mission is busy taking a close look at Ceres, having already passed and investigated Vesta in 2012.

Until quite recently the asteroids were regarded as fragments of planetary type material left over from the building of the Solar System. They vary in size from a few centimetres to nearly 1000 kilometres across. Most are irregular shaped rocks that have remained unchanged since the formation of the Solar System nearly five billion years ago and as such, represent primordial material. Examination of their spectra shows that some are similar in composition to the carbonaceous chondrites we see as meteorites. They contain certain amino acids and other organic compounds that form some of the building blocks essential for life. But until recently there was no evidence in the asteroid belt for the one essential compound necessary for life – Water but this was about to change.

Astronomers working at Mauna Kea in Hawaii began to study the spectra of certain asteroids as did the Spitzer Space Telescope. Initially two asteroids 24 Themis and 65 Cybele (dia. 290 Km) showed the presence of water and organics. In September 2007, NASA launched its ‘Dawn’ mission to the asteroid belt to examine Vesta in 2012 and then on to Ceres in March 2015. Vesta seems to be composed of basaltic minerals and is dry. This was expected as we have specimens of meteorites, the HED – Howardite, Eucrite, Diogenite meteorites known to have originated on Vesta. Ceres however, is a different ‘kettle of fish’. Ceres is just under 1000 km. in diameter and is the largest member of the asteroid belt and was the first asteroid discovered by Piazzi in 1801. It is composed of rock and ice and its composition resembles carbonaceous chondrite meteorites. But the main difference is that whereas Vesta is dry, Ceres is decidedly wet and is spraying water into space by a process of ’Cryo-Vulcanism’; it has been estimated that Ceres may actually contain more water than is in all the Earth’s oceans! These discoveries are causing Astronomers to revise their theories on conditions in the early Solar System – the asteroid belt is certainly not the desert we once thought it to be and asteroids themselves are proving to be very interesting bodies indeed. They seem to fall into two distinct types, those composed of dry basaltic minerals like Vesta and those that are a mixture of rock and ice. We did not expect to encounter ice so close to the Sun. But water, in the form of ice has also been discovered in deep permanently shadowed craters at the south pole of our own moon; few of us expected that. It was presumably deposited by huge icy bodies colliding with the moon shortly after it began to cool and develop a crust. Between 4100-2500 MYA the inner Solar System was suffering from the ‘late heavy bombardment’ and both Earth and Moon were liberally peppered with impacts. Was it at this time that Earth acquired some or all of its water?

One of the biggest surprises was delivered by the Cassini/Huygens mission to Saturn, when it was discovered that Saturn’s moon Enceladus has features that can only be described as geysers in its polar region that are spraying water into space and forming another ring of ice surrounding Saturn. Bearing in mind that the ambient temperature in the region is only a few degrees above absolute zero, it would seem that Enceladus is another moon that is being warmed by tidal forces with an icy crust overlaying a vast ocean of water.

Cassini/Huygens also gave us a brief glimpse of the surface of Titan, for ever shrouded in dense cloud. The Huygens probe was dropped through Titan’s dense atmosphere and during its brief descent it recorded a landscape of mountains, cliffs, rivers and lakes but not of water. Titan’s landscape has its water features replaced by liquid and solid methane and other hydrocarbons

So where did all the water on Earth come from? Until very recently we thought that it possibly came from comets which impacted with the newly formed planets very early in the history of the Solar System. The comets originated far out in the Kuiper-Edgeworth belt and the Oort Cloud, far across the protoplanetary disk where temperatures were lower allowing ices and more volatile compounds to form. The comets acted as a kind of delivery service, transporting water in the form of ice to the inner reaches of the Solar System. However, this theory may no longer be sound thanks to the recent observations, some of which were made by the Rosetta/Philae space probe which successfully placed a ‘lander’ on the nucleus of comet Churyumov-Gerasimenko in August 2014.

The observation concerns the proportion of deuterium in the comet’s water vapour. Deuterium is hydrogen plus an additional neutron, sometimes called ‘heavy hydrogen’ and the D/H ratio acts like a fingerprint for water. So far, eleven comets have been tested for D/H ratio and only one – 103P(Hartley2) has the same D/H ratio as Earth’s water. However, samples from asteroids do appear to have the required D/H ratio. So it may be that asteroids and not comets colliding with the Earth were responsible for our abundant water supply.

Moreover, as certain asteroids seem to contain a whole raft of organic compounds and amino acids as well as water, is it possible that they could have seeded the Earth with life? There is a certain irony in this as over geological time there have been several massive species extinctions on Earth due to the impact of asteroids and there are certain to be more in the future. It could well be the case that asteroids were responsible for life beginning on Earth and that one day they will also be responsible for its ending .

Stromatolites in Shark Bay Australia.
These specimens are over 1000 years old but
their ancestors may have been amongst the earliest life forms on Earth.

In the meantime, our search for planetary systems surrounding other stars continues and each year the count goes up and now stands at over 1000. It has recently been suggested that in fact all stars probably have planetary systems as they are a natural consequence of star formation. This means that in our galaxy alone there could be as many as 500 billion planetary systems.

Looking further afield, water and a whole range of organic compounds have been detected in the Orion Nebula, that gigantic molecular cloud 1600 light years distant. Here new stars are forming surrounded by dusty disks; these are embryonic planetary systems and they too will have water and perhaps will also have the right conditions for life to develop as well!

In the observable Universe there must be literally trillions of planets, many of which could support life. Surely we can not be so arrogant to believe that our tiny planet is the only abode of life in such a vast Universe. Although as yet we have no proof, I believe that life, like gravity is a property of the Universe and that given the right conditions and time scale it will take hold and evolve.

If we wish to discover signs of extraterrestrial life, perhaps we should concentrate on regions where we can detect the presence of water. The expression “The Water of Life” might prove to be an absolute truth.

DRAWING THE MOON

Doug Daniels

Until the application of photography to astronomy, in the early 19th century, astronomers were required to make drawing of their observations. Even today, when we have advanced photography and CCD imaging at our disposal, many of us still like to draw what we observe. Why? Few astronomers are trained artists and attempting to draw accurate representations of the sometimes complex and delicate images encountered in astronomy can be a daunting task. I believe that it is the very nature of the challenge that attracts many of us.

We could ask the question “Why bother to draw lunar formations at all?” since the entire surface of the Moon has now been photographed and mapped to a resolution of about a metre. “Why should we spend long hours in the dark squinting through a telescope often in the cold, at an image bubbling with atmospheric turbulence and all the while attempting to draw features which have already been well documented?” I believe that there are a number of reasons why we do this. To begin with, there is a far greater sense of achievement to make a drawing, combining the skills of both eye and hand. It is this sense of involvement with the subject that makes us look through telescopes in the first place. We could just look at pictures in books, many of these will show far more that most of us can see through our small instruments – but where is the fun in that!

For my own part it is a way of becoming really intimate with the lunar surface. If I take a photograph or a CCD image of a region of the Moon, I will study it for a while and then file it, but no matter how much I examine the image I will not really get to grips with nature of the surface until I draw it. When you draw, you have to look closely at each little feature - how it relates to its neighbour, how the shape of its shadow gives a clue to its real shape. It is only when you do this that you become really familiar with the lunar surface.

A small telescope, even binoculars will reveal an enormous amount of detail on the Moon, enough to challenge any artist, but when you use a large instrument the task can be monumental! So much detail is revealed that it is impossible to record it with any degree of accuracy before the Sun rising above the lunar surface alters its appearance, you have to constantly modify the drawing. For this reason it is best not to try to draw a large area, better to concentrate on one formation.

The drawings might take several hours to complete and because I am concentrating on small areas at a time I am in fact studying the image in great detail much more so than if I were merely looking at a photograph. It is this focussing of attention that ultimately leads one to a greater understanding of the lunar surface and the interaction of light and shadow. This is why, despite having the equipment to take photographs and CCD images, I still continue to draw the moon.

I can't believe that yet another year has passed! It seems no time at all since I was scratching my head trying to remember what happened during the previous year. Well, I think that the main event that stands out above all others is the rendezvous between ESA's Rosetta space probe and the comet Churyumov-Gerasimenko, and the crowning achievement of the mission, depositing the lander Philae on the comet's nucleus.

O.K – the lander could have landed in a better position to receive sunlight to charge its batteries, but it still managed to send back masses of data from the various exploration experiments on board. And consider for a moment what an achievement this has been.

The project began with the launching 10 years ago! The probe then spent a decade passing through the main asteroid belt, making fly-by's of two asteroids and then in 2007 a fly-by of Mars, and this was followed by two more asteroid fly-by's in 2008 & 2010. To conserve energy it was then put into hibernation from which it was successfully awakened on January 20^th 2014. When the rendezvous with the comet took place in August, the probe was 673 million kilometers from the Sun. The next triumph was putting Rosetta into an orbit around the comet, not at all easy because of the comet's odd double lobed shape and tumbling motion.

Then in November, right on schedule the lander Philae was dispatched but the 'harpoons' designed to anchor the lander, failed to deploy. This caused Philae to 'bounce' away from its intended landing site. When it fell back, the comet had rotated and Philae came down close to a cliff that shaded it from the sunlight preventing it from re-charging its batteries. Nevertheless, it managed to send back masses of useful data before the batteries finally died.

The comet's next perihelion passage will take place in August 2015 when it will be 186 million kilometers from the Sun. During this time, Rosetta might still be in orbit around the comet and as it has a planned lifetime of about 12 years, barring accidents, the amount of data it will provide will be truly incredible. Yes, I think we can say that the Rosetta Mission has been an unqualified success, a mission of which the 2000 people in total who contributed to it over a decade can be justly proud. But, please someone give Matt Taylor some advice about choosing a suitable celebration shirt and tell Monica Grady to "calm down a bit" – there's a lot more exciting stuff still to come.

Next meeting The next lecture meeting will be on January 15^th 2015 when Prof. Peter Simpson of Imperial College will talk on Fracking. This promises to be an interesting topic for discussion. I look forward to seeing you at the meeting.

Footnote to "Whither Batteries?"

Peter R Wallis

In the last paragraph of my article on batteries in the April 2014 newsletter, I referred to an important future requirement: batteries to store power for the nation's electric power grid. Many new sources of power are intermittent in nature, wind turbines and solar arrays; we need to store energy when they are working and release it to the grid when they are not. Mass and size will not matter as much as materials cost, low maintenance cost and long life. A recent article by a large team at the US laboratory MIT presents the results of their work on a lithium-antimony-lead liquid battery which potentially meets the performance specifications for such stationary energy storage [1].

They chose a Li/Sb based cell as it had already been shown to give a relatively high voltage of about 0.9 volts (compared with only 0.2v for Mg/Sb ) and both lithium and antimony are cheap and readily available. They chose to use liquid rather than solid electrodes as the latter can be limited in life due to corrosion and film problems. The liquid lithium is the negative electrode, the electrolyte is of molten lithium salts and liquid antimony is the positive electrode; these three liquids self-segregate by density into three distinct layers; no membranes or separators are necessary – they can limit the system life. Now lithium melts at 180°C, but pure antimony melts at 631°C; this would require an operating temperature of some 700°C, dangerously high. However, they were able to reduce the melting temperature of the positive electrode by alloying it with lead; Sb/Pb proportions of 18:82 mol% brought it down to 253°C and the cell operated well at some 450°C. They were able to show that the introduction of lead did not reduce the cell voltage significantly.

To demonstrate the scalability of the system, they made cells with a 62 Ah capacity which operated with a similar performance to those of 1.9 Ah. To optimise system costs they used a 40:60 positive electrode composition with a LiF-LiCl-LiBr eutectic electrolyte, operating at 500°C. They used these test results to demonstrate over 20 cycles and estimate the electrode costs to be 65 US dollars per kWh.

Editor's comment

It has always struck me that the way we generate and distribute electricity is somewhat 'eccentric'. Because we have no facility to store electricity, we have to generate it on demand. This requires a lot of power plants and machinery to sit there on standby waiting for a peak in demand. With existing generators we can switch them on when demand is high but you certainly can't do this with windmills or tidal generators. They will generate when the wind blows and the tide is high and that will not often coincide with a time of peak demand. The problem is to make reliable cost effective 'batteries' that can handle the high voltages required by the grid. This is now beginning to look quite feasible. In addition, low consumption appliances and domestic lighting for example, could work using LED's fed from a 24 volt supply via batteries. The batteries would be on constant charge using power generated at off peak times. They could also receive current from solar panels which only produce power during daylight. So we could have batteries for grid-level energy located in power stations coupled with low voltage systems installed in our houses.

Sad farewell

Older members will be saddened to hear that Joan Wolff, wife of past President Prof. Heinz Wolff (1968 - 1987) has recently passed away after a long illness. We send our condolences to Heinz and his family at this sad time.

At the Council meeting held on April 10^th the Secretary announced that she had received no new nominations to Council. Applying the new rule 'that one Ordinary member should retire each year, either voluntarily or having served the longest time, or where more than one qualifies, the one selected by a ballot of Council Members', and as no voluntary resignations were received, a ballot of Council members was taken and Peter Stern was selected as the retiree. We thank Peter for all his help and hope that he will return to Council in the future. Accordingly as no other proposals were received from the membership, your Council elected at the AGM is as follows:

In December, we received the sad news that our past President Professor Robert Weale had passed away, and in February we also lost Gordon Harding FRAS who served as an Observatory Assistant for many years. We extend our deepest sympathies to their families and friends. Obituaries were published on our web-site.

At the beginning of the year we received the welcome news that the Society was to be a major beneficiary in the will of the late John Hayden. This bequest, together with the anonymous donation last year to the Observatory fund, puts our Society on a sound financial footing for the first time in its history, and despite recent rises in insurance premiums, venue hire, postage and printing costs, enables us to keep our subscription rate at its present level.

Membership numbers remain fairly constant at around the 100 mark, and we are pleased to see some younger members and visitors attending lecture meetings. Let us hope that this trend continues as it is vital for the future of our Society.

The President then reported that the Hon. Meteorological Secretary was unable to attend and that the Met. Section report would be published on the web-site in due course.

Then assuming the 'hat' of Joint Astronomical Secretary, Doug reported that the open nights at the Observatory had proved as popular as ever and that despite poor weather conditions, over 1500 visitors had attended the public open nights during the session. He also reported that the section had acquired a Coronado hydrogen alpha telescope and that it was adding a new dimension to our solar observing sessions on Sunday mornings.

Enclosed with this newsletter, you will find the programme card for the next session of lectures.
The first meeting of the new session will be on Thursday September 18th. The subject will be:
THE SCIENCE OF COLOUR and will be given by Andrew Hanson CPhys from the National Physical Laboratory. I look forward to seeing you at the meeting.

RENDEZVOUS WITH A COMET

Doug Daniels

AUGUST 2014 – At last, after a ten year journey through the Solar System the European Space Agency (ESA) space probe ROSETTA* has finally arrived at its target – the comet 67/P Churyumov-Gerasimenko, and if all goes well, in November it will actually deposit a lander – PHILAE** on the comet's surface.

This is, of course, not the first time that a probe has been sent to rendezvous with a comet. In 1986 the probe GIOTTO was dispatched to have a close encounter with comet Halley. Giotto managed to fly past Halley and sample material from the comet's tail and it sent back images of Halley's dark nucleus. But despite Giotto's undoubted success, that mission still left many questions unanswered. Why do comets experience sudden outbursts, what is the nucleus made of, are comets just dusty snowballs, as frequently described, or are they much more substantial bodies? In fact, are comets really icy bodies? A previous NASA mission to comet Wild 2 returned samples of dust from the comet's tail that indicated that the dust formed in a high temperature environment, so what about the theory that most of the Earth's water was delivered by comet impacts, and could they conceivably support bacteria? Perhaps there are different species of comets, their composition depending on where and when they formed in the protoplanetary disk or in the Solar Nebula. Comets could throw new light on conditions in the early history of the Solar System as they contain primordial material which formed 4.5 billion years ago – as old as the Solar System itself.

To attempt to answer some of these questions, both NASA and ESA planned a number of joint missions to comets and asteroids, but drastic cuts to funding ruled most of these missions out. The original idea was to fly to comet 46/P Wirtanen, but in 2002 the rocket vehicle Ariane 5 blew up and future missions were cancelled until the problem was sorted out. This delay meant that the proposed trip to Wirtanen lost its launch window and the mission was cancelled. Eventually comet Churyumov-Gerasimenko was chosen as the target instead ( a pity, as Wirtanen is a lot easier to pronounce!).

In 2004 the Ariane rocket carrying Rosetta launched successfully from French Guiana and so began its 10 year journey using the gravitational fields of the Earth, Mars and two asteroids to slingshot it towards its target. To conserve energy when far from the Sun, Rosetta was put into hibernation for 3 years, and great sighs of relief must have been heard from mission control when it was successfully woken up on January 20 2014, especially from Gerhard Schwehm the outgoing mission leader, and Matt Taylor who now acts as Rosetta's mission scientist.

Over the last 7 months, Rosetta's speed has been gradually reduced to about 1 metre/second to keep pace with the comet now just 100 km away from the spacecraft. From now on it will slowly approach the comet until close enough to release the lander Philae in November. Rosetta will then go into orbit around the comet at a distance of just 30 km. This will be a tricky manoeuvre as jets of gas and dust emitted by the comet could push the probe out of position. Images of the comet taken in May indicated that it had already witnessed an outburst and as the comet nears the Sun more outbursts are to be expected. The next few months will be critical for the mission but if all goes well perhaps some of our questions regarding the nature and composition of comets may at last be answered.

ROSETTA* – named after the Rosetta Stone an ancient artefact discovered in the Egyptian desert in 1799 by a French soldier Pierre Francois Bouchard during a Napoleonic expedition. The Rosetta Stone was inscribed with text in Ancient Greek, Demotic Script and Ancient Egyptian hieroglyphics and proved to be the key to translating the hieroglyphics found in Egyptian tombs.
PHILAE** – An island in Lake Nasser, a sacred location in ancient Egypt as a possible burying place of Osiris. The Philae obelisk was taken to England in the 19th century by William John Bankes to compare the hieroglyphs with those on the Rosetta Stone. This proved helpful in understanding and translating ancient Egyptian hieroglyphs.

PLANETARY SYSTEMS

Peter R Wallis

As you all know, our sun is orbited by several planets. The four innermost (Mercury, Venus, Earth and Mars) are rather similar in size and have been categorised as "rocky planets". Those further out (Jupiter, Saturn, Uranus and Neptune) are much more massive and are called "gas giants". Astronomers have proposed how they came to be formed – the "core-accretion theory". This postulates that they formed from residual material and gas left behind in a thin circum-stellar disc as the sun's thermonuclear fusion ignited. Close to the sun it would have been too hot for water to be solid and the inner planets would have been formed from high-melting-point solids such as rocks and heavy elements such as iron. Further out beyond Mars there would be ice from which the giant planets would originate: their masses would continue to grow from the copious quantities of gas to form their present composition.

Then, in the mid-1990s, we started finding exo-planets. There are two ways of detecting them: one is by the regular shift in the frequency lines of a star's spectrum as it moves to counteract the gravity of a planet in orbit. This is easier to see if the planet is heavy and has a short-period orbital time. Such planets were indeed found; they were called "hot Jupiters". But they didn't fit well into the above theory as they were too close to the star. Perhaps they had migrated inwards due to friction with gases in the disc; if so, why didn't our own Jupiter?

The other method of finding exo-planets is by observing a short diminution in the brightness of a star as the planet transits the disc. For this NASA launched the Kepler satellite in 2009. This "transit" technique is able to find a wider range of planets, small as well as large. Kepler has been searching a single small patch of the sky containing over 100,000 sun-like stars for 4 years and has so far detected 974 exo-planets, with many more awaiting confirmation by ground-based telescopes. This has put the cat among the pigeons because the planets seem to be wildly different from our own and do not correspond to our theory.

A recent survey article by Ann Finkbeiner [1] says that the biggest surprise comes from the statistical findings. So far there appear to be three categories of exo-planets:

• a). Hot Jupiters--- less than 1%.
• b). Giant planets with idiosyncratic orbits--- maybe 10%.
• c). Super-Earths---about 40%.

The hot Jupiters could be the result of inward migrations, as mentioned before. The planets in eccentric orbits could have arisen from gravitational interaction between planets during such migration. The super-Earths present the biggest problem. There is no clear definition yet of these, many are bigger than Earth but they are not giants. They orbit their stars between 0.006 and 1 AU with periods from over 100 days to a few hours. They seem to come in compact systems of 2 to 4. There is none in our own system and it is difficult to explain them by our theory as it has too little material to make them so close to a star.

Speaking personally (PRW), it seems to me that the problem may arise from the limitations and selectivity of the transit detection process. Obviously it is unable to detect planets when the planetary disk is at right angles to our line of sight. But even when it isn't, planets in larger orbits will be less likely to transit their star. So the transit detection system will be biased in favour of seeing planets in smaller orbits. We clearly need more information. Kepler itself, though seriously affected by its loss of gyro control, has been approved to keep taking data. Ground-based programmes are starting with improved instruments. From 2017 NASA's TESS satellite will be able to see planetary transits across all the bright stars in the sky. So we may get to see planetary systems like our own.

BALLOONS AT THE AGM

Those who attended the AGM will recall that Jim Brightwell brought along a canister of helium and a supply of balloons. The balloons had a tag asking the finder to report where the balloon came to earth. A total of 40 balloons were released at the AGM and the remaining helium was used to fill a further 16 which were released at the Observatory picnic.

The 'finds' were as follows:

• Burnt Oak HA8 OJB sent by John Tennant at AGM
• Kingsbury NW9 7NX sent by Rob Grant at AGM
• Shetland ZE2 9RZ sent off at Observatory picnic.

The first two only travelled a short distance as it began to rain just after release. Shetland can be taken with a 'pinch of salt.' The wind on the day was about 10 MPH and going due east. As the balloon only stays up for about 5 hours, how did it get there? Maybe it was someone's idea of a joke!

On my own project, I have now sent up about 500 balloons which resulted in 22 finds. One landed very close to a friend in Portsmouth and the furthest so far was Folkestone.

I first did this project in the 1960's using coal gas. One got as far as Stuttgart in Germany! I repeated the project again in 1985/86 with 2,500 balloons which resulted in 150 returns. I had 123 from the UK, 4 Dutch letters, 5 Belgian letters, 7 German letters and 11 letters from France.

I would like to continue the project but the cost of helium is a problem. Hydrogen would be a lot cheaper and is safe with due care. Unfortunately, the Hindenburg disaster was a very bad PR exercise for hydrogen!

Jim Brightwell

As Rosetta makes its final approach to comet 67/P Churyumov Gerasimenko in August, let us remind ourselves of our first close encounter with a comet. That was in 1986, when the space probe GIOTTO flew past Halley and obtained this stunning image of the comet's dark nucleus and bright jets of ejected material.

Imaging techniques have vastly improved since 1986, so we are looking forward to even more exciting images from Rosetta and from the lander Philae when it (hopefully) touches down on the surface of the nucleus in November. Few images have so far been released but this one shows the rather odd shape of the nucleus and a lot of complex detail on the surface. But is the surface merely a thin crust of ice? And will the lander sink into it? We will have to wait until November to find out. Let us hope that all continues to go well with this exciting mission.

And finally …

Werner Heisenberg was out driving in his car when he was pulled over by the police. "Do you know how fast you were going sir?" asked the policeman. Heisenberg replied: "No, but I think I know where I am".

Last year the Society had unprecedented good fortune with an anonymous donation of £15,000 to the Observatory maintenance fund. Then shortly afterwards we were fortunate to receive a bequest from the late John Hayden's estate amounting to almost £12,000. These sums put the Society in a sound financial position, a condition never before achieved in its long history. This means that we can continue to keep our subscription at a low rate and we have already obtained a 'state of the art' Hydrogen Alpha Solar telescope and a robotic mounting to add to the equipment at the Observatory.

We have just two more lecture meetings in the current session. The next lecture of the session takes place on Thursday April 17^th at which Dr. Akram Alomainy from Queen Mary, University of London, asks the question CAN YOU MAKE YOURSELF INVISIBLE? – I just hope we can find him in good time. The final lecture of the session is on May 15^th when Prof. Steve Swithenby . Open University, talks on: THE WORKING BRAIN.

The final meeting of the session is the ANNUAL GENERAL MEETING which will take place on Thursday June 26^th with the usual wine & cheese and a scientific entertainment, for which there is a small charge of £3.

The agenda will include reports from officers and section leaders and the election of officers and 5 ordinary members of Council. Council proposes the following:

At present three ordinary members have served for four years. Under the revised Constitution (revised last year), Council will replace one ordinary member, from those who have served longest, each year. At the Council meeting on April 10^th by secret ballot, it was decided that Peter Stern should stand down on this occasion. We thank Peter for his support during the last four years and hope that he will return to Council in the future. This leaves a vacancy for one ordinary member of Council. Council invites further nominations for the above posts. Such nominees should be duly proposed and seconded and should have agreed to serve if elected.

Observing the Sun in a 'New Light'

Doug Daniels

Most of the objects that we direct our telescopes towards are comparatively faint, but the one exception is the Sun. The Sun is such a powerful emitter of light and heat, that observing it telescopically is fraught with danger. On a nice sunny day, a simple hand lens, focusing the Sun's rays on a piece of paper will soon have it smouldering and catching fire. Needless to say: Pointing any optical device at the Sun, such as a telescope or binoculars will magnify the light and heat to very dangerous levels indeed and if you are daft enough to put an eye to it, permanent damage to eyesight will be your reward. It is not even a good idea to look directly at the Sun with the naked eye. This intensity of solar radiation makes observing the Sun a difficult and dangerous business requiring special equipment.

Many years ago at the Observatory, we had a special diagonal eyepiece called a Herschel wedge. This consisted of a shallow angle unsilvered prism which reflected 10% of the light from the prism surface and allowed the remaining 90% to pass 'safely' out of the back. I remember one visitor using this device totally unaware that while he was enjoying a good view of a large sunspot group, the 90% excess light and heat was busily burning a hole in his tie! We no longer use Herschel wedges and today, ties are no longer de rigueur for solar observers.

The safest way to observe the Sun is by projection. Because the Sun is so bright, we can focus a projected image of it on to a white screen behind the telescope eyepiece. This will show the coarser features such as sunspots and faculae and it has the advantage that the view is available to several observers at the same time. We could also use multi-layered coated filters mounted in front of the objective lens. These filters can reduce the brightness of the Sun down to brightness of the full Moon. Such filters will allow us to see much finer detail such as the granular appearance of the Sun's photosphere. But the Sun has much more subtle detail to reveal such as the solar prominences – the flame-like features writhing up around the limb, the dark filaments, sunspots, flares, and the bright swirling 'plages'. These features are normally masked by the Sun's full spectrum white light radiation and to see them we need some very special equipment.

Hitherto, the only opportunity to view prominences was during a total solar eclipse or with a coronagraph located on a mountain top or with a specially designed spectroscope to view the image in the wavelength of hydrogen. Many years ago we actually had such a spectroscope, built by F.J Sellers, the renowned solar observer, but there were few observers with the patience to use it. One had to align the Sun's limb exactly on the Hydrogen alpha line in the spectrum, if you could find it, then slowly open the slit. If there was a prominence in that location you could just about see it before the inaccuracies in the telescope drive moved the slit off the H alpha line and the prominence promptly disappeared. Despite the difficulties using this instrument, the late Henry Wildey used it to great effect and made numerous observations and drawings of solar prominences in the 1950's. Sadly, the Sellers spectroscope was stolen from the Observatory over two decades ago and since then we have had to content ourselves with observing the Sun by projection.

But luckily for us, technology has moved on and we are now able to observe in complete safety, all those subtle aspects of the Sun formerly hidden from us with our recently acquired Coronado Solar Max telescope. This remarkable instrument employs narrow pass-band filters – etalons that allow us to view the full disk of the Sun in the H alpha wavelength. The prominences can be viewed all around the Sun's limb, slowly changing shape over time. We can observe the bright swirling plages, the fine detail around the sunspots, the full granular appearance of the photosphere and the dark filaments and flares which are all easily seen. This adds a new dimension to our solar observations and shows the Sun in a totally different light. If you haven't already done so, come and see what our closest star really looks like when viewed in the wavelength of its main constituent – Hydrogen. The Observatory is open for solar observation from 11.00 am-01.00 pm on clear Sunday mornings until May 18^th. Well worth a visit.

Whither Batteries?

Peter R Wallis

The enormous development of mobile miniaturised electronic devices over the last three decades has depended upon the parallel development of small rechargeable batteries. The winner today is the lithium-ion battery. They now offer an energy density of 250 Watt hours per kilogram (Wh/kg), five times the performance of lead acid and the nickel-cadmium of old AA batteries and twice that of the newer nickel-metal hydride in new AA batteries. The Li-ion battery has two electrodes, one of layered graphite, the other a layered metal oxide, separated by a liquid electrolyte through which the lithium ions flow. It is generally thought that they are near their limit, with only a 30% extra performance to be gained. So much thought is being aimed at where to go next. Li-ion is pretty fine for your mobile, camera and laptop, but as a power source for a motor car it will only achieve half the range of an IC engine and fuel tank, is more expensive and takes longer to recharge.

One chemical engineer Elton Cairns at Lawrence Berkeley National Laboratory is working on a lithium sulphur system which he says can save weight and might achieve 500 Wh/kg. Oxis Energy of Abingdon have run large cells of Li-S for 900 cycles and hope, with Lotus Engineering to reach 400 Wh/kg by 2016 for an electric vehicle.

Lithium is the lightest metal but its ion only carries a single charge. The use of magnesium has therefore been proposed as it carries two electric charges; however there are many uncertainties about what electrolyte to use.

Another line of study is air-breathing batteries for cars. These do not have to carry around one of their main ingredients. A Li-O battery could, in theory, store energy as densely as a petrol engine, more than ten times better than current battery packs. Na-O would be a much cheaper alternative, though it would have only half the energy density of Li-O, but that is still five times better than Li-ion. A team including Juergen Janek and Philipp Adelhelm at Justus-Liebig University of Giessen in Germany found that a Na-O battery recharges more efficiently than Li-O without complicating side reactions. Chemical giant BASF is now working with them.

There is another important area in which we are going to need energy storage: Electric Power. Too many of our future power sources will offer only intermittent power: wind turbines when there is no wind, solar power at night or in bad weather. Sometimes they offer more than we immediately need and it would be good to store it for later use. If batteries are to play a part, smallness and lightness will be unimportant; cost and low maintenance will be what matters. The field is wide open with many technical options. Flow batteries are an interesting idea, in which the fuel consists of two liquids which pass ions to each other through a membrane. The liquids can be held in separate tanks and pumped to flow past each other when power is needed. It is possible to store much larger power by using bigger tanks. Currently the world's largest flow battery is installed at a wind farm in China, but it uses vanadium, very expensive! Watch this space.

And finally: Physics teacher to students: "No, It's not an optical illusion, it just looks like one!"

The President and Council wish all Members a Very Merry Christmas and a Happy and Healthy New Year

It is customary, at this time of year, to relax by the fireside, take a sip of a stimulating beverage, consume yet another mince pie and reflect on the past year – and what a year it has been! At this time last year we received the sad news of the death of Sir Patrick Moore. It was not entirely unexpected but it still produced a shock wave that has reverberated throughout the Astronomical fraternity. On May 1^st, the BBC held a celebration of his life and work at which over 400 people attended. But soon after an ugly rumour began to circulate that the Sky at Night programme was to be terminated. Many members of the Astronomical Section sent letters of protest and the BBC was quick to respond denying the rumours and stating that the programme will continue, at least for another year. It remains to be seen exactly what form it will take – Patrick was a difficult act to follow; we will have to wait and see.

In last year's Newsletter, I made an appeal for donations towards the recent major restoration work at the Observatory. Many members responded and I would like to express our sincere thanks for their generous contributions. However I could not have foreseen the outcome of a chance meeting at the Observatory which resulted in our receiving a massive donation of £15,000 from a generous anonymous benefactor. This donation, the largest ever received, has enabled us to purchase a dedicated Hydrogen Alpha solar telescope which will be installed at the Observatory later this month. Huge thanks to our benefactor.

Membership numbers are now at 130 and it is good to see that we are attracting younger members, particularly as Assistants at the Observatory. Open nights are attracting many visitors due to the publicity gained from the BBC's Stargazing Live programmes which are now an annual event.

In July, at the annual Observatory picnic, Doug and Julia were totally surprised when they were awarded the Sky at Night Magazine's award for outstanding contributions to the advancement and promotion of astronomy. Doug & Julia wish to thank those responsible for their nomination – you know who you are! Thank you, but it is nice to know that one's small efforts are appreciated.

The major disappointments of the year were the two Comets – panSTARRS and ISON, neither of which lived up to early predictions. We did manage to just about see panSTARRS as a very faint misty patch with a short tail just after sunset in March, but ISON was the major disappointment. Early predictions led us to believe that we actually had a contender for 'Comet of the Century' outshining the full moon. In fact it never exceeded mag. +3.5. At the time of writing, indications are that ISON did not survive its perihelion passage unscathed; we may get a look at it as it gains altitude and heads for a dark sky. But as it moves away from the Sun, its magnitude rapidly decreases; but it just might 'flare-up' and surprise us all.

Impacts from comets could pose a threat to the continuation of life on Earth, but there are other dangers to consider as the following article on Super-Luminous Supernovae demonstrates.

Super-luminous Supernovae.

Peter R Wallis

Supernovae are probably the most cataclysmic events known to astronomers. Stars like our own Sun die relatively slowly when the elements that fuel their nuclear reactions are exhausted. However, stars with a mass between 10 and 20 times that of our Sun explode violently with a brightness a billion times that of the Sun today. When the star has exhausted its nuclear fuel its core of ash can no longer withstand the gravitational pressure above and collapses to a neutron star, releasing enough energy to blow away the outer layers in supernova explosion. If this were to occur near to us in our galaxy, it would be the end of us. Fortunately supernovae are not frequent; one occurred nearly 1000 years ago, leaving the Crab Nebula, luckily some 500 light-years away. Such supernovae have also a good side, in that they distribute into interstellar space the chemical elements higher than Helium [1]. These have been created in the thermonuclear reactions in the star and its explosion; life, and in particular our existence could not have evolved without them. Theory suggests that the presence of "metals" in stars allows them to shed material in winds so that they do not grow very massive; this may well help to limit the number of supernovae in the galaxy.

Astronomers have recently discovered a few new super-luminous supernovae which out-shine the other supernovae by a factor of nearly 100. They do not know what the progenitors are but some have speculated that they might be the much larger stars which formed in the early universe, when there was only hydrogen and helium in the interstellar medium. Such stars would burn these in their thermonuclear reactions to form elements such as carbon, nitrogen and oxygen and would continue to grow. It was shown in 1967 [2] that extremely massive stars larger than 140 solar-masses would become so hot in the interior that pairs of electrons and positrons would be spontaneously generated. The energy to make them would reduce the pressure support against gravity and the star would become "pair unstable". The core of carbon and oxygen would collapse, but still full of this fuel. Burning would increase exponentially, consuming all the fuel in seconds, blowing the star apart and expelling a massive cloud of highly radioactive debris. It was calculated that the rise-time of the radiation from such an enormous star would be at least 100 days as it had to penetrate such a large debris cloud. The radiation would fall over the subsequent 200 or more days as the radioactivity (of e.g. iron, nickel, cobalt) decays.

All this remained as theoretical speculation until a remarkably luminous supernova SN2007bi appeared to fit the prediction. There was however a problem: the galaxy in which it was found was not metal-free. Also, the rising phase of the light, indicative of the size of the debris cloud, was not seen in time. It was just a 'possible'.

But now a recent paper by Nicholl et al [3] reports two supernovae which are super-luminous and have slow-to-fade characteristics similar to those predicted for pair-instability explosions. They are PTF 12 dam, first detected by the Palomar Transient Factory on 23^rd May 2012 and PS1-11ap of 2^nd January 2011. The events were caught early, with a rise-time of 2 months, implying a moderate debris mass of 10 to 20 solar masses. Their colour is also more blue than expected. The authors conclude that they are not pair-instability supernovae but normal core-collapse supernovae of some 10 to 16 solar masses. They suggest this could apply also to SN 2007bi where the rise-time is not known...

However, they are undoubtedly super-luminous. They suggest that the radiation does not arise from radioactivity but from a highly magnetized neutron star (a "magnetar") spinning at nearly 1000 times a second. They say that, "the lack of unambiguous nearby pair-instability events suggests that their local rate of occurrence is less than 6 x 10^-6 times that of the core-collapse rate". Good, the threat of ordinary supernovae is quite enough. If we still wish to find pair-instability supernovae, we'd better look for them nearer the big bang.

1 Astronomers call these "metals"! Back

2 Rakavy G. et al Astrophys, J 148 803-816 (1967) Back

3Nicholl S. J. et al "Slowly fading super-luminous supernovae that are not pair-instability explosions" Nature 502 17^th Oct. 2013 Back

Professor Robert A Weale, BSc, MSc, MPhil, PhD, DSc (Lond.) Obituary

An agonizing back problem had prevented him from attending meetings for four months and he thanked Julia for standing in for him during his enforced absence. The sadness came on December 9^th 2013 when we received news of the death of Sir Patrick Moore. Patrick had a long association with our Society and we had been featured on the Sky at Night programme several times, the last being in October 2011. On May 1^st some 400 guests attended a celebration of Patrick's life and work organized by the BBC at New Broadcasting House. It proved to be a touching tribute to a man whose devotion to the popularization of astronomy was manifest and continued unabated for half a century.

The great joy came at the end of the session when a chance meeting at the Observatory resulted in our Society receiving an anonymous donation of £15,000 to the Observatory fund.

The pleasure continued when, at the annual Observatory staff picnic, Doug & Julia were presented with the Sky at Night Magazine Award for outstanding contributions to the advancement and promotion of astronomy for their combined 104 years volunteering at the Observatory.

Julia & Doug would like to say "thank you" to all those members who 'conspired' in this totally unexpected presentation. Thanks also to Keiron Allen from Sky at Night magazine who presented the award, Paul Abel from the Sky at Night programme for his support and Jon Culshaw for his witty tribute – you all made it a day to remember!

At the last Council meeting prior to the AGM, it was proposed that Julia Daniels be made a Vice President. Council approved the proposal and it was ratified at the AGM. As a Vice-President, Julia is entitled to attend Council meetings and so she resigned as an ordinary member of Council, thus freeing a position for a new candidate.

Council will encounter a problem next year when 4 out of the 5 ordinary members of Council will be forced to resign under the 4 year rule. Accordingly, it was proposed to change Clause 5b of the constitution. Under this new proposal, one member of Council, the longest serving or one wishing to resign voluntarily, will resign each year to be replaced by a new member of Council. This will save us from having to find several new members who are willing to serve on Council in the same year and allows willing ordinary members to continue to serve until new nominations are received. The proposal was discussed at the AGM and approved by all. Clause 5b now reads as follows:

The Council shall consist of the Officers of the Society, as defined in 5a, and five ordinary members, of whom at least one shall retire each year, either voluntarily or the one who has served for the greatest number of consecutive years, or where there is more than one who qualifies, the one selected by ballot of Council members. Any ordinary member of Council retiring under this rule shall not be re-eligible to serve on Council as an ordinary or co-opted member during the subsequent year, but shall be immediately eligible to fill any office as defined in 5a.

At the beginning of the last session, the President (and Astro. Sec.) announced his intention to appoint Simon Lang Joint Astronomical Secretary. There have been several Joint Astronomical Secretaries in the past so there is ample historical precedence for such an appointment. The present Secretary is beginning to feel his age and Simon contributes so much to the astronomy section and to the maintenance of the Observatory, that joint status seems totally logical.

We also congratulate Simon on his recent fellowship of the Royal Astronomical Society.

Prior to the AGM, the Hon. Secretary had received no new nominations for Council but due to the resignation of Julia Daniels there was now a vacancy. Accordingly, Julie Atkinson proposed David Brandt as an ordinary member of Council seconded by Doug Daniels and approved by the meeting.

Your Council elected at the AGM is as follows:

Due to an administration error, the Hon. Treasurer's report and balance sheet was unavailable at the AGM. It is now included with this Newsletter.

Also included is the new Programme Card for the 2013-2014 session. I am sure you will agree that once again Jim has put together an interesting and varied programme of lectures. Jim asks that if you attend an interesting talk and you think it suitable for our members, please let him have details and if possible contact details of the lecturer.

The next session of public open nights at the Observatory begins on Friday 13^th of September – provided that the sky is clear.

The first lecture of the new session will take place on Thursday September 19^th at 8:15 pm when Professor Jonathan Tennyson from University College London will talk on:
I look forward to seeing you at the meeting.

PROPOSED VISIT TO THE BRITISH LIBRARY

It is proposed to visit the British library for a conducted tour sometime in the near future if there are enough members interested. The British Library charge £85 for a conducted tour so if we can put together a party of 14 members willing to pay £6 each, then it would be possible to take advantage of their offer at reasonable cost.

If you would be interested in taking part in this visit, please register your interest with Peter Stern who is organizing the tour. You can contact Peter by e-mailing h p stern at childs hill dot u-net dot com. (Concatenate with no spaces and appropriate symbols for proper address.) If there is sufficient interest, we can then contact the Library to book a suitable date and time, during the autumn perhaps. It could be an interesting outing.

A Permafrost Problem.

Peter R Wallis

Three scientists have recently warned about additional economic costs arising from warming of the Arctic [1]. They are Gail Whiteman, professor of sustainability, management and climate change at Erasmus University, Rotterdam, Chris Hope, reader in policy modelling at Judge Business School, University of Cambridge, and Peter Wadhams, professor of ocean physics at the University of Cambridge. They are concerned at the prospect of the thawing of the offshore permafrost in response to global warming and believe that the economic costs have not been adequately assessed. Some significant economic advantages have been suggested: opened polar shipping routes and easier access to polar oil and gas. The scientists are concerned in particular at the release of large quantities of methane which are stored in hydrates offshore and believe that the consequences have not been appreciated. It is estimated that there are 50 gigatonnes (Gt) on the East Siberian Arctic Shelf which are likely to be released as the sea bed warms as hydrates are unstable at other than freezing temperatures. This would accelerate global warming, with ramifications far from the poles.

To quantify the effects, they use a mathematical model PAGE09 which has been developed to assess the impacts of climate change and the economic costs of mitigation and adaptation measures. An earlier version was used in the UK's 2006 Stern Review on the Economics of Climate Change. Ignoring for the moment the methane release, we can consider two standard scenarios: one is "Business as Usual", in which there is a continuing increase in carbon dioxide and other greenhouse gases, and the other is "Low Emission", where there is a 50% chance of keeping the rise of global mean temperature below 2°C. The model predicts the net economic costs as follows:

The scientists then superimposed on the model a decade long burst of 50 Gt of methane between 2015 and 2025. In the first case this adds $60 trillion and brings earlier by between 15 and 35 years the date at which the temperature exceeds 2°C. In the second case the methane burst adds $37 trillion. These costs remain the same even if the methane burst is delayed by 20 years or is spread out over two to three decades; they are halved if the burst is halved. The economic consequences will be distributed around the globe, but the model shows that about 80% of them will occur in the poorer economies of Africa, Asia and South America. The extra methane magnifies flooding in low-lying areas.

The writers point out that it will be difficult, if not impossible, to avoid large methane releases without major reductions in carbon dioxide emissions.

See also the article: METHANE & CLIMATE CHANGE by D.G.D. in the August 2010 Newsletter available on the web site

[1] Nature, 25 July 2013, p401-403.Back

And finally….

Barrister to Coroner: "How many autopsies have you performed on dead people?"
Coroner to Barrister: "All of them, the live ones tend to put up too much of a fight!"

Doug Daniels (HSS President)

Membership has remained fairly constant close to 120 and meetings have been consistently well attended. This is in no small measure due to the efforts of the Programme Secretary who, as always, strives to produce a varied and interesting lecture programme. He would like to hear from you, if you have suggestions for topics that you would like to see covered in future lectures.

There are now just two meetings to look forward to in the current session. The final lecture of the session takes place on May 16^th when Dr. John Eyre (University College London) will talk on:
DESIGN OF ENGINEERING STRUCTURES.

IMPORTANT NOTE: THE ANNUAL GENERAL MEETING IS: THURSDAY JUNE 20^TH AND NOT 16^TH AS PRINTED ON THE PROGRAMME CARD. Apologies for this printing error!
As usual the AGM will be preceded by wine & cheese and if time allows, followed by a scientific entertainment.

The agenda will include reports from officers and section leaders and the election of officers and five ordinary members of Council for the coming year. Council proposes the following:

Council invites further nominations for the above posts. Such nominees should be duly proposed and seconded and should have agreed to serve if elected.

According to the Constitution, Ordinary Members of Council are obliged to stand down when they have served four consecutive years. In June 2014 this will apply to four out of five Ordinary Members who will therefore need to be replaced all at the same time. Council considers that it would be more sensible to replace one Ordinary Member every year in future, ensuring a regular turnover of Council members without the risk of losing too many people at once. Council therefore proposes the following amendment to the Constitution (shown in bold) so that the new rule will apply at the next AGM in 2014:

5. Officers – Council (current wording)

1. The Officers shall be the President, not more than 6 Vice-Presidents, the Honorary Treasurer, the Honorary Secretary, the Honorary Membership Secretary, the Honorary Programme Secretary and the Honorary Secretaries of such Sections of the Society as shall be constituted under Bye-Law 6.
2. The Council shall consist of the Officers of the Society, as defined in 5a above, and five ordinary members, of whom each shall serve not more than four consecutive years. Any ordinary member of Council retiring under this rule shall not be re-eligible to serve on Council as an ordinary or co-opted member during the subsequent year, but shall be immediately eligible to fill any office as defined in 5a above.

Council proposes that Clause 5b is amended to read as follows:

2. The Council shall consist of the Officers of the Society, as defined in 5a above, and five ordinary members, of whom at least one shall retire each year, either voluntarily or the one who has served for the greatest number of consecutive years, or where there is more than one who qualifies, the one selected by a ballot of Council members. Any ordinary member of Council retiring under this rule shall not be re-eligible to serve on Council as an ordinary or co-opted member during the subsequent year, but shall be immediately eligible to fill any office as defined in 5a above.

