November 2008
Great Egg Race
The last Sherborne Science Café for 2008 was a departure from the usual format. The audience was challenged to attempt a number of mind-stretching problems set by Rob Bygrave, ably assisted by Louise Furre from the Gryphon School and SSC chairman Percy Seymour. The main task was to design and construct a model bridge, using only the very basic of materials, within a 90 minute time limit. If that wasn’t enough, there were a number of other puzzles and quizzes to solve at the same time. The weird and wonderful bridges that emerged from the chaos were judged on their ability to bear weight, on the imaginative use of materials by the team, and on aesthetic appearance and elegance of design.
After the final reckoning the judges awarded first prize (Mars bars for each contestant) to a crack team of brains calling themselves The Losers. Which just goes to show, at the Sherborne Science Café even the losers are winners.
October 2008
Rob Bygrave
MODERNISING MENDEL
What have Sir Humphry Davy and Dolly Parton got in common? They were both mentioned at The Science Café’s well-attended October meeting held at the new venue in the Day Centre Digby Road. Rob Bygrave, the speaker, is a descendant of Sir Humphry Davy and his talk ‘Modernising Mendel’ ended with a mention of Dolly, the cloned sheep, named after the famous country singer.
Starting with the original research of Gregor Mendel, the speaker outlined and explained the important stepping- stones in research and discovery from 1856 to 1953 which led to the successful configuration of the DNA molecule. He then touched upon the most important modern developments in Genetics such as genetic fingerprinting, cloning embryos and the Human Genome Project.
After a break for refreshments the lively audience discussed a range of related topics which will be an increasing cause of concern in the future. These included, designer babies, cryogenics, stem cells, gene therapy and GM crops.
September 2008
Paul Barnett
Exploiting science for the criminal justice system
Sherborne Science Café started its third season with it’s own ‘Big Bang’ last Wednesday, 24th September with a new venue, new time, many new faces among the regulars and in a large audience eagerly awaiting enlightenment about Police Forensic Science Techniques.
Paul Barnett from the Police Crime Scene Investigation Unit (CSI) began his talk with the statement ‘Every contact leaves a trace’ and we all shuffled nervously in our seats and surreptitiously slid our hands from the table. Any feelings of guilt rapidly evaporated, however, as we were became engrossed in his talk.
The techniques he discussed for recovering and analysing evidence and the theories behind them were based on many scientific spheres: the physical lifting of finger prints, DNA sampling, chemical analyses and electrostatic examinations to name but a few and he illustrated these with instances from his personal experience. A really impressive example was the demonstration where a member of the audience was invited to walk on a clean sheet of dry paper; it was a dry evening, his shoes and the floor were dry and there was no visible evidence of his step. Using an electrostatic technique which involved the passing of 9,000 volts through a silver coated film placed on the paper, a clear footprint emerged under a glancing torch light! A frequently updated list of the patterns of trainer soles, one of many data bases discussed, could have been used to identify this ‘villain’. Paul concluded with graphic details of the evidence his team had secured to convict a rapist/murderer in Bournemouth recently.
This was so much more than just a narrative and gave real insight into the workings of the CSI. The television programme ‘Waking the Dead’ will never be the same again!
July 2008
Mechanical models of the universe
Percy Seymour
The lecturer (Percy Sermour) started by pointing out that there were two conceptual models of the universe in Ancient Greece; one due to Aristotle and the other one associated with Aristarchus of Samos. Aristotle’s model consisted of the spherical earth at the centre, surrounded by the very large sphere to which the stars were affixed, and the space between them was filled with seven crystalline spheres, nestling, one with the other, to each of which was attached the Sun, Moon and planets. The other model had the Sun at the centre, with all the planets orbiting the Sun. This second model gave a very natural explanation for the complex motions of the planets, but to Aristotle’s model one had to add the refinements of the Ptolemaic spheres, in which the planets went around small circles, called epicycles, the centres of which orbited the Sun in larger circles called the deferents.
He then went on to discuss various mechanical models used to represent these conceptual theories, starting with the Antikythera mechanism, which is a nautical archaeological artefact, dating from around 80 BCE, but discovered in a shipwreck off the Greek island of Antikythera in 1900. This mechanism seems to have represented the Moon and Sun as going around the Earth, which is also the model used in several astronomical clocks found in churches and cathedrals across Europe.
The Dondi clock, the original of which was made in the fourteenth century, seems to have been one of the few clocks based on the Ptolemaic spheres.
The more modern orreries, mechanical models of the Solar System, make use of the Copernican model with the Sun at the centre.
Until a few years ago planetarium projectors were based on hollow celestial spheres, with a point light source at the centre, which projected the sky on to the inside of a large hemispherical dome. The motions of the planets were simulated by torch-like projectors controlled by the orrery principle. The more modern planetarium projectors use a computer generated sky which is projected on to the dome by a fish-eye lens.
