10:30 Registration and Coffee.
10:50 Opening Remarks.
11:00 Lecture: TBA.
12:00 Lecture: The Science of Taste and Flavour by Peter Barham. This is good for a Fusion audience, as somebody has to drink some wine at one point! It is good fun and shows that physics is rather more diverse than some might expect.
13:00 Luncheon.
14:00 Fusion Annual General Meeting: Consisting of a brief report by each Committee member on the Society's activities during 2006, followed by the election of Officers and Committee members for 2007. All positions are up for election, but the following posts will be vacant: Chairman, Events Organiser, Newsletter/Web Site Editor, OU Liaison.
15:30 Coffee.
16:00 AGM Lecture: Somewhere Between the Bright Lights and Nuclear Fusion by Nick Braithwaite, Head of the Department of Physics and Astronomy at the OU. This will feature Prof Braithwaite's particular interest in technological plasmas.
17:00 Fun Lecture: Juggling: Theory and Practice by Colin Wright. Dr Wright is an expert juggler, and will explain the mathematics of juggling tricks while juggling. This is a hugely entertaining show, culminating in a truly mind-boggling extravaganza of juggling, mathematics, particle physics and more juggling.
17:30 Close.
18:00 Dinner.
19:30 Lecture: Astronomy for Physicists by Ian Morison of Jodrell Bank Observatory.
20:30 Fusion Star Party (weather permitting). Ian will bring several telescopes with him, so bring yours or a pair of binoculars!
21:30 Socialise in the hotel bar!

S207 Preparation Weekend

After the success of the S207 Weekend in 2006 we are running the weekend again on 20-21 January 2007. The Weekend will be held concurrently with our AGM at Yarnfield Park in Stone, Staffordshire. S207 Weekend attendees will also be able to join the Fusion Star Party.

QUANTA AND CONTINUUM

Science Revision Weekend

I would just like to say a very big thank you to everyone involved in organising the Science Revision Weekend at Yarnfield Park. This was my first such weekend and I was very impressed with how smoothly it all ran, and how useful it was in focussing my revision. So thanks for all your hard work folks and I will be back for my next science course in a couple of years - Anita Bokisch.

Aye to the Telescope

BBC News Magazine's search for Britain's greatest unsung landmark came up with a classic science icon dating back to the fifties. Thousands of votes were counted and Jodrell Bank's Lovell telescope in Cheshire was the winner! 29,093 votes were cast for the final 8 unsung landmarks and Jodrell Bank received 21% of votes cast. Second place went to the Humber Bridge and third to the New Severn Bridge. The 76 m 3,200 tonne Lovell telescope will be 50 years old in 2007, and has featured in The Hitchhiker's Guide to the Galaxy and Dr Who. Full story on the BBC's web site.

More Fun With Anagrams...

In his autobiography What Little I Remember, the physicist Otto Frisch (who, with his aunt, Lise Meitner, had first explained nuclear fission in 1938, and had coined the term "fission" for the process) recalls a telegram that arrived in Britain from Niels Bohr during World War II, and which ended with the mysterious words "TELL MAUD RAY KENT". Convinced that this was an anagram, Frisch and his colleagues tried to unscramble it . "We tried to arrange the letters in different ways", explains Frisch, "and came out with mis-spelt solutions like RADIUM TAKEN, presumably by the Nazis, and U AND D MAY REACT, meant to point out that one could get a chain reaction by using uranium in combination with heavy water, a compound of oxygen and the heavy hydrogen isotope called deuterium, abbreviated D. The mystery was not cleared up until after the war when we learned that Maud Ray used to be a governess in Bohr's house and lived in Kent." The secret committee that was subsequently set up to investigate the possibility of nuclear weapons, which Frisch and others served on, was code-named the "Maud Committee" as a result. See Gulliver's Travels and Kepler's Mistaken Ingenuity for more fun with anagrams.

Another Nobel Prize for Radio Astronomy

The Royal Swedish Academy of Sciences has awarded the Nobel Prize in Physics for 2006 jointly to John C. Mather of the NASA Goddard Space Flight Center and George F. Smoot of the University of California, "for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation".

This year the Physics Prize is awarded for work that looks back into the infancy of the Universe and attempts to gain some understanding of the origin of galaxies and stars. It is based on measurements made with the help of the COBE satellite launched by NASA in 1989.

The COBE results provided increased support for the Big Bang scenario for the origin of the Universe, as this is the only scenario that predicts the kind of cosmic microwave background radiation measured by COBE. These measurements also marked the inception of cosmology as a precise science. It was not long before it was followed up, for instance by the WMAP satellite, which yielded even clearer images of the background radiation. Very soon the European Planck satellite will be launched in order to study the radiation in even greater detail.