Council also seeks ratification from members at the AGM to bestow Vice-Presidency on Julia Daniels.

Julia Daniels (nee Willcox) joined the HSS aged 18 in 1956 and was first elected to Council in 1959 (the same year as Heinz Wolff). She made observations of Mars and variable stars, and became an Observatory Demonstrator in 1960. She married Doug Daniels in 1965. She has been Astronomy Section Treasurer for 41 years so far (since 1972) and Roster Secretary for much of that time. She wrote the 16-page history of the Astro' Section in the Society's history, from the Society's yearbooks and from personal memory and records. Although physical frailty prevents her continuing as a regular Demonstrator, she is still a very active member of the Society and the Astronomy Section, and she helps out wherever needed at meetings.

WHITHER NUCLEAR POWER?

Peter R Wallis

Not everyone believes in the threat of global warming caused by our burning fossil fuels: oil, coal and gas, but all realize that these fuels will eventually run out.

Many are calling vociferously for us to change to renewable energy. We now have many giant windmills (often opposed by local residents and ship-masters when they are offshore) and occasional solar power arrays on roofs (in spite of the UK shortage of sun). But some of us realize that these energy sources are rather unreliable and when they are inoperable they need to be backed up by other systems. Those of us who are concerned about global warming hope that these can be low in the emission of carbon dioxide. At present the worst offenders by a long way are coal-fired power stations. In my view the most urgent UK requirement is to replace coal by gas – a dash for gas. Gas is still a fossil fuel of course and we have changed from being an exporter to become an importer. In the United States a new technology gas extraction from underground shales by hydraulic fracture (fracking) has greatly increased availability and lowered the cost by a factor of 3. We need to do the same if we can; it would be nice not to be dependent upon Russian gas. One of the potential areas is in Lancashire where the additional employment would be welcome and also attract other firms who need cheap power. There are similar rock formations in the Midlands and South East.

The only longer term solution however is the use of nuclear power. Nearly 20% of the UK's electrical power is already nuclear (in France the figure is 90%) but most of our nuclear stations are more than 30 years old and will need replacing. What system should we use? You may remember the HSS visit to see the Joint European Torus, JET, at Culham. This is a research programme to develop a fusion reactor, in which energy is released by the fusion of hydrogen to form helium; this is the reaction that powers all the stars. It's the ideal long term solution but may not be available in my view till the next century. An alternative approach in the US using lasers, the National Ignition Facility, failed to meet its objectives and has been terminated.

There are some 437 nuclear power reactors operating around the world. These are all based on the fission of uranium 235. Of these 356 are light-water reactors. These use ordinary water as a moderator to slow down the neutrons released from a split uranium nucleus from their original energy of some 2 million electron volts (ev) to less than 1 ev, which more readily split another uranium 235 atom in the chain reaction. The water also acts as a coolant for the core and to carry the heat released to the steam generator that drives the turbine and alternator. We have one such light-water reactor at Sizewell, but the others are gas-cooled using carbon dioxide and graphite as a moderator.

There are two problems with the light-water reactor. The first one is that a failure of the water flow allows the reactor core to heat up, even if nominally switched off, and it may melt down. Overheating occurred at Three Mile Island in 1979 in the US and also in three reactors at Fukushima Daiichi in Japan in 2011, though neither actually reached meltdown; in the recent case the zirconium cladding reacted with water to generate hydrogen, which exploded. Emergency back-up cooling systems are provided but, in the recent case, were overpowered by the tsunami.

A second problem arises from the use of slow neutrons. Natural uranium is only some 0.7% uranium 235, though usually increased to some 3% in the reactor fuel; the rest is uranium 238, which is non-fissile. Unfortunately some of the slow neutrons add themselves to the uranium 238 to form plutonium 239 and other heavy elements, eg neptunium, americium, curium etc. These can have a long life (the half-life of plutonium is 24,100 years) and are responsible for the nightmarish problem of radioactive waste disposal; nobody knows how to guarantee isolation over such long times. Plutonium, in particular, can be separated chemically and being itself fissile presents a proliferation problem. Indeed, in 1974, India tested a bomb made from plutonium separated from spent nuclear fuel. This led President Carter to ban all reprocessing in the US.

One solution to the waste problem is to have a "fast" reactor, ie one without a moderator. The fast neutrons may not hit their target so often, but they can split it reliably and are only rarely absorbed. They can also destroy many of the long-lived isotopes in the waste. To build a fast reactor one needs a coolant that doesn't slow the neutrons too much. One possibility is liquid sodium. The UK used this at Dounreay in Scotland but it has since been decommissioned. Sodium reacts violently with water to generate hydrogen so is not a good choice to drive a steam generator in a power station. General Electric/Hitachi in North Carolina have proposals for small fast reactors using liquid sodium (the S-PRISM ) aimed at destroying waste or unwanted stocks of plutonium.

There is another system which is now being considered to avoid the melt-down risk of the light-water reactor, a molten salt reactor. This was originally proposed at the Oakridge Laboratories in the US in the 1960s, but not followed through. The molten salt refers to the fuel of uranium tetrafluoride, which is liquid at operating temperatures when mixed with lithium fluoride and beryllium fluoride which acts as coolant. This is circulated through an external unit where the fission products that can poison the chain reaction are eliminated; it is claimed that it should be an easier process than in reactors with solid fuel which has to be replaced regularly. These fission products are short-lived and do not present such a problem as the fusion products mentioned above. Of course there is a risk of overheating if an emergency stops the liquid circulating. The company Flibe Energy proposes that a hole at the bottom of the reactor vessel is sealed by a plug of fuel which is kept solid by a refrigerator; if power is lost and the liquid heats up, the plug melts and drains the fuel into holding tanks with a geometry preventing further chain reaction. Being such a new design, it may well take a decade or more to be built, proved and accepted by the regulators.

But there is more. The proponents of the molten salt reactor say that, because it is a liquid system, it could use thorium as a fuel as well as uranium. This could be a fundamental game changer. Natural thorium is made up of thorium 232, an isotope which is non-fissile; it is estimated to be 3 or 4 times as abundant as uranium. When irradiated with neutrons however it changes in stages to uranium 233, which is fissile. (Details: thorium 232 captures a neutron and becomes thorium 233 with a half-life of 22 minutes, decaying to protoactinium 233. This has a half-life of 27 days, decaying to uranium 233. ) One cannot start a reactor with thorium alone, as we need the irradiation by neutrons, but if we start it using uranium (or possibly plutonium) we can keep it going using only thorium, I guess. This would mean that our power could eventually come from almost 100% of the world's thorium, instead of 0.7% of the world's uranium and building up massive stocks of plutonium and higher poisons. I do not know whether conventional solid reactors could also change over to thorium fuel.

It seems to me that it would be sensible for the UK to acquire some fast reactors to dispose of the legacy of plutonium and wastes. I think we should look seriously at the molten salt reactor system, if the ideas discussed above can be confirmed. No doubt this will take time. Serious consideration should be given to the use of thorium as fuel. We should eliminate coal-powered stations as soon as we can.

Editor's comment:

Doug Daniels

It is surely about time for the Government to get to grips with the whole energy problem. We have a diminishing supply of fossil fuels and much of the gas and oil on which we presently rely is imported from countries with less than stable political regimes. The emerging economies, China, India and South America are competing for increasing fuel supplies and consequently the pan-global price will inevitably rise. We have only to examine our domestic fuel bills to realize that this is already happening. The present and previous governments, have adopted an 'ostrich-like' policy to the problem, they seem unable to look further than five years ahead – the time to the next general election.

Vast amounts of money are being spent on 'renewable energy' programmes, building masses of giant windmills. But these are dependent on the weather which in this country is fickle to say the least; the wind may not blow at times of peak demand. Other 'renewables' such as tidal power generators, which could be more reliable than wind, are still in their early development stages.

Many of our existing nuclear power stations are soon due to be decommissioned with no plans having been made for their immediate replacement. Only now we hear that planning permission has been granted to the French company EDF to develop a reactor at Hinkley Point; it will be 10 years at least before it is fully operational, if in fact it does actually go ahead.

This country still has massive reserves of coal, the use of which is being phased out in favour of cleaner natural gas. The chief opposition to the use of coal fired power stations is the emission of carbon dioxide which may be contributing to accelerated climate change. To reinforce this position, Didcot A. power station was shut down on March 25th 2013 after 43 years supplying power to two million homes – to be replaced by what? Surely it is not beyond the wit of engineers to design a process that can clean up these emissions before venting them to the atmosphere, so that we could continue to use our coal fired power stations in the short term. In the meantime we should harvest our reserves of shale gas where it is safe to do so to lessen our dependency on imported fuels. But in the long term, we must develop strategies that do not depend on burning fossil fuels.

The greatest source of energy freely available to all is of course the Sun. If every house in Britain had roof top solar panels supplied by the generating companies and connected to the national grid, it would contribute greatly to our daily requirements. Making use of heat pumps and geothermal activity should also be exploited where possible, as well as wind and tidal power. We should certainly be building replacement nuclear reactors as soon as possible and more funds should be available for continuing research into nuclear fusion – the ultimate 'Holy Grail' of cheap energy.

Perhaps we should also consider using less electricity, although this tactic would be anathema to the supply companies who will always want to sell us more to increase their profits and dividends to their shareholders. For this reason it might ultimately be preferable if the generation and distribution of power were to pass from the hands of commercial enterprises to a government authority and treated as a strategic resource as it was during the second world war. The notion that putting energy supply into the hands of private companies would increase their competitiveness is clearly flawed. At least one supplier is currently facing charges of unethical sales techniques and ripping off their customers and has been ordered to make restitution. The overseeing authority 'Ofgem' has shown itself to be less than vigilant controlling these companies, all of whom have made it almost impossible for the average consumer to determine which supplier (if any) is the most competitive. Using any excuse, one of the suppliers will increase their prices, swiftly followed by all the rest. One could be forgiven for thinking that there is some form of cartel in operation, arranged by the suppliers to maximize profits at the expense of consumers.

In an increasingly populated and industrialized world, the demand for affordable energy appears insatiable so we should fully exploit all available sources of energy and formulate plans for the future when fossil fuel reserves are finally exhausted. If we fail to do this very soon, the lights will be going out a lot sooner than expected.

And finally….

Scientists have recently announced that the cure for agoraphobia is just around the corner!

As 2012 draws to a close, we can reflect on yet another year during which the Society has flourished.

Membership numbers are still around 130 and we are at last attracting some younger members particularly as assistants at the Observatory. On the subject of the Observatory: when was the last time you visited it? If you haven't been there recently go and have a look, you will be surprised by the changes we have made during the Autumn.

For the last few years the dome covering has been steadily deteriorating, as it was last re-covered 35 years ago! We decided that it was time for action and we began work in September to strip off the old roofing felt and replace it. As often happens with major building work, once the process began we discovered a whole lot of problems with the structure of the building in general. Much of the wood work was found to be in a poor condition and it was clear that simply re-covering the dome was not enough.

Accordingly we decided to engage the services of a skilled carpenter and builder, Peter Gould, to assist with the renovations. The current Astronomy section Secretariat, although willing, now lack the physical strength to tackle some of the heavy lifting work required. To reinforce this point, Doug Daniels was laid low with a recurring back problem and sciatica which prevented him from assisting in any meaningful way; he did manage to make the tea on one occasion.

Apart from the main dome, the annexe roof and tunnel have been re-covered and the annexe has been re-panelled inside. Rotten floorboards and window sills have been replaced, the building framework has been strengthened and the whole building has been re-wired and safety cut-out devices installed. Additionally we have fitted a low level red light illumination system in the rotunda that looks very pretty at night.

The work took over three months and was directed by Simon Lang with the assistance of many members who generously gave up their time to help and for which we heartily thank them. As is to be expected, a major renovation such as this has been costly, to date it has cost £7500 and this has severely depleted our contingency fund. Simon, Peter and all those members who assisted, have done a first rate job and the Observatory is now a much more pleasant place to work in and it no longer leaks. There are still a few minor jobs to be completed but these may have to be postponed until the Spring.

Accordingly, I am appealing to members for donations towards this major project which should keep the Observatory in good shape for the next 35 years at least. If you would like to donate to this worthwhile cause, please make cheques payable to the Hampstead Scientific Society Astronomy Section and send to : Julia Daniels (Section Treasurer) 25 Village Road Finchley N3 1TL. All contributions will be gratefully received.

SAD FAREWELLS

Members will be aware that during 2012 we lost two of our long standing members. Alfred Oppenheimer and John Hayden sadly passed away. We wish to convey our sympathy to their respective families and friends particularly at this time. Obituaries were posted on the Society's web-site.

Members will also be saddened to hear that Sir Patrick Moore passed away at 12:30 pm on Sunday December 9th at the age of 89. Patrick had a long standing association with our Society. No one has done more to encourage the study of astronomy in this country. He will be sadly missed by all who knew him.

SOMETHING TO LOOK FORWARD TO?

Doug Daniels

When our Observatory was built in 1910, the skies above it were graced by the appearance of two major comets, Comet Halley and the Great Daylight Comet. As it transpired, Comet Halley was not a particularly bright comet and the media (the press) at that time confused the two and thought the Gt. Daylight Comet was Halley. On its return in 1986, Halley was a disappointing object in the northern hemisphere but its arrival was again overhyped by the press who still managed to confuse it with the Great Daylight Comet of 1910. This resulted in over 1000 visitors queuing in freezing temperatures at the Observatory to observe the faint smudge that was Halley's Comet and they were not at all impressed.

During the latter part of the 20^th century we had a good crop of bright comets but none to compare with the Great Daylight Comet of 1910, none that could be described as a Great Comet. In the 1950's we had two naked eye comets Arend-Roland and Mrkos. In 1965 Comet Ikeya-Seki reached magnitude minus 10 before breaking up into 3 pieces.

1973-4 saw the disappointing Kohoutek but a year later comet West attained mag. -3 and could just about be seen in daylight. In 1996, Hyakutake sported a tail of 80 degrees and was circumpolar but poorly observed due to bad weather. 1997 saw the best comet for years – Hale-Bopp a comet that was visible to the naked eye for 18 months and which attained a mag. of -1. In 2007, McNaught was a wonderful sight in the southern hemisphere, also in 2007 Holmes unexpectedly flared up and reached mag. +2.8 its dust cloud expanding to twice the size of the Sun and was well seen in the northern hemisphere as it was almost on the zenith in Perseus.

Now, if we are really lucky, there are two comets to look forward to in 2013, one of which, Comet ISON, could become a Great Comet and earn the title 'Comet of the Century'.

In 2013 the first prospect however is Comet C/2011 L4 pan-STARRS which was discovered on Sept 4^th 2012 from Puerto Rico. Early calculations suggest that comet pan-STARRS could attain mag. 0 when it approaches the Sun to within 28 million miles in March 2013. At this time it will be fairly low down in Pisces, just below the Gt. Square of Pegasus close to the western horizon after sunset. If all goes well, it has the potential to become a striking naked eye object in the evening skies next Spring.

But it is Comet ISON that could just become the brightest comet to grace our skies since 1910. ISON was discovered on September 21^st by astronomers using the International Scientific Optical Network telescope (ISON) in Russia. At present, it is situated beyond the orbit of Jupiter and is a very faint object at about mag. +18 in Cancer. Preliminary calculations indicate that it could approach the Sun to within a distance of just 2 million kilometers on 28^th November 2013 at which time it could attain a magnitude of minus 11 to -16, the latter is 15 times brighter than the full moon (mag. -12.7) and it could easily be seen in daylight! Moreover, during December 2013, ISON will be moving upwards through Ophiuchus into Hercules, so it will be well placed for northern hemisphere observers and it could be visible for months.

Comets fall roughly into three main classes: short period, long period and single apparition. The long and short period comets are permanent members of the Solar System termed periodic. Such comets can be expected to become less spectacular with the passage of time as their frequent close approaches to the Sun cause their volatiles to sublime and deposit dust on to their crusts. After many solar passes, their crusts thicken and their volatiles become exhausted – they simply 'wear out' and become indistinguishable from asteroids. They also distribute dust along their orbits as well; it is dust from Comet Swift-Tuttle for example, that causes the annual Perseid Meteor shower. Short period comets are those with periods less than 200 yrs. The comet with the shortest period of all is Encke at 3.3 years and is responsible for the Taurid meteor shower.

Long period comets have highly eccentric orbits with periods ranging between 200 years to thousands, even millions of years. Hale-Bopp for example will not return to the vicinity of the Sun for 4000 years and McNaught won't be seen again until 92,600 years have elapsed.

The non periodic comets or single apparition comets come from the distant reservoirs like the Kuiper- Edgeworth belt of the Oort Cloud. Such comets can appear suddenly without warning, approach the Sun and are never seen again. They have extremely hyperbolic trajectories.

As comets travel through the Solar System, their orbits can be perturbed by the giant planets such as Jupiter. That mighty planet has a whole group of comets associated with it, some with periods in resonance with Jupiter's 12 year orbital period. On its last pass, Swift-Tuttle was perturbed and arrived 10 years later than predicted and some of us remember well how Shoemaker-Levy 9 was fragmented and subsequently swallowed by Jupiter with dramatic results in July 1994. We watched night after night enthralled by the spectacle as the 15 fragments of the comet ploughed into Jupiter's cloud belts leaving huge dark scars in their wake.

As comets get closer to the Sun they can be perturbed by the inner planets and as they warm up the gases streaming from their nucleus can act like little jets, subtly altering their orbits. It is believed that this jetting may have contributed to Swift-Tuttle's late arrival on its last visit.

There is also a sub-group of comets termed sun grazers which fly close to the Sun and can occasionally fall into it. At its closest approach, comet ISON will be just 2 million kilometers from the Sun so there is always the possibility that it may not survive its perihelion passage. Coming so close to the Sun, it may simply evaporate or violent outgassing may cause the nucleus to fragment.

There are many factors that can affect comets as they are drawn towards the Sun. So what are the chances that ISON will actually be a 'Great Comet' and that pan-STARRS will put on a decent display? Both are long period comets so they should contain masses of volatiles, and as they are new arrivals from the Oort Cloud, they will not have had their icy crusts thickened by large quantities of smothering dust built up over many apparitions. This all bodes well but as we know from past experience, comets are very unpredictable. As David Levy once said: "Comets are like cats, they have tails and they do what they like." As a long term cat owner and avid comet watcher, I couldn't have put it better! Let us hope that ISON lives up to early expectations and if it does we will be in for a very busy time at the Observatory – just as well that we have finished the renovations in good time.

Our Pills or Our Wildlife?

Peter R Wallis

Are our rivers and lake fish now on the pill? It would seem so as the European Commission proposes new regulations which would limit the concentration of ethynyl oestradiol, EE2, the pill's active ingredient, in rivers and lakes. The problem is that this hormone causes male fish to become more feminine, threatening the survival of the species. One study found incipient effects in fish living in surface water with a level of EE2 of one nanogram per litre. The EC proposed in January a limit of 0.035 ng/l, "to play safe and cover other species". This level may be guilding the lily, as has been argued by water and pharmaceutical companies.

The EC also proposed limits for diclofenac, an anti-inflammatory drug sold also as Voltarol, which is commonly used to ease the pain of osteo-arthritis in humans. It can disrupt cell function in the liver and gills of fish; it is already notorious for devastating vulture populations in Asia.

The EE2 standard above was planned to be discussed by the European Parliament's environment committee on 28^th November and, at the time of writing, may well be rejected because some very expensive estimates have been made for upgrading water treatment plants. For example, DEFRA has suggested £26 to £30 billions, though this was based upon a more stringent standard of 0.016 ng/l which may be ten or more times lower than is necessary, and assumed the expensive treatment technology of granular activated carbon would be necessary in all cases. As you can imagine there is much argument between the interested parties, water companies, pharmaceutical companies, customers and governments on one side and environmental scientists on the other. The latter say that the case will only get stronger and there could be a disaster for wildlife if the opportunity to ensure clean water is missed.

Indeed it could also affect our own health if we have too many drugs in our drinking water; for example anti-biotics could encourage anti-biotic resistance in bacteria.

Editor's comment:

Oh dear! I have been suffering from a very painful spinal disk problem and sciatica for the past three months. Part of the treatment included the use of diclofenac the non steroidal anti-inflammatory mentioned in the above text. I really had no idea that in my small way I was contributing to the devastation of the vulture population in Asia, particularly as the drug had no appreciable effect on my condition. Accordingly, I will stop using it immediately and offer my apologies to the vultures of Asia. I would also urge the manufacturers of this particular NSAID to include a caution on their leaflet of recognizable side effects.

Doug Daniels.

Reminder

The first meeting in 2013, will take place on Thursday 17th of January, when Professor Paul Leonard from Brunel University, will lecture on: The Uses and Abuses of Nuclear Energy. I hope to see you at the meeting.

Ordinary Members: £15 reduced to £14 if paid by Banker's Order

Junior Members (under 18 & full time students): £5

Country Members (over 30 miles distant): £5

Family Membership £23 reduced to £20 if paid by Banker's Order

Group Membership: £35

These rates were designed to keep the subscription for junior members and students as low as possible. Those members currently paying by Banker's Order are urged to inform their Bank of the changes before the 1st October or to fill in the form accompanying this Newsletter and return it to the Hon. Treasurer as soon as possible. I am sure you will agree that these new rates still represent excellent value for money.

Prior to the AGM, the Hon. Secretary had received no new nominations for Council and as there were no retirements your council elected at the AGM is as follows:

The programme card for the 2012-2013 session is enclosed with this newsletter. Once again our Programme Secretary has managed to produce a series of interesting lectures. The first in the series will take place on September 20^th when Dr. Kevin Devine (London Metropolitan University) will talk on the subject: The Missing Organic Molecules on Mars. I look forward to seeing you at the meeting.

STOP PRESS: Just two days after the programme cards were printed, we received news that the speaker booked for the October talk has cancelled. A replacement lecture has now been arranged:- Andy Overall, Group Leader of the London Fungus Group affiliated to the British Mycological Society will talk on:- The Fungi of Hampstead Heath.

ASTEROIDS GALORE

Peter R Wallis

Nowadays we know a bit more about the Moon than did Patrick Moore when he argued that the craters were of volcanic origin. It is now generally agreed that they were caused by the impact of asteroids. At least 30 lunar craters have diameters greater than 300 km. The largest is Aitken near the South Pole, at 2,500 km diameter and another, Mare Imbrium, is 1145 km diameter; such enormous craters are called "basins". The still limited exploration of the Moon makes it difficult to date them all but, from the analysis of shock-melted ejecta collected in the Apollo missions, they appear to be clustered between 4.1 and 3.8 billion years ago [1].

But if the Moon was battered by asteroids, what happened to the Earth? It is estimated that the much larger size and mass of the Earth would result in its being hit some 17 times as often; so where are the craters? Well everybody now knows of one impact quite recently (in geological terms) some 65 million years ago at the Cretaceous/Palaeogene boundary which is associated with the mass extinction that included the dinosaurs. The relevant crater is 180 km in diameter at Chicxulub in Mexico; the asteroid that caused it is estimated to have had a diameter of 9 to 14 km. We now know another crater of 100 km in diameter at Popigai 35 million years ago.

But when we look for older craters more comparable to those in the lunar history, we find them at less than half the age of the Earth. Two of the oldest are Sudbury in Canada of 250 km diameter and 1.85 billion years age and Vredefort in S Africa of 300 km diameter and 2.02 billion years age. The difficulty is that the surface of the Earth, unlike the surface of the Moon, is subject to continual erosion, tectonic plate movements and subduction. On the basis of the Moon's record, there must have been some 40 impact basins larger than 1000 km and hundreds of craters larger than 300 km at 3 to 4 billion years ago. It is probably impossible to find any craters from this age as there very few rocks still remaining. However there is another technique to reveal at least some of such past calamitous events.

When massive asteroids strike the Earth at velocities of 10 or 20 km per second they generate a mass of vapourised rock, comparable in mass to that of the impactor, which is ejected beyond the atmosphere; after a time it cools and falls back as a layer of "spherules". For impactors of more than 10 km diameter this will be a global layer. The 65 million years ago Chicxulub impact produced such a global layer of several mm or cm thickness, which was actually an important confirmation of the event hypothesised earlier by Alvarez et al. Because the layer is global it is more likely to survive erosion and tectonic events which would destroy the more local record of a crater.

A recent paper [2] has studied 14 known spherules layers. The authors reach the conclusion that impact velocity is the main determinant of the size of the spherules but that the size of the impactor can be estimate from the thickness of the layer, provided that it is global. Additional confirmation that the layers have an extra-terrestrial origin is shown by anomalous levels of iridium present and chromium isotope measurements. The authors regret that so far only two regions have been systematically searched for Pre-cambrian spherule layers (Pilbara Craton in Western Australia and the Kaapvaal Craton in S Africa, respectively 2.5 and 3.3 billion years ago); this only covers a tenth of Earth's impact history, so much more needs to be examined to get a complete picture. Nevertheless they offer an argument that the flux of impacts was higher at that time.

There is an existing theory to explain the lunar record of few impacts prior to 4.1 billion years ago and a reduced flux after 3.8 billion years ago. This is the hypothesis of a "Late Heavy Bombardment". This model suggests that the gas-giant planets Jupiter and Saturn were originally in slowly evolving near circular orbits. In this phase only a few asteroids would be dislodged, probably by Mars, from the asteroid belt between Mars and Jupiter. Then, about 4.1 billion years ago, the gas giants Jupiter and Saturn reached a 2:1 resonance, in which Jupiter's orbital period became equal to one half of Saturn's. This disturbed their orbits and eccentricities, also causing many asteroids to move into planet-crossing orbits . This is called the Late heavy Bombardment (LHB), lasting until 3.8 billion years ago.

A recent paper [3] extends this model. The authors suggest that the inner boundary of the asteroid belt was originally closer at 1.7 AU instead of the present 2.1 AU, set by a secular resonance. Their dynamic model shows that over about 4 billion years the inner belt between 1.7 and 2.1 AU would have been strongly destabilised by changes in the orbits of Jupiter and Saturn. These would impact at greater speeds of 20 km/sec than the asteroids of the outer belt and extend its period, virtually eliminating all the inner belt. They estimate that 15 plus or minus 4 basin-forming impactors would have struck Earth between 3.7 and 2.5 billion years ago. They comment, "The terrestrial consequences of these mammoth Archaean events have yet to be explored, but we suspect that they may have affected the evolution of life and our biosphere in profound ways".

1The age of the Earth is now believed to be 4.56 billion years and the Moon itself was formed early in this period. Back

2Johnson, B.C. and Melosh, H. J, "Impact Spherules as a record of an ancient heavy bombardment of the Earth", Nature, 3rd May 2012. Back

3Bottke, W. F. Et al, "An Archaean Heavy Bombardment from a destabilised extension of the asteroid belt", Nature, 3rd May 2012. Back

Impacts - V - Volcanism THE ORIGINS OF THE LUNAR CRATERS

Doug Daniels

I well remember attending meetings of the BAA way back in the late 1950's when arguments raged concerning the origins of the lunar craters. There were two distinct 'camps' those who supported the notion that the craters were formed by volcanic activity and those who believed that they were caused by impacts. Debates could become quite 'heated', particularly by the volcanologists! It was pointed out that many craters featured a central peak, surely this would not result from an impact. There were also numerous craters like Plato with distinctly flat interiors and other features such as the Sinus Iridium that exhibited obvious encroachment by flowing lava. Many of the lunar maria appeared roughly circular and featured wrinkle ridges indicative of flowing lava. Then there were the numerous crater chains and 'domes'; how might they be explained by impacts? Personally, I wondered if both processes might have been involved.

It should be remembered that at that time, all our knowledge concerning the lunar surface came from visual observations and drawings mostly made by dedicated 'amateurs'. The major observatories totally ignored the Moon and the best photographs obtained by professionals using the world's largest telescopes were inferior to images obtainable today with a 10-inch telescope!

It was argued that if the lunar craters were caused by impacts then surely the Earth would also have suffered a similar fate and where was the evidence for this? There was of course the single well known example, the Barringer meteor crater in Arizona and perhaps the report of the Tunguska event in Siberia; but information on this was scant because of secrecy during the cold-war between the USSR the USA and NATO. In any case, the Earth is a dynamic planet and the oceans, continental drift, active volcanism, weathering and erosion would have obscured much of the evidence of past bombardment.

The arguments raged on but resolution finally came when space probes were dispatched. Mariner showed the surface of Mars to be highly cratered, Mercury looked very much like our Moon and even Jupiter and Saturn's moons were peppered with impact craters. It soon became clear that the early solar system had been a very violent place indeed and it threw new light on the complex processes involved in the early stages of planetary formation. Apart from the impacts of asteroids, comets came under suspicion as well. Perhaps the Earth's oceans were the result of impacting comets delivering vast amounts of water in the form of ice from the cold depths of the outer Solar System.

Recent data has shown that some of the lunar craters that lay in perpetual darkness close to the Moon's poles do indeed contain ice and there is mounting evidence for the existence of salty oceans beneath the icy crusts of Jupiter's satellites Europa and Ganymede. Water appears to be essential for the existence of life so it may suggest that during the Solar System's early history, the periodic bombardment by asteroids comets and meteorites may have been vital factors in establishing life on Earth and perhaps even elsewhere in the Solar System. We may not have to wait too long for answers if the proposed mission by the European Space Agency (ESA) goes ahead in 2022. The mission called JUICE ( JUpiterICE) will take a closer look at Ganymede and Europa looking for conditions favourable for the establishment of life – we live in interesting times.

MORE ON CLIMATE CHANGE

Doug Daniels

2012 – Yet another disappointing summer, the first half was cool and very, very wet. It was in stark contradiction to the prophecies made in early spring that warned of imminent drought accompanied by the traditional 'hose-pipe ban.' Reporters were filmed standing in dried-up river beds and on the banks of depleted reservoirs. Farmers were shown bemoaning crop failure and predicting future 'dust bowl' conditions in East Anglia, pointing out that food prices were bound to rise as a result. But just a few weeks later, the rivers were in full spate and bursting their banks, the reservoirs were filling up nicely and by early July we ended up with warnings of potential flooding in many areas – the farmers warned of biblical floods in East Anglia destroying their crops and pointed out that food prices were bound to rise as a result.

Once again the jet stream got stuck across the southern half of the country and refused to move northwards until late July – no doubt due to climate change caused by mankind's industrial activities. Really? I have recently been reading Arthur Bryant's book on Samuel Pepys, the 17^th century diarist and it contained the following descriptions from Pepys' epic work.

In 1662, Pepys decided to improve his dwelling by adding another storey to his house. In mid July 1662 the workmen removed the roof. By July 15^th every tile had been lifted – "And then was seen the sad fate that befalls the man who ventures to uncover his house on St. Swithin's day" – it rained unceasingly for the following week. And then again in 1663 we find Pepys out of sorts because of the interminable wet summer "It scarcely ceased to rain for four months" he wrote. It goes to show that the jet stream was probably misbehaving in the 17^th century just as it does in the 21^st – long before mankind's industrial activities could have had any noticeable effect upon it. Could there be another explanation for these periods of unseasonable weather?

Between 1645 and 1715, the Sun produced very few sunspots and the period suffered lower than average global temperatures. This period has been described as the 'Maunder minimum' named after the Victorian solar observer E.Walter Maunder who described it. Maunder built on the earlier work of Gustav Sporer and published a paper in 1894 concerned with the latitudes at which sunspots appeared within the Sun's 11 year magnetic cycle. He produced the famous 'butterfly diagram' to illustrate the effect. Coincidentally, Maunder was the driving force behind the founding of the British Astronomical Association and was the first editor of its Journal.

Records also show that in 1770 the winter was so cold that the Thames froze – a period often referred to as 'the little ice age'. In all there are three identifiable historic 'cold snaps' in 1650, 1770 and 1850 perhaps occasioned by volcanic activity and/or the effects of El Nino or perhaps decreased solar output, or even a combination of all three. The extended period of bad weather at the end of the 18^th century and the resultant poor harvests and famine that it caused in Europe, led to civil unrest and may even have been the root cause of the French Revolution.

The most recent solar minimum of 2008-2009 featured a deeper and a more prolonged solar minimum than had been observed for almost a century. In 2008 there were no sunspots on 266 out of 365 days. There was a 20% lowering of solar wind pressure, a 12 year low in solar radiance .02% lower in visible wavelengths and 6% lower in UV and a 55 year low in solar radio emissions.[*] One wonders if this could perhaps have had any bearing on our recent unpredictable weather patterns? Apart from the 11 year sunspot cycle, the Sun has other long term cycles that we do not as yet fully understand because we have not been studying them for long enough. Such cycles are almost certainly bound to affect the Earth's climate and influence our seemingly unpredictable weather.

* Source - NASA Back

There are now only two meetings to come in this session. The final lecture of the session will be on Thursday May 17^th at 8:15 pm, when Professor Richard Nelson (Queen Mary, University of London) will talk about: PLANETARY SYSTEMS IN THE GALAXY: ARCHITECTURE, FORMATION & EVOLUTION. And on the same subject, you might be interested in Peter Wallis's article that follows.

The final meeting on June 21^st at 8:00 pm will be THE ANNUAL GENERAL MEETING and as usual will be preceded by wine & cheese and if time allows, followed by a scientific entertainment.

The agenda will include reports from officers and section leaders and the election of officers and five ordinary members of Council for the coming year. Council proposes the following:

Council invites further nominations to the above posts. Such nominees shall be duly proposed and seconded and will have agreed to serve if elected.

Planets and Gravitational Microlensing.

Peter R. Wallis

Most of the known extrasolar planets, those in orbits around other stars than our Sun, have been discovered by two different methods. One method is to observe the small reduction in the parent star's light when the planet transits the star's disc. Obviously only a small proportion of planetary orbits will be orientated for this to occur. The reduction may be easy to see if the planet is large like Jupiter, but may be missed if it is small like the Earth or if it orbits at a large distance from the star.

The other method observes the frequency shift of known lines in the spectrum of the star as it "recoils" from the planet's revolution. Again, it will be easier to detect a massive planet like Jupiter, which has 318 times the mass of the Earth, particularly if it is close to its parent star where it has a greater orbital velocity.

These methods are consequently biased in favour of finding hot massive planets in close orbits. They are not likely to present much possibility of hosting extrasolar life – at least life as we know it.

There is however a third method based upon Einstein's General Theory of Relativity, published in 1916. This predicted, amongst other things, that light passing near a massive body, such as a star, will be deflected. Sir Arthur Eddington led an expedition a few years later to confirm this; it was necessary to use a solar eclipse as only then would it be possible to observe the altered position of stars seen close to the sun. There was another consequence of the theory which Einstein himself reported [1] in 1936. If two stars happen to lie in the same direction, one a long way away and the other nearer, the gravitational mass of the nearer star will bend the light from the more distant star and act like a lens. When the two stars are precisely aligned, the light of the further star will be magnified and appear as a bright ring around the nearer star: this is called an "Einstein Ring". If the stars are slightly misaligned the ring may be split or distorted. The phenomenon is called gravitational microlensing.

Now when we use lenses in a microscope or a telescope, we use them to magnify or study the distant object. But in stellar microlensing it is not the distant star we are studying: we use that merely as a point of light. Our interest here is in the structure of the gravitational mass which forms the lens. For example, if the lensing star has a planet, the Einstein ring will be further distorted. We are now able to compute the mass distribution from the observed distortion.

We can now use such microlensing to study the probability of planetary systems around the stars in our own galaxy, called the Milky Way. The advantage of the system is that it can detect planets over a wide range of orbital distances from the parent star, typically 0.5 to 10 AU, and at any orientation. A disadvantage is that microlensing events are rare. Perhaps only one in a million stars has a lensing event at any one time, but there are many stars. We cannot pick and choose, but we can reach a general conclusion. A recent paper [2] reports on the conclusions from 7 years of microlensing events seen in the Milky Way (2002-2007) and concludes that on the average, every star hosts one or more planets in an orbital distance range of 0.5 - 10AU and mass from a few times Earth to Jupiter and more. For those of us who are interested in the possibility of extraterrestrial and extrasolar life, this is an encouraging result.

But there is more. The microlensing technique has also been used to study galaxies, not stars [3][4]. The lensing galaxy is an elliptical galaxy at red shift z=0.88 and is seen to have a bright Einstein ring. The background galaxy is at red shift z=2.06, imaged by the Keck telescope in Hawaii. The authors found that the distortion of the Einstein ring was caused by a dark satellite galaxy near the main lensing galaxy; it would not be possible to see it directly with current technology.

The objective of the authors in studying this lies in problems in understanding how galaxies form. The current theory is that galaxies form initially from dark matter and then they attract normal matter, which in due course coalesces into stars. But the theory seems to predict many more satellites around the Milky Way galaxy than we have yet found. So Vegetti and her team have demonstrated that it is possible to detect such elusive objects even at enormous distances where they could not possibly be seen visually. There is reason to think that such dark satellites are dominated by dark matter.

[1] Einstein, A "Lens-like action of a star by the deviation of light in the gravitational field" Science 84,506-7 (1936). Back

[2] Cassan, A et al "One or more bound planets per Milky Way star from microlensing observations", Nature 481, 167-169, 12 Jan. 2012. Back

[3] Vegetti,S et al,"Gravitational detection of a low-mass dark satellite galaxy at cosmological distance", Nature b>481, 341-343, 19 Jan. 2012. Back

[4] See also, 271-2, loc cit. Back

Editor's comment.

Doug Daniels

Just in case the conclusion reached by the authors in footnote 2 did not fully 'sink in', I should like to repeat it: "after 7 years of research using 'microlensing' techniques, the conclusion is that "every star hosts one or more planets". This is a profound piece of research and it has huge implications for the search for 'extra terrestrial life forms'. I have long held the view that if the present theories of star formation are correct, then it should be expected that the majority of galactic 'metal rich' population 1 stars ought to possess planetary systems. But then we learned that the first multiple planet system to be discovered was that surrounding a Pulsar: PSR 1257+12 - a most unlikely candidate for a planetary system. Recently, Kepler has discovered planets in orbit around the star KIC 05807617, a star that has passed the Red Giant phase - another unlikely candidate. All this adds considerable weight to this research which appears to push the boundaries even further by suggesting that 'every' star should host a planetary system. If this should prove to be correct, then in our own Galaxy alone there must be upwards of one hundred billion planetary systems, and in the observable Universe --- well, at the moment that's anyone's guess but it will be a lot!

For those of us interested in the existence of extraterrestrial and extra-solar life, Peter's observation that this is "an encouraging result" is something of an understatement! In a Universe consisting of billions of galaxies and trillions of stars and therefore by inference, trillions of planetary systems, the idea that just one planet orbiting an average star in an average galaxy could be the only abode of life is totally illogical and to quote the late Carl Sagan (Contact) it would seem to be "an awful waste of space".

Kepler's discoveries continue and recently it has detected a system containing two planets just 1.03 and 0.87 earth radii orbiting the G8 star Kepler-20. This system also contains previously detected planets of x2 and x3 earth radii. With diameters close to that of the Earth, Kepler 20e and Kepler 20f, could have similar compositions to Earth i.e. an iron core and silicate mantle, but at present an accurate determination of their masses has yet to be made and this determination will also indicate the chances of these planets possessing atmospheres and perhaps even liquid water.

Just two decades have passed since the first giant hot exoplanets were discovered. Now as our techniques become more refined we are beginning to detect the smaller rocky Earth sized planets and if the conclusions resulting from the technique of gravitational microlensing are correct, we can confidently expect to discover a whole lot more of them.

Doug Daniels

Important information regarding the annual subscription

Those who attended last years' AGM and studied the Hon. Treasurer's financial report will have observed that we suffered an excess of expenditure over income. I regret to report that a similar state of affairs will occur this year. Clearly, we cannot allow this to continue. Venue rental, postage, printing, insurance premiums, the web site and other expenses have all increased in cost and to mitigate these rises Council have reluctantly decided that the Annual Subscription will have to rise from October 2012.

The new rates that will apply are as follows:

Those members who pay by standing order will need to contact their Banks to make the necessary arrangements.

Members can greatly assist the Hon. Treasurer's cash flow by paying their subscription promptly.

It is many years since it became necessary to raise the subscription and Council hopes that these new rates will allow us to remain in a healthy financial state for the foreseeable future. We believe that these new rates still represent excellent value for money in these troubled financial conditions and have been calculated to ensure that Junior members and students are the least affected.

Doug Daniels President.

Well, another year has passed, at what to me at least seems an astonishing speed, and it has been another excellent year for the Society. Membership now stands at 140 – a record level and attendance at lecture meetings has been consistently high with capacity audiences on many occasions. All this is very gratifying to Council who work long and hard to ensure that our Society continues to thrive, and I take this opportunity to thank them on your behalf for their sterling efforts throughout the year.

I would also like to take this opportunity to thank all our visiting lecturers for their continued support in our mission to promote an interest in all branches of science to a wide audience.

It has also been another busy year for the Astronomy Section. Our participation in the BBC Stargazing Live programmes last January led to the Society being featured on peak time national television and this in turn led to record numbers of visitors to our Observatory which was opened throughout the week. Unfortunately, the weather failed to co-operate fully and we only managed two clear nights. We are now informed that the BBC is to run another Stargazing Live programme from January 16^th – 20^th 2012. Our participation is still at the planning stage, so check our web site for further details nearer to the event.

The Observatory was in the news again in November when the BBC Sky at Night team featured our Society in the November edition of the popular astronomy programme. All this has been excellent publicity for the Society, bringing our activities to a far wider audience. Most gratifying of all is the fact that this exposure has led to membership applications from younger people wishing to be involved. Let us hope that this trend continues; it is vital for the long term survival of the Society.

Towards the end of November we received the sad news that John Ellis had passed away on November 13^th. John was Hon. Treasurer of the Richmond Scientific Society. We send our condolences to John's family and his many friends in both the Richmond and Hampstead Scientific Societies.

The recent successful launch of the space probe 'Curiosity' to Mars and the fact that the planet will be in opposition in March, adds relevance to the talk at the December meeting at which Dr. Steven Cutts will discuss the possibility of LIFE ON MARS.

If the Curiosity probe makes a successful soft landing on the Red Planet next summer, we may at last resolve the enigma that has occupied the thoughts of astronomers since Mars was first systematically observed from the 18^th century onwards – Is there, or was there ever life on Mars?

The first lecture meeting in the New Year will take place on Thursday January 19^th 2012 when Professor Tony Watts from the department of Earth Sciences in the University of Oxford will talk on: MOUNTAINS UNDER THE SEA. I look forward to seeing you at the meeting.

Doug Daniels (HSS President) December 2011

THE LAST HALF CENTURY

Once again we stand on the brink of a 'New Year' and following the accepted convention, pause to reflect upon past events and look forward hopefully to interesting times to come. Last year the HSS Observatory celebrated its Centenary and it came as something of a shock to discover that Julia and I had been closely involved with it for half of that time, Julia for 55 years and me for 47.

I became keenly interested in astronomy when I was thirteen years old; that was in 1953. Whilst at school, I came across a book which showed how to make a simple telescope and described what might be seen with it. Within a few days I had built my first telescope from an old spectacle lens, a microscope eyepiece and a cardboard tube. Painfully crude though it was, it revealed to me the craters on the Moon, Jupiter's four principal satellites, Saturn's rings and much more. These first glimpses of the wonders to be 'discovered' in our Universe inspired me to build bigger and better instruments, an activity that has continued for 58 years! I say 'build', because way back in the 1950's, if you wanted a half decent instrument and you were not very 'well off', building your own was the only real solution. Such instruments that were available for purchase were mainly small aperture refractors built at the turn of the century, resplendent in burnished brass and very expensive. The 1950's were a time of bleak austerity following World War 2 and there was a countrywide shortage of everything.

How different things are today! One only has to look at the advertisements in the numerous glossy magazines and publications devoted to amateur astronomy to see the amazing variety of high quality instruments and accessories available to the contemporary enthusiast. In the 1950's there were few glossy magazines and certainly fewer devoted to astronomy. Now, to paraphrase a certain famous politician, "You've never had it so good!" Today the amateur has at his/her disposal instruments, to quote yet another famous politician, "Forged in the white heat of technology." With their built in computers and electronic drives they can, at the touch of a button or the merest click of a 'mouse,' automatically find the Dumb-bell Nebula for you, without you even needing to know where Vulpecula is. A current magazine advertisement for such an instrument proudly proclaims: – "No knowledge of the night sky is required. One touch innovation turns anyone into an instant astronomer"! – Really?

But I do have some concerns. A few years ago I took a group from the HSS on a visit to Mill Hill Observatory. It was on one of those very rare occasions when such a visit coincided with a clear night. Their newly restored 6-inch Cooke telescope was aimed at a first quarter moon. When one of our party asked if we could look at the Orion Nebula, the request was considered with some consternation. Unfortunately, we were told, the library was locked and they couldn't get an atlas to look up the co-ordinates! When I unclamped the telescope and aimed it at M42, the young chap 'on duty' seemed to regard me as if I had performed some form of 'sleight of hand'! I sometimes worry that computerised 'GoTo' telescopes could actually decrease today's amateur's familiarity with the night sky and that is surely totally missing the point.

There can be little doubt that the average amateur has to work a lot harder today to make any significant contributions to astronomy. The planets, once the domain of amateur observers, have been largely taken over by space probes and the Hubble Space Telescope. The Moon has been thoroughly mapped down to the last crater and the amateur comet hunter now has to compete with satellites such as LINEAR, NEAR and IRAS. CCD cameras have now overtaken conventional photography and fewer observers are tempted to put pencil to paper and make observational drawings. Many serious amateurs today would be quite lost without their CCD's, Digital cameras, computer controlled mountings and automatic guiders. Such equipment is beyond the scope of most make-it-yourself enthusiasts and acquiring it represents a considerable capital investment.