June 2008
Astronomical Pacemaker of Global Climate Change
Prof. Chris Wilson
On Wednesday, 25th June 2008, Sherborne Science Cafe was entertained to a thought provoking talk on the astronomical pacemaker of global climate change, given by Chris Wilson, Emeritus Professor of Earth Sciences at the Open University. He began by explaining how climate has changed over the past 20 thousand years, when the last glacial period was at its peak. Then sea ice extended as far south as northern Spain. By 15 thousand years ago the climate was warming, so Britain was experiencing permafrost and tundra vegetation although not glaciated. With continued warming, scrub vegetation appeared 10 thousand years ago, followed by forestation 5 thousand years later.The distinction was drawn between weather, which involves short term changes in atmospheric conditions, and climate, where the average variations of weather in a region are considered over long periods of time. Climate zones are defined by temperature and precipitation and can be mapped by using vegetation types.
The work of key contributors to the development of the theory of the astronomical pacemaker of climate change was reviewed. In 1837 Louis Agassiz, for example, was the first to propose that the Earth had been subjected to a Great Ice Age. Soon afterwards it was realised that there had been more than one period of glaciation and by the beginning of the 20th Century it was accepted that there were four Ice Ages. In the middle of the 19th Century James Croll proposed that one hemisphere or the other would experience an ice age whenever two conditions occur simultaneously: a markedly elongate orbit, and a winter solstice that occurs far from the sun. This would result in alternating glaciations in the northern and southern hemispheres. He also recognised the importance of the reflection of radiation from expanses of ice (the ice-albedo effect) which would enhance the cooling effect initiated by astronomical controls.
In the 1930s a Serbian engineer and scientist, Milutin Milankovich, published a series of papers linking mathematics, astronomy, geophysics and geology to explain the astronomical cause of climate change. His theory was greatly influenced by the pioneering climatologist, Vladimir Kloppen, who proposed that “It is the low summer temperature that produces glaciation. A large number of cold summers must be the cause of glaciation and they are the responsible for the formation of inland ice.” In other words, if winter snows survived the following summer, ice would begin to build up and cooling would be accelerated by the ice-albedo effect. Milankovich considered variations in the obliquity in the Earth’s axis of rotation to be crucial – a factor not considered by Croll.
In his seminal summary of his work published in 1941 (but not translated into English until 1969 and so overlooked by many paleoclimatologists), Milankovich showed how changes in the amount of radiation received at high northern latitudes acted as the pacemaker for the onset of glaciations. He presented calculations and graphs showing how the amount of solar radiation received at high latitudes was controlled by variations in the eccentricity of the Earth’s orbit, the tilt of its axis of rotation and the Earth-Sun distance in June.
The second part of the talk reviewed how modern analytical methods have revealed the Milankovich astronomical pacemaker in continuous fossil records of climate change. Unlike many land based records of climate change, cores of sediments taken from the floors of deep oceans contain continuous records uninterrupted by erosion. Analysis of the oxygen isotopes contained in the shells of microscopic single-celled animals known as foraminifera provided a breakthrough in unlocking continuous records of climate change. This is because when large ice sheets form, they contain more of the lighter isotope than is present in oceanic water. This means that oceanic water becomes enriched in the heavier oxygen isotope during glacial periods. Changes in this enrichment can be detected in the shells of foraminifera and so provide an excellent proxy record for past land-ice volumes. Such records show that sea levels have dropped by over 100 metres during glacial maxima. Mathematical analysis of such oceanic records reveals that the growth and melting of ice sheets was cyclic. The cycles have been shown to be linked to 100 thousand year cycles in changes in the eccentricity of the Earth’s orbit, 41 thousand year cycles in the tilt of its axis of rotation and 19 and 23 thousand year cycles in the Earth-Sun distance in June.
The same cycles have been found in a number of types of proxy records of climate change, including the record of temperature changes preserved in ice cores taken in Greenland and Antarctica. In the last few years EPICA, the European Project for Ice Coring in Antarctica, has extended ice records back to 800 thousand years ago. This project has cored ice formed between 430 and 390 thousand years ago – a time when astronomical controls were similar to those that have taken the Earth into the current warm interglacial period. If the ice record is a guide to future changes in climate, then it seems likely that the current interglacial will last another 10 thousand years at least – more than twice as long as the past three interglacials.
All the ice records show that the amount of carbon dioxide in the atmosphere has ranged between 200 (during glacial maxima) and 280 (during interglacials) parts per million (ppm). These variations track changes in global ice volume. Today the atmosphere contains 380 ppm of CO2 because of the effects of burning fossil fuels, felling rainforests, etc. over the last 150 years. So in such a short period of time, human activities have raised CO2 levels way above the norm for past warm interglacial periods. This is, perhaps, a global experiment that has some predictable – and perhaps some unpredictable consequences.