According to the Big Bang scenario, the cosmic microwave background radiation is a relic of the earliest phase of the Universe. Immediately after the big bang itself, the Universe can be compared to a glowing body emitting radiation in which the distribution across different wavelengths depends solely on its temperature. The shape of the spectrum of this kind of radiation has a special form known as blackbody radiation. When it was emitted the temperature of the Universe was almost 3,000 degrees Centigrade. Since then, according to the Big Bang scenario, the radiation has gradually cooled as the Universe has expanded. The background radiation we can measure today corresponds to a temperature that is barely 2.7 degrees above absolute zero. The Laureates were able to calculate this temperature thanks to the blackbody spectrum revealed by the COBE measurements.

COBE also had the task of seeking small variations of temperature in different directions (which is what the term 'anisotropy' refers to). Extremely small differences of this kind in the temperature of the cosmic background radiation - in the range of a hundred-thousandth of a degree - offer an important clue to how the galaxies came into being. The variations in temperature show us how the matter in the Universe began to "aggregate". This was necessary if the galaxies, stars and ultimately life like us were to be able to develop. Without this mechanism matter would have taken a completely different form, spread evenly throughout the Universe.

COBE was launched using its own rocket on 18 November 1989. The first results were received after nine minutes of observations: COBE had registered a perfect blackbody spectrum. When the curve was later shown at an astronomy conference the results received a standing ovation.

The success of COBE was the outcome of prodigious team work involving more than 1,000 researchers, engineers and other participants. John Mather coordinated the entire process and also had primary responsibility for the experiment that revealed the blackbody form of the microwave background radiation measured by COBE. George Smoot had main responsibility for measuring the small variations in the temperature of the radiation.
More >.

The Weakness
of Gravity

Maths Solution
by David Simpson

David Simpson provided us with his solution to last issue's Maths Quickie, where we calculated the gravitational force between two astronauts floating in space, but overlooked the fact that their resultant acceleration would not be constant, but rather it would increase as F_g increased as r got smaller. As before, the astronauts' motions start when they are a metre apart when r = a at t = 0 and 2a = 1 m.

Therefore T = 8,777 seconds (since 2a = 1 metre), so the time is shorter by a factor of π/4 compared to the constant acceleration model.

Also see an alternative derivation by Jim Grozier.

To SI or not to SI?

James Swallow asks: I wonder if you could clarify for me a small point in Paul Ruffle's article on Planetary Nebulae. In the first column it says "... density of ∼10³ cm^-3. Young PNe can have higher densities, ∼10⁶ cm^-3 ...". Surely we should be using SI units, and there is no indication of what mass is being referred to.

Paul Ruffle answers: ∼ 10³ cm^-3 should have read n ∼10³ cm^-3, i.e. the number density (of mainly ionised hydrogen) is around 1,000 particles per cubic centimetre. Astronomers always refer to the density of the interstellar medium (ISM) as a number density, but the 'n' often gets omitted, which I should have spotted. As to SI units, yes you are right, but again generations of astronomers have got wedded to cgs as opposed to SI units. As to why, I have no idea, as using smaller units is even more daft. Mind you, most people can picture 1,000 particles in a volume the size of a sugar cube, but 10⁹ particles in a cubic metre is harder to grasp, so cgs has its place.

Jim Grozier comments: I can remember being told by my school physics teacher that a new system of units called "MKS" (Metre, Kilogram and Second) was being introduced, and would become the standard. That would have been in the mid or late sixties. Up to then, everything had been measured in centimetres, grams and seconds - the "cgs" system - and indeed most or all of my school physics education was done in this system (although I can also remember using things like "foot-poundals" in Applied Maths).

Just a few years later, in 1971, the currency of the UK was changed from pounds, shillings and pence to a decimal system of pounds and pence. Some of us struggled with the "new money" for a while, but I think most people are used to it by now; some of us have even managed to get our heads round the centigrade scale of temperature! Unfortunately, the physics community has been rather slower to embrace what should have been a much simpler transition - changing numbers by powers of 10 rather than converting by factors of 5/12 (for pence) or 5/9 (for temperature). Many of those at the "top" of the profession - those who write the textbooks and, more importantly, those who referee the papers - are still firmly entrenched in the old system, and simply refuse to embrace the "new" one; this means that newer, younger researchers feel obliged to conform, and so, despite having been brought up entirely on SI units through school and undergraduate days, when one enters the field of postgraduate research one is simply bullied into submission. Personally, I have always quoted my results in SI even though all those around me are still using centimetres, but even I recently got worried when my supervisor screwed his nose up at my metres - would it affect my chances of getting the doctorate? (And I am not even going to mention electromagnetic units, where it isn't just a matter of conversion factors but of which units you should measure things in, and whether some quantities have units at all!)