I also worry that the very availability of all this sophisticated kit will ultimately lead to a loss of the amateur's skill at making telescopes. There can be few pursuits more rewarding than skilfully shaping a piece of glass to produce a lens or mirror that can literally 'open a window on the Universe' to you. From where, in the future, I wonder, will come the Henry Wildeys, the Ron Irvings, Jim Hysoms and Terry Pearces of this world? Thank heavens for our continuing affiliation with CATS – the Camden Amateur Telescope makers, who still soldier on building their own instruments from scratch, developing optical and mechanical skills in the process and without a computer in sight!

There are times when I think we are becoming just too dependant on the computer and we are too easily seduced by what it tells us. Let us not forget that believing the results of a faulty computer programme saw a badly figured mirror put into the Hubble Space Telescope. A skilful amateur mirror maker could have detected that fault armed with just a pin point light source and a knife edge!

There is no doubt that amateur astronomy has changed dramatically in the last half century. When I first joined the Junior Astronomical Society, as it was then called in 1958 – now the SPA, the local groups were mainly populated by enthusiastic teenagers. We held inter-group quizzes, and members of the North East London and Golders Green groups regularly pitted their wits against the likes of, Paul Murdin, Keith Brackenborough, John Murray and Rossie Atwell, the young 'alumni' of the Croydon group. Now local societies seem to attract fewer young people. I am a member of two local scientific societies and the average age of the membership is now above 50 years! If societies like ours are to survive in the new millennium, we must encourage young members to join in and help them to develop all the skills that our science demands.

The last half century has seen the most amazing discoveries in the science of astronomy. When I joined the B.A.A. in 1956, the Big Bang Theory was just 'having its fuse lit' but many preferred Fred Hoyle's elegant and far less violent Steady State Theory. Few people had ever heard of Dark Matter, no one had heard of WIMPS or MACHO's and if anyone ever mentioned 'Dark Energy,' they were probably describing a pint of Guinness! Arguments raged as to whether the lunar craters were caused by meteor impact or were volcanic in origin - the latter theory favoured by the then youthful Patrick Moore, and Sputnik 1 was still at the 'blueprint' stage. I remember attending an HSS lecture by one famous astronomer Dr. J.G. Porter, who proved conclusively to his audience that 'space travel would be 'an impossibility' as the navigational computer would need to be 'the size of the Albert Hall' and it 'would consume the electrical power of a town the size of Milton Keynes.' Little did he or we realise what was just lurking around the corner! There is no doubt that the microprocessor and the personal computer have added another dimension to both professional and amateur astronomy and some of today's amateurs are producing images that professionals could only have dreamed of two decades ago. IT Support Croydon have some excellent IT services.

These past fifty years have utterly changed our conception of the Universe and the way we observe it. I feel very fortunate to have lived during this era but I believe that as far as astronomical discovery is concerned, "we ain't seen nothin' yet." It is gratifying to know that organisations like the HSS, the BAA and the S.P.A continue to thrive and I am certain that amateurs have a continuing significant role to play in the 'Queen of Sciences.'

Doug Daniels

During the session Dr. Leo McLaughlin stated his wish to resign from the Council for reasons of health. We are sorry to lose him but we thank him for his help in the past and hope that he might return at some future time. Council proposed Dr. Kevin Devine to fill the vacancy. As there were no other proposals received from the membership, your Council, elected at the AGM is as follows:

The President then announced that Council proposed that Ray Softly be granted Honorary Membership. Ray, who must be one of our oldest members, was for decades the backbone of the Natural History Section during which time he accumulated an unrivaled knowledge of the fauna and flora of Hampstead Heath. Ray now lives in retirement near the Essex coast. The membership applauded Council's decision and they all wish Ray a long, happy and healthy retirement.

Enclosed with this Newsletter is the new Programme card for the 2011 – 2012 session. I am sure you will agree that as ever our Programme Secretary has managed to produce an interesting and wide ranging series of lectures for the forthcoming year. Jim wishes me to remind you that he is always interested to hear from members regarding their ideas for subsequent lectures. If you have attended an interesting talk and think it might be of interest to the membership, let him know about it and if possible provide contact details.

The new session of lectures begins on Thursday September 15^th when Dr. Michael de Podesta MBE from the National Physical Laboratory will talk on: GLOBAL WARMING FROM FIRST PRINCIPLES
I look forward to seeing you at the meeting.

Finally, a reminder that subscriptions this year remain the same despite inflation in most other areas, and represent excellent value for money; they are due on October 1^st. Please assist our Hon. Treasurer by renewing in good time. Better still – renew by Bankers Order and save money and the need to remember.

PLANET FORMATION

Peter R Wallis

Several studies and computer simulations have been carried out over recent years to explain how the planets and asteroids in the Solar System formed. Astronomical advances have also enabled the discovery of many extra-solar planets. So I was very interested to read a recent paper in Nature [1] suggesting how our planetary system may have evolved.

It was shown 25 years ago [2] that giant planets embedded in a gaseous planetary disc carve annular gaps as they grow and also migrate inwards. This seems to be consistent with observations of extra-solar planets, which are usually found close to their star, but this may well be because these are the ones that are easiest to detect! More recent studies and hydrodynamic simulations have shown that such an inward migration occurs in a time-scale of 100,000 years. But, surprisingly, the direction of migration may reverse if two giant planets are trapped in a resonance.

Walsh et al apply this to the case of Jupiter and Saturn in our solar system. They postulate that Jupiter initially formed at 3.5 AU or more from the Sun (1 AU is the distance of the Earth from the Sun) and migrated inwards to 1.5 AU. Saturn follows and becomes trapped in a 3:2 resonance with Jupiter, causing the migration of both to reverse. They recede and, through other resonances, push Uranus and Neptune out too.

It is obviously very difficult to prove that this was what occurred 4.5 billion years ago. However, the calculated consequences may provide support for the hypothesis. Firstly, our giant planets are clearly much further away from the Sun than those extra-solar giant planets so far discovered (commonly at 1.5 AU from their stars). Secondly, their outward migration has left an inner disc of planetesimals truncated at about 1 AU, a suitable environment for the subsequent formation of the rocky planets Mercury, Venus, Earth and Mars. Walsh et al performed 8 simulations of the formation of these planets over a further 150 million years. Their results match the positions of the planets and, in particular, reproduce the large mass ratio between Earth and Mars.

They also study the effect of the Jupiter and Saturn migrations upon the asteroid population. The volatile-poor planetesimals end up preponderantly in the inner asteroid belt. Their simulations show that many of the volatile-rich planetesimals are deflected into eccentric orbits crossing the planet-forming region near 1AU; they could well have represented a source of water for Earth.

It seems that we may well have a lot to thank Saturn for!

[1] Walsh K. J.,Morbidelli A.,Raymond S. N.,O'Brien D. P.,Mondell A. M., "A low mass for Mars from Jupiter's early gas-driven migration", Nature, 14^th July 2011 Back
[2] Lin D.N.C. & Papaloizou J., "Orbital migration of protoplanets", Astrophys. J, 1986 Back

EXOPLANETS

Doug Daniels

Although astronomers have for many years suspected that planetary systems other than our own must exist, it was not until the 1990's that evidence of their existence was confirmed. To date 1,230 systems have been identified surrounding stars within a radius of about 100 light years, and every year more are being discovered.

The first candidate was a rather unlikely one, in that the parent star involved was a Pulsar, the remnant of a Supernova. The Pulsar PSR 1257+12 is apparently accompanied by multiple planets. It is open to conjecture as to whether these planets are in the process of being formed from the material ejected from the Supernova, creating a nascent system or if they are merely the old cores, the cinders of previously existing planets that were destroyed by the blast from the supernova explosion.

The first 'Sun like' star discovered to be accompanied by a planet was 51 Pegasi, discovered in 1995. The first system with multiple planets to be discovered was the star Upsilon Andromedae and there are now at least 50 systems known to be supporting multiple planets. Of these the best known is the red dwarf star Gliese 581 twenty light years distant in the constellation Libra. At least 4 planets are known to orbit this star and one of them Gliese 581c is a possible contender for a planet orbiting in the so called 'Goldilocks' zone where temperatures would allow liquid water to exist. Gleise 581c has been described as a 'Super Earth' with a diameter of about 19,000 kilometres. But this is small beer compared to the planet in orbit around HD43848 which is estimated to be nearly 8,000 times the mass of the Earth.

Because of their relatively small size compared to their parent star, exoplanets only reveal their presence indirectly. They are detected when they transit their primaries in our line of sight, or by their gravitational effect on their parent star detected by redshift in the star's spectrum. However, the Hubble Space Telescope has recently obtained the first direct image of an exoplanet orbiting the star Fomalhaut. It can be seen clearing a path in the dust disk surrounding the star.

The majority of the exoplanets so far discovered are massive gas giants which appear to orbit close to their primaries. Many have been designated 'Hot Jupiters' and such systems are vastly different to our own. If planets occur naturally around pulsars, red dwarfs and main sequence stars, it begs the question do they exist around most stars? If our present ideas concerning the formation of stars and planets are correct, then planetary systems ought to be quite common. It seems that we still have a long way to go before we fully understand the complex processes and interactions that take place during the early stages of planetary evolution in protoplanetary disks. However, one thing is certain - there must be a whole lot of planets out there just waiting to be discovered.

TO 'Go To' or NOT to 'Go To' THAT IS THE QUESTION

Doug Daniels

Of course I'm biased. I belong to a generation that inhabited a world long before computers were commonplace. In my heyday there were not even such things as electronic calculators, and 'windows' were panes of glass that you looked through. The best calculating aids we had were slide rules and a book of log tables - oh yes and a set of tables drummed into our brains at the age of six plus, so thoroughly, that if you ask us to multiply 9x8, the answer 72 is delivered instantly without even having to think about it!

Today it seems everything just has to have a computer attached to it otherwise it is just not worth considering. Astronomical telescopes are no exception.

I recently spent an interesting yet frustrating few hours with a good friend who had just taken delivery of one of these small computerised 'Go-To' telescopes. Apparently it was able to automatically find upwards of 5,000 celestial objects all by itself and was designed to make 'finding celestial objects easy for the beginner.' Some mistake surely!

After inserting a handful of batteries, we switched it on. It asked us to enter the date and time; we complied. A message was spelled out on the handset warning of the dangers of looking at the Sun, spelled out at such an interminably slow speed that I was already beginning to feel my arteries hardening. Why for heavens sake? We have already told the wretched computer the date and that the time is 23.00 hrs UT - if it's that damned clever it should know that the sun is below the horizon! It then asks us if we would like a 'tour of the solar system?' No we would not we just want to look at the Moon! It proceeds to do it anyway. Motors hummed, the telescope swung wildly up and down and round and round, finally coming to rest pointing down towards the ground presumably attempting to home in on the Sun to justify its earlier warning.

After several abortive attempts to encourage it to point to the Moon my patience had run out and I switched it off, unclamped it and pointed it at the Moon manually. But even that was not so easy as the wretched device uses a built in diagonal and has no finder. I would hate to try to point it at something really faint, you would just have to rely on its computerised functions to do this and judging by our earlier attempts it could take all night to find the Andromeda Galaxy. O.K. perhaps I'm being too quick to judge and it will take some time to become thoroughly acquainted with its little foibles; hopefully before its batteries go flat.

But I still maintain that such a device could lead to enormous frustration for a real beginner. It's only a 70mm refractor for heavens sake! A simple alt-azimuth mount on a tripod would allow you to point it at the Moon and get an instant result without spending hours reading the instruction manual and then trying to identify certain stars to set its position. An absolute beginner would probably not be familiar with these stars anyway. Before even attempting to use a 'Go To' telescope it would be better to spend a few months getting acquainted with the night sky with a simply mounted telescope or a good pair of binoculars and a star map.

And whilst I am having a rant on the subject of unnecessary computers and telescopes, I strongly object to fitting computers to antiques. I recently visited the old Royal Greenwich Observatory and was appalled to discover that they had 'computerised' the historic 28-inch refractor. Using this wizard 'strap on' electronic gizmo meant that it only took them about 10 minutes to locate the Moon - a task that could have been accomplished manually in about 30 seconds by just squinting through the finder. I thought that computers were supposed to make life easier! Some mistake surely!

It's the same at Mill Hill Observatory. The 18/24-inch Radcliffe refractor, a magnificent example of Victorian engineering constructed by Sir Howard Grubb, is now draped with cables and electronics and thoroughly 'computerised.' I'm sorry but I just do not agree with this. I understand that students need to learn how to manage a computerised telescope but attempting to modify an ancient instrument is the wrong route to take. To see all this electronic paraphernalia attached to the works of traditional makers such as Grubb and Cooke is, to quote our esteemed heir to the throne: "Like seeing a monstrous carbuncle on the face of an old friend." Computers and brass fittings do not blend comfortably. If you must teach on a computerised instrument, and of course today you probably must, use one specifically built for that purpose, don't desecrate the works of historic telescope makers.

O.K. rant over. I shall now return to my cave, light a fire by rubbing two sticks together, suck the marrow out of the bones of a woolly rhinoceros and pay tribute to old King Ludd.

The agenda will include the annual reports from Officers and Sections and the election of five Ordinary Members of Council for the coming year. Council proposes the following:

Dr. Leo McLaughlin has resigned from the Council due to reasons of health, leaving a vacancy. Council proposes Dr. Kevin Devine to fill the vacancy but invites further nominations to the above posts; such nominees shall be duly proposed and seconded and have agreed to serve if elected.

STILL SEARCHING

Peter R Wallis

One of the most intriguing problems today in cosmology and physical science is that of Dark Matter. It seems to outweigh the ordinary matter seen in the universe by some 5.5 to 1, as evidenced by its gravitational effect upon stars and galaxies. But so far we have not been able to detect it by any other measurements. What is it?

Most of the attempts to detect it are based on a speculation that it consists of Weakly Interacting Massive Particles left over in the Big Bang in which our universe started 13.7 billion years ago. They are called WIMPs, but this is not an explanation, merely a description. Several searchers for WIMPs base their plans on the still controversial theory of 'super-symmetry', in which all the fundamental particles in the 'standard model' of physics have heavier, but so far unobserved, partners. One of these is the neutralino which seems to have appropriate properties to explain dark matter; it would have feeble interactions with conventional matter but have a mass in the range of 50 to a few thousand times that of a proton.

So several teams are building equipment to search for the neutralino. The philosophy is that one needs a very large detector, in view of the very weak interaction, and that it is composed itself of particles generally similar in mass to that postulated for the hypothetical neutralino, in order that a collision should have a sufficient recoil effect to be observable. And the detector should be placed deep underground to minimise cosmic and other radiation.

Several of the teams use tanks of liquid xenon, which has an atomic mass of 131, suitable for detecting neutralinos at the lighter end of the spectrum. One team is located at the Sasso National Laboratory, Aquila, Italy. It began operating in 2006 with 15 kg of xenon, finding nothing, but was upgraded in 2009 to 161 kg, called 'XENON 100'. So far an eleven-day run has found nothing. This suggests that neutralinos, if they exist, have a mass greater than 100 Giga-electron volts (Gev). Results from a recent 100-day run are, so far, obscure due to trace contamination of the xenon giving increased background noise. Two other larger xenon detectors in S Dakota and Kamioka, Japan, have not yet started operating. Other teams use germanium and silicon crystals, which are the only solid elements that can be made pure enough. CoGeNT, in Souda, Minnesota, has provisionally claimed detections of particles in the range of 7 to 11 Gev, but consider it necessary to delay publication till more results have been obtained, partly as the result conflicts with that from XENON 100.

Currently a debate has broken out [1] whether a different approach could be used. Apparently dark matter particles could have their own anti-particles. Put enough together in one place and some could annihilate each other, generating gamma radiation. Such a place could be the centre of our galaxy. Dan Hooper, an astronomer at the Fermi National Accelerator Laboratory at Batavia, Illinois, claims he has found such evidence from NASA's Fermi Gamma-ray Space Telescope, indicative of particles in the 7.3 to 9.3 Gev range, similar to the germanium results. Others are sceptical, as the centre of the galaxy is so complex and we know little about it.

The XENON 100 and CoGeNT teams are expected to release their full year's results this year and two other teams with larger xenon detectors are expected to start operating soon. One is the Large Underground Detector LUX, with 350 kgs of xenon, and the other is the Japanese XMASS, with 1000 kgs, but Japan's recent problems may delay it.

[1] Adam Mann, "Hunting of the Dark", Nature, 24 March 2011 Back

BUT DOES DARK MATTER REALLY EXIST?

Doug Daniels

Way back in the 1930's it was discovered that galaxies in clusters were moving too rapidly to be explained by the gravitational interaction of their individual components. This led astronomers to conclude that there was a huge 'Missing Mass', something unseen that was causing the discrepancy. The problem was compounded when in the 1980's the rotation of galaxies also showed that the stars in the outer regions appeared to be moving at speeds similar to the stars nearer the centre. It was as if the stars were 'fixed' to some gigantic wheel. In order to explain these anomalies using our present understanding of gravity, it was necessary to invent something that has a mass in the order of 5 times that of the calculated mass of the entire galaxy yet was totally invisible.

It was his work on the motions of galaxies in the Coma cluster in 1933 that led the Swiss astronomer and flawed genius Fritz Zwicky to coin the term 'Dark Matter' to account for the 'Missing Mass'. Working at Mt. Palomar, Zwicky employed the Virial theorem * which allows the total kinetic energy in complex systems to be calculated. His results indicated that the mass of the cluster based on the speed of its galaxies was at least ten times greater than the mass calculated from its light output. The search was then on to identify the origin and nature of 'Dark Matter' but so far, we have been unable to prove conclusively that it exists at all, let alone provide a convincing description of its composition. Terms like WIMPS, MACHOS and now NEUTRALINOS are bandied about in a vain attempt to describe its nature. Today according to some authorities 'Dark Matter' represents 80% of the matter in the entire Universe while ordinary baryonic matter (the parts we can actually see) represents just 20%.

But could there possibly be another explanation to the 'Missing Mass' problem that confounds cosmologists? Recently published work demonstrates a radical alternative approach to this long standing problem.

Consider this proposition: "What if gravity behaves differently when applied to the masses and comparatively low accelerations of stars in galaxies?" "What if Newton's second law (f = ma) is not sacrosanct and does not hold in certain special circumstances." After all, Einstein showed that Newton's laws do not hold in regions of intense gravitational fields and our understanding of gravity can hardly be described as complete. Is it remotely possible that Newton's laws also do not hold when considering the very low accelerations of stars in galaxies, where for a given force less mass is required? Newtonian laws of gravity work demonstrably in the Solar System but in the Solar System accelerations are in the order of a million times greater than the very weak accelerations acting on stars in galaxies. This is the basis for a study called MOND – Modified Newtonian Dynamics carried out by Mordehai Milgrom [1] of the Weizmann Institute.

In order to test this theory it is necessary to determine the mass and velocities of stars in a large sample of galaxies. Work on this has recently been published by Stacy McGaugh [2] of the University of Maryland. McGaugh studied gas-rich galaxies because determining gas mass is more reliable than determining stellar mass. The study has shown that the relationship between mass and velocity was indeed that predicted by MOND, and MOND has made some interesting predictions in other areas. However, all is not plain sailing as the theory has run into considerable trouble in other applications. For example, it underestimates the mass in galactic clusters by as much as 50%, it cannot account for bending light in examples of gravitational lensing and more seriously, it violates the law of conservation of momentum – although there is a relativistic version Tensor-Vector-Scalar theory (TeVeS) developed by Jacob Bekenstein [3] that does not violate this law and embraces the phenomenon of gravitational lensing as well.

All this has the potential for further study because although we have lived with the theoretical existence of vast quantities of 'Dark Matter' for eight decades, we are still searching and we still can't find any!

If we apply the principle of 'Occam's Razor' we might conclude that the reason that we can't find any is simply because it does not exist. Maybe there is after all another explanation for the 'Missing Mass' that does not rely on the 'invention' of ever more exotic and elusive fundamental particles.

References

1 Milgrom, Mordehai: "Does Dark Matter really exist?" Scientific American Aug 2002 42-50-52 Back

2 Sanders, Robert; McGaugh, Stacy S, "Modified Newtonian Dynamics as an alternative to Dark Matter" Annual Review of Astronomy and Astrophysics 40, 263 - 317 Back

3 Bekenstein, Jacob D (2004) "Relativistic gravitation theory for the modified Newtonian dynamics paradigm" Phys,Rev. D70 (8): 083509 Back

Further reading: "Can tweaking gravity make Dark Matter go away?" Longstaff. Alan: Astronomy Now April 2011

* The Virial theorem:
M = (V².R)/G where:
M = Mass
V = Velocity
R = distance from galactic centre
G = Gravitational Constant = 6.67 x 10¹¹
Back

The President and Council wish all Members a Merry Christmas and a Happy & Healthy New Year

Tempus fugit! The 'arrow of time', perhaps accelerated by 'Dark Energy', speeds on relentlessly and yet another year approaches its end. And what a year it has been for the Society. In April 2010 we celebrated the centenary of the foundation of the Observatory and the Met. Station. I doubt that the 'founding fathers', Col. Henry Heberden, Philip Vizard, Patrick Hepburn, Clement Bartrum et al, could have imagined that the Society they created to promote the study of science would be thriving a century later and they could never have imagined the discoveries made by science in such a comparatively short time.

The reason that the Society continues to flourish is due to the enthusiasm of its Council and membership and the generosity of our visiting lecturers. I take this opportunity to thank you all for your support in 2010 and express the hope that it will continue into the foreseeable future. May your thirst for knowledge never be quenched!

Our centenary year was, however, tinged with sadness by news of the untimely death of Caesar Kamieniecki who served as Minutes Secretary on the Observatory Sub-Committee and was an Observatory Demonstrator for over 30 years. Our thoughts are with his family at this time.

Doug. Daniels (HSS President) December 2010

N.B. There are two special events taking place in early January. Please see page 6 for details

The first lecture meeting of 2011 will take place on Thursday January 20th when Dr. Dewi W Lewis will be talking on the subject of 'ZEOLITES — MAGIC ROCKS.' I look forward to seeing you at the meeting. In the meantime, here is a little light reading matter to keep the 'grey cells' occupied during the 'festive season'.

Geoengineering

Peter R Wallis

The argument about geoengineering continues. In the US two official reports have been published, including a Congressional analysis calling for federal research. In his foreword to the report, Burt Gordon writes, "If climate change is one of the greatest long-term threats to biological diversity and human welfare, then failing to understand all the options is also a threat".

On the other side participants in the international Convention on Biological Diversity (CBD), held in October in Nagoya, Japan, included in their agreement a moratorium on geoengineering "until there is adequate scientific basis on which to justify such activities and appropriate consideration of the associated risks". They grant an exception for smaller studies conducted in a "controlled setting", but only if they are thoroughly assessed and "justified by the need to gather specific scientific data". Some scientists are concerned that the CBD's stance will lead to confusion and delay, although the moratorium is not expected to be in force until 2012.

Then again the Intergovernmental Panel on Climate Change is encouraging scientists to expand their geoengineering studies and is planning a meeting in June 2011 to discuss its scientific basis, its costs, impacts and side effects. Ottmar Edenhofer, co-chairman of the IPCC's working group on climate change mitigation, says that commitments to reduce greenhouse-gas emissions will probably not be enough to meet the climate goals, such as limiting global warming to 2oC over the next century. He says, "Geoengineering is one option and it should be included in a portfolio of other options". So watch this space!

THE THIRD POLE

Peter R Wallis

The North and South Poles are cold and remote, threatened by global warming. But there is also another region of similar nature in the Himalayas and Tibetan Plateau which, after the Arctic and Antarctic, has the Earth's largest store of ice; it has more than 46,000 glaciers. This has recently been called "the Third Pole". But it is also Asia's water tower, because its glaciers feed the continent's largest rivers, sustaining 1.5 billion people. Yet little is known publicly about how climate change is occurring there.

To rectify this, an international programme led by the Chinese Academy of Sciences' Institute of Tibetan Plateau Research in Beijing has been set up as the "The Third Pole Environment" (TPE); it held its second workshop in Kathmandu in October this year. Now you may remember that a claim in the 2007 report of the Intergovernmental Panel on Climate Change (IPCC) that Himalayan glaciers could disappear by 2035 was shown last year to be an error, casting doubt on the IPCC's reliability. The participants in the workshop argue however that the IPCC's broader concern about Himalayan ice was correct. It is not yet clear how fast is the loss and how it will affect water resources as there is no complete inventory of glaciers for the region and the terrain and harsh weather hamper ground measurements.

There is some evidence however and it is telling. Combining satellite and ground measurements, a Chinese team have documented some 24,300 of their glaciers. It shows that their total surface area has reduced by 17% and many have disappeared since the last inventory 30 years ago. Most of the glaciers that have been studied in the Indian Himalayas are also losing mass.

One possible cause is the deposition of 'black carbon' from fossil-fuel and biomass burning, as recorded in ice-cores from five glaciers since industrial growth in the area. Calculations suggest an increase of 12 to 34% in ice melting. As a consequence, glacial lakes are becoming larger and more numerous; their area on the plateau has increased by 26% since 1970 according to a study by the University of California and there have been more than 40 lake outbursts since the 1950s. One survey listed 20,000 glacial lakes, of which 200 were potentially dangerous and needed monitoring.

The loss of ice in the North and South Poles is of course important to the prediction of global warming and sea level, but that in the Third Pole could have a more immediate and devastating effect on the billions of people dependent on the rivers it supplies.

THE HISTORY OF THE COOKE TELESCOPE

Doug Daniels

2009 marked the 4th centenary of the invention of the telescope and in April 2010 the Hampstead Scientific Society celebrated the centenary of the foundation of its astronomical observatory. The main instrument at the Observatory is a 6-inch refractor made in about 1898 by T.Cooke & Sons of York. In 1988 the firm of Cooke, Troughton & Simms ceased trading, bringing to an end the long and distinguished history of one of the world's finest astronomical telescope makers. What follows is a brief history of that company. (The writer wishes to acknowledge 'Instrument Makers to the World' by Anita McConnell as his main reference source. D.G.D.)

In 1922 Thomas Cooke & Sons of York were merged with the old established firm of Troughton & Simms which was founded in London in 1750. Cooke Troughton & Simms Ltd. were finally taken over by Vickers in 1926 but it is the firm of T. Cooke & Sons of York that is renowned by astronomers world-wide, for the manufacture of excellent astronomical optics allied to mountings that were engineered to the highest levels of craftsmanship. Before we delve into the history of Thomas Cooke & Sons, it might be a good idea to remind ourselves about the early history of the astronomical refracting telescope.

Although glass making had been practised since about 3000 BC, it seems that the regular production of optical quality glass in Europe dates from the early 17^th century. There are records of crown glass production in London by 1678, but it must have been started earlier by experimenters because of the work of Leonard Digges for example.

Leonard Digges (1520-1559), was an English scientist/surveyor. We know something of his work from the writings of his son, Thomas, who in 1571 published the book Pantometria. In this volume, Thomas describes a theodolite made by his father that used a combination of mirrors and lenses to magnify distant objects. This pre-dates the patent for the refracting telescope applied for by the Dutch optician Hans Lippershey by 68 years! (1608)

The story of Lippershey's involvement is well known, albeit a little apocryphal. It is said that Lippershey's children were playing with some lenses, and by holding up a long focus convex lens with a short focus concave lens, they magnified distant objects, effectively inventing what we would describe as the 'opera glass'. Lippershey applied for a patent in 1608, but after much legal debate the patent application was rejected.

The application of the telescope to astronomy is usually attributed to Galileo, but there is evidence that the credit should go to one Thomas Harriot (1560-1621). Harriot is also credited with the introduction of the potato to England as he was on the expedition to the Americas with Sir Walter Raleigh. Harriot became interested in astronomy when he witnessed the return of what was to become 'Halley's Comet' in 1607 and in a letter to a friend, he describes an observation of the moon made with a telescope in the same year — pre-dating the observations of Galileo by 2 years.

The problem with all astronomical refractors at that time was the use of a single plano-convex objective. This introduced chromatic aberration and surrounded bright objects with a colourful fringe. To attempt to reduce this effect, early refractors were made with very long focal lengths and were as a consequence, very unwieldy instruments. Hevelius's 8-inch telescope, for example, had a tube length of 150 feet and that was not the longest.

Newton applied his mind to the chromatic aberration problem, but was unable to solve it and in 1666, thinking laterally, he invented the reflecting telescope instead. By using a concave mirror as the objective the light only had to pass through the lens of the eyepiece and this greatly reduced the dispersion. However, early telescope mirrors were not easy to make. Initially they were cast from 'speculum metal' a bronze-like alloy which quickly tarnished and frequently had to be re-polished and re-figured. It wasn't until 1865 that Leon Foucault described a method of depositing a reflective coating of silver on to glass, opening the way for the development of the modern reflecting telescope. Until that time the refracting telescope remained the preferred astronomical tool.

It was an English lawyer, Chester Moore-Hall, who finally came up with the solution. In 1729, Hall wrote a paper describing a compound lens using glasses of different refractive indices as a possible solution to reduce chromatic aberration. And in 1758, the optician John Dolland attempted to patent the idea but in the event his patent application was unsuccessful. After 1758, in England, there were several instrument makers producing small achromatic refractors. Dolland, Tulley etc. Achromatic objectives were of small diameter as the main problem at the time was in obtaining suitable supplies of glass of consistant optical quality, free of strains and air bubbles.

This was the situation when Thomas Cooke built his first telescope in1837. Thomas Cooke was born on March 8th 1807 in the Yorkshire village of Allerthorpe. His father was a shoemaker but Thomas's interests lay in a totally different direction. Inspired by the exploits of his namesake — Captain James Cook, Thomas wanted to be an explorer. To which end he rejected cordwaining (shoe making) and studied mathematics and navigation. At the age of 17 he was all set to depart to sea, but was persuaded by his doting mother to stay and take up teaching instead by opening a village school. From 1829-1836, he continued to teach locally and as a freelance tutor in York and meanwhile continued his own studies in maths, optics and mechanics.

At about this time Cooke made himself a small telescope, grinding one of the lenses from the base of a glass tumbler. The telescope worked well and he sold it to John Phillips, the curator of the Yorkshire Museum and an active member of the newly formed British Association for the Advancement of Science, (Now the B.S.A.) which held its first meeting in York in 1831.

Phillips and Cooke became friends and Phillips helped to promote Cooke's work within the wider scientific community. This in turn persuaded Cooke to embark on a full-time career as an instrument maker. To this end Cooke borrowed the sum of £100 from his wife's uncle and rented premises at 50 Stonegate in York. His wife, Hannah, worked in the shop and also took in lodgers to help with the rent so Cooke was able to concentrate on his optical and mechanical work. But first he had to build his own screw-cutting lathe and the grinding and polishing machines needed to produce lenses.

Cooke's first commission was from William Gray, a family friend who was a lawyer with a practice in York. Cooke built a 4½ -inch equatorial refractor for Gray and by all accounts it was a fine instrument. Instruments of that size were a rarity at that time, but Cooke was soon to push the boundaries even further. In 1851 he built an equatorial refractor of 7¼ -inches aperture for Hugh Pattinson of Newcastle. Pattinson was a friend of Isaac Fletcher, a well-known astronomer who was so impressed with Cooke's work that he recommended Cooke to Airy the Astronomer Royal. At about this time Cooke also met Norman Lockyer, (later Sir Norman) and sold him a telescope for his observatory at Wimbledon.

Cooke's reputation was spreading rapidly throughout the astronomical community and there was also increased demand for spectacles and opera glasses. So Cooke decided that it was time to expand and in 1855, leaving his brother Barnard to run the shop, he purchased land at Bishophill in York where he built the Buckingham Works. This was to become one of the first comprehensive instrument manufactories in the country with its own foundry, brass, glass and wood workshops, all powered by steam engines.

In 1855 Cooke was exhibiting at the Paris Universal Exhibition where a 7½-inch clock driven refractor won him the First Class Medal and universal praise. This was to be the first of many exhibitions that Cooke attended, both at home and abroad. At the London exhibition of 1862 he won two First Class Medals for his object glasses and telescope mountings and for a turret clock mechanism of advanced design, highly praised by Charles Frodsham, the eminent London clock maker.

By 1861 Cooke was employing 26 men and 14 boys at Buckingham Works engaged on the manufacture of telescopes, mountings, turret clocks, surveying instruments, opera glasses and spectacles, and Cooke's work was being praised at the Great Exhibition. In 1860 he was summoned by Prince Albert to Osborne House to discuss the construction of an observatory for the Royal Family. The telescope, a 5¼-inch refractor was proudly exhibited in Cooke's shop window for several days prior to its shipment to the Isle of Wight.

From 1863-1869, Cooke rented a shop at 31 Southampton Street in London. He was by then a fellow of the Royal Astronomical Society, elected in 1859 and he served on the Committee from 1865-66. During this time the Works were under the supervision of his sons Thomas and Charles Frederick. Thomas specialised in optics and Charles, always known as 'Fred' was a mechanical engineer — it was a genuine family business. The Cooke business was thriving during the1860's but there was a dark cloud looming on the horizon in the form of Robert Stirling Newall.

Newall was a wealthy industrialist — a producer of wire rope which he supplied to Cooke for his turret clocks. Newall had obtained from the glass manufacturers, Chance Brothers, a pair of huge glass disks suitable to produce a lens of 25-inches in diameter. This was a true giant at the time. Newall purchased the disks for £500 — a vast sum, and he sought quotations from all the reputable telescope makers, including Grubb of Dublin and of course, Thomas Cooke. Cooke was so keen to obtain the commission that he grossly underestimated the production time of such a huge instrument and quoted a totally unrealistic delivery time of one year. In the event, it took him many years before the lenses were perfected and even more years before the mounting was finished. During this time, Newall became more and more impatient with Cooke and threats were made and funds withheld forcing Cooke into near bankruptcy at one point. Cooke had bitten off more than he could chew. With a tube length of 32 feet, the instrument was too large to be assembled in the factory and had to be erected in the open air and it remained unfinished at the time of Cooke's untimely death in 1868. The years prior to Cooke's death were troubled by further problems. At the Great Exhibition, a certain Lt. Colonel Strange had seen Cooke's exhibit and wanted Cooke to manufacture a whole range of precision surveying instruments for the government to use in India. Cooke had no precision dividing engine at that time but Strange persuaded him to build one. In 1864, Cooke received an order for 16 precision theodolites. This was to be the first of many such orders to come from the government. But all this work coupled with the worry concerning the Newall telescope must have been a great strain on Cooke's health. The dividing engine was finished shortly before his death on 19th October 1869 at the age of 62.

Problems continued after Cooke's death. Without Thomas Cooke's guiding hand, the theodolites were found to be poorly divided and further orders were cancelled. Also at that time the works were engaged on building two transit instruments for longitude determination also destined for India. It took 3 years to complete this order and there were problems with one of the instruments when it arrived damaged and it had to be repaired locally.

Cooke's death put the company into turmoil. His will left everything to his widow and she was soon under pressure from Newall who attempted in 1879 to force the business into liquidation. Fortunately, a wealthy industrialist, Sir James Meek, the thrice Lord Mayor of York, came to the rescue and purchased the business, selling it on to James Wigglesworth, who was a family friend and the owner of a fine 6-inch refractor made by Cooke in 1853. In 1879, Wigglesworth went into partnership with Cooke's sons and after his death in 1888 his son Robert purchased the business for £4000 and remained a partner until the business became a limited company in 1897.

In 1870, the Newall telescope that had been a burden for so long was finally erected at Ferndean, Newall's estate near Newcastle. For a very short time it was the largest refractor in the world but it was to lose the title just a year later when the Washington Naval Observatory in the USA took delivery of a 28-inch refractor built by Alvan Clark.

After Newall's death in 1889, the telescope was transferred to Cambridge University Observatory where Newall's son Hugh was to become Professor of astrophysics. It was used in Cambridge until the1950's, after which time it was sold to the Greek National Observatory at Athens, where it remains to this day.

The end of the nineteenth century saw an upsurge in observatory construction both at home and abroad, and equatorial refractors continued to be the mainstay of the company's business, but orders for surveying equipment were still coming in. Many were used in the survey of India and in 1884 work began in Scotland on the Forth Bridge. Once again the orders for levels and theodolites came flooding in. Overcoming the earlier dividing engine problems, the Cooke instruments were once again lauded for their superb accuracy and quality of construction.

Cooke's now began to branch out, building observatory domes .as well as telescopes. Frederick Cooke devised a novel construction using papier mache panels and in 1893 they built the famous 'onion' dome for the Royal Observatory Greenwich. By the end of the century, Cooke domes could be found in astronomical observatories throughout the British Empire and beyond.

The latter part of the nineteenth century also saw rapid developments in Africa. Gold was discovered in 'them thar hills' and along with it the need for surveying instruments. Once again Cooke's order books bulged; they even opened a South African branch in Cape Town. By the end of the nineteenth century Cooke's had also diversified into military equipment and held patents for gun-sights and range finders, some of which saw action in the Boer war, which lasted until 1902.

In 1897 the company became a 'limited liability company' and after Fred's retirement in 1894, the optical department was in the hands of Dennis Taylor and was soon steered in a new direction — towards the new developments in photography. Cooke's soon devised a special 3 element lens that improved definition over a wide field. In 1893 it was awarded the Royal Photographic Society's medal for excellence. It was also in 1897-98 that Cooke's were asked by John Franklin-Adams to produce lenses for the proposed standard instruments to undertake a complete photographic survey of the heavens — the Franklin Adams Chart.

By the dawn of the 20th century, Cooke's was still a viable business, continuing to build astronomical telescopes, observatory domes, surveying instruments, military equipment and photographic lenses. In 1914 the First World War began and in 1915 Vickers acquired a 70% holding in the company, which began to concentrate on military equipment. Then after the war in 1922, Cooke's bought out Troughton & Simms to become Cooke, Troughton & Simms Ltd., operating under the Vickers banner where it remained producing a wide variety of optical equipment until final closure in 1988. — 'sic transit gloria mundi'.

To astronomers, both professional and amateur, the name Thomas Cooke of York will always be associated with equatorial refractors made during the 'golden period' at the end of the nineteenth century. They were made to the highest optical and mechanical standards which few if any instruments have equalled. My own 45 years experience with the Hampstead telescope has led to enormous respect for Cooke's work. The long focal length refractor is the ideal instrument for planetary and lunar studies and I have found few telescopes of equal aperture that can outperform it.

Our 6-inch Cooke refractor was manufactured in about 1898 and has been in use at the Observatory since 1923. It was finally donated to the Society by its owner George Avenell in 1928. It was originally mounted on a Cooke equatorial mount that was built to carry a 4-inch telescope. This mount was replaced with a stronger mount built by member Terry Pearce in 1976 and modified by Doug Daniels in 1980. At that time it was fitted with a new large diameter worm and wheel made by the late Hon. Member Ron Irving and the drive updated with a stepper motor drive unit designed and built by member Paul Clements. The Observatory, which celebrated its centenary in April 2010, continues its tradition of making this fine instrument freely available to visitors on public open nights throughout the winter months in accordance with the aims of the founders of the Hampstead Scientific Society — 'to promote an interest in all branches of science equally for the layman and the specialist.' During our centenary year some 1000 visitors to our Observatory took advantage of this unique facility, a service we can justly take pride in.

Forthcoming special events in January

On January 3rd-5th, BBC2 will be transmitting a series of programmes under the title of STARGAZING LIVE. The programmes will be hosted by Prof. Brian Cox and the timing has been arranged to coincide with the partial Solar Eclipse on Jan 4th , the Quadrantid Meteor shower — maximum also on Jan 4th and the Jupiter/Uranus alignment over the following few days. The programmes are designed to increase public awareness of astronomy. The HSS will be taking part in this event. The partial Solar Eclipse takes place at sunrise when from London, 67% of the solar disk will be obscured. Because a low south eastern horizon will be required, viewing will take place on Parliament Hill and not at the Observatory. Anyone interested please contact Simon Lang for details:- hampsteadobservatory@mulberry.myzen.co.uk.

On Saturday January 8th at 3:00 pm by kind arrangement with Peter Hingley, members are invited to visit the library of the Royal Astronomical Society at Burlington House Piccadilly. Members wishing to attend this visit should register their interest by contacting Doug Daniels as there are a limited number of places available:- starfields@tiscali.co.uk or by 'phone:- 020 8346 1056

Towards the end of the session, we received the resignations of Dr. Hemant Desai and Elizabeth Davies from the Council and at the end of the session Nayna Kumari had to stand down under the four year rule. We thank them for all their past work for the Society. Council then had to co-opt Martin Williams and Julia Daniels, in order to remain quorate and both were subsequently proposed and seconded as Ordinary Members of Council at the AGM, together with new Council members:- Roger O'Brien and Peter Stern.

We welcome Roger and Peter to the Council, which now has its full compliment of Ordinary members. Accordingly, your Council for the next session is as follows:-

Enclosed with this Newsletter, is the new Programme card for the 2010 — 2011 session. I am sure you will agree that once again our Programme Secretary has produced an interesting and wide ranging series of lectures for the coming year.

The new session of lectures begins on Thursday September 16^th when Peter Hingley from the Royal Astronomical Society will talk about ASTRONOMERS AND ODDITIES - I look forward to seeing you at the meeting.

British Science Association Branches Meeting

The BSA Branches Away Day will be held on Monday 13^th of September at Aston University Birmingham as part of the British Science Festival. All members who attend will receive a free weekly pass to the Festival which takes place 14-19 September on Aston University Campus and at Birmingham University Campus. The Away Day is open to all members. It will start at 10:am and close at 5:00pm. Lunch and refreshments are provided. Travel and accommodation expenses will be provided. If you wish to attend please contact.

Natalie Broadhurst, Regional Programmes Officer, Tel: 020 7019 4963 or by e-mail at:

Natalie.Broadhurst@britishscienceassociation.org For further details of the programme browse the website on:

www.britishscienceassociation.org/web/BritishScienceFestival/WhatsOn/Onlineprogrammessearch.htm

METHANE AND CLIMATE CHANGE

Doug Daniels

The debate on the role played by anthropogenic CO₂ in climate change continues. It has in some quarters, been singled out as the main cause of enhanced global warming, being produced by the ever increasing industrial activities of mankind. There is however, another possible culprit lurking in the shadows that has so far received much less media attention. This substance is 21 times more effective than carbon dioxide as a 'greenhouse gas' and there is mounting evidence that it has in the past been responsible for rapid climate change and species extinction. The substance is Methane CH4.

The analysis of gas bubbles trapped in deep ice cores obtained from polar regions has revealed enhanced concentration of methane at times of past planet-wide glaciations, which occur at approximately 100,000 year intervals. Methane is produced by bacterial activity and it was assumed that this was the cause of its increased concentration. Methane is produced anaerobically by bacteria in a process called methanogenesis which breaks down organic material particularly in marshland environments. In the presence of air, the gas forms an explosive mixture and its occurrence in deep mines was always a threat to safety before the invention of the miner's safety lamp. The presence of methane in planetary atmospheres could be interpreted as a signature of life, indicating bacterial activity and the recent detection of just such a methane signature in the Martian atmosphere, has caused some excitement, but methane occurs widely in the Solar System, produced by abiotic processes.

Apart from these natural sources, methane is also produced by the break down of organic compounds in landfill sites where we carelessly dispose of rubbish and by fermentation and bacterial action in the digestive tracts of ruminant animals and pigs and chickens bred in increasing quantities for 'fast food'.

It has been shown that vast amounts of methane exist on Earth in permafrost in polar regions and in the oceans in sedimentary deposits around continental margins. Under conditions of high pressure and low temperature, methane and water molecules combine to form clathrates or methane hydrates but the compound is unstable and it requires only a small increase in temperature or a slight decrease in pressure caused by falling sea levels for example, to release large quantities of the gas into the atmosphere. Just how much methane is stored in these conditions is as yet undetermined but it is estimated that it could be as much as 3000-4000 times the concentration found in the Earth's atmosphere today. Measurements of methane abundance in Earth's atmosphere have revealed a sharp increase in recent years. In 1998 methane abundance was calculated at 1,745 parts per billion (ppb). By 2008 this had risen to 1,800 ppb and in 2010 the figure is 1,850 ppb, higher than at any time in the last 400,000 years. Methane eventually breaks down in the atmosphere producing carbon dioxide and water.

During the 1980's, analysis of gas bubbles trapped in ice cores showed that the climate changes from glacial to warm periods were mirrored by rapid increase in atmospheric concentration of methane.1 It could well be the case that this increase is due to the release of methane from methane hydrates 2 There could be many processes that trigger the release. Changes in the temperature of ocean currents, lowering sea levels and earthquakes disturbing ocean floor sediments could all contribute to the destabilization of methane hydrates and release the gas into the atmosphere.

In view of its far greater efficiency as a 'greenhouse gas', the increased concentrations of methane in the Earth's atmosphere may be a greater cause for concern when determining the causes of climate change and global warming. This is another natural process over which we have (as yet) no control.

References

[1] E.G.Nisbet, Can.J.Earth Sci. 27, 148 (1990)

[2] J.P. Kennett, K.G.Cannariato, I.L. Hendy, R.J. Behl Science 288, 128 (2000)

Cezary Ludwik Kamieniecki — Caesar K (1950-2010) — Obituary

D.G.D.

In July 2010 we received the sad news that Caesar Kamieniecki had died aged 60 following a long illness. Caesar was a long standing member of the Society, having joined in the late 1960's, shortly after leaving school. His main interest was astronomy and it was during the first National Astronomy Week (NAW), in 1974 that our 'orbits intersected' and his enthusiasm soon earned him the position as a demonstrator at the Observatory. The 1974 NAW was organized to increase public awareness of astronomy and coincided with the apparition of the infamous Comet Kohoutek, promoted by the popular press as 'the comet of the century Although it never materialized as more than a faint blob, over 1800 visitors came to view it during the following weeks and resulted in 30 new members joining the Society. Caesar lugged his own home made 8-inch telescope up to the Observatory and helped to man the exhibition and show visitors other interesting objects as well as the dim comet. At that time he was still living with his parents in Crouch End. It was also in 1974 that I recruited him to the Astronomy sub-Committee as its Minutes Secretary, a position which he held until his illness forced him to give it up just two months ago — that is 36 years of continuous service to the Society. All the while that he was living in north London, in Crouch End and then later when he married Julie, in Edmonton, Caesar regularly demonstrated on public open nights at the Observatory. In more recent years, having fathered two children, Alexander and Katarina, the family moved to Betchworth in Surrey. Despite the considerable travelling distance involved he continued as a demonstrator, confining his duties mainly to Sunday morning solar observations, commuting to and from Surrey on his motorbike. He was a great motorcycling enthusiast

Caesar forged a career in IT troubleshooting, driving around the City on his motorbike, fixing computers for large companies. It was during these excursions that he got the idea to do the 'knowledge', eventually passing the test to become a licensed black cab driver. During the last few years, he supplemented his income with some part time cab driving. Whenever he was in north London, whether fixing computers or driving his taxi, he would often telephone me and drop in for a cup of tea and a chat. When his illness was diagnosed, he knew it was serious and he faced the treatment with great courage, enduring several sessions of chemotherapy. He openly discussed his condition and never once did I hear him complain about the 'rotten hand' that fate had dealt him.