May 2008
The Principles and Practices used to Ensure Public Protection from Nuclear Power Station Accidents
by Eric Forrest
The May meeting of the Sherborne Science Café was addressed by Eric Forrest, a retired Chartered Engineer with a wide variety of experience. Most of this was gained when he was involved in the design and operation of new technologies, first in the communications industry, but more recently in the nuclear power industry. He was involved in the design and operation of no less than six power stations. The talk was very topical, following recent incidents at nuclear power stations and the announcement of government plans to increase the input to the national grid from nuclear power. He started by considering the UK legislation involved with safeguards against the potential dangers from domestic electrical equipment, cars, lifts, chemicals and fuels, among others. He drew analogies with aircraft and industrial processes, which are hazardous, complicated and potentially catastrophic following accidents.
He went on to discuss how safety was achieved by adopting the principals of Quality Assurance, and pointed out that every aspect important to safety was carried out in accordance with strict formal procedures. He then went through the process of making a Safety Case and discussed the pessimisms and limitations adopted in the design, construction and operation of the system.
This led on to a discussion of the hazards, both external and internal, facing a nuclear power station. Some of the external hazards considered were; low and high temperatures, earthquakes, missiles and aircraft crashes, and floods. The internal hazards included explosions, vermin, fire, vibration and radio frequency interference.
Eric also considered the staffing structure within a nuclear power station. He showed slides, which included a general overview of a power station, a section through a nuclear reactor and the layout and operation of a typical control room. He also showed us a model of reactor and, to scale, a plan view of four fuel rods and the positioning of the control rods. The talk covered all the salient features of nuclear safety in power stations and led to lively discussions between the audience and the speaker.
April 2008
Bird Flu by Dennis Alexander
At our meeting of 23 April we were treated to a very interesting and detailed presentation on BIRD FLU by Dr Dennis Alexander, a consultant virologist to the Veterinary Laboratories Agency.
Dr Alexander started by showing the structure of the flu virus and pointed out that each virus was typified by two different types of protein attached to its surface. Glycoprotein Haemagglutinin denoted by H and Neuraminidase denoted by N were the substances in question. At present 16 different H subtypes have been recognised (H1 to H16) and nine different N subtypes (N1 to N9) have been identified. Each virus has one H and one N protein, in any combination. Few of the 16 H and 9 N subtypes have been isolated from mammals, but all subtypes have been isolated from birds in most possible combinations. There are enormous pools of influenza A viruses in wild bird, especially migratory waterfowl.
Flu infections in humans are marked by the emergence of new viruses, now and again, that spread around the World causing severe pandemics. In the 20th Century there were four pandemics of influenza due to the emergence of antigenically different strains in humans. The pandemic of 1918 was due to H1N1, that of 1957 H2N2, 1968 H3N2 and that of 1977 H1N1.
The RNA of influenza A virus is segmented into eight distinct genes and as a result genetic reassortment can occur in mixed infections with different viruses. The 1957 and 1968 pandemic viruses differed from the preceding viruses in humans by the substitution of some genes that came from avian viruses. This indicated that pandemic viruses may arise by genetic reassortment of viruses of human and avian origin.
Dr Alexander pointed out that simultaneous infection with both human and novel avian viruses raised the possibility of a hybrid form against which the human population would have no immunity.
The session ended with a great deal of discussion on a topic which is obviously of great interest to most people.
March 2008
Digital Electronics Unspun by Tony Allen
Tony explained how everyday consumer products are becoming digital and thus the way they work becomes harder to understand. In order to follow the basis of digital processing it is necessary to start with the binary system of numbering, used almost universally by digital circuits. It is then possible to see how basic digital logic gates work and how common electronic circuits are derived from them.
The talk briefly explored the concept and potential of Boolean Algebra before plunging into binary arithmetic and the circuitry that supports it. This led on to how negative numbers and fractions are stored, and how adders and subtractors work. Binary multiplication and division is an extension of addition and subtraction.
Having dealt with the underlying concepts of digital electronics, the personal computer was used to show how a complete working system can be put together. The workings of a PC and its common components and peripherals were described in varying detail. The audience had the chance to practice binary arithmetic and to try out simple electronic circuits.
February 2008
Space Tourism by Peter Marshall
On Wednesday, 27th February 2008, Peter Marshall, satellite communications expert, journalist and author, presented an extremely topical, informative talk about recent developments towards commercial Space Tourism to Sherborne Science Cafe, at Sherborne House, Newland.
Peter worked for the BBC as a journalist and editor before becoming involved in developing the use of international satellites for worldwide TV news coverage and distribution. He was the first Director of Broadcast Services at INTELSAT in Washington DC, before serving as a board member of the France Telecom subsidiary, Globecast.