So I can see how Paul has felt obliged to use the language of the astrophysics establishment, but it does worry me that this process could, if something isn't done about it, become self-perpetuating. If Paul is encouraged to continue thinking in centimetres, when he is a hoary old professor (and he has already taken to wearing a "Grumpy Old Man" T-shirt, so it won't be long) he may well insist on his students doing the same, and so on in the next generation, etc ... so I do think that someone needs to take a firm stand on this; for instance, journals could be asked to refuse to publish any article that isn't in standard units.

Bring on the SI police!

Juggling and Anti-Juggling

by Mij Reizorg

Have you ever seen Heisenberg's Uncertainty Principle applied to the case of a juggling ball? No? Well, Colin Wright managed it, and a great deal more besides, in a talk entitled "Juggling: Theory & Practice" given to the IoP South Central Branch at Sussex University in February.

Representing juggling tricks on paper is fiendishly difficult, but if you make some simplifying assumptions it turns out that you can construct graphical representations which look a bit like Feynman diagrams, and then you can model various tricks and predict new ones by tweaking the parameters.

Using this model, the length of time a ball spends in the air between throw and catch can be represented by a discrete variable (presumably it would become continuous in the limit, if anyone could juggle that fast) which can take negative values, in other words it can travel backwards in time! What's the interpretation of that? Well, as Colin reminded us, a particle travelling backwards in time is considered to be the same as an anti-particle travelling forwards in time; so why not an anti-ball?

As all particle physicists know, an anti-particle can be created as part of a particle-antiparticle pair if there is enough energy to produce the requisite amount of mass, and in fact such a pair can appear spontaneously for a short time as a result of the Uncertainty Principle, which predicts an inverse relationship between the uncertainties in time and energy. So, make your time period small enough and you may find that there is enough uncertainty in the energy to create a ball-antiball pair for one period! You don't actually see the antiball of course, or indeed its partner; what you see is the juggler's empty hand. But it's there all right; if you draw a line representing constant time across the diagram and count the trajectories crossing it, there turns out to be 2 more than there should be; the extra 2 are our short-lived pair.

If this was too much for any of the 50-odd people in the audience, they could always just enjoy the amazing juggling - not just by the speaker, but by a virtuoso undergraduate student who stepped up to perform a trick so complicated that even its inventor cannot do it properly.

Apparently there are juggling societies and juggling conventions, and a whole series of world records for the number of objects juggled, depending on the type of object. Rings are the easiest; the world record for these is 12, but for chainsaws it is only three. You are not recommended to try the latter at home (or, indeed, anywhere). But do come and see Colin Wright at the Fusion AGM this January.

Come to the AGM Star Party!

Fusion Day 2007 will take place on 20 January 2007, concurrent with the S207 Preparation Weekend, at Yarnfield Park Training and Conference Centre, Stone, Staffordshire.

As well as the 6th Annual General Meeting of Fusion - The Open University Physics Society - we are planning exciting activities in science and astronomy, including a talk on plasma physics from Nick Braithwaite, the OU's Head of Physics and Astronomy, the physics of juggling by Colin Wright, plus the first ever Fusion Star Party with Ian Morison from Jodrell Bank Observatory. See the full details on the left and check the Fusion web site for the final programme.

You can register your attendance by sending an email to Fusion or writing to the address below. To help with planning please let us know if you will require lunch and/or dinner. Complimentary lunch will be provided for all Fusion members in attendance. Dinner is also available for £17.00. Dinner, overnight accommodation on Saturday night and breakfast on Sunday morning is available for just £67.00.

Fusion Visit to Bletchley Park

Fusion members enjoying the June sunshine at Bletchley Park, the World War II codebreaking centre.

We were treated to detailed explanations about the 'Bombe' (above), an electro-mechanical machine to crack Enigma codes, and 'Colossus' (below), the world's first practical electronic digital computer.

Our Dusty Universe

by Dr Paul Ruffle

I summarise here the broader significance of dust in cosmic processes and our own existence. In fact, we humans are literally made of star dust, which is all the more sobering when one considers that, despite our position in a quiescent part of our Galaxy, we have the temerity to catch a few photons and try to fathom the very processes that brought about our existence.

Today's Universe is indeed dusty, with around one per cent by mass of the interstellar medium (ISM) in the form of dust. However, this was not always the case, as when the first nuclei formed during primordial nucleosynthesis (around t = 100-1000 seconds after the Big Bang, which according to cosmological models based on the Hubble constant and the densities of matter and dark energy, occurred around 13.7 billion years ago), the only stable elements formed, in addition to hydrogen and its isotope deuterium, were helium and lithium. Some time after the last interaction of matter and radiation (t ∼ 3 × 10⁵ yr), the first stars (and galaxies) formed from this gas. Nuclear fusion reactions in the cores of this first generation of stars synthesised heavy elements (or metals) such as carbon, oxygen and silicon. More massive stars created even heavier elements, all the way up to iron, cobalt and nickel. Successive generations of stars have increased this metallicity to that which can be observed in the local Universe today.