Caesar was a devoted family man, very proud of his children and he was always prepared to work hard to ensure that they had a secure and comfortable life. He was an enthusiastic amateur astronomer and a faithful servant of the Society. During his long membership, he would have introduced hundreds of people to the delights of the telescope and he will be sorely missed by his many friends in the Society all of whom convey their deepest sympathy to his wife Julie and his children Alexander and Katarina.

The funeral took place on Tuesday 27th July with a Requiem Mass.at St.Joseph's RC Church, Dorking Surrey, followed by a short Cremation service at Randalls Park Crematorium, Leatherhead, Surrey and a reception at the Burford Bridge Hotel, Boxhill. The family requested NO FLOWERS, but donations to the following charities would be gratefully received made through: Sherlock and Sons Funeral Directors of Trellis House, South Street, Dorking, Surrey.

• Cancer Research UK
• The Fountain Centre of St.Luke's Cancer Unit, Royal Surrey County Hospital, Guildford, Surrey.
• The Hampstead Scientific Society

The next ordinary meeting of the Society will be held on April 15^th when Dr. Paul Upchurch from the Dept. of Earth Sciences UCL will talk on:

DINOSAUR EVOLUTION ON DYNAMIC EARTH.

The meeting on May 13^th will feature Dr. Chris Duffin from the Ravensbourne Geological Society and he will be taking a light-hearted look at the origins of scientific names in a talk entitled:

WHAT'S IN A NAME?

The Annual General Meeting will take place on June 17^th and as usual will be preceded by wine and cheese (£2.00) and if time allows, followed by a scientific entertainment.

The agenda will include the usual reports from Officers and Sections and the Election of five Ordinary Members of Council for the coming year. Council proposes the following:

Following the resignations of Hemant Desai and Elizabeth Davies, Council invites nominations to the above posts; such nominees shall be duly proposed and seconded and have agreed to serve if elected.

Geoengineering the Climate

P R Wallis, January 2010

In the December 2009 Newsletter I wrote an article on "Our Restless Planet" describing the considerable changes which have occurred naturally. Some have been cyclical from orbital and eccentricity changes, causing a sequence of ice ages, modified by the movement of the continents on their tectonic plates. The latter are also responsible for volcanic eruptions, which spew out green-house gases and make the Earth habitable. Finally I mentioned the modern industrial green-house emissions which will warm the globe, with climate changes of a yet uncertain magnitude. I mentioned the possibility of "geoengineering" to ameliorate these if necessary and said that the Royal Society would be reporting shortly.

This report has now been published[1]. In his foreword the President Lord Rees accepts that our discharge of green-house gases is driving changes to the climate and the long-term consequences will be exceedingly threatening, especially if nations continue 'business as usual' in the coming decades. He says that most nations now accept the need to shift to a low-carbon economy but warns that this may achieve too little, too late, and there could be a pressure to counteract the effects by geoengineering. The report aims to clarify the scientific and technical aspects of this, though far more detailed study would be needed before deployment could be considered.

The report classifies the many proposals into two types:

1. (CDR) which reduces the level in the atmosphere, allowing thermal infra-red radiation from the earth to escape more readily.
2. Solar radiation management (SRM) which reduces incoming short-wave (visible and UV) radiation reaching the earth, by deflecting sunlight or increasing the reflectivity (the albedo) of the atmosphere, clouds or the earth's surface.

The report regards CDR as theoretically preferable, as it aims to tackle the root cause. However it recognises that no proven CDR techniques are available yet. For example biomass combined with carbon sequestration is expensive and requires land which competes for agriculture and biofuels. Enhanced weathering involves major mining and energy costs and so far unknown environmental effects. Fertilisation of the ocean with iron is not yet understood. Capturing carbon dioxide from ambient air has potential but a high cost. On top of this, all CDR methods would be very slow, taking many decades and do not present an option for a rapid reduction of global temperature.

Turning to SRM, the aim would be to balance the global mean radiative forcing of 4W/m² that would arise from the doubling from pre-industrial levels of carbon dioxide in the atmosphere[2]. It is estimated that a solar reduction of about 2% would be required for space-based methods. For surface-based or cloud methods an increase in the earth's albedo from 0.31 to 0.32 would suffice, but mean rather large changes locally. Even if the global mean temperature is compensated correctly, there would be regional differences; for example the solar reduction would impact more greatly on low latitudes than high latitudes. Compensating for changes in precipitation might need a smaller reduction in insolation, but a great deal more needs to be done to understand the complexities of such changes.

Of the SRM techniques considered, the report assesses the surface albedo change as vastly expensive and doubtfully effective. Cloud albedo increase, by spraying salt for example, is judged feasible at moderate cost but could make big regional variation. The enhancement of the stratospheric sulphate layer is better known, as volcanic eruptions have demonstrated such cooling[3]. The cost of it is low so it must be considered as the most promising option. Significant research would be required to identify potential impacts on the hydrological cycle, stratospheric ozone and biosphere.

Space-based reflectors have the advantage that no direct changes are made to the earth's chemical environment, but the costs would be much higher than stratosphere aerosols. One form of space system places reflectors near[4] the Lagrangian L1 point, 1.5 M km from the earth towards the sun; it would present no obstruction for satellites or telescopes.

A characteristic of SRM is that once a system is emplaced, it would be very quick, achieving the cooling effect in a few years. Detailed modelling studies so far suggest that the resulting climate, though not matching the pre-industrial climate precisely, would be far less damaging than the uncorrected consequences of doubled carbon dioxide.

The report's overall view is that early and effective action should be taken to reduce the discharge of green-house gases, i.e. mitigation, and adapting to climate change. Internationally coordinated research and development is needed to clarify the feasibility and environmental impacts of the more promising geoengineering methods. If CDR methods can be demonstrated to be safe, effective, sustainable and affordable, they should be deployed alongside conventional mitigation as soon as they can be made available. SRM methods should not be applied unless there is a need to rapidly reduce or limit global temperatures and they should only be applied for a limited time.

Other views on the subject exist, of course. Green Peace objects to any research on geoengineering at all on the grounds that it might be used as an excuse to stop or delay mitigation. A recent article in Nature[5] argues conversely for early studies on SRM. They say that due to the carbon cycle's inertia even a massive programme of emission cuts and carbon dioxide removal will take many decades to slow warming discernibly. SRM is the only technique which could have a virtually immediate effect and could be a vital resource in case climate is more sensitive than expected. It is also cheap. We need to find out more about its effectiveness and risks soon and not leave it till an emergency.

PeterWallis

There can be no doubt that climate change is a real phenomenon. Throughout Earth's long history, the climate has constantly changed. The question is: to what degree are we, that is, mankind, contributing to the problem? It is becoming difficult to hold a rational debate on this subject, as there is now a firmly established 'official view' that: climate change is caused by the industrial activities of mankind increasing carbon dioxide concentration to dangerous levels Q.E.D.. Politicians are now involved and anyone who dares to question this 'official view' is in their minds, guilty of something akin to heresy, particularly when they can sense a fertile area for taxation. The media fueled as ever by sensationalism, prefers to predict impending disaster and the scientific community, ever eager to grab research grants has done itself no favours by 'doctoring' some results to fit current theories and making predictions that have been shown to be totally false. What is required is an unbiased appraisal of the facts.

The problem with this contentious subject is that it tends to confuse, climate change, short term changes in weather patterns and atmospheric pollution. There is no doubt that we must concentrate on reducing the levels of atmospheric pollution as this can only be regarded as a benefit to all and the reduction of man made 'greenhouse gases' may have some, as yet uncalculated effect on the changing climate but this effect pales into insignificance when compared to the major factors that are responsible for dramatic climate change on Earth. These are natural cyclic phenomena over which we have absolutely no control and we have not been studying them in detail for long enough to make accurate predictions. It should also be pointed out that despite the fact that meteorologists have at their disposal some of the most advanced computers on the planet, they still find it impossible to produce an accurate long-term weather forecast! In fact their daily predictions are often wide of the mark.

If our political masters wish us to take seriously the idea that anthropogenic CO₂is the main cause of climate change, then they should lead by example. They should formulate legislation to prevent the ever increasing light pollution in towns and countryside wasting energy illuminating empty public buildings and office blocks and tax aviation fuel to reduce unnecessary air travel. Aircraft pump CO₂ directly into the atmosphere which causes measurable change in local weather conditions. If we are to make substantial reductions in anthropogenic CO₂ then we will have to make a paradigm shift in our way of life. Many of the suggestions currently proposed are akin to merely rearranging the deck chairs on the Titanic.

Doug Daniels.

[1] "Geoengineering the Climate - science,governance and uncertainty", Sept 2009.

[2]IPCC 2007a

[3]That of Mt Pinatubo in 1991 caused a global cooling of 0.5^o C.

[4] Slightly nearer the sun, to compensate for its light pressure.

[5] Keith D W, Parson E and Morgan M G "Research on global sun block needed now", Nature 28^th January 2010.

The President and Council wish all members a Merry Christmas and a Happy New Year.

The next lecture meeting will take place on Thursday January 14th 2010 when the subject will be: THE PSYCHOLOGY OF CREATIVE PROBLEM SOLVING to be given by Professor Fairfid M Caudle from the College of Staten Island, The City University New York.

There can be no doubt that one of the biggest challenges to Creative Problem Solving at the present time is to be found within the continuing debate concerning Climate Change and enhanced Global Warming. There has been much written on this subject and quite a lot of it can only be described as 'Bad Science'. What we at Hampstead know for certain is, that our century-long meteorological records show a rise of 2 degrees Celsius in average temperatures recorded at the Observatory during this period. But whether this is due to natural cyclic phenomena or to the industrial activities of mankind, is still open to debate. In the following article, Peter Wallis reminds us of the numerous factors that can influence climate change on our Restless Planet.

OUR RESTLESS PLANET

Peter R Wallis

It would be wrong to think that our planet has persisted much as it is today. There are many natural causes which have produced changes. When it first condensed, some 4.5 billion years ago, from the solar nebula it was under intense bombardment. Indeed, early in its life, it collided with another planet, destroying its original form and losing much mass to space. This mass eventually condensed into our satellite, the Moon. Evidence of such turbulent times is clearly recorded in the moon's maria, as the Moon has insufficient mass to hold an atmosphere to protect it from impacts or erode the evidence.

Other influences have been more gradual and others of a cyclical nature. A Scotsman James Croll in 1912 first described the variations in the earth's orbit and the precession of the earth's axis of rotation. His work was followed up by Milutin Malenkovitch in 1920 and is usually associated with the latter's name. The significance of these cycles for the variation of solar energy input to the Earth was proved in 1976 by scientific studies of oxygen isotopes over half a million years in cores drilled from deep ocean sediments: they show a 100,000 year cycle due to orbit eccentricity, a 43,000 year cycle from the variation in axial tilt (between 21.5 and 24.5 degrees) and a 20,000 year cycle due to axis precession.

But there have been much greater and more mysterious changes to Earth's climate – the ice ages; the geological and fossil record demonstrates their occurrence. We now recognise that the Earth has generally been much warmer than it is today but has occasional periods lasting several million years during which there are alternating 'glacial' and 'interglacial' periods with a roughly 100,000 year cycle. At present we are in the Pleistocene Ice Age, which started some 3 million years ago in the northern hemisphere. The ice started to retreat 20,000 years ago and we are now in an interglacial stage. We now recognise that the glacial/interglacial sequence is caused by the astronomical cycles mentioned above.

We know of at least four earlier ice ages:

Permocarboniferous	300 million years ago
Late Proterozoic	600 – 800 million years ago
Early Proterozoic	2.2 – 2.4 billion years ago
Archean	2.9 billion years ago.

What on Earth – or off it – caused them?

It is probable that the major cause is the movement of tectonic plates on which the continents stand, first discovered by Wegener. At one time all the continents were together, Pangea, though they are now widely distributed. Wegener showed that at the time of the Permo-Carboniferous ice age all the southern continents were together, Gondwanaland, near the south pole. These varying dispositions of continents are important to the amount of solar radiation absorbed by the earth, as land has a greater reflectivity than sea. Snow and ice have an even greater reflectivity than either land or sea. So once ice forms there is an escalating move into an ice age. Indeed there is accumulating evidence that in the late Proterozoic ice age all the land and much, perhaps all, of the sea was completely frozen; it has been called 'Snowball Earth'.

So our next puzzle is: what brings an ice age to an end? The answer is green-house gases. Most people now know about them from the current political problem of global warming caused by our burning fossil fuels, coal, gas and oil, for modern industry, transport and heating. I'll put that on one side for the moment however. It is the emission of carbon dioxide from volcanoes which stops an ice age after a few million years. Without volcanoes we would be a frozen planet. We may take note that volcanoes are closely related to the tectonic plates of the Earth. They appear at ocean spreading ridges and at subduction zones, particularly around the Pacific Ocean.

Volcanoes may have saved us from a frozen world but they can also be disasters for our environment. There are some 'small' ones we know about as they are recent: Mt St Helens in Washington State 1980, Mt Pinatubo in the Philippines 1991. There are older ones for which we have records: Mt Vesuvius near Pompeii in 79AD, Tambora 1815, Krakatoa 1883. Geological evidence shows that there were also 'super volcanoes' in the past. The US Geological Survey defines these as discharging more than 1,000 cubic kilometres of ash, lava and pumice in a single event. There is believed to have been such a one, Toba, in Indonesia some 74,000 years ago.

The remains of supervolcanoes are not so easy to recognise as the smaller ones that leave mountains; supervolcanoes destroy mountain ranges. There was one in the Rocky Mountains of Wyoming which left such an enormous caldera instead of mountains that it failed to be recognised until 1870. It is Yellowstone National Park. It erupted some 640,000 years ago. In fact there is a 350 mile string of volcanic fields generated over the last 20 million years by a hot magma chamber over which the American Plate is moving. [1]

Apart from the localised effect of volcanic eruptions, lava and pyroclastic flow, there are many noxious gases discharged into the atmosphere. Sulphur dioxide leads to aerosols which can block the sun's radiation for years and further stress life. Some thought is turning to the possibility that eruptions could be responsible for some of the mass extinctions of extant life. Over the last 550 million years five great extinctions have been deduced from the fossil record as well as lesser events. We have some clues to what happened 65 million years ago as there is evidence of an asteroid or comet impact at that time on the Yucatan Peninsula. We can only speculate about earlier ones. Recently suggestions have been made that the Toba supervolcano 74,000 years ago may have been responsible for a disastrous reduction in the human population. We know from the study of mitochondrial DNA across the world that all humans now living are descended from a very small group at such a time.

So what conclusions can we draw? Our planet is a restless one, rearranging its continents, suffering repeated ice ages and green-house warming, massive volcanic eruptions and asteroid impacts. And we must expect from time to time the extinction of many species. Against this background the current political excitement of anthropic global warming seems a very small event. It may perhaps speed up the end of the Pleistocene Ice Age, but they have come and gone many times before. And the effect will be over when all the fossil fuels have been used.

Nevertheless our modern knowledge of the planet's history and our dominant position among its living species suggests we should do something to ameliorate the changes we are making. I am not sanguine that we will cease to exploit the coal, oil and gas, however many nuclear power stations and tidal barrages we build. The growth of the human population and its wants is inexorable.

We need to devote more thought and money to engineering the planet to slow down the rate of warming and the consequent rise in sea level. Schemes to deploy a sunshade in space have been dismissed as impossibly expensive. Moreover it might be very difficult to remove it if we discovered consequences which had not been foreseen. One relatively inexpensive solution has been put forward recently, to build a fleet of wind-powered automatic ships to sail the oceans, sucking up sea water and spraying it to encourage cloud formation and reflect sunlight back to space. [2] It has been calculated that a reduction by 1 or 2 % would be enough to cancel the green-house effect of our carbon dioxide emissions. It may well be that such a plan would be cheaper than the current politically correct one of reducing carbon dioxide emissions and it would be easy to modify the scheme if necessary. The Royal Society is expected to report on the idea shortly.

[1] Achenbach J,"When Yellowstone Explodes", National Geographic, August 2009. Back

[2]"Cloud ships on course to save the World", The Times, August 7th 2010 Back

Editor's Footnote. In their recent book: 'Global Warming & other Bollocks' [*], Professors Stanley Feldman and Vincent Marks, describe an online survey carried out in the USA, in which over 33,000 senior scientists have cast doubts about the supposed link between anthropogenic CO₂ and enhanced Global Warming. They believe that there is no evidence that the warming over the last century is 'outside the parameters of natural temperature variability'. Their conclusion is that:"It is unlikely that there is any significant warming caused by anthropogenic CO₂ and the 'officially' released scare stories are without scientific justification."

HSS OBSERVATORY & METEOROLOGY STATION CENTENARY APRIL 2010

Astronomers are currently celebrating the 400^th anniversary of the invention of the telescope and it is a sobering thought that in 2010, the Hampstead Scientific Society will celebrate the centenary of the foundation of its Observatory. So we have been in existence for a quarter of the entire history of optical astronomy. The meteorological station was also founded at the same time and can now boast a record of 100 years of continuous daily observations from the same site. Apart from a short period during the second World War, the Observatory has provided regular public open nights throughout the winter months and is the only observatory in London that can claim this level of public service. We feel that this centenary is an event that should be celebrated. Accordingly, the Astronomy and Meteorology sections will hold a special Open Day at the Observatory on Sunday April 25^th 2010. Members of the Society and invited guests are welcome to join us from 12:30 pm for a glass of wine and a light buffet and to view the small exhibition detailing the history of the Observatory & Met. Station.

In the meantime, just to remind you about the early years of the Society and the founding of the Observatory & Met. Station, I append a short history. A more detailed description can be found in: HAMPSTEAD SCIENCE 1899-1999. This excellent book edited by Philip Eden, is still available at £5.50 inc. postage from the President.

IN THE BEGINNING

The roots of the Hampstead Scientific Society go back to Christmas 1898 when P.E.Vizard learned that a Hampstead resident, Colonel Henry Heberden J.P. had a 10.5-inch reflecting telescope that he would be happy to donate to a Society that was prepared to make it available to members of the public. Thus it was that in July 1899 at a public meeting, the Hampstead Astronomical and General Scientific Society was formed. There were many trials and tribulations in the beginning but in 1910 the Observatory, as we know it today, was established, built on top of the newly constructed underground reservoir, the property of the then Metropolitan Water Board, on a site that was the highest point in London. It was also in 1910 that Patrick Hepburn came on to the scene. Hepburn was a keen amateur astronomer and was described in the Society's history by the late Ben Boltz, as 'a man of demonic energy'. Hepburn and Vizard were the first joint Astronomical Secretaries. 1910 was the year of the return of Halley's Comet but it was rather overshadowed by the Great Daylight Comet of the same year. Halley's Comet was observed from the Observatory in 1910 and again on its return in 1986 when on that occasion, over 800 members of the public came to see it.

In the early years, the Observatory enjoyed dark skies and many valuable observations were made. Hepburn became the Director of the Saturn section of the British Astronomical Association (BAA) and the Society's 1911 report contains drawings and a map of the surface features of Mars made by members. Over the years many planetary drawings made by members have been submitted to the various observing sections of the BAA and the Society has an archive of drawings of Mars covering many oppositions from 1911 to the present day. Over the years, many amateur astronomers and even a few professionals had their first introduction to observational astronomy at the Hampstead Observatory.

In the early part of the 20th century it was still possible to make valuable observations but the Society never neglected its prime duty to allow the public access to the telescope, a duty that it has met for a century. During the winter months, from mid September to mid April, the Observatory is open on clear Friday and Saturday evenings from 8.00pm-10.00pm and on Sunday mornings from 11am-1.00pm. Visitors can just 'turn up' and view interesting objects through the fine 6-inch Cooke refractor that was presented to the Society by George Avenell in 1928. Members of the section are on hand to show visitors such sights as Saturn's rings, Jupiter's cloud belts, the craters and mountains on the Moon and some of the brighter 'deep sky' objects - star clusters, nebulae and galaxies. On Sunday mornings we can safely project an image of the Sun to reveal sunspots and faculae, when they are present.

IMPORTANT ANNOUNCEMENT: SEPTEMBER MEETING

Well, we were expecting it really. When did builders ever quote an accurate completion date?

The work on the crypt room at the church is behind schedule and this means that we have had to change the venue for the first meeting of the session. We expect things to return to normal for the October meeting but to make sure, please check our web site.

Our first meeting on Thursday September 10^th will be held at: Age Concern Resource Centre, Henderson Court, Prince Arthur Road Hampstead NW3 on the corner of Fitzjohn's Avenue. This is the same location as the last two meetings of the last session. If you are in any doubt about the location, please consult the map which can be found on our web site.

The subject of the first meeting is: SCIENTIFIC METHODS IN ARCHAEOLOGY and the lecturer is Dr. Caroline Cartwright from the British Museum. The October meeting (Thursday 8^th Oct.) will hopefully be in the crypt room at St. John's Church and the subject will be: MAGNETIC FIELDS IN THE SOLAR SYSTEM to be given by: Professor David Price (Department of Earth Sciences) University College London.

Enclosed with this Newsletter you will find our lecture programme card for the forthcoming session. I am sure you will agree that once again our Programme Secretary, Jim Brightwell has put together a programme covering a wide range of diverse and interesting topics

As members who attended the AGM will be aware, Peter Wallis has now retired from the position of Hon.Treasurer. Our new Treasurer and Membership Secretary is John Tennant and members can help John by renewing their subscriptions, which fall due on October 1st, promptly. His address is: 121 Victoria Avenue Wembley MIDDX HA9 6PZ and it is printed on the back of the programme card. Why not take advantage of the reduced rate for payment made by Bankers Order?

COUNCIL FOR 2009/10:-	PRESIDENT/Astro.Sec	Douglas Daniels
.	GENERAL SECRETARY	Julie Atkinson
.	TREASURER/MEMBERSHIP SEC	John Tennant
.	PROGRAMME SECRETARY	Jim Brightwell
.	METEOROLOGY SECRETARY	Philip Eden
.	ASSISTANT Astro. Sec	Simon Lang
.	ORDINARY MEMBERS OF COUNCIL:-	Hemant Desai, Leo McLaughlin, Nayna Kumari, Elizabeth Davies.

'DIAMOND LIGHT' VISIT

We are arranging a visit to the Diamond Light Source at Harwell Science and Innovation Campus. See web site: http://www.diamond.ac.uk/home.html

Diamond Light Source is the UK national synchrotron facility. It generates brilliant beams of light, from infra-red to X-rays, which are used in a wide range of applications, from structural biology through fundamental physics and chemistry to cultural heritage. They have an open day on Saturday 3^rd October 2009. Visitors need to register to obtain free tickets. If you wish to attend this event, please contact: Rob Grant: Daytime telephone number: 020 7625 7744 (Rob or Sarah). E-mail with name Rob Grant no spaces and domain name semaphore-systems.co.uk (please use Subject: Diamond when e-mailing). The data required for each visitor is: Title, First Name, Surname, Car Registration Number (optional) & Mobility requirement (optional). We are offered the following advice/restrictions by the organizers:

"Due to the size of the facility, the guided tour will involve extensive walking, so we advise all visitors to wear comfortable footwear. Due to the nature of the facility, we do not admit visitors under the age of 5 and a minimum age of 10 years is recommended. We have very few restrictions due to health or mobility issues, although we ask you to tell us of any special requirements during registration."

The session typically lasts about 2 hours and consists of a talk followed by a guided tour of the facility.

TOTAL SOLAR ECLIPSE JULY 22^ND 2009

A total Solar Eclipse took place on July 22^nd visible from locations in south-east Asia. Several of our members including Jerry Workman, Jim Brightwell, David Brown and Trevor Law, travelled to several locations in China and south-east Asia to witness the event. The eclipse featured a very long - 6 minute totality and promised to be a spectacular event. However, poor weather conditions over the whole area obscured the eclipse. Jim Brightwell reports that from Shanghai it was raining during the entire event and brought back memories of the HSS eclipse expedition to Cornwall in 1999.

ANOTHER COMET COLLISION WITH JUPITER

On July 19^th 2009, Australian amateur astronomer Anthony Wesley was imaging Jupiter with a 14-inch Newtonian reflector from his observatory in Marrumbateman NSW. He noticed a dark spot in Jupiter's south polar region. At first he thought it was a shadow transit, but then observed that it was rotating with the planet. The dark spot had the appearance of the scars left by the impacts of comet Shoemaker-Levy in July 1994. It seems certain that Jupiter has once again suffered an impact from a comet or small asteroid. Members with moderate sized telescopes may like to observe this feature before it fades. It was located at approx LCM (System 3) 315°, high in the south polar region. Full discovery details and images are on: http://jupiter.samba.org.

A short while ago, I happened to watch the television quiz programme QI, which apparently stands for 'Quite Interesting.' During the programme, hosted by Stephen Fry, it was boldly stated that the Earth had two moons! This is of course totally incorrect. So to put the matter right I have written the following account.

EARTH'S SECOND MOON?

Apart from Mercury and Venus, the major (and some minor) planets of the Solar System are all accompanied by moons. In this respect, some are better endowed than others. I have now lost count of Jupiter's and Saturn's moons, every space probe visiting these planets seems to find more of them. But the Earth has only one. Yet there was a time in late 1986 when it was thought that the Earth might have a second moon.

On October 10^th 1986 Duncan Waldron developed a photographic plate taken with the UK Schmidt telescope at Siding Spring Observatory in Australia that revealed the presence of an unusual object. This object had in fact been recorded earlier in 1983 by Giovani de Sanctis and Richard West at the European Southern Observatory in Chile. The object appeared to be an asteroid. Its orbit was calculated by Paul Wiegert and Kimmo Innanen at York University in Toronto and Seppo Mikkola at Turku University in Finland.[1] The orbit was highly unusual and the asteroid, formally known as 1983 UH or 1986 TO, was named Cruithne after the leader of the ancient tribe of Picts who long ago roamed Britain, Scotland and Ireland.

Although Cruithne actually orbits the Sun, it is in a 1:1 resonance with the Earth and it orbits the Sun in 363.9 days, very close to Earth's orbital period, so it appears to be accompanying the Earth around the Sun. For this reason it has been described (incorrectly) as Earth's second moon.

Cruithne is a small body just about 5 km. in diameter. It rotates on its axis in about 28 hours and its closest approach to the Earth is about 12 million kilometres. Its orbit is inclined at about 19.8 degrees and since its orbit and the Earth's do not cross, there is little or no chance of a collision, which is fortunate as a 5km. asteroid could make a nasty dent!

Because of Cruithne's greater orbital eccentricity, its orbital speed and distance from the Sun varies more than the Earth's does, this produces an odd effect, as if Cruithne's orbit is kidney shaped as seen from our perspective, and as it takes slightly less than a year to complete a circuit, the Earth slowly lags behind. Then as the years pass, Cruithne seems to be catching the Earth up from the opposite direction. There then comes a time when Cruithne will be seen to make annual close approaches to the Earth. When this occurs, about every 385 years, the Earth's gravitational field will alter Cruithne's orbit by as much as half a million kilometres and similarly, Cruithne will alter Earth's orbit but only by a few centimetres. Because of this change, Cruithne will now take slightly more than a year to orbit the Sun. Then Cruithne's orbit appears to move away from the Earth in the opposite direction and instead of lagging behind, the Earth now appears to be overtaking Cruithne.

And so the strange celestial dance continues, taking 770 years to complete a cycle. With the Earth alternately speeding up and slowing down Cruithne's orbital period, the two partners move towards and then away from one another as they both orbit the Sun. Cruithne's next close approach to Earth (perigee) will be in 2292 when it will be just 12.5 million kilometres away. At such a time Cruithne will be at its brightest but at a magnitude of just +16, it will not be shedding any extra 'moonlight' on to the Earth, in fact it will be a very difficult object to find!

Cruithne, is not Earth's second moon, it is merely an asteroid, but one with a unique relationship with our planet, a relationship that has existed for millions of years and it is not alone. In recent years, three more near-Earth asteroids (NEAs) with similar resonant orbits have been discovered. It is not entirely out of the question that one or more of these bodies might at some time in the distant future actually become a true satellite of the Earth, but for now the Earth has but one moon.

[1]Paul Wiegert, Kimmo Innanen, Seppo Mikkola - Nature June 12th 1997. Back

WEATHER FORECASTERS GET IT WRONG AGAIN!

In April, the long-range weather forecast predicted a 'heat-wave' summer, some 'authorities' even warning of 'life threatening' temperatures and of course linking it with 'climate change' and 'global warming'. Well, once again the accuracy of long-range weather forecasting has been brought into question. If you want to know what the weather in August will be like, best look at the weather conditions in mid July.

It has long been a tradition in the British Isles, that if it rains on St. Swithin's day (July 15^th), then it will rain for the next 40 days and we will experience a cool wet summer.

'St. Swithin's day if thou dost rain, for forty days it will remain,
St. Swithin's day if thou be fair, for forty days 'twill rain nae mair'

Swithin was the Saxon Bishop of Winchester and when he died in AD 962, he left instructions for his remains to be buried outdoors. There he stayed for 9 years and then the monks decided to bring him in to the Cathedral and bury him in a smart shrine. When they attempted to remove his body on July 15^th AD 971, the legend says a great storm broke and it continued to rain for forty days.

Forty days of rain may be an exaggeration but there just could be a grain of truth in the old adage. At this time of year, if the jetstream tracks to the north of the country, weather systems bringing rain pass us by and we enjoy fine weather. But sometimes, the jetstream tracks towards the south of the country and the low pressure systems from the Atlantic bring rain and cooler conditions to much of the British Isles. For some reason, if the jetstream tracks south, it seems to get stuck and remains in that position for quite a while. It is this fluctuating position of the jetstream that determines our summer weather patterns and has done so for centuries. This year it rained on July 15^th and at the time of writing, August 7^th, the weather is still cool and wet. Weather forecasters nil, St. Swithin 1 - Q.E.D.

Doug Daniels.

The next two meetings cannot be held in the Crypt Room at St John's Church as it is currently being redecorated. They will instead be held in a room at The Age Concern (Camden) Resource Centre in Prince Arthur Road, a turning off Fitzjohn's Avenue, NW3. It's only a couple of hundred yards away.

The last lecture this session is at 8.15 pm on May 21^st by
Dr Peter Grindrod (Dept of Earth Sciences, University College London) on:
"Water on Mars: Where should we be looking?"

ANNUAL GENERAL MEETING on Thursday June 25th at 8 pm.

This will start with wine and cheese (£2 each) and the AGM itself will start at 8.45 and if time allows will be followed by a scientific Call My Bluff.

The agenda will include the usual reports from Officers and Sections and the Election of Officers and five Ordinary Members of Council for the coming year. Council proposes the following:

Secretary	Julie Atkinson
Treasurer & Membership Secretary	John Tennant
Programme Secretary	Jim Brightwell
Ordinary Members (max 5)	Hemant Desai	Elizabeth Davies
	Nayna Kumari	Leo McLaughlin

Council invites further nominations to the above posts and ordinary members; such nominees shall be duly proposed and seconded and have agreed to serve if elected.

A specific item on the agenda will be a proposal by the Council to appoint Professor Robert Weale to be a Vice President and Honorary Life Member.

Summer Visit. A Summer visit by the Society to the Royal Greenwich Observatory on Bank Holiday Monday the 4^th May has been organized by Hemant Desai.

2009 - THE INTERNATIONAL YEAR OF ASTRONOMY

Doug Daniels

This year, astronomers are celebrating the 400^th anniversary of the invention of the telescope and next year we at HSS will celebrate the centenary of our own observatory; so we have been around for a quarter of the time and in that 'last quarter' we have witnessed discoveries that have totally changed our perception of the Universe. These discoveries have been made possible by the evolution of telescopic optics and observational and imaging techniques all of which have seen gathered momentum in the last two decades culminating with the launch of the Hubble Space Telescope in 1990. Hubble at last gave astronomers their first opportunity to make observations unhindered by the Earth's troublesome atmosphere. The fact that it was initially placed into orbit with a defective mirror was soon forgotten once a corrector was fitted and for the last 18 years the results obtained have been truly staggering and exceeded all expectations.

Who can forget the fantastic images such as 'The pillars of creation' - actually the 'Eagle nebula' showing star formation. Or the evolving star V838 Monocerotis, or the one million pixel image of the Orion Nebula, showing dusty disks surrounding young stars - literally nascent Solar Systems. Hubble also showed us the fantastic beauty of planetary nebulae, the Cat's Eye, the Tea Tray and the Spirograph nebulae. But apart from the stunning images available free to all, Hubble has provided astrophysicists with masses of hard data in almost every aspect of astronomical research. The life cycle of stars, Black Holes, Gravitational lensing, Galaxy evolution and the distribution of gas in the Universe and refining distance scales via stellar parallax are but a few subjects from a list too long to quote in full. But to me, the outstanding image is the Ultra Deep Field image, a three-month exposure on a seemingly blank region of space that revealed countless galaxies in full bloom 13 billion years ago when the Universe was just 5% of its present age. Now to put all this into perspective, let us remind ourselves of some of the milestones encountered along our 400 year journey of discovery.

Astronomy is a very visual science. Everything we know or think we know about those remote sparks - the stars or the less remote moon and planets, has been obtained by systematic observations and records made over long periods of time by dedicated observers. For thousands of years, these observations were made with the naked eye and although we can still admire the results and marvel at the surprising accuracy of the work carried out by our ancestors using nothing more than cross staffs, quadrants and astrolabes, it was the application of the telescope to the night sky that made all the difference and elevated astronomy to the status of a proper science by divorcing it from its mystic astrological antecedents. Although such luminaries as Kepler were still not averse to earning a few extra quid by producing the odd astrological chart, if asked.

History tells us that the telescope was invented by a German optician - Hans Lippershey, who was working in Holland around 1608. Lippershey attempted to patent the invention, but his application was not allowed as there was evidence of a predecessor. This seems very likely as we now know that the English explorer Thomas Harriot was using some sort of telescope at about this time and he was making drawings of the moon with it. Harriot's telescope was a gift from a friend, it was described in his writings as a 'Dutch Trunk', so Holland seems to have been the epicentre of telescope production in the early 17^th century. It has always seemed strange to me, given the relatively simple optics involved, that the telescope was not invented centuries earlier. After all glass had been around for 3000 years and lenses from at least Roman times.

It was, however Galileo Galilei who made his own telescope and was the first person to apply it systematically to the study of astronomy, beginning in January 1609. In just a few months Galileo had clocked up a record of observational 'firsts': Craters and mountains on the moon, Jupiter's 4 main satellites, Venus' phases, Sunspots, hordes of stars in the Milky Way, Saturn's 'handles' - he didn't figure that one out but who would have at that time? Well, in fact Huygens did from his observations made a few years later in 1655. By this time telescopes were already showing distinct improvement. Huygens got rid of the concave eye lens and made a proper eyepiece consisting of two plano-convex lenses. This meant that from then on astronomical telescopes produced an inverted image but this was a small price to pay for increased definition and a better field of view.

Galileo's telescope was a very primitive affair. It used a simple plano-convex lens as an objective and a plano-concave lens for the eyepiece. Such a combination is only seen today in low power opera glasses. It would have provided a small field of view and bright images would have been fringed with false colour. Eliminating this 'chromatic aberration' was to occupy the minds of telescope makers for many years. In an attempt to reduce it, telescopes with monstrous focal lengths of 100 feet or more were constructed and even Isaac Newton declared the problem insoluble so in 1668 he went off to invent the reflecting telescope instead. But like many problems in science, given enough time and thought, a solution will often present itself. In 1758 John Dollond invented the compound achromatic object glass based on the earlier work of Chester Moor-Hall. Thanks to them and to Newton, astronomers now had two types of telescope to play with, the refractor and the reflector.

Initially, reflectors used mirrors made from speculum metal, an alloy similar to bronze. The early 18^th century saw the construction of some really large telescopes, it was the age of the Herschel's following William's discovery of Uranus in 1781, the first 'new' planet to be discovered and by an amateur astronomer observing from his back garden with a home-made telescope. Metal mirrors soon gave way to glass thanks to the work of Liebig, Steinheil and Foucault who demonstrated a method of chemically depositing a film of silver to the surface of glass. He also invented the Foucault 'knife edge' test for concave mirrors in 1851, which might have saved NASA a whole load of trouble had it been applied to the Hubble mirror before its launch in 1990!

In 1845 the biggest telescope in the world resided between two huge brick walls in a field in Ireland. The 72-inch reflector built by William Parsons the third Earl of Rosse at Birr Castle revealed spiral structure in certain nebulae. Just a year later in 1846, Galle and D'Arrest discovered Neptune at the Berlin observatory. Then at the middle if the 19^th century, photography made its tentative debut. In 1882, David Gill's photograph of the Great Comet of that year also revealed many star images and paved the way for star mapping using photography. A few years earlier in 1862 Thomas Cooke of York completed the 25-inch Newell refractor which was at that time the biggest refractor in the world but by 1897 the Yerkes refractor in the USA took the title and still holds it! At 40-inches, refractors had got as big as they were going to get; from now on the worlds largest telescopes would be reflectors and most of them would be in the USA.

The nineteenth century in England was a time of rapid industrial and scientific expansion and a time that saw the foundation of the Royal Astronomical Society and The British Astronomical Association. Astronomical discoveries were coming in thick and fast and a lot of them made by amateurs. This was the era of the skilful amateur mirror maker. Men like Calver, With and the Rev.W.E.Ellison produced telescope mirrors of unsurpassed optical quality whilst the UK professional instrument makers: Grubb Parsons, Cooke, Troughton & Simms, Adam Hilger, Wray & Browning tended to concentrate on refractors.

This then was the period in history when the Hampstead Scientific Society was founded - in 1899. Astronomy has always featured strongly in the Society's activities and just a few years after its foundation saw the erection of the Observatory in 1910. In the early years the Observatory site was dark and it was still possible to make original observations. Sadly, light pollution today prevents this but we still open to the public regularly during the winter months and we are proud of our small contribution to the massive bank of data that began to accumulate in Italy in 1609 and has continued to expand almost exponentially ever since.

The twentieth century saw the construction of the World's largest telescope the 200-inch Hale telescope at Mt. Palomar in the USA but it wasn't long before the Russians topped it with a 300-inch. Then began the serious 'Space race' that saw unmanned space probes sent to all parts of the Solar System even to Halley's comet and culminating with the USA manned Moon missions of the 1960's. But the great telescopic achievement of this time was the launching of the Hubble Space Telescope in 1990.

Now at the dawn of the 21^st century, astronomical telescopes have progressed to such a degree of sophistication that even the humble amateur can own a robotic instrument that can automatically locate several thousands of celestial objects. Using computers and the Internet, astronomers can manipulate telescopes thousands of miles away and direct them to secure images. Imaging using conventional film has been largely superceded by digital CCD cameras and amateurs can produce images with small telescopes equivalent or better than those obtained by professional observatories two decades ago.

And what of the professionals? They are now using multi-mirror telescopes, telescopes of enormous aperture using light-weight mirrors, dual instrument optical interferometers and adaptive optics that can neutralize the adverse effect of the Earth's atmosphere. Plans are afoot for the European Extra Large Telescope with a 30 metre aperture and for OWL - the Overwhelmingly Large Telescope, originally proposed to have a 100 metre mirror, but since scaled down to half that size. Still orbiting far above is the Hubble telescope, shortly to receive new instrument packages to extend its working life and there are plans for a new orbiting telescope 40 times as powerful as Hubble to ultimately replace it.

Galileo could not have imagined in his wildest dreams what he was setting in motion when he pointed that tiny crude telescope towards the night sky just 400 years ago.

My first action, in Council, was to propose Dr. Julie Atkinson, our General Secretary, to the position of Vice President. This proposal was ratified, as per the constitution, by members at the first general meeting in September. I am sure that everyone is aware that in any society, it is the general Secretary who does most of the work! Julie has been working hard for the Society for many years and her 'elevation' is scant reward. Nevertheless, she will be the first female Vice President in the history of the Society, reinforcing our intention that this should be an equal opportunities Society.

I now take the opportunity to pay tribute to our retiring President, Robert Weale who has served the Society diligently for some twenty years. In this respect, his was the second longest Presidency in the history of the Society, only just exceeded by Sir Flinders Petrie - 1910 - 1933. It is proposed that we offer Robert, Honorary life membership and Vice Presidency at the next Annual General Meeting. We must also recognize the contribution of Betty Weale, who for well over a decade, missed the last ten minutes of every lecture to attend to the tea urn and who generously made her home available for Council meetings for two decades.

Council is also sad to lose the services of our Membership Secretary, Elisabeth Fischer. Elisabeth has served the Society for thirty years - a working lifetime and the Society owes her an enormous debt of gratitude. In the future, the roles of Membership Secretary and Treasurer will be combined as Peter Wallis has also decided to retire at the next A.G.M. After that time, John Tennant will be our Treasurer and Membership Secretary. Members can greatly assist our Treasurer by making sure that their subscriptions are paid on time, better still, by bankers order.

As you can see from the foregoing, there are many changes taking place in the administration of the Society. These changes are the direct result of the second law of thermodynamics - entropy (disorder) increases with time! Your council is ageing and it is vital that we recruit younger members if the Society is to continue to thrive. There are still vacancies on Council, so why not take a more active role in your Society - many hands make light work.

Finally, I wish all members a very merry Christmas and a prosperous and interesting New Year.

WHEN IS A PLANET NOT A PLANET? - WHEN IT'S A TNO?

How many planets in the Solar System? Well, that's an easy one, at least it used to be! Prior to January 29^th 1930, the answer was eight but then the American astronomer Clyde Tombaugh developed the photographic plate that revealed the tiny image of Pluto; and then there were nine. This was not an accidental discovery. Years earlier it was found that the then furthest planet, Neptune, was not orbiting quite as it should. It was as if some unseen force was acting upon it, tugging it out of position and the logical explanation was that there must be another more distant planet waiting to be discovered. Percival Lowell, the astronomer best known for his eccentric ideas about life on Mars, was convinced of the existence of a trans-Neptunian planet and in 1905 he began to calculate a possible orbit and to begin an organized search for it at the Lowell Observatory. Lowell's calculations were not completed until 1914 and they predicted that the 'new' planet would be about 6 times the size of Earth and lie at about 4000 million miles from the Sun. Lowell did not live to see the fruits of his labours. He died in 1916 and the 9^th planet had still not been detected.

The search was resumed in 1919 by Humason at Mount Wilson, but he was also unsuccessful, so in 1929 Clyde Tombaugh returned to the problem at Lowell Observatory and just a year later, Pluto was finally discovered. It must be said that Pluto was a bit of a disappointment. It was much smaller and less massive than expected. Also, its orbit was a bit odd in that when Pluto is nearest to the Sun, it lies within the orbit of Neptune. Its distance from the Sun varies from 4,400 - 7,400 million kilometres. It orbits the Sun once every 248 years and has a diameter of just 2,300 km

Little more was discovered about Pluto until 1978, when J. Christie discovered that Pluto had a moon, subsequently named Charon. Charon turned out to be peculiar as well. It was quite large in relation to Pluto, being about 1/3 of Pluto's diameter and orbits at a distance of 17,000 kilometres every 6 days, which is the same time as Pluto's axial rotation. This means that an observer on Pluto would see Charon permanently stationary in the sky from one hemisphere, but totally invisible from the other hemisphere.

The fact that Pluto's size and mass were insufficient to account for the observed perturbations of Neptune's orbit indicated that there must be something else out there that was responsible, so the search has continued and since 1992 over 1000 Trans-Neptunian Objects (TNOs) have been discovered. Of these, only 132 have well defined orbits and only the seven largest have been observed in any detail. The largest of these, Eris, named after the Greek Goddess of discord and strife, is actually larger than Pluto with a diameter of around 2,500 km.; it was discovered by Mike Brown at Palomar in 2003-5. Its 45 degree orbit takes it out to 96.7 AUs from the Sun, nearly three times Pluto's mean distance and it has a tiny satellite named Dysnomia. Eris was at first categorized as a Scattered Disk Object (SDO) - yet another confusing category, and there are even more of those - Plutinos, KBOs (Kuiper Belt Objects) or Cubewanos and Centaurs to name but a few.

Five of the other major TNOs have been given names: Sedna, Orcus, Quaoar, Varuna and Makemake, formally 2005 FY₉, pronounced Makimaki, named for the Polynesian God of fertility. This was another discovery by messers Brown, Trujillo & Rabinowitz in 2005. One more has yet to be named, that is 2003 EL₆₁. Its shape is highly elliptical due to its rapid axial rotation of slightly less than 4 hours, and it has two small moons, so far also unnamed. Sedna and Makemake have diameters of around 1,700 km and Orcus and Varuna barely reach 1000 km. But at these distances, accurate sizing is difficult, relying on occultation timings and infrared measurements by the Spitzer Space Telescope.

The discovery of these TNOs, and the fact that Eris, is actually larger than Pluto, led to the recent demotion of Pluto to the status of 'Dwarf Planet' and the upgrading of Eris from an SDO to that of 'Dwarf Planet' as well, causing a certain amount 'discord and strife' in the process.