After retirement he returned to the UK where he currently works as a writer and as a Director of the Arthur C. Clarke Foundation.
Using his considerable expertise, Peter explained how Space Travel, which hitherto has been government run, is being developed by the private sector. Only five hundred astronauts and cosmonauts have travelled into space so far, but it is predicted that about five thousand civilians will go up there within the next five years. Richard Branson’s Virgin Galactic project should start next year, when, for $200 000, after a day’s preparation, space tourists will travel 62 miles high and experience weightlessness. In the next few years, it is forecast that the cost could reduce to about $40 000.
There are more than forty companies worldwide involved in the development of Space Tourism. With over 30 billion dollars invested, space stations are big business. INTELSAT, the intergovernmental body, was owned by 111 governments, so although it possessed much knowledge, many resources and engineers, it was so large that bureaucracy and wastefulness impeded progress. In Peter’s time there in the late 1980s, more money was being spent on conferences than on satellites! It was recently privatised, demonstrating that commercial enterprise tends to be more efficient, so Peter is convinced that Space Tourism will become a reality when run by the private sector.
Peter then gave a brief potted history of the development of space travel to date. During WW2, Werner Von Braun developed the V2 rocket. His team gave Hitler a demonstration in 1943. Hitler was so impressed, he ordered 10 000 to be built. They were fired to a height of 50 miles loaded with heavy warheads. Our troops headed north after D-Day to take out these rocket sites. Many people were unaware that 2000 V2s fell on SE England with thousands of casualties.
Post war, Von Braun went to America, becoming a US citizen. He became one of their key scientists, being involved in space and moon travel in the 1950s and 60s. Interestingly, some of Von Braun’s original team joined the Russian space development programme, so much early space research, on both sides of the Atlantic, was derived from that original rocket work in Germany.
Peter then praised the role of Arthur C. Clarke as a great scientist, who predicted the arrival of rockets capable of launching geostationary satellites and providing global microwave transmission as early as 1944.
Fast forward to the present day, when the audience were shown ideas for concept rocket ships, shuttles and even inflatable space hotels where people will be able to relax while undertaking their holiday in space. European engineers are designing an eight seater spacecraft which will take off and land conventionally, but it will convert to rocket power once airborne. In the future maybe supersonic destination flights via space will be possible, extending the idea started with Concorde: or even a trip round the moon. All that will be needed will be plenty of cash!
There were many questions after this truly fascinating talk. It was very thought provoking.
January 2008
GM - Boon or Bane?
Sherborne Science Café was treated to an interesting and informative talk on GM Crops by Professor Dixon, who was very well qualified to do so, having worked either as a professor or as a specialist researcher in many of the educational and research organisations of the UK.
He started by considering the differing roles that natural and man made evolution played in the development of plants, paying particular attention to the brassicas, which started in Africa, but took slightly different paths is Europe and Asia. Before serious work could start on selective breeding it was necessary know and understand about sex in plants. Although the Greeks were aware of this issue, they did not know enough and development had to await the Renaissance, the Reformation and the Enlightenment, when much more work was done, driven by trade and commerce. In the seventeenth century there developed a division between botanists, who went for purity in species, and plant breeders, who experimented with hybrids.
Professor Dixon then went on to briefly discuss the work of Carolus Linnaeus (1707-78), the Swedish botanist, who travelled around Europe collecting and describing new plant species, and by 1735 he had named and described about 100 new species. It was Linnaeus, who, in 1749, announced the binomial system of naming plants – one name for the genus and one for the species – which is still in use today.
This led on to a discussion of the work of Charles Darwin (1809-82) and Alfred Russell Wallace (1823-1913) on evolutionary theory by natural selection. Professor Dixon also mentioned the important work of Johann Gregor Mendel (1822-84) on the laws of inheritance. This work was ignored during Mendel’s lifetime, but they were rediscovered in 1900 by Bateson and de Vries. These laws led to a completely new understanding of genetics and opened up the possibility of further developments in the application of genetics to plant breeding. The year 1905 saw the use of single gene inheritance for disease resistance and this was applied to Yellow Rust in wheat and Blight and Wart in potatoes.
The next great leap forward in genetics came with the working out of the structure of DNA in 1953 by Francis Crick (1916-2004) and James Watson (1928- ), building on the work of Maurice Wilkins (1916- ) and Rosalind Franklin (1920-58). This work brought in a completely new age for plant breeding, as it was now possible to alter the characteristics of plants at the level of the actual genes. Professor Dixon explained how this was done by inserting parts of the genes from one organism into the genetic makeup of another. Much of the rest of the meeting was devoted to the advantages, and also the possible disadvantages, of manipulating the genetic ingredients of plants to make them more disease resistant and to produce species that had a higher yield per hectare.
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