These recent re-classifications have caused astronomers to re-examine the qualities that define a planet. This might, at first glance, appear to be a simple task but in practice has proved to be much more difficult. The word 'planet' means 'wanderer' and was originally applied to any body 'wandering' against the background of the 'fixed' stars and at one time included the Sun and the Moon. More recently, the term has been applied to 'large' bodies that orbit the Sun in elliptical orbits that lie more or less in the same plane. But then one must be a little more specific about the term 'large'. Pluto is not that large and several of the TNOs are not much smaller. And what about the asteroids? The largest, Ceres is a fair size with a diameter of 900 km, considerably larger than the rest of the asteroids and only slightly larger than Varuna. Asteroids have also been called 'minor planets'. The problem becomes more difficult when we pass Neptune and enter the realm of the TNOs because at these distances it is easy to mistake a dormant comet nucleus for a TNO. This in fact has already happened to Chiron, an object found orbiting the Sun between Saturn and Uranus - formerly described as a Centaur (neither man nor beast!). Chiron was discovered in 1977 by T. Kowal but it soon became evident that Chiron was in fact a comet, when it underwent a flare up in 1988. As we probe further into the far reaches of the Solar System we are very likely to encounter more bodies from the Kuiper-Edgeworth belt - the distant reservoir for periodic comets.

Faced with the problem of classifying these new members of the Solar System, the International Astronomical Union met in Prague in August 2006 to re-define the term 'Planet' and they decided on three main categories, albeit less than 500 members (4% of the total membership), turned up to vote on the resolution. The three categories that they finally came up with are as follows:

1. Planets - The eight major planets from Mercury to Neptune are 'true' planets
2. Dwarf Planets - Pluto and any other 'round' body that has not cleared the neighbourhood around its orbit
3. Small Solar System Bodies - all other objects orbiting the Sun.

It seems to me that this classification is less than satisfactory. I have no objections to (1). But regarding (2), the condition 'round' worries me. How then do we categorize TNO 2003 EL₆₁? This body is quite elliptical in shape. And few planets can be described as truly 'round'- not even the Earth satisfies this condition. I am also unhappy about the 'clearing the neighbourhood' bit. Jupiter, for example, which is also not 'round', has at least 50,000 Trojan asteroids within its orbit! I have no real objections to category (3), but I feel that there is perhaps a better definition.

I should like to propose a new taxonomy for Solar System components called: 'The Hampstead Scientific Society Classification of Solar System Components' -- the HSSCSSC for short.

1. Major Planets - The eight major planets from Mercury to Neptune
2. Minor Planets - Any body greater than 2000 km. in diameter orbiting the Sun in an elliptical orbit not covered in (1).
3. Asteroids - Solid bodies of less than 2000 km. in diameter in orbit around the Sun.
4. Periodic Comets

Using the HSSCSSC system of classification, the answer to the question: How many planets in the Solar System? Is: eight major planets and two minor planets. All the rest being either asteroids or comets. But as the exploration of the Solar System continues, I am sure we can look forward to discovering even more new members of the Sun's greatly extended family and experience yet more 'discord & strife' attempting to classify them.

Doug Daniels (HSS President & Astronomical Secretary, August 2008)

I Know His Face

Peter R Wallis.

In recent years the technique of functional Magnetic Resonance Imaging (fMRI) has discovered interesting things about how our brain works. The technique originated as NMR imaging but the letter N stood for nuclear and was later dropped to avoid any connection with nuclear radiation, energy or weapons. But it still refers to the nucleus of the atoms which make up our bodies, in particular to the hydrogen atoms present in enormous numbers in our soft tissue. The nucleus of hydrogen is a proton and has 'spin'. In a strong magnetic field their spin axes can be aligned with the direction of the field. If disturbed, however, they precess like a spinning top around that direction; this can be detected as a small radio signal. In a field of 10,000 gauss the signal is at 42.65 MHz. If we apply a radio signal to the protons we can detect the resonance at this frequency. It can be as precise as 1c/s.

To use this for imaging of the body, we introduce a small extra magnetic field so that protons on one side have a slightly different resonant frequency to those on the other; the resulting spectrum shows the density of protons across the body. Repeating this in other directions allows us to measure the number in any specified position. MRI provides a non-invasive way of imaging the soft tissues of the body which are virtually transparent to X-rays.

But the technique of functional MRI goes much further than simple body-scanning. It is used to determine which neurons in the brain are active when we think or receive sensory inputs. Now neuron activity in the brain depends greatly on the supply of blood and we are able to determine which part of the brain is active by seeing where the blood is flowing.

As an example of what can be done, I shall report on some recent work on face recognition. We are remarkably good at recognising faces, even though they are all much the same: one nose, one mouth, two eyes and two ears. We are also good at discriminating emotions: anger, hate, sympathy or love. How do we do it?

About ten years ago brain imaging studies revealed that certain discrete regions of the temporal lobe fired up more strongly when people looked at faces rather than other objects. More recently Doris Tsao at Harvard Medical School and her colleagues located certain patches of neurons in monkeys which were dedicated to faces, in that they only fired when the monkey observed a face.

She has continued her studies on monkeys at Bremen University and reports that such 'face patches' are to be found in many places in the brain. She has used direct electrical stimulation and finds that stimulation in one face patch seems to cause reactions only in other face patches. The interconnectivity between them appears to be very strong.

She has also located 3 discrete patches in the frontal lobe, a region of the brain involved in goal-directed behaviour. One of the patches reacted particularly to emotional faces, unlike patches in the temporal lobe.

The picture emerging is that primate brains including ours have built-in face recognition capability. It seems that this must have evolved. Why? Because we are social creatures. Faces are important for our survival. We need to know who is a friend and who is an enemy.

One Hundred and Fifty Years Ago.

Peter R Wallis.

150 years ago, at a meeting of The Linnean Society on 1^st July 1858, the geologist Charles Lyell and naturalist Joseph Hooker communicated "On the tendency of species to form varieties; and on the perpetuation of varieties and species by natural means of selection." The papers presented were separately written by Charles Darwin and Alfred Russel Wallace; it was the first publication of the Theory of Evolution by Natural Selection. Neither author was present as Darwin had lost his youngest child to scarlet fever two days earlier and Wallace was seriously ill in New Guinea.

The story behind this has been described recently by Andrew Berry and Janet Browne in Nature [1]. Darwin had been working on the theory for the previous 20 years but had not previously published. Wallace, little known, was a poor itinerant naturalist, funding his travels since 1848 by selling exotic specimens to museums and collectors: somewhat of a contrast with Darwin's voyage on the Beagle as the captain's paying guest. After 4 years collection on the Amazon, Wallace headed home. Unfortunately he lost most of his collections and almost his life when the ship caught fire in mid-Atlantic and so lost his chance of showing his scientific credentials. In 1854 he set off for Southeast Asia to do it all over again.

In 1855 he was confident enough of his ideas on evolution to publish in a respected periodical [2]. It was clear to him that life consisted of a diversifying genealogical process; but the article failed to result in the scientific recognition he had hoped.

Early in 1856 Lyell told Darwin about the article and warned him that he might be scooped. Edward Blyth, an English naturalist in Calcutta also wrote to Darwin, "Wallace has, I think, put the matter well; and according to his theory the various domestic races of animals have been fairly developed into species". In May 1856, not especially worried about Wallace, Darwin began to write the long-planned tome he expected to call "Natural Selection". He opened a correspondence with Wallace, noting that Lyell and Blyth had drawn his attention to the article and sympathising over the apparent lack of scientific reaction. Better still, Darwin wrote that he agreed with Wallace's conclusions. Wallace was thrilled to receive this accolade from a major star in the scientific firmament.

Wallace's theory was still only half a theory. In February 1858 he glimpsed that other half, the mechanism. Recalling the writings of the economist Malthus, he recognised that better-adapted groups would gradually replace less well-adapted ones. He wrote a paper entitled "On the tendency of varieties to depart indefinitely from the original type." But then, rather than submitting it to a journal, he sent it directly to Darwin, the only person who had shown any interest in his work.

In June 1858 Darwin read the handwritten essay, writing on the 18^th June to Lyell, "I never saw a more striking coincidence. If Wallace had my MS sketch written out in 1842 he could not have made a better short abstract." Darwin had been forestalled and honour required him to let Wallace take the credit. But Lyell and Hooker persuaded him not to lose his claim as originator of the theory. Despite some misgivings, Darwin agreed and sent them selections from his unpublished writings to prove priority. These were published, together with Wallace's essay at the Linnean Society meeting on 1^st July 1858 and in the Society's Journal in August 1858.

Thomas Bell, the President of the Linnean Society guaranteed himself an unfortunate footnote in the history books by writing of the year1858, "The year that has passed has not indeed been marked by any of those striking discoveries which at once revolutionise, so to speak, the department of science on which they bear" It took Darwin's On the Origin of Species, 1859, to effect the revolution.

One year later, with it in his hands, Wallace was enthralled, "Mr Darwin has given the world a new science; his name should stand above that of every philosopher of ancient and modern times".

Berry and Browne discuss why the name of one so prescient and so generous faded from popular view, though it still inspires those who find the modern infatuation with Darwin stultifying. They suggest that the structure of science plays a part, in that precedence is everything; posterity ignores the second-placed. And Wallace always accepted his position. He wrote [3] "I feel truly thankful that Darwin had been studying the subject so many years before me, and that I was not left to attempt and to fail, in the great work he has so admirably performed".

Whereas Darwin continued to publish more evidence in support of the theory, Wallace wrote on a myriad of other topics, from the true identity of Shakespeare to the advisability of labour strikes. He was an outspoken socialist and was attracted to radical issues, later becoming a spiritualist and opposed to vaccination. Unlike Darwin he was not buried in Westminster Abbey, though a plaque was unveiled there in 1915.

Nevertheless, I believe that in this year of celebration we should also honour Alfred Russel Wallace as an independent founder of the Theory of Evolution through Natural Selection.

[1] Berry A & Browne J: "The other beetle-hunter", Nature, 26 June 2008 Back

[2] Wallace A R: "On the law which has regulated the introduction of new species", The Annals and magazine of Natural History, 1855. Back

[3] In a letter in 1869. Back

ANNUAL GENERAL MEETING on Thursday June 19th at 8 pm.

This will start with wine and cheese (£2 each) and the AGM itself will start at 8.45 and if time allows will be followed by a scientific brains trust.

Important Announcement: At the last meeting of Council on 10th April, Professor Robert Weale announced that he was retiring from the post of President after 20 years. In accordance with Rule 6b.of the Constitution, Council appointed Douglas Daniels as President for the coming session. Council thanked Professor Weale for his able leadership over so many years; they agreed to propose the award of Vice President to him at the AGM.

The agenda will include the usual reports from Officers and Sections and the Election of Officers and five Ordinary Members of Council for the coming year. Council proposes the following:

Secretary	Julie Atkinson
Treasurer	Peter Wallis and John Tennant (jointly)
Membership Secretary	Peter Wallis and John Tennant (jointly)
Programme Secretary	Jim Brightwell
Ordinary Members (max 5)	Hemant Desai	Elizabeth Davies
	Nayna Kumari	Leo McLaughlin

Council invites further nominations to the above posts and ordinary members; such nominees shall be duly proposed and seconded and have agreed to serve if elected.

Summer Visit. It is proposed to organize a Summer visit by the Society to the Greenwich Planetarium on Saturday 31st May. Details will be announced at the May meeting; they can also be obtained from Hemant Desai, 079470432968 . *** POSTPONED - DATE TO BE ANNOUNCED ***

OTHER WORLDS THAN OURS

Doug Daniels

When the Hampstead Scientific Society was formed, a little over a hundred years ago, our Solar System was regarded as unique. Although, in some quarters, there was speculation regarding the possible existence of other 'solar systems', the stars were regarded as being far too remote for any meaningful investigation. It is only in the last two decades that instrumentation and techniques have been developed to such an extent that we are now beginning to discover that planetary systems surrounding other stars may in fact be quite common. Astronomers have coined the term 'exoplanets' to describe bodies orbiting distant stars and more and more are being discovered year on year. At the time of writing, 270 exoplanets are known to exist and we can confidently expect this number to rise with the passing of time.

Searching for exoplanets is a difficult business and one that requires very sensitive instrumentation and much patience. Compared to the stars that they orbit, planets are relatively small bodies. As they shine by reflected light they are dim, by a factor of about 10¹⁰ in visible wavelengths, compared to their primaries. This makes direct observation almost impossible so astronomers have to apply more subtle techniques in order to detect their presence.

Many exoplanets have been detected by observing a star's wobble as it is pulled about by the orbiting planet's gravitational field. This is observed by measuring the shift in the star's position relative to more distant stars. This astrometrical technique requires very delicate measurements and can only detect massive planets. A refinement employs measurement of the Doppler shift in the star's spectrum. This shift in the wavelength of the visible light is proportional to the ratio of the masses of star and planet but it can be a lengthy process, as at least one complete orbit of the planet must be observed to obtain meaningful results.

Another technique is to observe the dimming of the light from a star when a large planet transits the star. This can only work in a small number of cases, when planets transit their primaries in our direct line of sight. Nevertheless, it is able to identify a Jupiter sized planet transiting a Sun sized star. During such a transit, the light from the star could decrease by as much as 1%. This amount of dimming is easily detectable with relatively small earthbound telescopes employing state-of-the art photometry. Even so it is necessary to check out a large number of possible candidates, seeking the few that might exhibit periodic dimming.

Another more complex technique makes use of the effect of gravitational lensing. In this case the light from a more distant star in the field of view, is bent by the gravitational field of the star/planet system and periodic changes in this distortion can infer the existence of a large planet orbiting the star.

All of these techniques can be exploited to reveal much more information about exoplanets. The Doppler technique can describe the planet's size, its orbital period, inclination and eccentricity and its mass. The transit method provides the planet's radius and orbital inclination. Combining these techniques provides the planet's mass, size and density, which in turn provides a clue as to the possible composition of the planet.

Most of the exoplanets so far discovered turn out to be 'gas giants' with masses between 150 and 1,000 times that of Earth with radii somewhere between 0.8 and 1.7 times that of Jupiter and many appear to be less dense than current theory concerning planetary formation expects. A possible explanation proposes that these less dense planets must be very hot bodies and have been designated as 'hot Jupiters'. They orbit very close to their parent stars unlike our own Jupiter, and these low-density planets may consist mainly of hydrogen and lack any substantial heavy elements in their cores. Such a planet is that known as HD 189733b, which has been closely observed with the NASA infrared Spitzer space telescope. This planet orbits its parent star at a distance of .03 AU, that is just 3% of the Earth/Sun distance. Because of the close proximity of the parent star, the planet's axial and orbital rotation periods have become synchronized so that it always keeps the same face turned towards the star. This planet has been observed being occulted by its parent star and emerging on the other side of its orbit. This has enabled Spitzer to measure the temperature difference between the 'day' and 'night side' of the planet, and found it to be about 230 degrees C. It also found asymmetry of the hottest and coldest regions, which do not correspond to points exactly facing towards and away from the star. From this we can conclude that the planet possesses a very turbulent atmosphere with strong currents and high wind speeds which circulate the heat. Spectroscopic observations have revealed the presence of atomic sodium, hydrogen and water in the upper atmosphere of HD 189733b and water has also been detected on two other 'hot Jupiters' -- TrES-1 and HD209458b.

It seems possible that a whole menagerie of exoplanet types can exist, ranging from hot and cool gas giants to 'super earths'- rocky planets with 5-10 times Earth's mass. At least two such planets orbit the star Gliese 581, a small cool star 75 times less luminous than the Sun. Their orbital positions suggest that they may exist in a region with a temperature range between 460° C to minus 55° C similar to temperatures on Venus and Mars. It is possible that these 'super earths' may be ocean planets having been formed in the cooler regions of the protoplanetary disk, and subsequently being forced to migrate inwards by a third Neptune-mass planet that also orbits the star.

Another interesting exoplanet recently discovered is that found to be orbiting the young star TW Hydrae, which is less than 10 million years old and situated 180 Lt.Yrs. from Earth. The planet -- TW Hya b. orbits its parent star in just 3.56 days at a distance of only 3.7 million miles from its primary and has a mass 9.8 times that of Jupiter. The planet appears to have swept clean a region of the protoplanetary dust disk up to 5.6 million miles from the protostar and may still be accreting material. At a mere 10 million years old, TW Hya b is the youngest planet to be discovered so far and could help to refine our understanding of the mechanism of planet formation from the protoplanetary disks surrounding young stars in the very early stages of planet formation.

So far our instruments and observational techniques have only succeeded in detecting massive planets, so what are the chances of discovering smaller Earth-like rocky planets? The search has already begun with space missions such as COROT, launched in Dec. 2006 and NASA'S Kepler probe due for launch in 2009. As imaging and detection techniques become more refined we can look forward to more significant discoveries in the not too distant future.

It is just 13 years since the discovery of the first exoplanet and new discoveries are being made almost on a monthly basis. We now know for certain that our own Solar System is certainly not unique and that throughout the Universe there are certainly many 'other world than ours'. Many of these 'new worlds' will be vastly different from our own but considering the potential numbers of 'extra Solar' planetary systems that must exist in such a vast universe, it is no great stretch of the imagination to envisage many Earth-like planets and some perhaps capable of supporting life. But what that life might be - well, that can certainly stir the imagination.

Source & Further reading: Nature Vol. 451/3 Jan. 2008.

1. Extrasolar planets. Dimitar D. Sasselov.
2. A young massive planet in a star-disk system. J. Setiawan, Th. Henning, R. Launhardt, A. Muller, P. Weise & M. Kurster

MORE DEBATE ON GLOBAL WARMING

Doug Daniels

The scientific community appears to be polarising into two distinct factions: those who think that climate change is all 'our fault' and those who don't.

I think it fair to say that there is no longer any doubt that the phenomenon is 'real' and that there is certainly more than enough evidence that average pan-global temperatures are at present increasing with time. Our own meteorological records at Hampstead Observatory, which span almost a century from the same site, indicate that from Hampstead at least, average temperatures have risen by about 1° Celsius during the last 100 years. While there is almost total agreement that this is happening, there is little or no agreement as to the cause.

The opinions of the two main factions are that (1) the problem is caused by mankind contaminating the atmosphere by burning fossil fuels and consequently increasing the concentrations of 'green-house gases' or (2) that climate change is a natural cyclical phenomenon and has little or nothing to do with any of the activities of mankind.

Over geological time, the Earth's climate has changed many times. There have been periods when the planet has cooled down dramatically causing catastrophic species extinctions and at other times it has heated up producing the same results. These episodes have occurred long before the evolution of Homo Sapiens. It is argued that such fluctuations in climate must occur given the mobility of the continents caused by plate tectonics and the variations in Earth's axial tilt, axial direction and perihelion distance (due to variations in orbital elipticity) - the famous Milancovic Cycles.

But there is also a sub-division of the 2nd faction that postulates that the main cause of Earth's climate change is due to variability in the energy output of the Sun. The Sun is a variable star and despite its proximity, there is still much that we do not know concerning its long-term cyclic phenomena.

It has recently been suggested ^{[1] [2]} that the Earth is not alone in experiencing enhanced global temperatures. In 2005 The Mars Global Surveyor and Odyssey missions (NASA) indicated that the Martian ice caps had been steadily shrinking for three successive summers. These observations have led Habibullo Abdussamatov^[3], head of space research at Pulkovo Observatory, to come to the conclusion that Mars too is experiencing enhanced global warming and that the culprit is the Sun. According to Abdussamatov, there is a pattern of solar fluctuations that fits the observed changes in the climate patterns of both Earth and Mars. He predicts that the solar radiation, which began to decline in the 1990's will continue to fall until 2040 and this will actually lead to dramatic cooling of Earth's climate in 15-20 years.

These observations are not supported by the anti CO² adherents, who attribute Mars' temperature increase to the Martian version of Milancovic Cycles. These are more enhanced on Mars due to its greater orbital eccentricity and by the fact that Mars does not possess a large moon like ours to dampen the effects. They say that it is 'pure coincidence' that both Earth and Mars are experiencing enhanced global temperature at this time. The debate continues.

[1] Kate Ravillous National Geographic News Feb. 28 2007 Back
[2] & Steinn Sigurosson- Global Warming on Mars Back
[3] Pulkovo Astronomical Observatory Back

Peter R Wallis

HSS Lecture Meetings in the Crypt Room at St John's Church, 8.15 pm.

• December 13th: Professor Matthew Davidson "Sustainable Energy"
• January 17th: Dr Philip Jones "Laser Tweezers & applications to Biology, Chemistry & Physics"
• February 14th: Dr Oliver Rackham "Woodlands"
• March 13th (Science Week): Jerry Stone "Colonies in Space"
• April 17th: Dr Roger Wise "Welding Plastics, from rubber to wood"

THE STRANGE CASE OF COMET HOLMES

Douglas Daniels

Towards the end of October we received news that Comet Holmes had suffered a sudden, major outburst. The comet was initially discovered on November 6th 1892 by Edwin Holmes working in London. This was just 7 years before the formation of the HSS, and gives us a clue to the clearer skies enjoyed by urban observers at that time.

Comet Holmes is one of the Jupiter family of comets with a perihelion of 2.2AU and it has experienced similar outbursts before. At the time of its discovery it had remained bright for some weeks but then faded and erupted again in mid-January 1893 raising its brilliance to naked-eye status. During following returns, the comet remained very faint and this year was expected to be at about 17th magnitude. But comets are unpredictable beasts, that is part of their charm, and Holmes had a surprise in store for us this year.

On the24th of October, the outburst was reported by amateur observers working in Spain. At the time Holmes was past its earlier perihelion in May, but close to opposition. Original estimates put its magnitude at +2.5, rendering it an easy naked eye object in Perseus. This is a 14 fold increase in magnitude equivalent to almost a million fold increase In brightness!

During the outburst, Holmes appears to have thrown off a huge shell of material which appears to consist largely of dust, giving the comet an almost circular appearance with a bright central condensation and a tiny off-centre star-like nucleus. With an angular diameter of 15 arc/mins. and considering its distance, this equates to a physical diameter about the same as the sun! At the time of the outburst, the comet was situated in the constellation of Perseus, near alpha (Mirfak), close to the galactic equator and almost on the zenith at midnight.

We were fortunate to have had several clear nights between Oct 28th and Dec.1st and this gave us the opportunity to observe and take images of the development of the outburst. During this period, the dust disk expanded to approx. twice its original size and its brightness gradually declined. The bright central condensation became more elongated and the following edge of the dust disk became fuzzy and indistinct. At the time of writing on Dec.1st Holmes was no longer visible to the naked-eye from London and the dust disk had expanded to well over ¾ degree.

Holmes is presently performing a loop in Perseus and will therefore be visible well into the new-year. This gives us the opportunity to continue to monitor its progress. It may well be the case that the major outburst is now over, but it has brightened again in the past. It will be worth keeping it under surveillance in case of further activity as it is in an ideal location close to the zenith, well above atmospheric pollution

Holmes is a strange comet and the reason for such an outburst remains unclear. It has been suggested that a collision with some other small body may have caused it. This would seem very unlikely since the comet has undergone similar outbursts before, shortly after its discovery in 1892 and again in 1893. One collision might be a possibility, but three seems unlikely in the extreme. It seems more probable that the periodic outbursts are a result of fractures of the nucleus produced by the release of pent-up gravitational tidal stresses, causing a sudden violent eruption of volatiles from within. Whatever mechanism may be responsible, the result was very dramatic, increasing Holmes' brightness by a million times, over 14 magnitudes, and throwing out a dust/gas shell that rapidly expanded to more than twice the diameter of the sun. Holmes' brief 'blossoming' may now be coming to an end and it will revert to its former state, indistinguishable from the faint background stars of the Milky Way through which it is still slowly progressing.

Holmes may well turn out to be the most photographed comet of recent years. With many amateurs and professionals alike using 'state of the art' imaging techniques and the comet occupying an ideal position close to the zenith in the northern hemisphere. Holmes has given many astronomers a wonderful opportunity to obtain a full pictorial record of the rapid development and decline of a unique comet.

To see images showing the development of Comet Holmes.

VENUS EXPRESS

Peter R Wallis

The three Terrestrial planets with atmospheres in the solar system are Venus, Earth and Mars; they have many features in common. Venus and Earth, in particular, are nearly the same size and are at similar distances from the Sun. The table below summarises the main astronomical characteristics of the two planets:

Indeed the similarities are so great that astronomers consider that they were formed from the solar nebula at similar epoch and position and were constituted of the same materials. Today, however, they have remarkably different surface conditions. On Earth the most volatile compound is water, and forms oceans which are 300 times as massive as the atmosphere. On Venus there are no oceans as the surface temperature, 457°C, is too high for water to be liquid; it is only present in the atmosphere and in trace amounts. Carbon dioxide is present in both planets but is distributed differently. On Venus it is the major constituent of the massive atmosphere, which creates a pressure at the surface 92 times that on Earth; on Earth the carbon dioxide is mainly locked up in limestone deposited from the oceans.

The big question is why the two planets have evolved to be so different today. More than 30 spacecraft have made the trip to Venus since the American Mariner 2 in 1962, to establish the basic parameters of the planet and answer this question. Now the European Space Agency has sent the Venus Express spacecraft to study the atmosphere in detail. It was launched from Baikonur in Kazakhstan on 9th November 2005 and became fully operational in June 2006. In Nature of 29th November 2007 there are 8 papers (pp 629 - 662) presenting the results of the first year's observations; there is also a commentary paper (p 617) by Andrew P Ingersoll to summarise the results.

Ingersoll speculates that being closer to the Sun may be the reason for the different evolution of Venus. More of its original ocean of water would have been in its original atmosphere. But water vapour is a potent green-house gas, warming the planet further, and all the ocean could boil off. The water vapour could be split into hydrogen and oxygen by the ultraviolet of sunlight, the hydrogen escaping into space and the oxygen oxidizing the crust. Hydrogen is lost faster to space than its heavier isotope deuterium, so the fact that the ratio of deuterium to hydrogen on Venus is 150 times that on Earth suggests that this was indeed how the water was lost. The massive atmosphere of Venus is 96.5% carbon dioxide, also a potent green-house gas. It has a depth of 100 km, with a thick cloud layer between 40 and 60 km altitude composed primarily of sulphuric acid droplets.

The leading paper [1] presents a summary of the atmospheric conditions on Venus, including the circulation in the lower and middle atmosphere and in both North and south polar vortices. The Planet has no internal magnetic field and the solar wind can interact directly with the upper atmosphere above 100 km. The escaping ions are mainly hydrogen and oxygen, consistent with the continuing loss of water. The paper concludes that the two planets were similar initially but evolved differently. Earth's oceans converted most of its atmospheric CO₂ to carbonate rocks while Venus lost most of its water to space.

Venus is also a very slow rotator; it spins once relative to the stars every 243 Earth days. Oddly, it spins backward to its orbital motion. Indeed, the atmosphere also spins backward. It is not known how it got into this odd situation. This slow spin may be the reason for its lack of a magnetic field.

One of the papers [2] reports measurements by the Venus Express magnetometer in the ionosphere which reveal strong, circularly polarized electromagnetic waves with frequencies near 100 Hz. They appear as bursts of radiation lasting 0.25 to 0.5 s; they appear to be whistler-mode signals generated by lightning discharges. The existence of lightning on Venus has been a matter of controversy; this is now confirmed. The mechanism of generating it is not yet known. However, members will remember our October lecture by Dr Peter Grindrod on "Volcanism on Venus". Radar studies of the planet's surface show many volcanic features, but are they active or extinct? Perhaps active volcanoes are the source of Venus's vestigial water and its lightning discharges.

[1] H. Svedhem, D.V. Titov, F.W.Taylor & O. Witasse, "Venus as a more Earth-like planet", Nature, 29/11/2007, p629. Back

[2] C.T.Russell, T.L.Zhang, M.Delva, W. Magnes, R.J.Strangeway & H.Y. Wea "Lightning on Venus inferred from whistler-mode waves in the ionosphere", Nature 29/11/07 p 661 Back

The first lecture on Adult Brain Stem Cells by Dr Kaylene Young of UCL will take place at 8.15 pm on Thursday 13th September in the Crypt Room at St John's Church, Hampstead.

Council for 2007/8

Membership of Council for this year is:

President - Professor Robert Weale

Secretary - Julie Atkinson

Treasurer - Peter Wallis

Membership Secretary - Elisabeth Fischer

Programme Secretary - Jim Brightwell

Ordinary members - Aileen Cook, Elizabeth Davies, Hemant Desai, Nayna Kumari, John Tennant.

Astronomy Secretary - Doug Daniels

Assistant Astronomy Secretary - Simon Lang

Meteorology Secretary - Philip Eden

THE ANTIKYTHERA MECHANISM

Doug Daniels

At the beginning of the last century in 1900, just a year after the H.S.S. was founded, some Greek sponge divers working off the coast of the Greek island Antikythera, discovered the wreck of an ancient ship on the seabed some 42 metres below sea level. Amongst the various items of the ship's cargo to be salvaged were amphorae, pottery, coins, jewellery, glassware, statues and in particular one item that ought to have made a profound impression on the archaeologists of the time; but somehow failed to do so. The object in question was a fragment of what appeared to be some mechanical device. A very corroded circular bronze wheel with two spokes at right angles to one another showed evidence of gear teeth on its perimeter and there were less obvious traces of other geared wheels embedded in the highly petrified and encrusted structure that was still attached to the decomposed fragments of a wooden case. The amphorae and other artefacts from the ship's cargo enabled archaeologists to date the ship's demise to about 85 BC. Moreover, many of the salvaged artefacts appeared to have originated from the island of Rhodes. It is strange that the recovery of any mechanical device that was over 2000 years old did not cause more of a stir in the world of archaeology at the time of its discovery. This is especially so, since mechanical 'clocks' with geared wheels did not come on to the scene in Europe until the fourteenth century. To discover a device with this level of mechanical sophistication and of such great antiquity is absolutely staggering. The more so since recent investigations into the design and structure of this remarkable device have shown it to be a complex astronomical instrument, a computer that could show the positions of the Sun and the Moon relative to the Zodiac, the phases of the Moon, the positions of planets and it could even indicate when eclipses would occur.

Recent investigations of the device using high resolution X-ray tomography have shown it to be far more complex and sophisticated than initially suspected. The mechanism has a train of over 30 toothed gear wheels and the circular dial is covered with many inscriptions of astronomical significance. These inscriptions have only recently been enhanced and deciphered using new scanning techniques. By counting the number of teeth on the gears and referring to the inscriptions, it is possible to understand how the device may have worked. It would appear that the large surviving dial showed the Metonic cycle - 235 months - 19 years, the time taken for the Moon to return to the same phase on the same day of the year. Another dial would have displayed the 223 month Saros cycle used to predict Solar and Lunar eclipses. Yet another dial recorded the 76 year Callippic cycle, an improvement on the Metonic cycle with an error of just one day in 553 years, equivalent to four Metonic cycles minus one day. Although these lunar cycles were well known to earlier Babylonian astronomers, to actually replicate them mechanically in a device of such antiquity is truly amazing. But possibly the greatest discovery was that the device also featured two eccentric gears coupled with a pin sliding in a slot that took account of the apparent irregular motion of the Moon due to its elliptical orbit about the Earth.

This familiarity with the motions of Solar System bodies begs the question: 'Who made it?' The fact that the ship that was carrying it appears to have come from Rhodes may provide a clue. During the first and second centuries BC, Rhodes was the centre of the astronomical research world. From 140 BC until his death in 120 BC, the Greek astronomer Hipparchus worked there and he was succeeded by the philosopher Posidonius.

Hipparchus had already worked out a theory to account for the Moon's irregular orbital motions based on epicycles and it is this feature that is incorporated in the mechanism. A further clue to the device's origins may come from the writings of the Roman lawyer Cicero in the first century BC. Cicero, who spent some time on Rhodes as a student, later wrote a description of an instrument that he had seen and which he attributed to Posidonius. The instrument that he described, accurately depicted the movements of the Sun, Moon and planets about the earth. Could this have actually been the Antikythera Mechanism? We may never know for certain but the very existence of this remarkable instrument engenders enormous respect for its designer and maker, whoever they were. The fact that such a complex astronomical computer was constructed at such an early date raises further questions. Why was this advanced technology not continued and further developed? Why was it on that ship and where was it going? Did its tragic loss effectively hold back technological advance in astronomical instruments for thousands of years? It would appear that the Antikythera Mechanism is a truly unique and anachronistic artefact that provides us a glimpse of a technology that existed briefly in the eastern Mediterranean that went largely unrecorded for two millennia. (For a more detailed description of the origins, workings, and reconstruction of the Antikythera Mechanism read Nature 30 November 2006.)

Our Island

Peter R Wallis

Britain owes much to being an island - its maritime capability, its relative freedom from invasion. But it was not always so. It is known that it was once joined to the continent of Europe if only because during a glacial period, of which there have been many during the last 3 million years[1], the sea level is more than 100 metres lower, leaving the North Sea and English Channel as dry land. But there was once also a more permanent land bridge across the Dover strait, a bridge of chalk rock called the Weald-Artois Anticline. Then the North Sea and the English Channel were separate embayments with separate river systems.

The destruction of this barrier has been a matter of controversy, with little evidence to decide the mechanism. Smith [2], in 1985, proposed that a catastrophic flood eroded it. It is only now that we have clear confirmation from a study by Gupta et al [3] of the morphology of the bottom of the Channel. They use detailed sonar data provided by the UK Hydrographic Office and show that the sea bed rock has been deeply eroded by two massive floods. They are able to make comparison with the Channeled Scabland region of Washington State US caused by the Lake Missoula mega-flood.

A commentary by Gibbard P, another worker in the field, is in the same issue. Gibbard considers that the Weald-Artois anticline was formed ½ million years ago during a major extension of the continental ice-sheet into lowland Europe and Britain and was 30 m above today's sea level. Thus the Scheldt, Rhine, Meuse and Thames rivers would have had no outlet either north or south and built up a vast glacial lake covering the southern part of the North Sea and the low countries. This eventually overtopped the barrier, which was eroded away by the torrential flow. Gupta estimates that the peak flow was about one million cubic metres per second, perhaps the largest seen on Earth. He says that the breach reorganised the palaeodrainages of Britain and north-west Europe by re-routeing the Rhine-Thames river flow through the Channel river during low sea-level glacial periods. It led to separation of Britain from continental Europe during high sea-level interglacial periods, with consequences for early human presence. He also suggests that the massive pulses of freshwater into the eastern Atlantic could have caused episodes of climatic cooling through weakening of the Atlantic overturning circulation as happened more recently with the flooding from Lake Agassiz only 8,000 years ago.

[1] For background information on ice ages see HSS Newsletter for April 2005. Back

[2] Smith A J, "A catastrophic origin for the palaeovalley system of the eastern English Channel", Mar Geol 64, 1985. Back

[3] Gupta S, Collier J S, Palmer-Felgate A & Potter G, "Catastrophic flooding origin of shelf valley systems in the English Channel", Nature, 19th July 2007. Back

May 24 Nick Ward (Institute of Neurology, UCL) on The Plastic Brain: Adaptation with Age, Experience & Injury.

ANNUAL GENERAL MEETING on Thursday June 21st at 8 pm. This will start with wine and cheese (£2 each) and the AGM itself will start at 8.45 and if time allows will be followed by a scientific entertainment on Domesday Scenarios.

The agenda will include the usual reports from Officers and Sections and the Election of Officers and five Ordinary Members of Council for the coming year. Council proposes the following:

Secretary	Julie Atkinson
Treasurer	Peter Wallis
Membership Secretary	Elisabeth Fischer
Programme Secretary	Jim Brightwell
Ordinary Members	Aileen Cook
	Nayna Kumari
	John Tennant
	Hemant Desai
	Elizabeth Davies

Council invites further nominations to the above officer posts and ordinary members; such nominees shall be duly proposed and seconded and have agreed to serve if elected.

A special item will be the ratification of the MoU with the BA. Please see the website for details.

Visit to the Regional Planetary Imaging Facility

Sunday afternoon, 27th May at University College London, organized by Julia Daniels.

Dr Peter Grindrod of UCL has agreed to come in specially to host the joint visit by members of the HSS and the Amateur Geological Society. He will present some of the amazingly detailed images of planetary surfaces that we are now getting from NASA and ESA for study by geology students. There will also be a display of maps and globes of Mars, Venus, The Moon and other satellites with solid rocky surfaces.

It may be necessary to limit the number of visitors. Dr Grindrod said that about 30 would be possible but the room is small and with only 10 chairs. He will therefore stay open from 12 to 4pm and Julia will allocate staggered arrival times. There will be 4 groups, arriving at 12noon, 1pm, 2pm, and 3pm. You can stay longer than an hour; it's just the seat that you are booking.

To book a place and time slot, and to receive a map and directions to the RPIF, please give your name, phone number and address to Julia Daniels (tel: 020-8346 1056, 25 Village Rd, London N3 1TL) or see her at the next meeting.

The Centre of the Galaxy.

Peter R Wallis

An article in Nature [1] reviewed recently our knowledge about the mysteries at the centre of our galaxy. For many years astronomers have suspected that a massive black hole is there, seen by us in the direction of the constellation of Sagittarius. The first hint came from Shapley's study of globular star clusters [2] which he found to be concentrated there. In the 1930s Karl Jansky of Bell Labs detected a strong source of radio noise from that direction but it was not until 1968 that the source was precisely located and seen in the infra-red to be the 'star' Sagittarius A (Sgr A*). This was a time when astronomers had seen many very bright objects in the universe called 'Quasars' which were so powerful that it seemed possible that they were powered by black holes. Donald Lynden-Bell [3] suggested in 1969 that our galaxy and its neighbours could all have 'dead quasars' at their hearts. The implication was that Sgr A* could be a massive black hole.

Confirmation of this was not easy as telescopes using visible light could not see clearly through the clouds of dust. It is only in recent years that large radio arrays, infra-red and X-ray telescopes, detectors in orbit and adaptive-optics telescopes on earth have been able to reveal the region close to the central engine. It seems to be very small, perhaps no larger than the solar distance but containing a mass of 4 million suns. Yet it isn't very bright! Perhaps that is as it should be for a 'black' hole, which cannot itself emit any radiation. But radiation can be expected from the matter falling onto the accretion disc around it. Maybe this emission is variable according to the amount of gas and stars available at any time.

There is some information that Sgr A* was perhaps 100,000 times brighter in the X-ray spectrum in the 1950s than today, probably because it swallowed a planet's or star's mass of gas in one gulp. But we had no X-ray telescopes then as they only work in space. But all is not lost: at the January 2007 meeting of the American Astronomical Society in Seattle, Michael Muno of Caltech announced that he and his team had managed to see part of the 1950s outburst reflected off clouds on the far side of the galactic centre [4]. The clouds were a few tens of light years away from the center, so the reflected X-rays took half a century longer to reach NASA's Chandra X-ray telescope.

New instruments in radio, infra-red and millimeter wave bands have revealed much detail of the region near the black hole but have not so far been able to image its horizon - the boundary beyond which no light can escape. The best we have done is to link radio telescopes across the world, very long base line interferometry. In principle this should be able to resolve details as small as the earth's orbit. But the radio waves come through intervening clouds of ionized gas which distort the image. It is hoped that future interferometers in the millimeter and sub-millimetre bands, which are less subject to distortion, will reveal the event horizon. This would be the final part of the proof that Sgr A* is a massive black hole.

[1] Jeff Kanipe, "A long time ago, in a galaxy not so far away", Nature, 5th April 2007. Back

[2] Shapley H, Contributions from the Mount Wilson Solar Observatory No. 152, 1918. Back

[3] Lynden-Bell D, Nature 223, 690-694, 1969. Back

[4] Muno M P, Baganoff F K, Brandt W N, Park S & Morris M R, Astrophys. J,656, L69-72, 2007. Back

December 14^th: Dr Graham Wallis (Hampstead Scientific Society)

ROBOTICS.

January 18^th: Dr Elspeth Garman (University of Oxford)

WHY WE KEEP CATCHING THE 'FLU

February 22^nd : Dr Chris Welch (Kingston University)

SPACE KITES.

March 22^nd: Dr Pamela Greenwell (University of Westminster)

MOLECULAR BIOLOGY.

April 26^th: Professor Robert Weale (Hampstead Scientific Society)

BROCCOLI AND EYESIGHT.

ATMOSPHERIC POLLUTION & URBAN ASTRONOMY

Doug Daniels, Astronomical Secretary Hampstead Scientific Society

It comes as something of a sobering thought that I have been demonstrating at our Observatory regularly for a little over 40 years. Thanks to our dedicated band of enthusiasts, the Observatory is opened regularly during the winter months on clear Friday and Saturday evenings and Sunday mornings, to afford members of the public the opportunity to view some of the wonders of the Universe through a decent telescope. It is an equally sobering thought that this service has been provided, almost unbroken, for the best part of a century. During this time, we have observed a steady decline in observing conditions up at Lower Terrace.

I am not just talking about light pollution. When the Society was founded in 1899, the local area up on Hampstead Heath was totally dark and visitors could view the full splendour of the Milky Way. The greater part of London was still lit by gas lighting and vehicles were horse-drawn. Of course even then there was atmospheric pollution, mainly from the burning of high sulphur content coal in domestic grates by a rapidly expanding population and from the equally rapid expansion of industry in the city below. London fogs were a regular feature of autumn and winter months, but the Observatory, situated at the highest point in London, was often above them. Atmospheric pollution continued to increase for decades and in the 1950's one of our Society's members, Leo Bonacina, made a study of the visibility across London. For years, he took sightings from a spot on Parliament Hill, making daily recordings of the visibility of distant horizons according to a scale which he had devised. His observations showed a steady decline in visibility over time.

In the 1960's the Clean Air Act was introduced which banned the burning of coal in domestic grates and imposed strict regulations on industry. For a short time air quality and transparency showed steady improvement. This improvement was, however, to be short lived due to the increased numbers of motor vehicles and the resultant increase in pollution from their exhausts.

Now we are facing a new menace: pollution from aircraft. Over the last few years the number of aircraft movements over London have increased and they are set to go on increasing in the future. From my own observatory in Finchley, I have witnessed an enormous increase in aircraft movements during the last 40 years, currently running at about 250 per day. Aircraft release tonnes of carbon dioxide and water vapour directly into the atmosphere, which can severely affect local atmospheric transparency; they can literally alter local weather conditions. This was clearly demonstrated in the USA when all aircraft were grounded for a short period following the terrorist attack on the World Trade Centre.

Pollution from aircraft is probably the greatest contributor to the effect known as Global Dimming. This phenomenon has been confirmed by examining the records of 'pan evaporation' experiments, in which an open pan of water is allowed to evaporate naturally. The time taken for the water to evaporate is a measure of solar radiation. World-wide records of pan evaporation experiments over time have shown a marked increase in evaporation times, indicating a diminution of solar radiation, caused by atmospheric pollution. It is somewhat ironic, that without this effect, Global Warming might be even more pronounced! Nevertheless, two 'wrongs' do not make a 'right'.

When the Hampstead Observatory was founded, a century ago, visitors could see the Milky Way and stars down to the sixth magnitude with the naked eye. Now we feel lucky if we can see stars of the fourth magnitude. But our records indicate other worries concerning the frequency of clear nights. Three decades ago one could expect that at least one in three weekends would produce a clear night. That is no longer a reasonable expectation. In 2003 I recorded the number of clear nights at weekends. I discovered that from mid September until January there were a possible 48 occasions on which the Observatory could have been open. In the event, 42 nights were totally cloudy. From October 18^th until December 28^th there was not a single Friday or Saturday evening or Sunday morning that was clear. That is an interval of 10 successive weeks when observations were impossible at weekends. I have noticed this disturbing trend developing over the years.

Why is it now less likely to be clear at weekends? It has been suggested that it is due to the steady build up of pollution caused by industry and vehicles during the week that reaches a maximum on a Friday. It then decreases over the weekend to begin a new cycle again on Monday. I am not entirely convinced by this argument. As we now live in a society that sees almost everything open at weekends, I see traffic congestion just as heavy at weekends as on weekdays; in some areas it is even worse! However, when people go on holidays abroad, more often than not they depart at weekends. Does this not mean that there is increased air traffic at such times?

The Hampstead Observatory also features a meteorological station that now holds a record for continuous daily observations from one site. Our records show conclusively that between 1900-2000 the mean annual temperature at the Observatory has increased by fully one degree C. But whether this is a result of the industrial activities of mankind or natural cyclic phenomena is still open to debate. The only thing of which I am certain is that over the last four decades I have seen a steady increase in both atmospheric pollution and light pollution at the Hampstead Observatory coupled with a decline in the number of nights when it is clear enough for observations to be made. These are worrying trends for the future of urban observatories like ours.

Better eyesight with less colour vision?

Robert Weale.

The interesting article in the August Newsletter told us that mankind lags behind some other species who can make use of ultra-violet radiation, whereas we cannot. The tentative explanation was Tim Goldsmith's speculation that vertebrate species have evolved with four types of cone, but that the development of rods, useful at night, led in our ancestors to the loss of two types of cone. Of the two types of cone left, one mediates shortish (blue) wavelengths, and the other the longer (yellow-green) ones. The need to distinguish red fruit from green foliage led to a useful mutation in that the cone responding to longer wavelengths evolved to form one responding to a somewhat shorter (green) wavelength. This left two types of cone mediating information on food.

The question arises why, if other species apparently needed for survival cones responding to the ultra-violet part of the spectrum, we had to do without them - and managed to survive. In this connection it is useful to remind ourselves that evolutionary biology operates on Thatcherite principles of economics: it does only what it has to do and, when necessary, sacrifices an existing advantage if the mutation offers a better chance of survival. In our case, our eyes found themselves in a body capable of living much longer than the species considered by Goldsmith. With long life, there also goes a long exposure to sunlight. Added to which, we appear to have originated in Africa, which may have been cooler during our sojourn there but certainly exhibited no shortage of light.

There is an unresolved debate going on whether light affects our eyes in ways other than those mediating vision. For example, as we age, the lenses in our eyes become yellower, transmitting less and less blue and violet light for the retina to see. Parts of the yellowing substances have been attributed to photic effects. Also populations exposed to sunny environments tend to have yellower, or darker, lenses than those less exposed to the sun. On the other hand, direct measurements of ultra-violet exposures did not seem to correlate with lens colour.

However, strong radiation appears to exert an adverse, if not damaging, effect on the retina at the back of the eye. This has been dubbed the Blue-light Hazard because blue light seems to be very effective. Detailed studies on rhesus monkeys and other mammals have shown, however, that the peak of the hazard occurs not in the blue part of the spectrum, but in the ultra-violet part or UVB, with a peak at ~ 335nm. At the moment there is no reason to assume that this does not also apply to our eyes. Now it can be shown that we have evolved a very effective defence mechanism against the noxious radiation, and that is to be found in the yellowing of the lens. The risk to the eyes appears to be highest in youth and declines after the age of ~ 20 years partly because of the reduction in the size of the pupil, which controls the entry of light into the eyes, but mainly because of the progressive coloration of the lens.

It would clearly be poor biological economics to maintain a photoreceptor sensitive to ultra-violet light while evolution has endowed us with a mechanism that absorbs that light, thereby preventing it from reaching a set of retinal cones sensitive to ultra-violet light. Note that the mechanism of lenticular yellowing gets into its stride in our twenties, at an age when our ancestors had to be possessed by good eyesight if the next generation was to be enabled to survive a hostile environment. Tim Goldsmith's birds can probably afford to maintain cones for the ultra-violet because they are unlikely to live long enough to regret it.

The formation of C.A.T.S. - Camden Amateur Telescope Society

Doug Daniels

In 1966 May Ammon, the Principal of the Ackland-Burghley School approached Doug Daniels to start an astronomy adult evening class at the school. After a year, due to the pressure of work, Doug handed the class over to Terry Pearce, a long-term friend and a keen amateur telescope maker.

During the subsequent years, by popular demand of the students, the class evolved into not just an astronomy class, but a telescope making class, where members were encouraged to grind, polish and figure their own telescope mirrors and build their own instruments from scratch.

By introducing many people to the study of astronomy and telescope making, the class also became a natural source for demonstrators and assistants at the Hampstead Observatory, many of the alumni became members of the Hampstead Scientific Society.

The class continued to meet weekly throughout the intervening years, surviving the closure of the original Ackland-Burghley venue and finally moving to the Westminster Kingsway College. It was at this institution that it was finally closed down two years ago due to 'economic cutbacks'.

The remaining members were not happy with this decision and so the Camden Amateur Telescope Society (C.A.T.S.) was formed to carry on the good work and application was made to affiliate it to the Astronomy Section of the H.S.S.

C.A.T.S. now meets fortnightly at the Highgate Newtown Community Centre and it was at that location that past and present members gathered on the evening of October the 11^th to honour their mentor Terry Pearce, for 38 years continuous service to the study of astronomy and telescope making.

At the ceremony, Terry was made Honorary Life President of C.A.T.S. and was presented with a certificate and a trophy, in the form of a model telescope, designed and made by Simon Lang.

FUSION RESEARCH

Peter Wallis

The recent summer visit by the HSS to the Culham laboratory was a success. Sited there is the Joint European Torus (JET), involving nuclear scientists from all over the continent, and the UK's own fusion research programme MAST. But only two weeks ago there has been a formal international agreement to construct at a cost of some £7 billion the next stage in the development of power from nuclear fusion, the process that powers the sun. This is called ITER, an acronym for International Thermonuclear Experimental Reactor, but also latin for 'the way'.half the cost will be borne by the EU, with the rest shared by the US, China, India, Japan, Russia and S. Korea. It will be built in Cadarache in France and work will start there in 2008.

Nuclear fusion involves the fusion of hydrogen atoms to form helium, with the release of energy in high velocity neutrons (14 MeV). In the center of the sun it occurs at temperatures of 10 million °C , but we cannot achieve comparable pressures on earth and need at least 100 million °C . The reaction occurs in a plasma of positively-charged nuclei and negatively-charged electrons, contained by magnetic fields to keep it away from the walls.

The raw material for the reactor is water,but we actually fuse two of its heavier isotopes, deuterium and tritium. One litre of water contains 35 mg of deuterium; its fusion with tritium releases as much energy as 340 litres of gasoline. The tritium is manufactured in the reactor by the reaction between the neutrons, which are not constrained by the magnetic fields, and a blanket of lithium to form tritium and helium-3, an inert and harmless gas. The heat in the lithium blanket is removed by a 'coolant' and heat exchangers to steam turbines which generate electricity. There is no chain reaction, so no risk of explosion.

The waste from a fusion plant of 1000 MW power is only 250 kg of helium per year, which is not a green-house gas. Comparable wastes from other power plants of the same power are:

• Coal -- 7.2 Mtons of CO2, 5.8 ktons of SO2.
• Gas -- 3.6 Mtons of CO2.
• Fission -- 32 tons of radioactive spent fuel.

The Geminid Meteor Shower is to be seen in the night of 13/14 Dec, low in the east in the early evening and high in the south after midnight. 60 or more per hour are likely.

Mercury, Mars and Jupiter are close together in a 1° circle in the dawn sky around the 10^th December.

PRW

Council for 2006/7

Membership of Council for this year is:

• President - Professor Robert Weale
• Secretary - Julie Atkinson
• Treasurer - Peter Wallis
• Membership Secretary - Elisabeth Fischer
• Programme Secretary - Jim Brightwell
• Ordinary members - Aileen Cook, Hemant Desai, Nayna Kumari, John Oakes, John Tennant.
• Astronomy Secretary - Doug Daniels
• Assistant Astronomy Secretary - Simon Lang
• Meteorology Secretary - Philip Eden

Festival of Geology

Julia Daniels reports that this will be held at University College London on Sat 4^th November.

This is an annual event organized by the Geologists' Association but this year is open to the public from 10 till 4.30. Associated with it, UCL will be opening the Regional Planetary

Image Facility (the UK archive of NASA images and data), the Petrie Museum of Egyptian Archaeology and the Grant Museum of Zoology; the Discovery Room exhibits will be greatly expanded, with a stunning range of activities for all ages. There will be local society displays and 3 talks, including one on the Geology of the Moon. There will be geological walks on the Sunday morning.

Better Colour Vision?

Peter R Wallis

With a few exceptions all human beings have colour vision based on the cone cells in the retina of our eyes [1]. Each cone cell contains a pigment which is a variant of the protein opsin, linked to a small molecule called retinal. When the pigment absorbs light, the added energy causes the retinal to alter its shape and trigger the neurons which send information to the brain via the optic nerve. We are able to see trichromatically because we have three types of cone cell that are sensitive to different frequencies of light; each covers a wide band, but they have maximum sensitivities at light wavelengths of 424, 530 and 560 nanometers (nm) respectively. What we describe as "colour" is not an absolute property of light or of the object, but the brain's interpretation from the levels of activation of the three different cones.

All this is well known to us. However, I was greatly intrigued by an article by Timothy H. Goldsmith [2]describing the superior colour vision of birds, based upon four rather than three types of cone, one being sensitive to the near ultraviolet of 300 to 400nm which we cannot detect [3]. With some space free in the August newsletter, I decided to pass on his information to you.

Ultraviolet vision in insects was discovered in the 19^th C., at first by Sir John Lubbock (Lord Avebury), a friend of Charles Darwin, from his observation of ants. Then Karl von Frisch and his students demonstrated in the early 20^th C. that bees and ants not only see UV but use it to navigate. Work of the past 35 years has shown that birds, lizards, turtles and many fish have UV receptors in their retina. But we don't; why not?

Goldsmith says that the different opsins in different species offer a way to study the evolution of colour vision. Examination of the DNA sequencies that code for the opsins reveal the evolutionary trees for different species. He claims that opsins are ancient proteins that existed before the emergence of the dominant groups that exist today. He traces four lineages of vertebrate cone pigments named after the spectral regions where they are most sensitive: long-wavelength, mid-wavelength, short-wavelength and ultraviolet.

Modern birds have four spectrally distinct cone pigments, typically peaking at 370, 445, 508 and 565 nm. Mammals, however, generally have only two pigments, one peaking in the violet and the other at longer wavelengths. He offers a 'likely' explanation for their loss of two. He suggests that it occurred in the Mesozoic Period (245 Myrs to 65 Myrs ago) when Saurians were the dominant species and mammals were nocturnal; in low light conditions they would need the more sensitive rod cells to see. With the extinction of the dinosaurs 65 Myrs ago, the mammals were able to diversify, taking up diurnal life.

He believes that one group of mammals - among which were the ancestors of today's humans and other primates - spread out into trees and made fruit an important diet. But, with only one long-wavelength cone, they would have been unable to discriminate between green, yellow and red. He suggests that mutations occurred to provide a second long-wave cone; other research supports this hypothesis [4]. We primates thus have today three types of cone and trichromatic vision, unlike most other mammals. But our colour vision is far from ideal. Not only do we have no UV cone, but our long-wave cones are 'something of an evolutionary reclamation job'. The genes for both lie on the X-chromosome; males only have one copy of this so mutations of either gene can damage their ability to discriminate between red and green.

The presence of four types of cones in birds, sensitive to different wavelengths, certainly offers much better colour vision and Goldsmith and his students have done colour-matching tests on budgerigars to prove this explicitly, including ultraviolet. How might the birds make use of the wealth of colour information? One possibility is mate selection; researchers have shown from measurements of the light reflected from their plumage that the eye of a bird sees differences between males and females not known to ornithologists. UV receptors may give the animal an advantage in foraging for food. Jussi Viitala has also reported that kestrels can detect the voles whose scent trails of urine and faeces reflect UV light.

Some conclusions can be determined by experiment, as above, but others may remain as speculation in view of our much more limited colour capability. Evolution is however an immensely powerful process. It gave us our brains and power of speech and we now think of ourselves as masters of the world. But it has given others their own special capabilities that we lack - the colour vision of birds, the infrared sensors of the pit vipers, the echo-sounding of bats - and we do not know what the future has to offer.

[1] The rod cells do not contribute to colour vision but provide more sensitive vision in low light conditions. Back

[2] "What Birds See" by Goldsmith T. H., Scientific American, July 2006, p51. He is a professor emeritus at Yale and has studied the vision of crustaceans, insects and birds over 5 decades. Back

[3] Ultraviolet light of wavelength less than 300nm is absorbed by the ozone in the upper atmosphere and plays no part in the birds' vision. Back

[4] Jeremy Nathans & David Hogness at Stanford University suggest that an extra copy of the long-wave opsin gene that can arise naturally in a reproductive cell subsequently suffered a mutation varying its peak wavelength, conferring a selective advantage. Back

May 25 Dr Mike Holwell (King's College, London) on Medical Physics. NOTE: this is a change to the published programme.

VISIT

Telescope manufacturing

ANNUAL GENERAL MEETING

This will start with wine and cheese (£2 each).

The AGM itself will start at 8.45 and will be followed by a scientific entertainment.

The agenda will include the usual reports from Officers and Sections and the Election of Officers and five Ordinary Members of Council for the coming year. Council proposes the following:

Secretary	Julie Atkinson
Treasurer	Peter Wallis
Membership Secretary	Elisabeth Fischer
Programme Secretary	Jim Brightwell
Ordinary Members	Aileen Cook
	Nayna Kumari
	John Tennant
	Hemant Desai
	John Oakes

Council invites further nominations to the above officer posts and ordinary members; such nominees shall be duly proposed and seconded and have agreed to serve if elected.

Rule Change. The Council will be proposing a small change to Rule 4c to the effect that those whose subscriptions are in arrears by four months will cease to be Members.

Nuclear Power

Peter R Wallis

The government has announced that it will be reviewing its energy policy, including the potential for new nuclear power stations, in view of the need to reduce carbon emissions which cause global warming. Most of our existing ones will have reached the end of their life in ten to twenty years. Politicians are reluctant to take decisions on issues several elections away, particularly when they see the issue as being unpopular to the UK public, who associate nuclear power with nuclear weapons and possible nuclear disasters. There are also anti-nuclear pressure groups which claim that:

• Nuclear waste will require safe storage for 10,000 years and no way has been found to do so,
• Nuclear technology involves enrichment of uranium and the manufacture of plutonium, which could be diverted by terrorists to make bombs,
• Before long, the readily available sources of natural uranium will be exhausted and have to be replaced by more expensive supplies, making nuclear power even more non-competitive.

These arguments arise mainly from the type of nuclear power stations in use today.

All commercial power reactors in existence today produce energy by splitting the heavy elements, mainly uranium or elements derived from it, which were formed billions of years ago in the supernovae explosions of stars. Natural uranium comes in two forms. The lighter isotope U235 is only 0.7%, the rest being U238. The U235 is called fissile as it is easily split by when struck by a neutron to form lighter elements, with the release of energy and several more neutrons; this allows a chain reaction [1]. The heavier isotope is U238; this is much more stable and neutron capture is more likely to mutate it into plutonium 239 than to split it. Plutonium 239 is also fissile.

The neutrons released in fission are very fast but in the majority of civil power reactors they are deliberately slowed down by successive collisions with light elements in a moderator, to thermal velocities which are well suited for the establishment of a stable chain reaction. These reactors are called 'thermal reactors'. The most common moderator is ordinary water, used also to carry away the heat to the steam generators and turbines, which drive the alternators to produce electricity. These are called 'light water reactors' and, since the water needs to be kept liquid at high temperatures, it needs to be at very high pressures; they are 'pressurised water reactors', PWRs., as at Sizewell B in the UK and in great numbers elsewhere in the world. The rupture in the reactor's pressure vessel could be disastrous, the water changing to steam. Though this would stop the chain reaction, there would be insufficient cooling of the reactor. In the worst case it might catch fire [2], releasing radioactivity to the environment; strong outer containment is therefore required.

The initial fuel in a PWR is usually enriched significantly in the U235 proportion, usually to 3%, using an array of centrifuges. This process means that at most only about a fifth of the uranium ore is actually used in the reactor, the remaining U238 being rejected. After about 3 years of power generation in the reactor much of the U 235 has gone and more than half the power comes from the fission of the plutonium created by neutron capture in U 238. The spent fuel is then removed. It is interesting to note that only about 5 or 6% of heavy atoms in the original fuel have actually been burnt up. The spent fuel contains the remaining 94% plus the ash of the nuclear fire. In some countries, the spent fuel is reprocessed to recover P 239 for reuse in the reactor. This is not done in the USA, President Carter having ruled in 1977 against such processing to avoid the risk of plutonium, which can be used for bombs, becoming available [3]. Without reprocessing, thermal reactors are pretty wasteful in their use of uranium, in that only one hundredth of the original ore is used!

The ashes, 5% of the spent fuel, are a mixture of lighter elements which remain radioactive for several years but, after a decade, the activity is dominated by caesium 137 and strontium 90. They are both soluble in water and so must be contained very carefully. Their activity decays a thousand-fold in 3 centuries and ceases to be a difficult problem. The largest part of the spent fuel, 94%, is depleted uranium, ie without most of the fissile portion, and can be stored safely in lightly protected facilities. The really troubling part, 1%, consists of transuranic elements, mainly plutonium isotopes and americium. Their half-lives range up to tens of thousands of years and this is the most important challenge to the waste technology. In the US there are plans to store waste in Yucca Mountain for such lengths of time. But is there another way to exploit the hidden energy in uranium?

A possible answer lies in using a fast reactor rather than a thermal one; this is argued in an article by W H Hannum, G E Marsh and G S Stanford in the Scientific American [4]. The fast neutrons released in fission are more likely to induce fission in U238 and the heavier transuranic atoms than thermal neutrons. A fast reactor does not use a moderator, but still has to be cooled. A number of prototypes have been built using liquid sodium metal to carry the heat to the steam generators and turbines. One such was the 'fast breeder reactor' at Dounreay in Scotland, though this was not designed specifically as a civil power reactor and is now decommissioned. France has the Phenix and Super-phenix. One advantage of this technique is that the reactor does not need to operate at the high pressures of a PWR, with the serious problems if the pressure system fails. Design problems remain however as sodium catches fire if exposed to water; maybe lead would be a better coolant.

The authors claim that such reactors offer the prospect of generating energy from 99% of the uranium ore instead of less than 1% and that there is already plenty of uranium available in the spent fuel of existing thermal reactors and further mining for uranium may not be needed for centuries.

They say that waste management would be greatly simplified, as most of the transuranics would have been consumed in the reactor itself. Only a few centuries of storage would be needed for the ash. Some reprocessing of the spent fuel would be needed to separate the ash from the heavy metals, a complex mixture of uranium 238, plutonium isotopes and other transuranics, for re-use in the reactor. These metals would however not be useable for bomb-making and there would be no need to separate the dangerous plutonium 239 which would be. Both the US and Russia have advocated techniques of high temperature electro-refining to separate the metal from the ash. It is claimed that the amount of spent fuel would be much smaller than with a thermal reactor and reprocessing could probably be sited at the reactor, reducing the need to transport radioactive material, which is probably the most vulnerable stage to terrorist attack. Both India and China have recently announced their intention to deploy fast reactors to extend their energy resources. This form of nuclear power when fully developed could provide answers to the challenges listed in the first paragraph.

There are still prejudices against nuclear power in the UK, so political acceptance of a government decision to deploy new reactors of whatever type might be slow. The public is however more understanding of the threat of global warming and in many areas are less than happy at windmills covering the country and the power cuts that would occur when there is little wind. They have also noticed the increase in gas prices and doubt the wisdom of relying entirely on overseas sources of gas and oil when our own has gone. It is of interest that not all countries are unhappy at the prospect of more nuclear power. France already has 58 nuclear reactors generating three quarters of all their electricity and President Chirac has recently announced [5] that a third generation is planned for 2012. He said that by 2026 no train in France will be powered by conventional fossil fuels. He called for the ITER project, an experimental fusion reactor that will be based in southern France, to demonstrate "the ability to harness the energy of the sun by the end of the century".

Let us in the UK also show that we can think sensibly about the future and deploy science to solve the world's problems.

[1] This is well-known to be the basis for the atom bomb dropped on Hiroshima. For civil power generation the process has to be controlled of course. Back
[2] As at Chernobyl. Back
[3] France, Japan, the UK and Russia did not follow his example and continue to reprocess for plutonium, which can be re-used in the reactor. More of the uranium is therefore used. Back
[4] "Smarter Use of Nuclear Waste", Scientific American, December 2005. Back
[5] His New Year Address, 5th January 2006. Back

IS THE 'BIG BANG' A 'DAMP SQUIB'?

Doug Daniels

When I first became interested in astronomy, way back in the 'dark ages' of the 1950's the favoured theory concerning the creation of the Universe was the Steady State Theory, the chief proponents of which were Herman Bondi, Thomas Gold and Fred Hoyle. Simply stated, this theory proposed that the Universe had always existed and looked much the same everywhere to all observers, in other words it was homogeneous and isotropic. In this respect it conformed to the perfect cosmological principle and it would continue 'ad infinitum'. The expansion of the Universe was accounted for by postulating the continual creation of matter at a rate of just 10-10 nucleons (protons or neutrons) per cubic metre per annum. However the mechanism for this creation of matter was never convincingly described. The Steady State Theory was in many respects an elegant theory that appealed because of its non-violent origin and by virtue of the fact that it allowed the Universe to continue forever - a comforting notion. The theory also added weight to the idea of nucleosynthesis whereby the heavy elements were brewed up in the cores of massive exploding stars, and this part of it still holds today.

However new evidence was accumulating and observations using the 'new technology' of radio astronomy were being made that were soon to cast serious doubt on the veracity of the Steady State Theory. From then on its chief rival, the Big Bang Theory, proposed earlier by Friedman, Lemaitre and Gamov, took precedence.

The 'death knell' of the Steady State Theory was finally sounded with the discovery of the cosmic Microwave Background Radiation (MBR), discovered by Penzias and Wilson in 1964. George Gamov had suggested the possible existence of this radiation as early as 1945 and in 1948, Alpher and Herman went so far as to calculate a predicted temperature for it of about 5degrees K. But its discovery had to wait for the application of radio telescopes, the technology for which had been accelerated by the rapid development of radio physics in the Second World War.

When discovered, the microwave background radiation (MBR) was found to be highly isotropic (the same in all directions) and was described as 'the echo of the Big Bang'. Its presence suggested an explosive, violent creation of the Universe at a singular point in time and space. From then on the rival Big Bang theory was generally accepted as more likely to be correct.

Detailed examination of the MBR had to wait until space probes could be built because the Earth's atmosphere hindered observations in the MBR's millimetric wavelengths. COBE, the cosmic background explorer satellite launched by NASA in 1989, demonstrated that the MBR's spectrum conformed to a perfect black body radiation curve for a temperature at 2.735degrees +/- 0.06degrees K. (just 2.735degrees above absolute zero). It also revealed slight temperature fluctuations in the order of one part in 100,000. These fluctuations were very important for an understanding of how large-scale structures like galaxies could possibly form in the early Universe. More recently, the Wilkinson Microwave Anisotropy Probe (WMAP) has revealed even more detailed temperature fluctuations down to 1 millionth of a degree. The results from WMAP have caused cosmologists to re-examine the timings of events in the early Universe and have concluded an age for the Universe of 13.7 billion years.

The Big Bang theory has held sway now for over 40 years but there are many problems associated with it. Not least is the question as to whether or not the Universe is 'open' closed' or 'flat'. The resolution to this is dependent on the mean density of matter and energy in the Universe and how close this value approaches the 'critical density'. Observations from WMAP suggest that the Universe is 'flat' in other words its expansion is equal to its escape velocity. Over time, the expansion rate of the Universe ought to slow down constrained by the gravity of matter, yet in fact the expansion rate appears to be increasing with time. In order to accommodate this phenomenon it has become necessary to 'invent' a new force in the form of 'Dark Energy', a kind of anti-gravity repulsive force which nobody can yet explain but which nevertheless appears to comprise 73% of the mass of the Universe!

Another big problem with the Big Bang is concerned with the formation of galaxies in the early Universe. A recent image from the Hubble Space Telescope - the Deep Field Image, is so far our furthest view of the early Universe. It shows countless galaxies fully formed around 13 billion years ago, when the Universe was just 5% of its present age. To achieve this speed of galaxy formation it has become necessary to postulate the existence of large quantities (23%) of 'Dark Matter', an invisible substance, the existence for which we have, as yet, no direct observational evidence. What we can actually observe is just the 4% of baryonic matter that comprises everything that we can actually see in the Universe. In point of fact, we have, as yet no convincing model describing how galaxies are formed and how they are maintained. Recent observations indicate that many spiral galaxies (perhaps all such galaxies) have super-massive black holes at their centres. These appear to be orbited by swarms of massive hot blue stars, which in the light of present understanding should not be able to exist in such a region.

Finally, to return to the Cosmic Background Radiation, the Big Bang theory does not adequately predict the observed uniformity in this radiation. This is only achieved by postulating 'Inflation' - a process of sudden ultra-rapid expansion, possibly as much as x10⁵⁰, that mysteriously took place just 10^-35 seconds after the initial Big Bang explosion and ended before 10^-30 seconds. It is during this brief period of change that the electromagnetic and strong nuclear forces are deemed to have separated to different values and in so doing, released the energy to power this ultra-rapid expansion. During this period of 'symmetry breaking' certain defects in 'spacetime' would have been created. These have been described as 'monopoles' and 'domain walls' Monopoles are extremely massive single units of magnetic charge that do not exist in the present Universe. Domain walls are two-dimensional defects in spacetime that similarly and conveniently could not exist in the present Universe.

There is also the vexed question as to what exactly lit the Big Bang's fuse in the first place? The answer to this we are told is that it can never be known because the physical laws that govern the behaviour of matter/energy only came into existence at the moment of creation and what occurred before that is pure conjecture. Perhaps someone said: "Let there be light"?

The test for a good theory is in the predictions which it makes and which can be supported by observation and experiment. This is after all, how the Steady State Theory met its demise. At the moment it would seem that the Big Bang theory is also failing these criteria.

We have seen in the past that when a 'grand theory' begins to fail, those who favour it do all in their power to prop it up - it's human nature after all. Before Kepler, astronomers added epicycle upon epicycle in an attempt to force the planets into circular orbits. Fred Hoyle tried very hard to prove that the fossil Archaeopteryx in the Natural History Museum was a fake because its age did not fit with the timescale required by the Steady State Theory, and even the great Einstein added a fake term in his equations because he didn't like the idea of an expanding Universe.

It occurs to me that if we are to construct theories concerning the formation and evolution of the Universe based on observations of a mere 4% of it, then we must not be too surprised if the best theories which we can come up with are apt to be found wanting from time to time.

HSS Lecture Meetings in the Crypt Room at St John's Church, 8.15 pm.
December 15th Professor Bill McGuire (University College London): Surviving Armageddon, Solutions for a Threatened Planet.
January 19th Ray Batchelor (Buckinghamshire Chilterns College): Why Anything can mean Anything.
February 23rd Dr Philip Jones (MatraBaeDynamics): Satellite Navigation.
March 23rd Professor Helen Haste (University of Bath): The Moral Messages of Science.
April 27th Professor Basil Hiley (Birkbeck College): Einstein and Quantum Theory.

Gravitational Tractor for Towing Asteroids.

As you can see above, our December lecture concerns various threats to our planet. One such is a collision with an asteroid or a comet. Such an event some 65 million years ago is thought to have killed off the then dominant species on the planet, dinosaurs. I suspect that they had little foreknowledge of what was coming, but our scientific knowledge and astronomical technique allows us to know several years before impact and offers the possibility that we could destroy or deflect the asteroid. An interesting article in Nature [1] by Edward T Lu and Stanley G Love of NASA under the above title proposes a method of deflection.

There have been several proposals, and films, about docking a space craft to an asteroid and using a rocket engine to push it into a different orbit. The authors point out several problems: the surface is likely to be rough and unconsolidated, asteroids rotate and propulsion would have to be intermittent or time taken to stop the spin. Their suggested alternative is for the spacecraft to hover above the surface using the force of gravity as a tow rather than a physical connection. The rocket thrusters would be canted miss the asteroid. The scheme is insensitive to the nature of the surface and the internal state of the body and its rotation. The engines would need to be controlled, since the hover point is unstable.

The authors calculate that a spacecraft of 20 tonne mass could tow a 200m diameter asteroid provided it can maintain a thrust of 1 newton. The change in velocity is small but they calculate that it would be able to deflect adequately given a lead time of 20 years. They say that the 20 tonne nuclear-electric vehicles proposed in NASA's Prometheus programme would use 4 tonnes of fuel to achieve the 15 km/s rendezvous and 400 kg for the deflection.

Deflecting a larger asteroid would require a heavier spacecraft and more hover time or lead time. However in the special case of a close approach followed by a later return, the deflection needed to prevent impact can be many orders of magnitude less if applied before the first approach [2].

For example asteroid 99942 Apophis, a 320 m asteroid will swing by the Earth in 2029 at a distance of about 30,000 km; it has a small probability of returning to strike the Earth in 2035, but a very small deflection made a few years before 2029 could ensure that it does not. The authors say that a 1 tonne gravitational tractor with a conventional chemical rocket providing only 0.1 newtons of thrust for 1 month would suffice.

And now for the bad news ----

Flu.

Another threat facing us rather earlier is that of a human flu pandemic originating from bird flu. There has been much publicity already in the media about the virulence of the H5N1 virus among birds but so far only about 60 people have died and it is thought that they caught it directly from birds. Unfortunately the influenza virus is capable of enormous variation in the surface proteins which enable it to attack human cells and our immune system is hard put to keep up. But is it that important as flu is only a mild and brief illness? This may be true of the current strains of human flu, to which we have developed some immunity. Moreover we are able to manufacture vaccines to encourage immunity amongst the more vulnerable people. But there is a lesson to be learnt from previous pandemics.

The "Spanish" flu of 1918 was truly deadly. It killed some 50 million humans, more than the number killed in the 1914/18 war. Scientists have now completed the last three segments of its genome [3]. They have done so in order to understand its origin and its unusual virulence. All eight segments of its genome differ in significant ways from other human flu sequences, suggesting that it did not come from a strain that had previously infected people. Taubenberger says, "It is the most bird-like of all mammalian flu viruses".

In Science [4] in the same week a laboratory in Atlanta has used the sequence to replicate the virus and test it on mice. After four days it had generated 39,000 more virus particles in the animal's lungs than a contemporary 'Texas' strain; all mice died within 6 days of infection, none from the Texas strain. The team has tried replacing some of its genes but has been unable so far to determine what combination is critical to virulence. Eventually our improved understanding should be of use in vaccine and drug design.

Other scientists have, however raised concerns about "the danger of reconstructing a virus that represents perhaps the most effective bioweapons agent now known." [5] The scientists are still arguing whether the 'biosafety level-3' is sufficient as there have been three escapes of the SARS virus from such labs. Maybe the consequences would not be as serious as there is some human immunity to the 1918 virus because subsequent strains are in part derived from it [6].

The whole genome sequence has now been put on the GenBank database - a condition of the paper's publication. There are currently no government controls on what sequences can be used, though some synthesis companies screen their orders for pathogenic sequences. Taubenberger admits that there can be no absolute guarantee of safety, "But what we are trying to understand is what happened in nature and how to prevent another pandemic. In this case, nature is the bioterrorist".

Back to today's avian flu. It has already mutated from chickens in 1997 to water birds and in October 2004 23 tigers died in a cat to cat infection. We must assume that it will mutate to a human virus. If so, much will depend on its human infectivity and mortality. Too great and rapid a mortality would kill off an epidemic before it could spread, so the real fear is of a high infectivity and moderate mortality that with modern air travel would become a global pandemic. Antiviral drugs like Tamiflu may help to palliate, but a vaccine will be critical.

We must bring our modern scientific knowledge and techniques to prevent a pandemic, but pestilence is one of the four horsemen of the apocalypse.

Peter R Wallis.

HAPPY CHRISTMAS.

[1] Nature, 10th November 2005, p 177. Back
[2] Carusi et al., Icarus 159, p 417, 2002. Back
[3] J K Taubenberger et al, "Characterisation of the 1918 influenza virus polymerase genes", Nature 6 Oct 2005, p 889 Back
[4] T M Tumpey et al, 310, p 77. Back
[5] Richard Ebright, Rutgers University of Piscatawy. Back
[6] Tumpey. Back

Council for 2005/6

Membership of Council for this year is:
President - Professor Robert Weale
Secretary - Julie Atkinson
Treasurer - Peter Wallis
Membership Secretary - Elisabeth Fischer
Programme Secretary - Jim Brightwell
Ordinary members - Simon Lang, Eric Morgan, John Oakes, Michael Sabel, Betty Weale.

Einstein Centenary Year.

1905 was Einstein's annus mirabilis. He published five seminal papers on Physics. One, on light as quanta, effectively invented Quantum Optics; two demonstrated the reality of the kinetic-molecular theory of heat; two more resolved the fundamental problems between classical mechanics and electrodynamics through his Special Theory of Relativity and postulated E=mcxb2. But it took ten more years to develop his General Theory of Relativity; this offered the only development in gravitational theory since Newton's in 1687. The article by Doug Daniels overpage will bring you up to date.

Planetary Formation

The conventional theory for the formation of the gas giant Jupiter postulates its growth from a core of solid material by the gravitational attraction of gas, mainly hydrogen and helium, from the protoplanetary nebula until it reached its present size of 318 earth masses. It is argued that the solid material could only collect in relatively cool regions beyond the 'ice line', typically at least 3 AU from the star. (An astronomical Unit, AU, is the sun-earth distance). So far we have been able to detect spectroscopically many extra-solar planets, mainly by the perturbation of the radial velocity of the star; the method favours the detection of massive gas giants with short orbital periods. Ten years ago 'Pegasi' planets were discovered - giant planets 100 times close to their star than those in the solar system. Astronomers have argued that they were formed as above and then migrated inwards through gravitational interaction with the disc to become "hot jupiters" with an orbital period of 3 to 9 days. Recently Maciej Konacki of CalTech has reported [1] the discovery of an unusual hot Jupiter orbiting the primary star of a triple stellar system HD188753. The planet has a minimum mass of 1.14 Jupiters with a period of 3.35 days at a distance of about 0.05AU. The primary is 1.06 times the mass of the sun and the secondary is a binary star system of total 1.63 solar masses at an average distance of only 12.3 AU. It is calculated that this would have truncated the disc round the primary to only 1.3 AU and heated it enough to prohibit planetary formation. A real cat among the pigeons! Clearly our ideas of planetary formation need reconsidering.

[1] Konacki M, "An extrasolar giant planet in a close triple-star system", Nature, 14th July 2005, p. 230 Back

Peter R Wallis.

THE GRAVITY OF THE SITUATION

Doug Daniels

Gravity or Gravitation is probably the most fundamental force in nature. It is the mutual attractive force exhibited by all material bodies. Gravity is the force which keeps the planets orbiting the sun, the force that anchors us to the surface of the earth, the force that holds galaxies together and it is the force that causes massive stars to collapse into 'Black Holes' from which nothing, not even light can escape. Gravity is all pervasive in the Universe and it is a force that we still do not entirely understand.

In the early 17th century it was established that the planets of our Solar System orbited the sun, and Kepler formulated his famous laws of planetary motion between 1609 and 1619 to describe their motions, but the forces responsible for these motions were not at all understood. Galileo had an inkling of an idea when he dropped unequal weights from the leaning tower of Pisa, observing that they hit the ground simultaneously, and he also conducted experiments with inclined planes, but it was Isaac Newton who formulated the basic laws of gravitation in 1687.

Everyone is familiar with the story (probably untrue), of how Newton observed an apple falling from a tree and experienced a 'eureka moment.' Newton's work, however inspired, established the basic law of gravitation, which states that: "The force of attraction between two bodies is equal to the product of their masses and is inversely proportional to the square of the distance between them" This is expressed mathematically as:

F=Gm₁m₂/d²

G, the constant of proportionality, is the Gravitational Constant, often called Big G. Newton demonstrated that the gravitational force acts from the centre of mass and on a line joining the centres of the two bodies concerned. The gravitational constant can also be defined as: 'The force of attraction between two bodies of unit mass separated by unit distance.' It has been calculated to be equal to:

6.672 x 10^-11 N m² kg^-2

But there is still some uncertainty about this value and we still do not have a precise value for 'Big G'. The Brans-Dicke theory of gravitation predicts that the value of G will decrease with time by about one part in 1010 but so far this has not been substantiated.

Had Newton actually observed an apple falling from a tree, and I am sure he must have done so at some time, he might well have pondered that it took the entire mass of the earth to dislodge it. This suggests that the forces holding the apple on the tree are orders of magnitude greater than the force of gravity which was pulling it off! In fact, gravity is the weakest force in nature, far weaker than the Strong, Electromagnetic and Weak nuclear forces acting within the cells of the stem. These forces, however, operate over very small distances whereas gravity operates over incredibly vast distances. But you might well dispute the weakness of gravity if you climb a tree to pick an apple and accidentally fall out of it!

Newton's laws of gravitation hold for most circumstances but they were to be challenged by Einstein's General Theory of Relativity published in 1915, following on from his Special Theory of Relativity proposed in 1905. General Relativity Theory described the way in which very strong gravitational fields could alter the 'geometry of spacetime'. It described how massive bodies can literally warp or curve space and time surrounding them. In Einstein's own words: "Matter tells Spacetime how to curve and Spacetime tells matter how to move."

Einstein showed that in contrast to electric and magnetic fields, gravitational fields exhibit an important and fundamentally different property. Objects moving solely under the influence of a gravitational field "receive an acceleration which does not in the least depend either on the material or physical state of the body". It is for this reason that a lump of lead and a feather would fall at the exact same rate in a vacuum. It is this property that Galileo tried to demonstrate at Pisa and Neil Armstrong did demonstrate on the surface of the moon. Einstein went on to state that : "The same quality of a body manifests itself according to circumstances as 'inertia' or as 'weight so the Gravitational mass of a body is equal to its Inertial mass." This is the famous principle of Equivalence, one of the foundation stones of GR Theory.

According to General Relativity (GR), bodies in motion follow the shortest path, a straight line referred to as a Geodesic. But the geometry required to describe motions in four dimensional spacetime is complex and the familiar Euclidean geometry has to be abandoned in favour of a system using Gaussian co-ordinates which can be applied to a continuum of four or more dimensions where straight lines become deformed by the curvature of space. General Relativity may therefore be regarded as: a theory of gravitation which deviates from the Newtonian version only where gravitational fields are very intense.

The test of a good theory is in the experimental confirmation of the predictions which it makes. One of the first tests of curved Spacetime concerned the motions of orbiting bodies in a strong gravitational field. This was first demonstrated by accurate measurements of the advancing perihelion of Mercury, measured at about 43 seconds of arc/century, almost exactly the figure derived from GR theory.

The fact that strong gravitational fields can bend light was first demonstrated during the total eclipse of the sun in 1919. The positions of stars close to the sun's limb were measured and shown to have been deflected by the sun's gravitational field almost precisely as Einstein had predicted. (For a ray of light passing the sun at a distance n sun-radii from its centre, the angle of deflection A should amount to: A = 1.7 arc secs/n ) Half of this deflection is produced by the Newtonian field of attraction by the sun and the other half by the 'curvature of space' caused by the sun.

Today, of course we can observe many instances of the effect of strong gravitational fields deflecting light in deep space. The phenomenon known as 'gravitational lensing' occurs when very strong gravitational fields, surrounding distant clusters of galaxies for example, bend the light from more distant objects to a focus, acting in the manner of a lens.

Another prediction from relativity theory concerns the effects of strong gravitational fields on the radiations from massive bodies such as stars, causing red shifting of the spectral lines.

In attempting to escape the star's gravitational field, the radiations loose energy. The frequency therefore decreases and the wavelength is increased. This is the so called 'Einstein Shift' expressed mathematically as:

dK/K = Gm/c²r

Einstein's general theory of Relativity also predicted gravitational waves, ripples in spacetime which travel at the speed of light. The waves should be produced by cataclysmal events such as stars exploding as supernovae, merging galaxies or massive binary stars and should affect all matter, but they are very weak waves and consequently very difficult to detect. So far our best evidence for the existence of gravitational waves is indirect and is derived from the observations of a binary pulsar. Delicate observations show that its orbital period is decreasing with time by about 75 microseconds per year. This value is exactly that predicted by (GR) as a result of the emission of gravitational waves. However, this is just one observation and so far all other methods of detecting gravitational waves have failed to confirm their existence.

The theory of General Relativity also predicted the existence of 'Singularities' or 'Black Holes' - regions with intense gravitational fields, so intense that even light is unable to escape. Although we have no direct evidence of the existence of Black Holes, there are now numerous contenders for the title and their existence is now more or less generally accepted.

Although we cannot say that Relativity Theory has been definitely proven, it has so far stood up well to all the tests applied to it and at present it's the best theory of gravitation that we have to work with.

Gravity is a property of matter, but what actually is it about matter that endows it with the power to attract? Matter is composed of atoms and atoms are built from fundamental particles. Einstein's general theory of relativity (GR) predicts the existence of gravitational waves but we appear to live in a quantum universe, a universe constructed from and dependant upon the interactions of fundamental particles and ruled by the laws of Quantum Mechanics. So is there a fundamental particle responsible for that property of matter known as gravity? And how is gravity propagated and does it travel at the speed of light? Recent experiments suggest that it does.

Light sometimes behaves as if propagated by waves, and at other times by particles - Photons. Does gravity have a quantum equivalent of the photon? Some scientists have suggested that it does - the Graviton. The Graviton has been predicted as having zero charge, zero rest mass and a spin of 2 but as yet this particle is purely hypothetical - it has not so far been detected.

Einstein spent the latter part of his life attempting to unify his theory of General Relativity and gravitation with the laws describing electromagnetism and failed. His efforts were not helped by the fact that he found the whole concept of Quantum Mechanics and its reliance on chance and probability, abhorrent. It proved to be totally at variance with his deep rooted religious beliefs, exemplified by his famous retort to Neils Bohr: "God does not play dice!" The work continues and scientists are still struggling to incorporate a quantum theory for gravity into a single 'Grand Unified Theory' (G.U.T.) - the so called T.O.E - Theory Of Everything, so far without much success.

Now, of course, we have a 'new' force to contend with - Dark Energy. Certain observations have indicated that the expansion of the Universe is accelerating with time, which is counter intuitive to our understanding of the basic theories of Relativity and gravitation. Dark Energy appears to be a repulsive force, a force acting against gravity. It is interesting to reflect that Einstein, who was also unhappy about the whole idea of an expanding universe, incorporated a constant into his field equations to hold the Universe static. His 'Cosmological Constant' - a force acting against gravity, was according to him, 'his biggest blunder'. Dark Energy, on the other hand is a force acting against gravity that is accelerating the expansion of the Universe. Understanding this force and its interaction with gravitation is going to take a little more than the contemplation of a falling apple!

Over 300 years have passed since Newton laid the foundations for our understanding of the universal force of gravity and a century has now passed since Einstein first proposed his Special Theory of Relativity but we still lack any significant understanding of the weak force that holds the Universe together and even less concerning the 'new' force- Dark Energy, that may one day rip it apart!

ANNUAL GENERAL MEETING

This will start with wine and cheese (£2 each).
The AGM itself will start at 8.45 and will be followed by a scientific entertainment.

The agenda will include the usual reports from Officers and Sections and the Election of Officers and five Ordinary Members of Council for the coming year. Council proposes the following::

Secretary	Julie Atkinson
Treasurer	Peter Wallis
Membership Secretary	Elisabeth Fischer
Programme Secretary	Jim Brightwell
Ordinary Members	Simon Lang
	Eric Morgan
	Michael Sabel
	Betty Weale
	John Oakes

Council invites further nominations to the above officer posts and ordinary members; such nominees shall be duly proposed and seconded and have agreed to serve if elected.

ANGUS McKENZIE - 1933 - 2005

It is with great sadness that we have to record the death of Angus McKenzie MBE at the age of 71 after an illness lasting for several months.

Angus was a well respected and long standing member of the Hampstead Scientific Society, having joined at the age of 14 in 1947. He was interested in all aspects of science, in particular, chemistry, radio and above all else, astronomy. As a youthful enthusiast, he was greatly encouraged during the 1950's by our late astronomy secretary, Henry Wildey.

Angus was born in September 1933 and was educated at St.Paul's School Hammersmith. He went on to study for City and Guilds in electronic engineering and acoustics, but failing eyesight caused him to abandon the course at the end of the second year. It was typical of Angus, that even the total loss of his eyesight in 1959, did not prevent him from remaining passionately interested in astronomy for the rest of his life. Having joined the British Astronomical Association in his teens, he remained a member until his death and would frequently attend meetings accompanied by his faithful guide dogs Simon and, latterly, Ward.

It is often said that the loss of a sense, such as eyesight, leads to the development of other senses to compensate. In Angus' case this was clearly demonstrated. He built a career in audio and radio, at first running a recording studio and later becoming an audio and radio consultant. He engineered and produced numerous recordings of classical music and carried out much research into stereo, binaural and quadraphonic sound. He has written many technical papers and given many lectures on topics as diverse as: radio and hi-fi, amateur radio, classical music, astronomy and the London underground railway. He has broadcast on both radio and television and was the author of many books on the subjects of hi-fi and amateur radio.

His great passion for the London Underground, on which he travelled frequently, led him to produce an auditory guide to the system in 1994 which was available free of charge to blind persons. This innovative guide, a kind of 'sound map', led the user from station to station providing clues as to their location from the pitch of track noises and the different sounds emitted by tube train brakes. I well remember the lecture he gave to the Society in which he vocalised the different noises made by different makes of tube train and the sounds which they emitted when accelerating, braking and passing over points.

Angus was also a regular speaker and fund raiser for the Guide Dogs for the Blind Association and in recognition for this work he was awarded the MBE in 1997. He was the first blind member of Mensa and was a fellow of the Institution of Electrical Engineers and the Audio Engineers Society.

For many years Angus lived in Finchley in a house crowded with electronic equipment and with shelf upon shelf of records and CD's, each labelled meticulously in Braille. I always marvelled that he could find a particular recording instantly. He had a talking computer and the house was equipped with a gigantic rotating radio aerial which could be seen from miles away and used by him to communicate with fellow radio 'hams' throughout the world.

Angus leaves two daughters, a son and two grand daughters and a multitude of friends who will mourn the passing of man who never let a physical disability get the better of him.

Doug Daniels (Astro. Sec.)

Science in the city. May I remind you of the guided walk to be held on Saturday 14th May, details of which were given in the Christmas Newsletter. Meet the leader, Mike Howgate, at 11am at the entrance to the Museum of London ; nearest tube Barbican. Would those planning to come please let Doug Daniels know on 8346 1056, so that he can inform Mike of the numbers.

Ice Age

We are currently in the grip of an ice age! This may seem a ridiculous statement when we see the mountain glaciers of the world retreating and the talk is all about Global Warming. However, the term ice age, as used by geologists, applies to a whole period during which there is a sequence of glacial and warmer interglacial periods. Our present ice age, sometimes called the Pleistocene Ice Age, has been with us for 3 million years; during this time there have been alternating cold and warmer periods with roughly a 100,000 year period. The ice started to retreat about 20,000 years ago, so we are currently in an interglacial. But, even so, 75% of all the fresh water on the planet is frozen in glaciers.

How do we know all this? Why does it occur? Has it happened before? What does it imply about the future climate? These are questions to which I will try to provide broad answers.

Geological Evidence

There is today a wealth of evidence from the shapes of valleys, moraine deposits, the grooves and scratches on bed rock, the existence of erratic boulders (rocks found distant from their place of origin), and the spread of chaotic sediments called glacial drift. These signs are not difficult to see, but they were not recognised as the result of glaciers for a long time. The first to do so was Louis Agassiz of Switzerland in the 1830s. He presented his observations and theory in a book in 1840 [1] , including the radical claim that ice had once covered the whole of Europe. Ice ages became one of the fiercest scientific controversies of the 19th century. Eventually, with careful mapping of the deposits and attention to how they sometimes overlapped, geologists came to recognise that there had been several expansions of ice far south in Europe and N. America during the Pleistocene Age.

Fossils

Fossils provided further evidence that the interglacial periods had been long enough for the recovery of flora and fauna. In particular it was shown that the sea level had been altering due to the volume of water trapped in the glaciers. At the peak of the last glacial period, 20,000 years ago, the sea level was some 120 m lower than now, as shown by fossil corals found at such depths.

Coring the Sea Floor

A problem with the geological observations was the uncertainty in the dates. Coring of the sediments on the ocean floor can answer this. It began with the exploration of the oceans by the Royal Navy's survey ship HMS Challenger in 1872-5, which traversed all the world's oceans and made landfall on all the continents, including Antarctica. But all they could do about sediments was to dredge samples. The technique has been developed since by the Swedish oceanographer Bxf6rje Kullenberg in the Albatross in 1947-9, using a piston-operated corer to obtain cores up to 15 m in length. One of the scientists on board was Gustav Arrhenius, a grandson of the great chemist Svante Arrhenius who was the first to suggest that the concentration of carbon dioxide in the atmosphere could affect the climate through its ability to trap the solar heat. Gustav showed that the sediment layers were alternately rich and poor in calcium carbonate (from fossil shells); this was later shown to correspond with the large changes in carbon dioxide associated with the glacial-interglacial cycles.

Since then, cores of several kilometres length have been obtained by drilling from the Glomar Challenger and the Resolution. The dating of the cores is assessed by measuring the remanent magnetism and comparing it with our current knowledge of the pattern of reversals in the magnetic field of the earth, as found from sea floor spreading. The time before the present is limited to a maximum of about 200 million years by the destruction of the sea floor at subduction zones.

Very significant measurements can be made of the isotopic composition of oxygen atoms in the fossil shells. Harold Urey, the discoverer of deuterium, had shown that the proportions were changed when the oxygen in the sea changed to carbonate in the shells and that the amount of change was affected by the water temperature; so the cores could provide a temperature record. Cores have shown that the ocean temperatures have gradually reduced over the last 55 million years, with particularly sharp drops at about 35 million years, when glaciation of Antarctica commenced, and during the last 3 million years when it began in the Northern Hemisphere.

Coring the Glaciers

Coring has also been used on the Greenland ice sheet. The cores not only provide information of climate change but contain air bubbles which record the ancient atmosphere. They have demonstrated that the content of greenhouse gases is closely correlated with temperature.

The cores do not go as far back as the ocean sediment cores. Recent ones from the Antarctic go back only 750,000 years. Drilling at the Russian Vostok base was stopped short so that a large subterranean Lake Vostok was not polluted. However it shows that over the last 400,000 years a regular oscillation in both temperature and carbon dioxide levels, with a 100,000 year period. During the cold periods there was more dust, indicative of higher winds during glacial periods.

Astronomy

It is characteristic of ice ages to have cold and warm phases; could this provide a clue to their existence? Agassiz himself showed little interest but in Britain, a hotbed of geological activity, there were many hypotheses. The right answer was proposed by James Croll a self-educated Scotsman. He suspected there was an astronomical cause. Obviously a major determinant of climate was the heat the earth receives from the sun, so he looked into the variations in the earth's orbit. His definitive book was published in 1875 [2].

The earth's orbit is not a circle but an ellipse and the solar distance changes annually. The eccentricity also changes due to the gravitational effects of the major planets, with a period of 100,000 years. It will reduce to nearly zero in about 30,000 years. Also important is the rotation of the earth itself around an axis inclined at present at 23xbd xb0 but, like a top, this tilt precesses due to the combined gravitational influence of the moon and sun. Taking into account the eccentricity of the earth's orbit, we find a 'precession of the equinoxes' with a slightly different period of 23,000 years.

Croll realised that the change in insolation would be rather small and sought ways in which it might nevertheless generate the glacial/interglacial cycles. He calculated the variation in eccentricity over a time from 3 million years in the past to one million in the future and argued that ice ages would only occur when the eccentricity was high; the curves showed regular peaks at about 100,000 years.

By 1912 Croll's work had been largely dismissed by geologists because it failed to match the estimated ages of glaciation very well. His work was taken up by Milutin Milankovitch, an engineer in the Austro-Hungarian Empire (later to become a Serb), with better data on the sun's heat and the earth's orbital and rotational variations. His work was held up during the Great War and was not published, in French, until 1920. He collaborated with the German scientists Kxf6ppen and Wegener of continental drift fame.

Milankovitch considered that the amount of tilt of the earth's spin axis, which actually varies between 22xbdxb0 and 24xbdxb0, could be important and pointed out that cool summers rather than cold winters were what could initiate a glacial. A cool summer would leave snow on the ground to be added to over the winter. He also recognised, as had Croll, that there was a positive feedback from the greater reflectivity of snow returning more of the sun's heat back to space. His major work [3] was published in German and an English translation was not available until 1969.

The astronomical theory did not go well however for many years, largely from the lack of time correspondence. It was not until the development of the coring of ocean sediments described earlier with their high quality time-scales that Milankovitch's predictions were confirmed. Final confirmation came in 1976 [4] from the oxygen isotopic variation of a core over 550,000 years which showed a 100,000 year cycle from the eccentricity change, a 43,000 year cycle from the axis tilt variation and a 20,000 year cycle close to the axis precession cycle.

The Earth's Past

The development of coring with its clear time-scale has provided a good picture of the Pleistocene Ice Age of the last few million years, but this is but a fraction of our 4xbd billion years history. Geologists have however been able to find evidence of consolidated glacial drift lying on top of grooved bed rock of ancient periods; such drift turned to rock is called tillite. Many of these finds are in what are now tropical areas. Geologists now believe that there were at least four major ice ages before the Pleistocene [5] :

Permo-Carboniferous	300 my bp
Snowball Earth	600 - 800 my bp
Early Proterozoic	2.2 - 2.4 by bp
Archean	2.9 by bp

The first of these is of particular interest because Wegener, who worked with Milankovitch, had searched the separate continents for common geological features as a part of his investigation of continental drift. He was struck by the apparently contemporaneous glacial deposits on all the southern continents and noted that a single ice sheet could account for it if the continents were all together and further south. However it was only many years later when his theory had been translated into plate tectonics that his conclusion was seen to be correct. The location of Gondwanaland near the South Pole explains how such glacial records appear in now tropical countries. An estimation of the spread and duration of the glaciation suggests that the total volume of ice exceeded that of the Pleistocene glaciation.

The next listed above occurred near the end of the Proterozoic eon and is actually called the Late Proterozoic glaciation, but is here named Snowball Earth as there is evidence of its being extremely severe, to the extent that glaciation reached low latitudes. The evidence is from remanent magnetic field of low dip angle in the sedimentary rocks. But even if all land areas were glaciated, it doesn't prove that the sea was frozen. Joe Kirschvink, a geochemist at CalTech, pointed out in 1992 that there are banded iron deposits (BIF deposits) associated with the glaciation. These are quite well known from early in the earth's history when the atmosphere had little oxygen, but how could they exist when the atmospheric oxygen level was high? Kirschvink argued that it was only possible if the sea was frozen. Without contact with the atmosphere the sea below the ice would become depleted in dissolved oxygen, allowing iron concentrations to increase; when the ice melted contact with the atmospheric oxygen would resume and deposit the BIFs.

Snowball Earth is still a matter of controversy; if it did occur, we have to ask how it terminated, as the global ice and snow would reflect most of the sun's heat back to space. Kirschvink argued that carbon dioxide in the atmosphere would continue to be supplied from volcanoes but the two main mechanisms for its removal, photosynthesis in the sea and the weathering of rocks on land, would have stopped. The concentration would rise and the green-house effect would melt the glaciers.

There is now further evidence to support the snowball earth hypothesis. Studies of sedimentary rocks in Namibia using the isotopes of carbon rather than oxygen show the cessation of the fractionation by plankton during the glacial interval. Similar results elsewhere in the world suggest a global change. We do not know whether there were earlier episodes of a similar nature, but the absence such an episode later may be due to two factors: that the sun's radiant heat has been increasing and that in the Late Proterozoic the continents were all in tropical regions. This would have meant more heat reflected from the tropical land (with no vegetation at the time) and less absorbed in the sea.

Our ability to analyse the earlier ice ages listed is much reduced in view of the time elapsed and our ignorance about the locations of the continents. Nevertheless, geologists consider that the Early Proterozoic and Archean ice ages have occurred. The long gap between the former and Snowball Earth, 1.4 billion years, seem not to have any, but we don't know why.

Recently there have been suggestions for a possible cause of our present Pleistocene ice age. About 50 million years ago the Indian Plate began to collide with the Asian Plate and the Himalayas and the Tibetan Plateau were formed some 35 myrs ago; this is the time when glaciation began in Antarctica. It is proposed that the immense high-altitude area allowed increased weathering, reducing the carbon dioxide and causing cooling. The positive feedback from ice reflecting energy back to space led to today's ice age.

Conclusions

For much of its history the earth has been very warm, but there is reliable evidence of at least five ice ages, periods of several million years with alternating cold and warmer phases; we are at present in one of the latter. Some of the ice ages may have been extreme enough to cover all the continents and freeze the seas.

It seems that a basic cause for the ice ages is the disposition of the continents on the globe and the greater reflectivity of the land compared with the sea, with its ability to store the sun's heat. There are two important phenomena conspiring to cause rapid changes to the climate. One is the positive feedback arising from the high reflectivity of snow and ice. The other is the importance of greenhouse gases in keeping the planet warm. Without the continual discharge of carbon dioxide into the atmosphere from volcanoes, we would be a frozen planet.

The technique of coring of sea sediments and ice fields has demonstrated that astronomical effects have a major influence on the variations within each ice age. The variation of the eccentricity of the earth's orbit is the dominant cycle, of 100,000 yrs.

The burning of fossil fuel by humanity may have a short term effect in terminating the current ice age, though this may well occur anyway as the eccentricity is now reducing. In longer geological terms, the fossil fuels will soon have gone.

I recommend Doug Macdougall's book Frozen Earth - the once and future story of ice ages for further reading.

Peter R Wallis.

[1] xc9tudes sur les glaciers. Back
[2] Climate and Time in Their Geological Relations: A Theory of Secular Changes of the Earth's Climate, 1875. Back
[3] Milankovitch, Canon of Insolation and the Ice Age Problem, 1941. Back
[4] Hays, Imbrie & Shackleton, "Variations in the Earth's Orbit: Pacemaker of the Ice Ages",Science, 1976. Back
[5] D Macdougall, Frozen Earth, 2004, University of California Press, London Back

HSS Lecture Meetings in the Crypt Room at St John's Church, 8.15 pm.

December 16th Explosions from the Sun by Louise Harra (University College London).

January 13th A Neuroscientist's View of Metastatic Disease by Professor Mustafa Djamgoz (Imperial College).

February 10th Human Embryos, Stem Cells and Cloning by Dr Joyce Harper (University College London).

March 17th Science, History, Art and Computers by Professor Robert Weale (HSS).

Science in the City

Leader : Mike Howgate M.Sc

1. Museum of London. A working, we hope, Roman water lifting machine - was this the first machine in London?
2. Postman's Park. Tree ferns are classic 'living fossils' and have been virtually unchanged since the Jurassic period.
3. 81 Newgate Street . BT offices on the site of Giglielmo Marconi's first public transmission of wireless signals on 27th July 1896.
4. Just off Newgate Street . Passage through Merrill Lynch contains benches of Portland Stone 'Roach Bed' with abundant fossils.
5. Saint Paul's Cathedral. On the main entrance steps are sections through primitive 450 million-year old straight nautiloids, relatives of the later ammonites and present-day nautilus, squid and cuttlefish. The bollards in front are of Shap granite. In the churchyard to the north is a large Gingko biloba or Maidenhair tree, another living fossil from the Age of the Dinosaurs.
6. Aldermanbury. The museum of the Worshipful Company of Clockmakers contains a small display and clocks by John Harrison (1693 - 1776) of Longitude fame, including a half-scale model of H1 and H5, his last timepiece.
7. Fore Street. The Post Office is fronted with slabs of 450 million year old Green Volcanic Ash with evidence of an earthquake.
8. Fore Street.The Salter's Company, one of the City Livery Companies, still has interests in Chemistry, mainly promoting education in the science.
9. St. Alphage Gdns & Wallside. On the way back to the Museum of London we will pass several remaining stretches of the Roman/Medieval wall of the City. There is a convenient cafxe9 beside the museum and those who wish to make a day of it are advised to see the London before the London and Roman galleries.

An Ancient Remedy?

Some of our older members may well have problems with their joints. I myself take a non-steroidal anti-inflammatory drug (NSAID) for my knees, but I am aware that prolonged use can lead to stomach and renal problems. Another drug often used is a 'cox2 inhibitor' but one of these, VIOXX has recently been withdrawn as a side-effect is an increased risk of heart attack! The other main option is a knee replacement, but this involves major surgery and is more complex than a hip replacement. A recent article in Nature[1] by Helen Pilcher reports studies which suggest the use of an ancient treatment for such osteo-arthritic problems - leeches.

The use of leeches in human medicine has a long history: images of leeches have been found on the walls of ancient Egyptian tombs and it has been reported that Marcus Aurelius used them for blood-letting 1500 years later. After the 19th century they fell from favour though, surprisingly, they are still used post-operatively in plastic surgery units.

The studies [2] reported a trial of 24 people with knee problems. Up to 6 leeches were applied for about an hour till the leeches fell off gorged with blood. Control patients were given an anti-inflammatory gel twice a day for a month. One week after treatment started, the leech-treated patients reported a 64% reduction in pain, compared with 17% for the controls. Michalsen and Dobos have since carried out a study with 400 patients, not yet published, and claim even better results.

It is not easy to validate such claims as they are based on the patients' own reports and consequently open to auto-suggestion. Nor is yet clear what precise bio-chemical action may be responsible. The leech certainly injects complex proteins into the patient prior to sucking out the blood and some of these may have an anti-inflammatory effect. But nor is it certain that the pain arises solely from inflammation as Nsaids do not work for all patients. There may be a vascular disorder and the leech saliva may act as an anti-coagulant.

At present the verdict is "not proven", so no leeches for Christmas, thank you!

PRW

[1] Nature, 4 Nov 2004, pages 10,11. Back
[2] Michalsen A et al., Ann. Intern. Med.139, p 724 - 730 , 2003. Back

Oxygen.

Probably the most remarkable thing about the earth's atmosphere is the high proportion of the gas oxygen --- about 21%. No other planet in the solar system has more than a trace. Oxygen is also a very corrosive element; life could not have arisen spontaneously in such an environment. Yet we and the majority of life on the planet cannot live without it. How 'on earth' did this paradoxical situation arise?

It is generally accepted by earth scientists that the earth (and the other inner planets) was formed by the collection of the many planetesimals orbiting the sun in the inner regions of the solar nebula. The gases left in the nebula after the formation of the sun were driven off from this region to where it coalesced into the gas giants, probably by the solar wind and the magnetic field of the fast rotating sun [3]. The planetesimals were generally too small to hold an atmosphere themselves, so the nascent earth started cool and without an atmosphere. It heated up due to the deposition of the gravitational energy of the in-fall and the radioactivity of the elements uranium, thorium and potassium. Over time this boiled out volcanically a gaseous atmosphere, probably one largely of nitrogen, carbon dioxide and water vapour. There would have been no significant free oxygen. At the present time there are some 500 active volcanoes around the world which add an estimated cubic mile of solid material to the surface each year; at this rate, between 3xbd and 4xbd million cubic miles of solids would have been added by volcanoes in the life-time of the earth, comparing well with the total volume of the continental crust --- and volcanism may have been greater in the early days. But it is the gases with which we are concerned here.

It is not known whether this original reducing atmosphere remained or whether there was some major astronomical event to start one again. Professor Cloud [4] has suggested that some 3xbd million years ago the earth captured the moon, an event of such violence to destroy the previous atmosphere and start a new one. He based his hypothesis on geological evidence for much larger stromatolites [5] in the Pre-Cambrian, showing considerably greater tides than today's. The tidal effects would have strongly heated the earth and in time caused the moon to recede to its present distance. Whatever the early history, we still have to explain the source of the oxygen atmosphere of today.

In the early reducing atmosphere, any life must have been confined to anaerobic bacteria and primitive single-celled organisms. They could only have operated by the biological process of fermentation, a much poorer source of energy than respiration. The first source of oxygen must therefore have come from the photo-dissociation of water vapour by ultraviolet light, of which there was a plentiful supply from the sun. Ozone would also be formed and would initially react at a high rate with surface rocks. Calculations [6] show that this accounts for the oxidation of sedimentary rocks on the continents and in the sea over geological time. However it could only lead to an atmospheric concentration of oxygen one thousandth of that today, because of a self-limiting mechanism, called the 'Urey Effect' [7] , in which the ozone protects the water vapour below from dissociation.

This ozone would also offer some limited ultraviolet protection to life in water. The life could still not tolerate the UV at the surface, but at a few metres depth it would be safe. It is believed that this allowed some photosynthetic processes to evolve. This releases oxygen from water during the reduction of carbon dioxide into carbohydrate, employing visible light so not subject to the 'Urey Effect'. The build up of the oxygen concentration would have been very slow at first due to the capture of oxygen elsewhere and the limited areas of shallow water; deeper waters would have had convection bringing the bacteria to near the surface where they were still vulnerable to ultraviolet.

A major step in the build-up came when the oxygen concentration rose to above one hundredth of that today. Then respiration was able to evolve and replace fermentation as the energy source; this offered 30 to 50 times the energy release per molecule, as noted by Pasteur 150 years earlier when studying wines. At this oxygen level, ultraviolet can only penetrate some 30 cm into the sea. The evolution of more complex and efficient biological systems allowed life to colonise the deeper seas. This major evolutionary event occurred at the beginning of the Palaeozoic, 600 million years ago. Before this there is only fossil evidence for primitive life. Within a few million years we have the multiplicity of fossils of the Cambrian, Trilobites etc.

This burgeoning of sea life continued to raise the oxygen level until, at about one tenth of the present level, the deeper ozone layer cut off the ultraviolet at the surface and allowed life to colonise the land in the late Silurian, some 400 million years ago. Forests appeared in the early Devonian, producing more oxygen.. The eventual levels may have exceeded the current level in the Carboniferous: such an excursion could have led to a reduction in carbon dioxide, reducing the greenhouse effect and causing the ice ages of the Permian, 200 million years ago.

Well, that is my story. It's really about how you and I came to be. Without oxygen, we wouldn't be here. But without us and all our precursors, nor would the oxygen atmosphere. Perhaps there is a hint that we shall not find intelligent life on the other planets of the solar system, as they do not have a similar atmosphere.

Peter R Wallis

[3] Fred Hoyle first published this idea, explaining the segregation between the dense inner planets and the outer gas-rich giants and also the reduction in the angular momentum of the sun. Back
[4] Prof Preston Cloud, University of California, Santa Barbara, 1969. Back
[5] Stromatolites are dome-shaped structures found only in the intertidal range. Back
[6] Lloyd V Berkner and Lauriston C Marshall, Texas, 1965. Back
[7] Dr Harold Urey published it in 1959. Back
and a Happy 2005
to everyone of you

Like the rest of the world - barring exceptions - I am imbued with the Christmas spirit, and can hear the herald angels sing. I will not, therefore, echo warnings about what food we should or should not be consuming ("it's only once a year"). Nor will I make any remark about drinking ("the odd half dozen glasses can't cause any harm"). And I shall keep one of my chief concerns entirely to myself, namely the media's unremitting references to the Nanny State. I shall not point out - it being Christmas - that their attitude testifies to their basic ignorance of science; that the very invention of the term "Nanny state" proves that there is no reply to sarcastic or ironic remarks; that, in fact, we ought to thank our lucky stars that a caring state makes information available for our potential benefit; and that the media ought to adopt a more responsible attitude in explaining the links between society, science, and survival. I shall refrain from mentioning that, in my view, the all-pervasive plugging of personal choice can be overdone. It is overdone, when the chooser is ignorant of the consequences of his choice.

As I promised, I shall not mention any of the above, but - Scrooge or not - shall wish you again
and a Happy 2005
to everyone of you

Robert Weale

HSS President

The first lecture will be on HOW WE REACHED THE MOON by Jerry Stone a Fellow of the British Interplanetary Society. As usual, it will be held in The Crypt Room at St John's Church, Church Row, NW3 and will be on Thursday 16th September.

The Council

For those members who were unable to attend the AGM, the Council is as follows:

President:	Professor Robert Weale
Secretary	Julie Atkinson
Treasurer	Peter Wallis
Membership Secretary	Elisabeth Fischer
Programme Secretary	Jim Brightwell
Ordinary Members	Brian Bond
	Simon Lang
	Angus McKenzie
	Eric Morgan
	Michael Sabel
	Betty Weale
	John Oakes
Section Reps: (Meteorology)	Philip Eden.
Section Reps: (Astronomy)	Doug & Julia Daniels

Feel free to contact any of them with your suggestions.

Peter R Wallis

Venus in Transit

Doug Daniels (Astronomical Secretary)

Because the orbit of Venus lies between the Earth and the Sun, every so often, as the planets rotate about the Sun, all three bodies will find themselves 'in line'. However, the orbits of the Earth and Venus are not in the same plane, Venus' orbit is tilted by about 3 degrees with respect to the plane of the Earth's orbit. This slight tilt ensures that on most occasions when Venus passes between us and the Sun, it will transit either above or below the solar disk and it will be invisible, lost in the solar glare. However, if Venus happens to cross the Sun at the point where the orbits of the Earth and Venus intersect, Venus will be seen to transit the solar disk. On such occasions, Venus is seen as a jet black spot crossing the bright disk of the Sun. Due to the complexity of celestial mechanics, this condition occurs infrequently. Transits of Venus take place in 'pairs' separated by about 8 years at intervals of about 125 years. Just like total solar eclipses, not all transits will be seen from convenient locations on the Earth's surface. On June 8th 2004 all these rare conditions were met and Venus transited the Sun and moreover, the whole event from ingress to egress was visible from Hampstead.

In the past, transits of Venus were important because if they were observed from widely separated locations on the Earths surface, and accurate timings were taken, they provided a convenient method of determining the Earth-Sun distance - the Astronomical Unit (AU). Knowing this measurement accurately is vital to determine the distances of all the other planets in the solar System. Today, of course, we have other methods at our disposal to determine this distance with considerable accuracy, but the transit of Venus was going to be of interest for other reasons. Since the last transit occurred in 1882, seventeen years before our Society was formed, no one living today has ever witnessed such an event.

The last transit occurred at a time when photography was in its infancy, so we really had no accurate record of what would be seen. For example, in 1882 it was reported that it was impossible to obtain accurate timings due to a phenomenon known as the 'black drop' effect. As the black disk of Venus touched the inner edge of the Sun's bright limb, a distortion took place, drawing a column of black between the limb of the Sun and the disk of Venus. This effect was shown in many of the drawings made from visual observations at the time. In addition, no one has ever witnessed a transit of Venus using an Hydrogen Alpha filter. Could the silhouette of Venus actually be seen against the Solar Corona or perhaps against a Solar Prominence, just before it touched the solar disk? Would we be able to see Venus' atmosphere illuminated by the Sun as it touched the solar limb? We were about to witness a very rare astronomical event, an event to which modern imaging technology had never before been applied, so we would just have to wait and see.

The astronomy section began to prepare early. After our experience with last year's transit of Mercury and anticipating that the 'mass media' would soon become aware of the forthcoming event and whip up public interest, we anticipated that we would be in for a busy time! Simon Lang produced a useful information sheet and some advance publicity appeared in the Hampstead and Highgate Gazette two weeks before the event. Simon and John Hayden both volunteered to open the observatory shortly after sunrise as the transit was due to commence at about 05.20 hrs.UT. On the preceding the day, Simon, Ron Smith and Gordon Harding put in an enormous effort and a considerable number of man hours to prepare the Observatory for the anticipated hordes of visitors. Simon worked all through the night to erect a series of sun screens to provide shade for the visitors. We sincerely hoped that these would be required, for although the weather on the preceding day was fine and clear, there was no guarantee that the same conditions would prevail on the day of the transit. We still retained the vivid memories of the ill fated total eclipse expedition to Redruth/Cornwall in 1999!

The sunscreens were adorned with information sheets which Simon had produced on the subject of the Sun, Venus and transits in general and he was still working frantically when I arrived at 5.00 am, greatly relieved to see the sun rising in a clear blue sky. It looked as if we would by lucky and that we would see the transit under almost perfect conditions. My only concern was with the contrails from numerous passing aircraft which could impair the definition, as had happened to me last year during the transit of Mercury.

We set about preparing the 6-inch Cooke and fitting it with its projection screen, greatly relieved to find that at low declination the screen just cleared the dome rail. We were also pleased to discover that the trees to the east would not cause a problem at ingress. We then set up the Wildey 6-inch telescope outside the main dome together with my own 6-inch Helios refractor. This was to be the first 'outing' for the Wildey telescope, the last instrument made by the late Henry Wildey. This alt-azimuth mounted, short focus 6-inch refractor was acquired from Henry's family after his death at the great age of 90 last October. Both the Wildey and the Helios instruments were equipped with safe objective solar filters made by Terry Pearce. These consisted of optical glass vacuum coated with layers of aluminium and titanium. Terry began experimenting with these filters well before the transit of Mercury last year, so we knew they would be safe and would allow members of the public to see the transit in all its glory with the jet black disk of Venus passing over the granulated solar photosphere. In addition to the Wildey and the Helios, Simon also bought along his 4-inch refractor, also fitted with a Wildey object glass and a Pearce filter, and Jacquey Oppenheimer came well equipped with her 8-inch Meade Schmidt Cassegrain, fitted with a '1000 Oaks' solar filter. As it transpired, all these instruments were put to very good use as we were at times almost overwhelmed by the sheer number of visitors taking full advantage of the near perfect weather conditions to observe this historic transit.

Visitors began to arrive early to witness the ingress of the planet and observe the famous 'black drop' effect which to me did not seem at all pronounced. At high magnification the jet black silhouette of Venus could be seen clearly touching the inner edge of the sun's limb. Every so often, as the atmosphere rippled the limb, the image of Venus distorted to produce a tiny dark connection to the limb. These effects were clearly due to atmospheric turbulence but at no time did they resemble the drawings made during the last transit of 1882. One can only conclude that the Earth's atmosphere was more troubled during that event, or that telescope optics had vastly improved in the intervening period.

At first contact, just as Venus took a bite out of the Sun's limb, we looked to see if any light was refracted by Venus' dense atmosphere. Nothing of the sort was observed - just a jet black silhouette, but we were all surprised at the size of it compared to image remembered from last year's transit of the diminutive Mercury.

Many parents brought their offspring along on their way to school and throughout the morning many classes of school children accompanied by their teachers came to observe this rare once in a lifetime event. We estimated that in all about 200 children observed it together with about 300 adults.

I had intended to make timings but the sheer volume of visitors kept me constantly occupied at the 6-inch Helios. I did at least manage to take a few digicam images around the times of ingress and egress and these were swiftly posted on the website on the following day thanks to Julie Atkinson. The 6-inch Cooke was used to project the image and John Tennant did sterling work within the dome demonstrating continuously to a packed and at times overheated audience. This event also gave us our first opportunity to put the Wildey telescope through its paces, ably manned throughout the session by Gordon Harding.

The large crowds were also very generous with donations to the Society encouraged by Michael Wynne and later Ron Smith, to part with a total exceeding £500 towards the upkeep of the observatory. When Michael asked me if we had a bucket, my first thought was that he was intending to rig up emergency toilet facilities, facilities sorely lacking in the vicinity of the observatory, but no, it was to be used to collect the money! It is entirely due to him that we collected so much!

The whole event, which lasted the best part of 7 hours was a total success and certainly raised the profile of the Society particularly to local schools and their science teachers. We thank all those members who came along to assist on a long, hot, exhausting but exciting day. Our special thanks must go to Simon Lang who cheerfully took on the 'lions share' of the hard physical work and organisation which made this historic astronomical event an unmitigated success and provived an exciting climax to a very eventful session at the observatory.

Our last lecture meeting this session will be:
Thursday May 20th, Dr Gerald Roberts (Birkbeck College) on Earthquakes and Active Faults in Italy.

ANNUAL GENERAL MEETING on Thursday June 24th at 8.15 pm.

This will start with wine and cheese (£2 each).
The AGM itself will start at 8.45 and will be followed by a Scientific Quiz.

The agenda will include the usual reports from Officers and Sections and the Election of Officers and Ordinary Members of Council for the coming year. The Council re-appointed Professor Robert Weale to be President at its meeting on 21st April. Council also proposes the following::

Secretary	Julie Atkinson
Treasurer	Peter Wallis
Membership Secretary	Elisabeth Fischer
Programme Secretary	Jim Brightwell
Ordinary Members	Brian Bond
	Simon Lang
	Angus McKenzie
	Eric Morgan
	Michael Sabel
	Betty Weale
	John Oakes

Council invites further nominations to the above officer posts and ordinary members; such nominees shall be duly proposed and seconded and have agreed to serve if elected.

Special Business. Council proposes to amend Clause 5b of the Constitution to reduce the number of ordinary members on the council from 8 to 5; in their view the present total, inclusive of Vice-Presidents and the Secretaries of Sections, has become too unwieldy. The reduction would be effected by natural wastage as members retire from Council under the four-year rule.

HSS Visit to the London Wetland Centre, Saturday June 12th.

The award-winning London Wetland Centre is the first project of its kind in the world ---more than 40 hectares of created wetlands in the heart of a capital city. In February 2002 the center was designated a Site of Special Scientific Interest (SSSI), supporting nationally important numbers of Gadwall and Shoveler duck.

Meet at the Bus station adjacent to Hammersmith Tube Station at 1230. Then take the 283 "Duck Bus", arriving at 1pm. Sandwiches or lunch in the Cafeteria. Tour, with guide commences at 2pm.

The entry price is £6.75, with £5.50 for Seniors and £4 for children; the bus fare is extra, though covered by your Freedom Pass or Oyster Card as appropriate.

A Note to all members from the President:

Those of you who attended the March and April meetings of the HSS may have been justified in wondering what is going on with our planning and organization. In March we arranged an ex tempore debate on the scheduled speaker's topic at three days' notice because the speaker was prevented from coming, his father being about to die. This was not a contingency to be foreseen. In April it was a little more predictable that London traffic would wreak havoc with the speaker's transit through it so that his talk on the Transit of Venus became compromised.

Lightning obviously does strike twice (a topic for a talk?), but someone has to carry the can for the Unexpected. Please accept my apologies for any inconvenience you may have suffered, and also my thanks for your good humour in the face of adversity.

Robert Weale, President HSS

Royal Society Summer Science Exhibition.

It is held at the Royal Society at 6-9 Carlton House Terrace, London SW1Y 5AG and is open to all, with free entry. The nearest underground stations are Piccadilly Circus, Charing Cross and Green Park; the nearest bus-stops Trafalgar Square, Haymarket and Lower Regent Street.

Times of Opening:

HSS Lecture Meetings in the Crypt Room at St John's Church, 8.15 pm.

December 11th Sea Level Change, Old and New by Professor Michael Tooley of Durham University.

January 22nd Machine Minds, What do they tell us about the real thing? By Professor Igor Aleksander of Imperial College.

February 19th Dinobirds by Dr Angela Milner of the Natural History Museum.

THE 'DARK SIDE' OF THE UNIVERSE

Doug Daniels

It was, I believe, Iain Nicholson who, at a lecture to the H.S.S, some years ago, described the Universe as "rather like a pint of beer", the froth on the top representing all the matter that we can see and the greater volume of the 'beer' beneath, representing the 'Missing Mass' - the major constituent of the Universe that we cannot see. That oblique reference to the product of the brewers' art may now be even more appropriate. Was it not the purveyors of that well known brew - Guinness, who described their product as 'Dark Energy'? It now seems that 'Dark Energy' is the new 'force majeure' in cosmology.

If we accept the standard model of an expanding Universe created from an initial hot 'Big Bang' and we can determine the rate of expansion, we should be able to calculate its approximate age and deduce a pattern for its evolution and ultimate fate. There are three possible outcomes:

(1) The Universe will continue to expand forever as predicted in the 'Open Universe' model. In the course of time, with increasing entropy, the stars will eventually use up all their fuel, cool, fade and die in accordance with the laws of thermodynamics. Such a Universe is described as having 'negative curvature', it is usually depicted as a 'saddle shape' on which parallel lines diverge.

(2) It will stop expanding at some point as predicted by the 'Closed Universe' model and then possibly begin to contract again back to its point of origin to end in a 'Big Crunch'. This model is harder to swallow as it involves a reversal of the 'Arrow of Time' and is not consistent with the laws of thermodynamics. Described as having 'positive curvature', this model can be visualised as a sphere on which parallel lines converge.

(3) It will remain more or less 'Flat', a condition where the expansion rate of the Universe is equal to its escape velocity. Visualised as a flat plane, parallel lines will always remain parallel, so this model at least conforms to the principals of Euclidean geometry.

In the theory of General Relativity, Einstein states that "Matter tells space how to curve" and whether the Universe is 'Open', 'Closed' or 'Flat,' depends upon the 'Mean Density' of matter and energy. If this density exceeds an amount known as the 'Critical Density', the Universe will be 'Closed', if less it will be 'Open'. If equal, it will be 'Flat'.

To determine which of these three models is correct, it would help if we knew the total mass of the Universe. It is here that we run into difficulty. Observations of the behaviour of galaxies in galactic clusters, for example, indicate an overall mass for the cluster as much as ten times that of the luminous matter which we are able to see. This differential has been described as the 'Missing Mass.' It has been suggested that the 'Missing Mass' could be accounted for by the presence of dark matter and that this might exist in two possible varieties: 'Cold Dark Matter' and 'Hot Dark Matter'.

Cold Dark Matter may exist in the form of exotic elementary particles called WIMPS, short for Weakly Interacting Massive Particles, particles that interact only weakly with radiation and matter. Early in the history of the Universe, such particles may have clumped together to begin to build the framework for the formation of larger structures like galaxies.

Hot Dark Matter particles are believed to possess large random velocities and could include such particles as neutrinos, if they actually possessed a small mass. These particles would predominate during the decoupling era of matter and radiation and would build large scale structures first which would ultimately fragment to form clusters of galaxies. Such theories for an evolution of a Universe modelled on the existence of either hot or cold dark matter remain unproven.

Some of the 'Missing Mass' might be accounted for by less exotic materials. Cold dwarf stars, dead stellar remnants, neutron stars and black holes, are examples of objects called 'MACHO's' - Massive Astrophysical Compact Halo Objects, believed to exist in a vast roughly spherical halo surrounding our galaxy and, by inference, other galaxies as well. It has been postulated that as much as 90% of a galaxy's mass might consist of such material in the halo.

In whatever form it exists, there can now be no doubt that the Universe contains far more dark matter than luminous matter and there is evidence that the total density is still less than 30% of the 'Critical Density' required for a 'Closed Universe.'

Recent detailed examination of the Cosmic Microwave Background (CMB) in 2001 by the Wilkinson Microwave Anisotropy Probe (WMAP), has indicated a new composition and age for the Universe. WMAP has plotted temperature fluctuations in the CMB down to one millionth of a degree. These fluctuations are a kind of 'fossil record' of density fluctuations that existed in the early Universe just 380,000 years after the initial 'Big Bang'. Observed as irregular patches they vary in size according to the curvature of space. Experiments carried out by WMAP seem to indicate that the Universe is in fact 'Flat' i.e. it has zero curvature and is 13.7 billion years old. It appears to be composed of 4% Baryonic Matter (the atoms which make up everything), 23% Dark Matter and 73% Dark Energy.

So what is this 'Dark Energy' that now appears to dominate our Universe? At this juncture, it is safe to say 'nobody knows!' But there is evidence from another source to suggest that it does actually exist - from a recent observation of a type 1a Supernova.

Type 1a Supernovae occur when a White Dwarf, which is part of a binary star system, draws off material from its companion star and in so doing increases its mass to a critical level. At this point it is destroyed in a violent explosion of energy. As there is a close relationship between the mass and luminosity of such stars when they become Supernovae, it is possible to determine their distance from observations of their observed and predicted luminosities. Such events occur from time to time in distant galaxies and therefore the distance of the galaxy itself can be calculated. As the mean density and curvature of space will affect the relationship between the red shift and brightness of such Supernova outbursts, observations of such events can provide valuable information on the rate of expansion of the Universe. Recent examination of the red shift and luminosity of a type 1a Supernova in a very distant galaxy, the furthest so far observed, seem to indicate that the expansion rate of the Universe is increasing and not as we might expect, decreasing with time. It is as if some repulsive force is at work acting against gravity. It must be borne in mind that this conclusion is derived from a single observation, but its conclusion is, nevertheless, supported by the results obtained from WMAP.

When the concept of an expanding universe was first proposed, it did not appeal at all to Albert Einstein, so he suggested a force to keep the Universe static, building it in to his field equations. He called this mathematical proposition the 'Cosmological Constant', a force acting against gravity. Later, when observations proved the expansion of the Universe to be an irrefutable fact, Einstein admitted that his Cosmological Constant was the 'biggest blunder' that he had ever made! It now seems that such a force might exist after all but not quite as Einstein had envisaged it. Far from holding the Universe static, Dark Energy is actually causing it to expand at an increasing rate.

At this moment we know next to nothing about Dark Energy, except for the fact that it appears to currently pervade the Universe. This may not always have been the case, as in the early history of the Universe gravity would have slowed down the expansion. Later on when the energy density of matter and radiation fell below that of Dark Energy, possibly when the Universe was just half its present age, Dark Energy took control and begin to accelerate the expansion of the Universe. Investigating this 'Dark Side' of the Universe is the new challenge for cosmologists.

Junk DNA?

By Peter Wallis

It was 50 years ago that the discovery of the double helix was announced and it has been in this year that the 'Human Genome Project' announced the completion of the "final draft" of the DNA sequence for Homo sapiens. Until now the work of the scientists has concentrated on the genes, those sections of the DNA that encode proteins, regarded as the basis of heredity and the 'blueprint' of all life.

The central dogma so far has been that DNA makes messenger-RNA, RNA makes protein and proteins do all the biological work. They do this through their ability to twist themselves into intricate three-dimensional shapes; some form muscles and organs, others become enzymes to catalyse, metabolise or signal. The number of genes that code for proteins in human DNA is estimated to be about 25,000 [1], but this represents only 1 or2% of the total DNA sequence, estimated to be 3 billion units long. Oddly enough, the number of genes in different organisms does not appear to correspond closely to the complexity of the organism; rice plants have more than humans, 30,000!

In 'higher' organisms, such as humans, there are extensive sequences which do not code for proteins, some separate from the genes and called "junk DNA" and others inside genes and called "introns" which are spliced out in the transcription process. It appears that the amount of all these corresponds more closely with the complexity of the organism. Previously ignoring them as contributors to inheritance, scientists are now recognising that some of these additional sequences have a part to play; they may not code for a protein, but are transcribed into RNA which can alter the behaviour of cells. This was discovered from studies of the genome of mice, but a team of scientists at the National Human Genome Research Institute has recently compared excerpts from the genomes of pigs, humans, dogs, rats and 7 other species and found that many of them appear with only minor changes in many species ; this is a strong indication that they contribute to evolutionary fitness.

Biologists are now turning to studies of 'active' RNA. One form is called "anti-sense RNA". This is made from the complementary DNA strand that sits opposite a DNA-coding gene on the double helix. This is usually not transcribed into RNA and biologists think of it as a back-up copy which can be used by the cell to repair damage to the gene. However, while the gene is producing a sensible RNA message, its alter ego can produce an anti-sense RNA with a complementary sequence; if this meets its pal, they can form a double-stranded ladder which interferes with the intended protein manufacture. Until recently, this was thought to occur only in plants and bacteria, but it has now been shown to occur in humans. It is thought that these interact with another part of the cell's machinery, the "RNA interference machinery", which chops up double-stranded RNA; this helps to protect against viruses which penetrate the cell in that form

Another form of active RNA is "microRNA", first observed in roundworms, as short non-coding RNAs that fold back on themselves like hairpins. They appear to originate from the 'introns' that are snipped out from the gene before the messenger RNA can be generated to code for a protein. Together with the interference machinery, they can control other genes.

There is a great deal more to learn about the genome, and we have clearly been wrong to speak so disparagingly about "Junk DNA".

Dr Ewan Birney of the European Bio-informatics Institute at Royal Society lecture on 4th Dec 2003

Henry Wildey 1913 - 2003.

We are very sorry to announce the death of our Vice-President Henry Wildey, just hours after celebrating his 90th birthday. One of the oldest members of the Society, his contribution to it is immense; he was Astronomical Secretary from 1946 to 1988. He was active all his life in the field of Astronomy and the manufacture of astronomical instruments for both amateurs and professionals. He enjoyed wide interests in opera and in Egyptology.

A fuller obituary written by Doug Daniels is to be found on the Society's website www.hampsteadscience.ac.uk and will be in the journal of the British Astronomical Association.

The first lecture will be on Thursday 18th September at 8.15 pm in the Crypt Room at St John's Church, Church Row, NW3. It will be on Food as Fuel and given by Professor Harold Baum of Kings College, London.

The Council.

For those members who were unable to attend the AGM, the Honorary Office-holders and Members of Council for 2003/4 are as follows:

President: Professor Robert Weale

Feel free to contact them with any suggestions.

The British Association.

The AGM also decided that the Society should affiliate to the BA for a trial period as shown by their logo on the Programme Card. I have enclosed with this posting a notice on the Festival of Science. HSS members will be entitled to join the BA as individuals at a 20% discount. I'll announce details for doing so in the Christmas Newsletter.

LIGHT POLLUTION - NOT A NEW PROBLEM FOR ASTRONOMERS

By Doug Daniels

I got my first look at a really dark night sky when I was just four years old - it was in 1944 during the second World War. At that time, cities had a night time blackout imposed upon them. There was no street lighting, no advertising lighting and even the buses and the few cars moving on the roads had their headlights reduced to narrow slits. In consequence, the night sky was so dark that the Milky Way could be seen even from London! It must have created quite an impression on me because less than a decade was to pass before I built my first telescope. During that decade however, the rot had already began to set in and by the time I was ready to take a closer look at the night sky, the Milky Way was no longer visible and at least two stellar magnitudes were lost to view.

I began to think seriously about the effects of light pollution recently, because I was asked to submit evidence to a Parliamentary Select Committee which is currently considering the threat imposed to the study of astronomy by this insidious menace. It was pointed out that the night sky is in fact a Site of Special Scientific Interest (an S.S.S.I.), which has at present no legislation to protect it.

Recalling the wartime blackout, reminded me that it was only due to such a blackout imposed on the city of Los Angeles, that the American astronomer Walter Baade was able to make the observations that were to totally alter our conception of the Universe.

The first reasonable 'modern' estimate of the extent of the Universe was made in 1906 by Jacobus Kapteyn. At that time photography was the 'new technology' and astronomers were taking full advantage of it. By taking numerous photographs of the Milky Way and counting the numbers of stars of different magnitudes contained in different sections, and assuming that the stars were all of average size, Kapteyn was able to estimate the distances that the stars would have to be in order to register their magnitudes on the photographic plates. These observations were based on the relationship between a star's apparent and absolute magnitude. Just as when we look down a road at night illuminated by the dreaded street lamps - the lamps close to us look brighter than those further away, although they are all actually the same brightness. The amount by which light diminishes with distance obeys a law, which states "the apparent magnitude is proportional to the absolute magnitude divided by the square of the distance to the observer." Astronomers define the absolute magnitude of a star as the apparent magnitude that it would have if placed at a distance of 10 Parsecs from Earth.

Kapteyn conceived our galaxy as a lens shaped structure 23,000 light years thick with the Solar System close to its centre. He came to this conclusion because the Milky Way divides the sky roughly into two halves and it appears more or less evenly bright in all directions. This assumed symmetry however, had one significant flaw - the globular star clusters are not evenly distributed over the whole sky but are found in far greater concentrations only in certain areas.

Just six years later, in 1912, Henrietta Leavitt was studying the stars of the Lesser Magellanic Cloud (LMC). She discovered that the LMC contained a number of Cepheid Variables. These are stars, which vary in magnitude in a very precise way. Henrietta's study revealed a relationship between the brightness of the stars and their period of variability. She plotted the results on a graph and produced the Period/Luminosity Curve. The LMC was particularly convenient for this study, as all the stars are more or less at the same distance from us.

It has to be remembered that at this time, our 'galaxy' was considered by many astronomers to comprise the entire 'Universe'. They had no real conception of 'other galaxies'. However, it was also in 1912 that Vesto M. Slipher first described the 'red shifts' observed in the spectra of certain 'nebulae', indicating that they were moving away from us. This work was to be developed later in 1929 by Edwin Hubble.

In 1918 Harlow Shapley used the Period/Luminosity curves for RR Lyrae stars to show that the Globular star clusters were distributed as a kind of 'halo' which surrounded the central bulge or nucleus of our Galaxy. These observations indicated that our sun was nowhere near the centre of our Galaxy.

Two years later, in 1920, Edwin Hubble used the newly constructed 100 inch telescope on Mount Wilson to take long exposure photographs of the Great Andromeda Nebula (M31), resolving the outer region into stars. So M31 was really another distant galaxy. Hubble searched for Cepheid Variables amongst the stars of M31 and was successful. Using the Period/Luminosity relationship he calculated the distance of M31 to be in the order of 750,000 light years. He then went on to measure other galaxies of similar structure. The trouble was that all these galaxies seemed so much smaller than our own and furthermore, spectroscopic observations of these galaxies were now indicating that the Universe as a whole was expanding - despite what Einstein thought! To add to the confusion, the figures obtained from these observations were indicating an age for the Universe of just 2 billion years. Geologists knew that the Earth was at least twice as old as this! Clearly something was amiss!

Now we come to the part played by light pollution. The outbreak of World War two and the imposition of a blackout on the city of Los Angeles allowed the astronomers at Mount Wilson to re-photograph the Andromeda Galaxy. The darker skies freed from the curse of light pollution, allowed far longer exposures and they were able to resolve the central region of M31 into stars. Walter Baade found that the stars in the central region were redder and fainter than the stars in the outer spiral arms. There appeared to be two distinct types of star in the Andromeda Galaxy. Baade called the blue outer stars Population I and the redder stars of the central region Population II.

Because of our Sun's position in our Galaxy, most of the stars we see are Population I. Such stars occur in the outer spiral arms of galaxies where they are formed from the high concentrations of dust and gas to be found in these regions. Now the size of our Galaxy was determined from the Cepheids in the LMC, which actually belong to Population II. The LMC is not a spiral galaxy and contains little or no dust and gas. The size of the Andromeda Galaxy, on the other hand, was deduced from the study of Population I stars in the outer spiral arms. If the Cepheids of Population I stars behaved differently from the Cepheids of Population II stars, then this might explain the apparent smallness of other galaxies and resolve the discrepancy concerning the age of the Universe.

Baade made a careful study of the Cepheid Variables of both Pop.I and Pop.II stars and by 1952 was able to announce that Pop.I stars did not comply with the Period/Luminosity law of Henrietta Leavitt. By virtue of the fact that Pop.I Cepheids were over four times brighter than previously assumed, they were therefore twice as distant.

Overnight the Universe doubled in size. The distant galaxies became bigger and once again our bit of the Universe was relegated to the fourth division! The Andromeda Galaxy was now at least 50% bigger than our own and some 2.25 million light years away. Because the galaxies were further apart, the Universe was therefore much older too, so the conflict with the geological evidence on Earth was also resolved.

It is a sobering thought that all these discoveries were possible because the lights of Los Angeles were turned off!

Hampstead SS Lectures in the Crypt Room, St John's Church, at 8.15 pm.

Richmond Scientific Society in Vestry House, Richmond, at 8 pm.

National Science Week, March 7th to 16th, 2003.

British Association.

Lots Road Power Station.

David St George

On arriving at the station, I was reminded of Ronnie Barker in "Porridge". There is a massive gate with a small door inset and on ringing the bell I was admitted and after stating who I was, I was shown (or escorted!) into a small guard house where I had to give all possible details and fill in a form. I was then given a pass 'to be worn at all times whilst on the premises'.

After a short while a very pleasant gentleman appeared and I was shown up two flights of stairs to an immaculate 'chemi lab' which my guide explained was a very necessary part of the station. (He was a chemist by profession.) From this pristine atmosphere I was escorted through a long passage to the heart of the station. Here things were very different, noisy and dirty! Looking down into the generator hall was like looking into a large cathedral with the alternators lined up neatly in a row. Lots Road Power Station provided, together with Greenwich power station, the motive force of the London Underground.

There is an ancient rumbling lift which took us to various stages including the boilers (gas fired) and the switch room. From the roof I can see Chelsea's football ground and a large distance up and down the Thames. When the District Railway acquired the power station site in 1902/3 the houses on the north side of Lots Road had already been built. In 1901 James R. Chapman, chief engineer to the MDET Co. who had come from America with Yerkes, invited tenders for the supply and installation of plant at Lots Road. The Westinghouse Electric Manufacturing Co. of Pittsburgh was invited to tender for four 7000 HP compound engines and The British Westinghouse Co. for four 5,000 kW, 11,000 volt, 25 Herz alternators.

A letter of intent to purchase four steam turbines with four alternators for £152,000 was issued in August 1901. This was subject to arbitration over the system of electrification to be adopted jointly for the Circle Line. The decision in favour of the D.C. system as opposed to the GANZ three-phase overhead conductor system was given in December 1901. However the capacity of the generating station would have to be increased to 40,000Kwts to provide for the requirements of the three tube railways beside the District Railway. The contract was therefore placed for eight steam turbine alternators each having a nominal output of 5,500 kW and operating at 1,000 RPM to give a frequency of 33.3 Hz (as compared with 5,000 Kw and 25 Hz originally specified). Construction work began in 1902.

The first through trip from Mill Hill Park to Bow Road and back was made on the 28th March 1905. On the 13th June 1905 a public service was operated from South Acton through Mill Hill Park to Hounslow and from that date the District Railway began to depend on the output from Lots Road. Steam locomotives continued on the Inner Circle until 23rd September and almost all steam trains were withdrawn from the District Railway by 5th November 1905. Only four machines were available for the June 1905 railway service although a fifth set became available in July. The last of the eight units contracted was in service in May 1906. Numerous problems arose with vibration and erratic governing, with failures of the automatic stop valves, the circulating water pump drives and the vacuum pumps. In early 1905 - before commercial operation had started - Yerkes was complaining to Geo. Westinghouse that he was receiving threats of legal action from owners of the neighbouring properties because of the noise and vibration. On the 10th March 1905 Westinghouse replied that "every possible effort will be made to hasten forward the needed changes. No one however is better aware than you are, how much time is consumed in England in doing even ordinary work". Alterations to the enclosures of the alternators were made in 1906 with satisfactory results on both temperatures and noise, although there was still doubt about the machines meeting the specified 50% overload.

A contract with C.A. Parsons & Co., dated 31st December 1908, provided for the installation of four steam turbines to drive four of the existing alternators, with the resulting sets having a rating of 6,000 kW. A second contract followed for four further units and all the Westinghouse turbines had been replaced by 1910. The contract price for each turbine was £8,100, which may be compared with the original Westinghouse tender price of £31,000, although this had been reduced in subsequent negotiations. The load on the generating station increased as the tube lines were opened. The Baker St and Waterloo Railway was opened on March 10th 1906 between Baker Street and Kennington Road and was extended to Elephant and Castle on August 5th 1906 and to Edgware Road during 1907.

The general strike of 1926, when the power station was manned by naval personnel, had drawn attention to the risk of the underground associated with its independent power supply system at a non-standard frequency. The extensions to Morden and Cockfosters had already been supplied from public supply undertakings at 50Hz. After the formation of the London Passenger Transport Board in 1933, the need to co-ordinate the separate power supply systems of the constituent undertakings was recognised and it was decided that the standard supply frequency of 50Hz should be eventually adopted.

The 1939/1940 New Works programme included the first stages of modernisation at Greenwich and Neasden Generating Stations, and the provision of a link between Lots Road and Neasden by connecting transformers installed at both stations with 22,000 volt cables. This was during the Second World War, and apart from numerous incendiary bombs there was only one direct hit on the station, although there were many in the surrounding streets. A bomb was also reported to have fallen in the Creek and a splash of mud was found on the south wall. As happened elsewhere, women were recruited to the staff as Fitter's Mates and Cleaners, including boiler cleaner! But it seems that the only woman on the Operations Staff was a control room assistant.

It had been assumed in various modernisation reports that Lots Road would continue to be coal fired, but post-war the use of heavy fuel oil in power stations had been developed to provide an economic alternative. This had the advantage of not requiring such complex and costly fuel handling plant, which would have been very difficult to accommodate on such a congested site. Work started at Lots Road in 1963 at the west end of the site. The first boiler and turbine were commissioned in July 1965. This was the first Membrane Wall boiler to be commissioned in this country, the second boiler and turbine followed shortly. Many of the substations fed from Lots Road at 33.3 Hz had been prepared for the change of frequency by diverting one of a pair of high voltage feeders to Cromwell Curve or Coburg Street so that part of the load could be transferred to the 50 Hz system almost immediately, followed by a phased programme to build up the load on Lots Road within the 30 MW firm capacity.

Deliveries of coal by rail ceased in 1965, and the Lots Road modernisation programme was completed in 1969 resulting in the power system being supplied from two sources independent of the National Grid for the Underground sections and from a bulk supply on the grid at Neasden for the surface section, in accordance with the recommendations of the 1960 report.

The boilers at Lots Road had been designed to burn heavy fuel oil with a sulphur content not exceeding 1% to limit the emission of sulphur dioxide. This was relatively cheap at that time as the quantity of H.F.O. produced by the oil industry was linked to the demand for petrol and diesel fuel rather than to the market for fuel oil. Natural gas from the newly discovered North Sea gas field was made available in 1974, initially at Greenwich but shortly afterwards at Lots Road. The GLC, now controlling London Transport, approved the conversion of both stations for dual fuel operation. The work was completed in 1977.

By 1980, the power supply system was again under review. The cost of electricity generated at Lots Road was found to be higher than that purchased from the Central Electricity Generating Board. The value of independent generation was no longer accepted, given the improvements in technology, in plant availability and inter-connection which had been introduced on the National Grid since the previous study twenty years before.

A Future Power Supplies project was drawn up which envisaged three dedicated Bulk Supply Points from the National Grid, any two of which would be capable of meeting the full load of the system and a last-resort emergency supply from the Greenwich gas turbines to feed essential lighting, ventilation pumps and communications. Approval in principle was given in 1985, and construction of the Mansell Street supply point and alterations to the 22,000 volt distribution system were well in hand when the Government announced its policy of de-nationalisation of the electricity supply industry.

The prospect arose of using the two sites for modern generating stations to feed into the local public supply network as well as continuing to supply the Underground. Further work on the Future Power Supplies project was suspended in 1990, while this was investigated by a joint venture between London Underground Ltd with Scottish Power plc and Veba Kraftwerke Ruhr AG. After the difficulties became more apparent, however, work on the Future Power Supplies project recommenced in 1992, on construction of the Lots Road intake and on planning the station and tunnel emergency lighting systems. It was envisaged that Lots Road would be closed in 1997 after completion of the schemes for emergency lighting and the refurbishment of five of the Greenwich gas-turbine units. But in March 1995 the department of Transport decided that private sector finance must be sought for these projects. This resulted in delays which lasted to the time of the visit, in spring 2002. Since then, Lots Road has finally been closed!

The Creek where warm water is exuded from the station is full of fish and the herons and other birds have a ready supply. The water for cooling is taken from a large filter structure protruding from midstream. I was very impressed with the control room with its switchboards and Apple computers. It is such a contrast with the grime down below in the boiler house.

Peter R Wallis

The first lecture will be on Thursday 19th September at 8.15 pm in the Crypt Room at St John's Church, Church Row, NW3. It will be on Death after Life in Ancient Nubia and our speaker is Dr Margaret Judd, a Canadian who has been working for the past year in the Department of Ancient Egypt and Sudan at the British Museum.

Diary Date. Science Week 2003 will be March 7th - 16th.

Enigma

P R Wallis

The earliest known cryptographic machine was invented by Leon Alberti, an Italian architect in the 15th century. He arranged the alphabet around the circumferences of two concentric discs, one smaller than the other. This provided a convenient tool for the encryption and decipherment of messages using the simple 'Caesar' substitution cipher which is mentioned in Julius Caesar's Gallic Wars and described later by Suetonius. Having only 25 possibilities, it is easy to decode. However, Alberti showed that his cipher disc could be used to generate a 'polyalphabetic' by changing the setting of the discs after each letter according to a known key-word. It becomes then a mechanized version of the 'Vigenxe8re Cipher', more difficult to break. It came to light that Babbage broke it in 1854, though the first publication of the method was by F W Kasinski in 1863.

In 1918 the German inventor Arthur Scherbius and his friend Richard Ritter set up an innovative engineering company. One of their developments was a piece of cryptographic machinery, essentially an electrical version of Alberti's cipher disc. Called 'Enigma', Scherbius' invention would become the most fearsome encryption machine in history.

The machine has three parts: a keyboard, a scrambler and a lamp display board. In the simplest form the scrambler is a rubber disc (the 'rotor') riddled irregularly with wires which changes the plain-text letter to the cipher-text letter. Scherbius' idea was for the scrambler rotor to rotate for each letter encrypted, achieving a polyalphabetic cipher with 26 different alphabets. However, every 26th letter uses the same alphabet, which would be a serious weakness once discovered. Scherbius therefore used three rotors, clocking round as in a mileometer, giving a total of 26 x 26 x 26 = 17,576 distinct scrambler arrangements. He also added a 'reflector', to send the electrical signal back through the rotors. This doesn't increase the number of alphabets, but it makes the procedure for decryption identical to that for encryption. All signalmen have the same machine, but need to know the initial settings of the rotors to use each day, the 'day-key'. He went further. He made the three rotors interchangeable, increasing the number of possible initial settings by a factor of 6. He also added a 'plug-board' to swap 6 pairs of letters out of the 26; this multiplied the number of keys by 100,391,791,500! Overall there were some

10,000,000,000,000,000 keys.

Such an encryption system cannot be broken by the technique of frequency analysis. He believed it to be impregnable.

His patent was filed in 1918, but did not meet with immediate commercial success. However the German military were shocked into appreciating the importance of such a machine by the revelations in 1923 by Winston Churchill (in his book 'The World Crisis') and the Royal Navy's 'Official History' of the first world war that their ciphered messages had been broken. So, in 1925, enigma went into service in the German military; they bought over 30,000.

Cracking the Enigma

The Allies, secure in their victory, made very little effort to break the new cipher but Poland, squeezed between the Soviet Union's ambition to spread communism and Germany's desire to regain the territories ceded to Poland, were desperate for intelligence information. They were able to determine the design of the enigma machine, with the help of the French intelligence authorities and a disaffected German. But that was only a first step which the Germans expected anyway. The real security lies in the key: the scrambler sequence, the scrambler initial orientations and the plug-board arrangement for each day.

The breakthrough at the Polish Biuro Szyfrow was made by the young mathematician Marian Rejewski. He realized that a weak point lay in a repetition occurring in the German messages. They had appreciated that the more messages they sent using a single key, the easier it would be for cryptanalysts to break the system by statistical techniques. They therefore changed their key everyday. But in addition, they provided a different individual key for every individual message. At the beginning of every message they sent three letters for new initial orientations of the three rotors, but not changing the rotor arrangement or the plug-board; this was the 'message key', as distinct from the 'day key'. It ensured that only a limited amount of text had a particular key. But they sent it twice to ensure it was safely received. It was of course protected by the day key encryption, but the repetition was a weak point. Rejewski saw that the 1st and 4th letters of the cipher text originated from the same letter, ditto for the 2nd and 5th, 3rd and 6th . He discovered that there was one very abstruse pattern* which was dependent on the scrambler settings alone. Having access to a replica Enigma machine, he was able to catalogue all possible patterns for the 105,456 settings; it took a year to do this. As the number of messages built up each day, he was able to deduce the settings for the day key. Establishing the plug-board settings, though larger in number, was less difficult. The Poles were able to read Enigma for most of the 30's!

By 1938, German cryptographers increased the Enigma security. The operators were given two additional rotors, so the number of arrangements, 3 out of 5, increased to 60.They also increased the plug-board cables from 6 to 10. The number of possible keys became:

159,000,000,000,000,000,000.

The Poles recognized that they did not have the facilities to crack this improved Enigma system and, with Germany withdrawing on 27th April 1939 from its non-aggression treaty with Poland, they sought the help of the British and French . On 24th July, British and French cryptanalysts visited the Polish Biuro to see their feats; two spare Enigma replicas were offered, one of which reached London on the 16th August in the baggage of Sacha Guitry and his wife. Two weeks later, Germany invaded Poland.

Bletchley Park, which the HSS visited in 2000, became the center of burgeoning activity, with more staff and resources than the Poles could have found. They were able to find other weaknesses in the practical use of Enigma. Operators were liable to pick obvious rather than random keys for the message keys, eg QWE from the keyboard or their girlfriend's initials. They also discovered that the system deliberately avoided a rotor being in the same position on consecutive days; this reduced the number of options by a factor of 2. Enigma kept changing and the team of cryptographers at Bletchley were "like a pack of hounds trying to pick up the scent"(Gordon Welchman in charge of Hut 6). If any is to be singled out, it is Alan Turing, who identified Enigma's greatest weakness and ruthlessly exploited it.

He followed Rejewski's strategy of separating the search for rotor settings from the determination of plug-board settings. He ignored the message keys as he expected the Germans to cease the repetition. Instead he used 'cribs', guesses at plain text words and phrases, such as 'wetter' appearing in regular weather reports. He also mechanized the use of loops by connecting three enigma replicas in series and wiring them to cancel the effect of the plug-board. He produced, at a cost of £100,000, an emulator with 12 sets of linked Enigma scramblers, which he called 'bombes' after the earlier Polish machines. The first arrived on 14th March 1940 but was too slow. Four months were to go by before an improved design was available and, in the meantime, the Germans dropped the message key repetition. Within 18 months there were15 more bombes in operation and by the end of 1942, 49. Even if the code-breakers guessed a plain text crib, they had to associate it with the correct bit of cipher text before the bombes could be used. Fortunately there was another characteristic of the Enigma machine that could be used to provide a check. The presence of the reflector meant that no plain text letter could be translated into itself. Thus the crib could be slid along the cipher text until no letter was the same in both; the longer the crib, the better it worked.

There were several different Enigma networks. The Naval one was the most difficult, having a choice of 8 rotors and a reflector variable in 26 positions. More techniques were required if the U-boat was to be beaten in the battle of the Atlantic. In one, mines were sown by the RAF so that German messages would report the map reference for use as a crib. Raids were made to capture German code books.

Overall, Bletchley Park was able to obtain vital information which avoided defeat in the U-boat war and many other operations. Sir Harry Hinsley wrote, "The war, instead of finishing in 1945, would have ended in 1948 had the Government Code and Cipher School not been able to read the Enigma ciphers and produce the Ultra intelligence".

Hitler used an even more impressive machine, the Lorenz SZ 40, to communicate with his generals. Though based on Enigma it set Bletchley a task beyond the capability of Turing's bombes. Eventually Max Newman designed a more flexible and powerful machine drawing heavily upon Turing's concept of the universal machine. It was shelved at first on the grounds of impossibility, but taken forward by Tommy Flowers in the Post Office Research Station at Dollis Hill. Colossus, the world's first computer, was delivered to Bletchley Park on 8th December 1943. But that, and the whole future story of encryption and electronic security is another story.

Finally, I must reveal my source. It is Simon Singh's book The Code Book- the secret history of codes and code-breaking, 2000, Fourth Estate. He also wrote Fermat's Last Theorem and lectured for our Science Week this Spring. Many thanks.

Selected References

• Hinsley, F H, British Intelligence in the Second World War: Its Influence on Strategy and Operations, 1975, HMSO. The authoritative record of intelligence, including the role of Ultra.
• Hinsley, F H and Stripp, Alan (eds), The Codebreakers: The Inside Story of Bletchley Park, 1992, Oxford University Press. Illuminating essays by the men and women who were part of one of the greatest cryptanalytic achievements in history.
• Hodges, Andrew, Alan Turing: The Enigma, 1992, Vintage. The life and work of Alan Turing. One of the best scientific biographies ever written.
• Kahn, David, Seizing the Enigma, 1996, Arrow. Kahn's history of the Battle of the Atlantic and the importance of cryptography in particular, including the 'pinches' from U-boats which helped the codebreakers at Bletchley Park.
• http://www.cranfield.ac.uk/ccc/bpark The official website, which includes opening times and directions.
• http://www.attlabs.att.co.uk/andyc/enigma/enigma_j.html
• http://www.izzy.net/~ian/enigma/applet/index.html Two emulators that show how the machine works.

*: He constructed 26-letter rows comparing the 1st and 3rd letters. He then followed a chain using the rows alternately until the original letter appeared again. His great insight was that the pattern of the lengths of the loops was independent of the plug-board settings. Back

ANNUAL GENERAL MEETING on Thursday June 20th at 8.15 pm

This will start with wine and cheese (£2 pp), followed by the AGM at 8.45 and then a Scientific Lucky Dip, chaired by Juliette Soester. Please submit interesting scientific questions suitable for a one-minute answer (or deviation) in writing to Julie Anderson before the meeting at Flat 3, 33 Glengall Rd, Kilburn, London NW6 7EL or by e-mail to: secretary@hampsteadscience.ac.uk

Agenda for the Annual General Meeting.
1. Minutes of AGM on 21st June 2001.
2. President's Remarks.
3. Secretary's Report.
4. Treasurer's Report.
5. Election of Officers and Council.
6. Election of Auditors.
7. Report of the Meteorological Section.
8. Report of the Astronomy Section.
9. Any other business.

Notes

• 1. At its meeting on 18th April, Council re-appointed Professor Weale to be President for the following year.
• 2. With reference to Item 5, Council proposes the following members as Honorary Officers and Ordinary Members of Council:

Council invites further nominations to the above officer posts and ordinary members; such nominees shall be duly proposed and seconded and have agreed to serve if elected.

Planetary Line-up

This month we have a rare opportunity to see all five naked-eye planets lined up for our delectation. Look at the north-western horizon after sunset and, weather permitting, you will see them all in a line descending from Jupiter through Saturn, Mars, Venus to Mercury in late April. Venus will be the brightest at -3.8 magnitude, Jupiter next at -2.0, Saturn fainter at +0.1 and reddish Mars faintest at +1.6 magnitude. Mercury is bright , -1.5, initially and will fade to zero magnitude by the April 30th, disappearing from sight by the naked eye after the 6th May. On the latter date Saturn, Mars and Venus will be in a close group together, with Venus brightest and Mars faintest. By the end of May Mercury and Saturn will have left the evening sky, Mars may in London be too low to see and Jupiter and Venus will be close together. Above them will be the stars Castor and Pollux.

Death of a Star

Towards the end of life of a massive star, the star expands into a Red Super giant. It is now thought that this changes into a Blue Super Giant phase shortly before the star blows up catastrophically as a Supernova. Recent observations by the Hubble Space Telescope have shown several ring-like structures associated with the death of such stars. One of particular interest is SN 1987A. (The name means it is a supernova first seen by us on earth in 1987)

The telescope shows three rings, one in the equatorial plane of the star, at a distance of 0.7 light-years. The other two rings are of twice the size and lie at latitudes of plus and minus 45 degrees. Two Japanese astrophysicists have offered an explanation of this using a magnetohydrodynamic simulation [1].

They argue that in the red supergiant phase a dense and relatively slow stellar wind is generated by the star. The star then evolves into a blue supergiant just before the supernova explosion and this sends out a more dilute but faster stellar wind which sweeps up the previous wind. The winds are anisotropic due to the magnetic field of the star, being slower at equatorial latitudes. What we see as rings are traces of the colliding winds illuminated by the recombination processes following the ionization by the ultraviolet flash of the supernova explosion.

Their computer calculations, albeit with assumptions tweaked to suit, show a three ring structure at 1600 years after the supernova explosion which corresponds closely to that seen by the HST.

Ref 1: Science, 12th April 2002, "Formation of the Three-ring Structure Around Supernova 1987A" by T Tanaka and H Washimi. Back

Peter R Wallis

Hon Treasurer

Hampstead SS Lectures in the Crypt Room at 8.15 pm.

• January 24th: Cosmic Collisions & Catastrophes by Dr Monica Grady (Natural History Museum).
• February 21st: The Higgs Particle by Dr David Bailin (University of Sussex).
• March 21st: Our Changing Climate - Past and Future by Philip Eden (HSS).
• April 25th: Does Alternative Medicine Exist? By Michael van Straten.
• May 23rd: Gamma Knife Surgery by Mr Ian Sabin.

World Pathogen Strategy Disclosed

Thomas Eisner of Cornell University and Paul R. Ehrlich of Stanford University claim in an editorial in Science of 29th June 2001 to have obtained a leaked copy of a keynote address by President Prion of the World Pathogen Association which portends a threatening shift in policy by our major predators. An abbreviated version of his speech is given below and may offer a salutary dampening of any undue Christmas cheer:

"I must inform the infective community," Prion warns "that most of our natural hosts are disappearing. Never has our future been bleaker, threatened as it is by a reality that was unthinkable a mere 5000 years ago. Our food supplies are being displaced by a single species, Homo sapiens, which has come to reign dominant on Earth. It is dominant by weight of numbers and extent of spread, and has become - for all of us - the great challenge that we can no longer afford to ignore.

"Action is called for. Indeed, in this disaster there is a germ of an opportunity and an opportunity for the germs. In our evolutionary tradition, we must prepare ourselves to change our tastes, shift hosts, and take advantage of the single most appealing and available addition to our menu. Homophagia is the way of the future.

"But first some congratulations are in order. To HIV, for making the big leap most recently and for killing slowly enough to share the host with many of the rest of us. To the tuberculosis bacillus, for its unexpected renewed success. To the viruses - Ebola, Hanta, Lassa and Marburg - for their gallant efforts. To Legionella pneumophila, for its stealth. And to those already at the trough - the great pioneers such as Plasmodium, the dengue virus, and Treponema, and that great debilitator, the common cold virus - for setting splendid examples to ensure that success is within the grasp of all.

"There are many factors that give us hope. Homo is remarkably hospitable to us. In extraordinary numbers they are undernourished and immuno-deficient, and they have a penchant for keeping on the move, thereby spreading us veterans and providing many new opportunities for the novices among us to join in the feast. They expend their medical resources on the few while failing to exclude us from drinking water supplies and foods. They misuse antibiotics, among their best weapons against us, blind to our evolutionary capacity to develop resistance.

"The only dark cloud on our horizon is Homo's propensity for self-injury. They have on occasion threatened to modify some of us for use in intra-specific competition - "germ warfare" they call it. That might cause a food availability problem for us, but they are such prolific breeders that we could wait out a population crash until they once again achieve the biomass necessary for our appetites.

"All in all, my fellow pathogens, Homo is the opportunity that can benefit us all. Although they themselves deny that there is such a thing as a free lunch, we know better. There is a free lunch, and it is them!"

_________________________

The First Stars

The Big Bang theory is now dominant among cosmologists. They also estimate the age of the universe since then to be 12 to 14 billion years. With the best telescopes available today we can look back in distance and therefore in time to when the Universe was about 1 billion years old, seeing ancient galaxies and quasars. But what had happened before then? The principal evidence for such early times comes from the cosmic microwave background which was emitted about 400,000 years after the big bang and has now been red-shifted by the expansion of the Universe down to a temperature of only a few degrees K. The uniformity of this background shows that matter was then hot and rather uniformly distributed, but with some small-scale density fluctuations. Further expansion allowed the Universe to cool; it would have been dark for some 100 million years.

Today we have a Universe full of brilliant stars and galaxies and know quite a bit about how stars are born by gravitational contraction in gas and dust clouds. Sir James Jeans was an early worker in this field. He showed that a clump of gas must have at least a minimum mass, now called the Jeans mass, to be able to contract into a star; this mass is proportional to the square of the gas temperature and inversely proportional to the square root of the gas pressure. Astrophysicists are now turning their attention to such star formation in the primordial universe between 1 million and 1 billion years after the big bang (see for example "The First stars in the Universe" by Richard B Larson and Volker Bromm in Scientific American, December 2001).

The authors point out two important differences between the environment then and now. The early galactic clouds would have been preponderantly made up of dark matter, that mysterious entity which seems to provide 90% of the mass of the Universe. In today's galaxies the dark matter remains scattered through an enormous outer halo, with the baryonic matter confined to the flattened spiral of the galaxy. Secondly, the ordinary matter would have been made up of the hydrogen and helium formed in the big bang, with no significant amounts of higher elements (inaccurately called "metals" by astrophysicists). These latter are in abundance today, having been formed by thermo-nuclear fusion inside stars or in supernovae explosions.

Several teams have recently been using computers to simulate star formation in the rather simple environment of the primordial universe. They show that gas clouds would have formed and contracted under gravity, the compression heating the gas to temperatures above 1,000 kelvins. Some hydrogen atoms would have combined in the dense gas to form hydrogen molecules and these molecules would emit infra-red radiation after colliding with hydrogen atoms. This would lead to cooling of the densest regions to between 200 and 300 degrees K, reducing the pressure and allowing further contraction into gravitationally bound clumps. This would separate the ordinary matter from the dark matter which, as far as we know, could not radiate and cool.

Star formation would begin in a similar way to that we observe today in molecular gas clouds. However, today's clouds include dust grains and heavier molecules which allow the cloud to cool to temperatures of some 10 degrees K. At this temperature and pressure the Jeans mass is calculated to be about the mass of the Sun, leading to the formation of stars like our sun. But in the primordial gas clouds, with no metals, the temperature is some 20 to 30 times higher and the Jeans mass will be up to 1,000 times larger. The simulations have all shown that the early star forming masses would have been of several hundred solar masses. It is not yet certain what size the resulting stars themselves will be, estimates varying from 100 to 1,000 solar masses.

If these theories are confirmed, these stars would have had a dramatic effect on the primordial universe. Apart from being bigger, their metal-free material results in higher temperatures for thermo-nuclear burning. Calculations suggest that their surface temperatures would have been 100,000 degrees K, 17 times that of the sun, with intense ultraviolet radiation. Their lives would have been short, a few million years. Stars between 100 and 250 times as massive as the sun are predicted to blow up at the end of their lives, discharging large amounts of higher elements (metals). Such a high early supernova rate might explain the observed scarcity of metal-poor stars in galaxies. Stars more massive than 250 solar masses would collapse into black holes. The latter could be the energy source for the quasars and become the immense black holes in galactic nuclei. Perhaps future telescopes will look back far enough in time to confirm these predictions.

Peter R Wallis.

The Next Generation Space Telescope

The Hubble Space Telescope is now more than 10 years old and a successor is being planned by NASA, ESA and the Canadian Space Agency. It is to have a mirror about 6 metres across instead of the 2.4 m of the HST; this will be able to collect 7 times the light. It is also designed to work at longer wavelengths and will be several thousand times as sensitive to infra-red wavelengths as the largest current telescope on Earth. This is important if it is to see back to the primordial universe because the expansion of the universe means that the light from more distant objects has been shifted into infra-red wavelengths. In addition, infra-red can penetrate the dust clouds in both nearby and remote star-forming regions, while visible and ultraviolet cannot.

The detectors will have to be cooled to some 30 deg K and a giant sunshield provided to shade the telescope from the sun. Instead of flying in an earth orbit like the HST, it will be placed in a solar orbit at the second Lagrangian point, a constant 1.5 million kilometers from the Earth. It will not be serviceable by astronauts during its lifetime.

Maybe in 10 years time we shall have confirmation of the ideas in the previous article!

________________________

Eddington

This is a space mission proposed by Professor Ian Roxburgh of Queen Mary College (see the Summer 2001 issue of Frontiers). It has two objectives: the first and most likely to capture the public imagination is the search for habitable planets. From the ground we have already detected some 60 large hot gaseous planets, but only a space mission can detect smaller Earth-like planets which might be able to support life. The technique employed is to observe the minute decrease in the light from the star as the planet transits it. If we looked at our own sun from afar, we would see a reduction by about 1 part in 10,000 lasting 11 hours if we are in the orbital plane, the probability being 1 in 200. One such change is clearly not enough for proof, but if we can see the pattern repeat over several years, we may be confident of the detection. Eddington is designed to study a region of the sky 3 degrees in diameter over 3 years, observing a total of 500,000 stars. It is estimated that it will detect some 20,000 planets, of which there may be 100 Earth-like ones in the 'habitable zone'.

The other objective is to study in minute detail the dynamic behaviour of stars, to improve our understanding of stellar evolution. Eddington is a proposal included in the European Space Agency's Programme Horizon's 2000 +, which sets out the suite of space-science missions from 2008 to 2013.

PRW

The first lecture will be on Thursday 20th September at 8.15 pm in the Crypt Room at St John's Church, Church Row, NW3. It will be on Railway Signalling by R S Wyatt.

CLIMATE CHANGE-- MAN MADE OR NATURALLY CYCLIC.

DOUG DANIELS

There has been much debate on the subject of "global warming" and how the activities of industrialised countries are affecting the weather. But as more research is carried out into the complex events which drive our weather systems and control our climate, we are beginning to discover hitherto unknown cyclic events. These events have the potential for far more dramatic climate changes than anything mankind can do to alter the climate.

Recent research by scientists from the University of Copenhagen has uncovered what appears to be a very worrying cyclic event. An event which could, if it proves to be correct, have a devastating effect on the climate of western Europe. If one looks at a globe of the Earth and compares the latitude of, say, London with that of Moscow and parts of Siberia, and then we compare the average Winter temperatures of these locations, we can see at once something strange. Whereas the Winters in Siberia are viciously cold, western Europe enjoys a far more temperate climate. This is due to the warming effect of the Gulf Stream, a vast ocean current which conveys warm sea water up from the tropics along the eastern sea-board of the United States across the north Atlantic and thence to our shores. This current of warm water has the effect of warming the air above it by an average of 15 degrees C. during the Winter months. It is the reason why it is still possible to grow palm trees, which are tropical plants, in some Devon and Cornish seaside resorts. Without the heating effect of this benign current our Winters would resemble those of Siberia!

Fortunately for us, the Gulf Stream has been comforting our shores for about 16,000 years but, according to the research by the University of Copenhagen, the Gulf Stream has in the past ceased to circulate and, on these occasions, it has stopped flowing quite suddenly.

This discovery was made by examining ice cores drilled in Greenland. Core samples of the Greenland ice contain sample of frozen atmosphere laid down thousands of years ago; by analysing these samples it is possible to discover the temperatures endured by northern Europe in the distant past. These temperatures are ascertained by calculating the ratio of two isotopes of oxygen: oxygen 16 and oxygen 18. In very cold conditions the percentage of oxygen 18 is greater. The Copenhagen team have discovered that prior to about 16,000 years, the oxygen 18 content was far greater and for a considerable period prior to this the ratio of 0-16 to 0-18 was subject to wild fluctuations, suggesting chaotic climate variation. It is believed that the reason for this is that the Gulf Stream stopped flowing.

The Gulf Stream conveys warm water from the tropics and flows northwards. Warm water is less dense and forms the surface layers. As it warms the air above it, this mass of water gradually loses heat and by the time it reaches the north polar ice cap, it has cooled. The fresh water freezes out and the heavier salt water sinks. It is this convective process which drives the current. In order to maintain this current it is necessary for the Earth to have a northern polar ice cap.

The Earth's northern ice cap has no land mass beneath it. It is composed wholly of floating ice with an average thickness of 3-4 metres. For many years now the thickness and extent of the polar ice has been monitored by Earth-orbiting satellites and by the sonar of nuclear-powered submarines, which regularly patrol beneath it. There is now no doubt that our northern polar ice cap is shrinking, both in thickness and extent. Computer predictions indicate that it may disappear entirely in a matter of decades. When it does, the Gulf Stream will cease to flow, with dire consequences for the climate of western Europe.

As the Copenhagen team have shown, this has occurred before in the distant past, so we cannot blame it on man-made global warming. This discovery is another example of the cyclic nature of the Earth's dynamic systems, systems which are still not fully understood.

Methane-eating Archaea.

Another example of mechanisms which can affect our climate but are not fully understood is the greenhouse effect caused by methane. Molecule for molecule, methane is 25 times more potent than the carbon dioxide of which we now hear so much. Moreover there are 10 trillion tons of it buried in the ocean floor, twice the amount of all known coal, oil and other fossil fuels. This could play havoc with the world's climate if it were to escape into the atmosphere! William Reeburgh of the University of California and other geochemists demonstrated in the 1970s that methane-producing microbes were continually producing the gas deep below the sea bed, but found that it had all but disappeared in the mud near the ocean floor. They suggested that other microbes might be eating it up as soon as it arrived. It would also explain why carbonates found there were low in the ratio of carbon-13 to carbon-12, just as methane is. Methane-eating bacteria were well-known in fresh water, but seemed to need oxygen; there is none however in the ocean sediments.

Evidence is now mounting that the microbes responsible are archaea; these superficially resemble bacteria but are a separate domain of life. Proof of this has now been reported by a team (V J Orphan, C H House, K-U Hinrichs, K D McKeegan and E F DeLong) in Science of 20th July this year using secondary ion mass spectrometry and other techniques. They showed that the archaea cells were highly depleted in C-13 and must have lived on methane; they also formed a symbiotic relationship with sulphate-reducing bacteria.

These methane-eating microbes now look profoundly important to the planet's carbon cycle. Hinrichs and Boetius estimate that they devour 300 million tons of methane each year, about equal to the amount we inject into the atmosphere by agriculture, landfill and fuel burning. It may be speculated that the evolution of these microbes may have saved the planet from a run-away greenhouse catastrophe in its earlier days with a reducing atmosphere, as happened to Venus.

Peter R Wallis

Thursday May 17th, Dr Christopher Walker (British Museum) on Numbers in Mesopotamia.

There will not be a July meeting this year.

ANNUAL GENERAL MEETING on Thursday June 21st at 8.15 pm.

This will start with wine and cheese, followed by the AGM at 8.45 and then a Brains Trust, chaired by Martin Williams. Please submit your scientific questions in writing to him at the beginning of the evening or send them beforehand to him at 2, Highpoint, London N6 4BA or martin@g4grs.co.uk .

Agenda for the Annual General Meeting.
1. Minutes of AGM on 22nd June 2000.
2. President's Remarks.
3. Secretary's Report.
4. Treasurer's Report.
5. Proposal by Council to amend Rule 5b of the Constitution to reduce the number of ordinary members of Council from 8 to 6 and to reduce their service time from 5 to 4 years.
6. Election of Officers and Council.
7. Election of Auditors.
8. Report of the Meteorological Section.
9. Report of the Astronomy Section.
10. Any other business.

Notes:

• 1. The size of the Council has increased over the last few years and there is danger of its becoming unwieldy; hence the proposal in Item 5. Council also wishes to encourage new blood, hence the reduction in the maximum tenure. An alteration will require a 2/3rds majority at the meeting.
• 2. At its meeting on 24th April, Council re-appointed Professor Weale to be President for the following year.
• 3. With reference to Item 6, Council proposes the following members as Honorary Officers and Ordinary Members of Council:

Council invites further nominations to the above officer posts and ordinary members; such nominees shall be duly proposed and seconded and have agreed to serve if elected.

LIFE IN THE UNIVERSE, SO WHERE IS EVERYBODY?

Doug.Daniels.

Whenever a discussion arises on the possibility of life existing elsewhere in the Universe, it is often assumed that, if intelligent life does exist elsewhere, it must be far more advanced than we are. Furthermore, the fact that we have not been contacted by these advanced aliens, is taken as proof that our species is probably unique. We must surely realise by now that there is probably nothing unique about us, our Galaxy or our Solar System.

Not long ago it was assumed that life could not exist without an atmosphere containing oxygen. We now believe that this assumption was incorrect. When life began on Earth there was no oxygen in the atmosphere. It appears that water is the key to the development of life and there is no shortage of water in our Solar System. If our system is typical then water will exist in other systems as well and with it, life in some form or other.

It is how this life evolves which is open to question. It is not inevitable that life will evolve to produce species resembling Homo Sapiens. On our planet, the dinosaurs were the highest form of life for millions of years and may have continued to be so had not some chance accident in nature wiped them out. That chance event allowed evolution to take a different course, resulting in the evolution of mankind. It may prove to be the case that very intelligent species are very rare but even if that were true, in a universe composed of billions of galaxies there ought be millions of advanced civilisations.

So where are they all. Why the silence? One reason may be that it is not inevitable that an intelligent civilisation would necessarily develop an advanced technology. We only have to look at the history of past civilisations here on Earth to realise that many ancient civilisations developed to quite a high degree of sophistication without the recourse to technology. The ancient Chinese could predict eclipses without a telescope, they had a vast trading empire but did not invent the wheel. The ancient Egyptians built the pyramids without much mechanical assistance and other primitive civilisations explored the world's oceans without a compass.

Australian aboriginals have survived since the very dawn of time without recourse to any form of technology.

It may very well be the case that technological civilisations are destined for a very short life span. The development of technology produces terrible pollution and rapidly consumes the natural resources of the planet. We have only had advanced technology for a little over a hundred years. In that time we have cut down much of the tropical rain forest, caused damage to the ozone layer, greatly increased the quantity of greenhouse gases in the atmosphere - changing the climate and we have produced weapons of mass destruction - both mechanical and biological. Electrical generation by nuclear power produces dangerous radioactive waste which must be isolated for hundreds of years. We have introduced poisonous chemicals into the food chain from pesticides and fertilisers. Intensive farming has led to the rise of dangerous contaminants causing diseases like BSE and CJD. The indiscriminate use of anti-biotics fed to farm animals has caused harmful bacteria to become resistant to them. Unrestrained sexual practices have led to the spread of diseases like AIDS and there is compelling evidence that birth control drugs eliminated into the water supply are causing male sterility. Easy world wide travel allows the rapid spread of disease.

We are over fishing the oceans and contaminating them by the careless transportation of crude oil and other pollutants. We have caused the extinction of thousands of species of plants and animals and we are now about to begin genetically modifying those that are left.

The above are but a few examples of the potential dangers facing an advanced technological civilisation like our own, any of which could ultimately lead to its extinction long before it had time to communicate with a similar civilisation across the vast reaches of space. That is, of course, assuming that it is not terminated prematurely by impact from a comet or asteroid .

Second Thoughts on the Ages of Stars.

Peter R Wallis

For several decades there has been controversy over the age of the universe. Observation of the rate of expansion from the "red shift" suggest that it is 14 billion years old or younger; but observation of ancient stars found some of 15 billion years age! An interesting article in the May issue of the Scientific American (Rip van Twinkle by B C Chaboyer) now reports that, "The age crisis is over".

Till now, most astronomers have blamed the cosmologists for getting either the expansion rate or the cosmological model wrong but have been confident that their assessment of stellar ages was correct. The calculation age is based on our understanding of the nuclear reactions that power a star, essentially the fusion of hydrogen into helium. Four protons weigh 0.7 % more than a single helium nucleus, the missing fraction being converted into energy according to Einstein's equation E=mc2 .The sun emits 4 x 1026 watts of light and is therefore transmuting 600 million tons of hydrogen into 596 million tons of helium every second. Over a billion years the sun burns 1% of its mass. It is estimated that under normal circumstances only about 10% of the sun's mass in the core can reach the temperatures needed for fusion, giving the sun's life in this phase of 10 billion years, known as the "main sequence". When a star exhausts the hydrogen in its core, it progressively taps the gas in surrounding layers, causing the star to balloon into a "red giant" phase, so-called because of its higher luminosity but lower surface temperature.

In the stable main sequence phase it can be calculated from the laws of hydrostatic equilibrium, gas laws and laws of radiative heat transport that stars heavier than the sun will burn hydrogen at a faster rate. It is calculated that the luminosity varies as the 4th power of the mass; as the fuel available scales directly as the mass, the lifetime on the main sequence is approximately proportional to the inverse cube of the mass. This evolution shows clearly on the Hertzsprung-Russell diagram plotting visual brightness (indicative of energy output) against colour (related to surface temperature). Stars in their main sequence phase fall on a slanted line. When one becomes a red giant, it turns onto a near horizontal line.

Although we can estimate the total lifetime of a star from its absolute luminosity, the inherent stability of its main sequence phase means we cannot tell how old it is, how much of its life has been spent. It is only when it turns off the main sequence that its age begins to show. Astronomers therefore look at groups of stars which they judge to have been born at the same time. A special class of star groups, the globular clusters, are thought to include some of the oldest stars in our galaxy. They were first recognized as different by Walter Baade in the 1930s; he called them "Population 2" to distinguish them from the bright blue stars of "Population 1". The latter are bright blue - and therefore must be young - and are to be found only in the galactic disk. Population 2 stars are generally fainter and redder and are found in the galactic halo. Globular cluster stars are of the latter kind and this is also true of other galaxies near enough for us to see them.

We now understand why. The galactic disk is full of gas clouds, leading to lots of star formation and massive young flamboyant stars with short lives. They have significant quantities of elements higher than helium and lithium which can only have been formed in stars; supernovae produce the highest elements. The sun, for example, has about 2% by mass. The stars in a globular cluster have no more than trace quantities of higher elements and are now generally believed to be left over from the earliest days of our galaxy, before there had been sufficient novae to pollute space. They appear to have been formed at the same time and should be able to give an estimate of the age of the universe.

The heavier stars among them have all left the main sequence as red giants, the lighter stars are still there. This shows up on the Hertzsprung-Russell diagram as a sharp edge to the main sequence. Assessing their age depends on three factors: the proportion of higher elements, the accuracy of the modeling and the absolute luminosity of the stars. Chaboyer reports that recent measurements using the Keck Observatory have now determined the metal abundance with unprecedented precision. He and his colleagues claim also to have refined the modeling, reducing the estimated ages by 14%. The third problem was the assessment of the distances of these globular clusters, since distance must be known to convert relative luminosity into an absolute one, and this is still controversial. Chaboyer reports that the data from the ESA's Hipparcos satellite, which measures parallax to an accuracy of .001 arcseconds, has now pinned down the distance to similar metal-poor stars within the galactic disk, though it has not the accuracy to reach the globular clusters. Assuming however that these stars have a similar intrinsic luminosity, he claims that the distance to the globular clusters is perhaps 10% greater than thought previously. So they must be brighter, and therefore younger. He says that a best guess is that the oldest stars are 13 billion years old - consistent at last with the age of the universe from red shift measurements. New orbiting observatories are scheduled for launch later this decade and, with 250 times the resolution of Hipparcos, they should be able to resolve some of the remaining uncertainty.

But perhaps we should be careful, as there are arguments about whether the expansion of the universe is accelerating. This would allow its age to be greater.

Healthy Milk?

Some of you may not have seen the report by Miranda Ingram in the Times about the work of Dr Corran McLachlan into links between heart disease and the type of cows' milk that we drink. He is a New Zealander with a degree in chemical engineering from Cambridge and runs a company there producing cholesterol-free dairy products. It has been known for some time that the risk from heart disease varies considerably from country to country. Dr McLachlan believes that the protein in cows' milk explains the differences. The protein is largely made up of caseins, beta casein A1 and A2. He says that if your body has been compromised by smoking, fats etc, A1 could be fatal while A2 is safe. He claims that the proportions of the two types of casein in the cows' milk correlates with the observed risk. Finland, for example, consumes the highest amount of A1 and has the highest heart-disease rates in the world. Guernsey cows produce almost exclusively A2 milk and deaths from heart attacks are 27% lower there.

He claims that intensive breeding in westernized countries has led to the production of A1, and that careful selection of bulls and females could achieve its elimination; indeed he suggests that the cull rates and controls occurring in Britain to counter BSE and Foot and Mouth disease would allow it to be eliminated in 3 years at very little cost.

While there is interest amongst UK trade bodies, eg the Dairy Council and NFU, there is also suspicion, since McLachlan runs a company, A2 Productions, and holds the licence for the A1/A2 screening process. Miranda Ingram suggests that the milk sellers could well be forced to act if supermarkets decide that customers want it.

PRW