However, compared to our Sun, the relative abundances of metals, i.e. elements heavier than helium, is greatly reduced in the gas phase in the ISM, with elements that can form refractory (heat stable and resistant) solids having the highest depletions. Examples include silicon and oxygen, which can form silicates with magnesium and iron; iron particles; silicon carbide, graphite and metal oxides. This suggests that elements that can form refractory solids are removed from the gas phase as solid particles, i.e. dust. In fact, small particles or grains are found in molecular clouds and dark nebulae throughout the ISM. The sizes of dust grains range from 0.001 μm to 0.1 μm, and they account for around one per cent of interstellar mass, with a low spatial density of around one grain for every 10¹² hydrogen atoms, for grains of radius a ∼ 0.1 μm, where the average H-nuclei density in the ISM, as opposed to clouds, is about one per cubic centimetre (n_g, the number density of dust grains is proportional to a^-3.5, so there are more smaller grains than large). Dust in the ISM is composed primarily of carbon and silicate material, often with mantles of water and ammonia ice or solid CO.

The presence of dust is revealed by dark regions in otherwise rich star fields, e.g. Barnard 86 (Fig. 1), where the dust grains heavily extinguish starlight. Dust is also found in circumstellar shells, causing an infrared excess in the spectrum of many stars. In fact, for any line of sight, the existence of dust in the ISM is revealed by the reddening of starlight, where shorter wavelengths are more affected than longer wavelengths. This extinction can be measured by comparing stars of similar mass, temperature and composition (revealed by their spectral signatures), and therefore similar intrinsic luminosity. Differences in detected luminosity can be attributed in part to differences in their distances, but the degree of reddening will indicate the amount of extinction for the respective lines of sight through the ISM.

The observation that, in general, starlight is partially linearly polarised also confirms that dust grains cause interstellar extinction, where the amount of polarisation appears to be proportional to the amount of extinction. For this to be so, isotropic interstellar grains must be non-spherical and there must be some degree of alignment of these elongated grains, so that radiation with electric vectors parallel to the grain's longer axis will be more extinguished than vectors parallel to the short axis. Aligned grains of anisotropic material, such as graphite, may also cause polarisation. Dust grains will normally be rotating (angular frequency ω ∼ 10⁵ Hz), and if they are paramagnetic and a magnetic field exists in the interstellar gas, this will tend to align the grain's axis of rotation with the magnetic field, although this will counteracted by collisions, which will randomise the spin axis of a grain.

Fig. 1: The open star cluster NGC 6520 and the dark nebula Barnard 86 (B86). NGC 6520 consists of young blue stars, possibly just a few million years old, and most likely formed from the molecular cloud B86. Dust from the leftover material in B86 blocks light from other stars that are behind the cloud. The background of the image is the central bulge of the Milky Way. Credits: Fred Calvert, Adam Block, NOAO/AURA/KPNO/NSF.

Dust grains also reveal their existence by scattering starlight, thereby filling the Galaxy with diffuse light, which can be directly observed as a reflection nebula, such as in the Pleiades (Fig. 2), or as reflected light from shells of dust that are ejected during the latter phases of a star's evolution, such as V838 Monocerotis (Fig. 3). Dust particles also cause several strong infrared absorption lines in the light from background stars. Examples include the Si-O stretching and bending modes in amorphous silicates at 9.7 and 18 μm respectively, the O-H stretching mode in amorphous H₂O ice at 3 μm, and the vibrational excitation of CO ice at 4.7 μm, as well as various hydrocarbon C-H stretching modes between 3.3-11.3 μm.

Fig. 2: IC 349 or Barnard's Merope Nebula illuminated by strong radiation from the nearby hot bright star Merope, located in the Pleiades star cluster. Credits: NASA and The Hubble Heritage Team (STScI/AURA).

Timescales for dust formation by condensation within interstellar clouds are very long (> 10⁹ yr), so denser regions with shorter timescales are required. Outflowing gas from cool stars provide the initial densities (n ∼ 10¹³ cm^-3) and temperatures (∼ 10³ K) for particles to nucleate and settle out, as the cooling gas is blown clear into the ISM (see the Spring 2006 Newsletter, on how the formation of planetary nebulae returns stellar material to the ISM). The type of particles that form is sensitive to the cosmic abundance of the elements, with successive generations of stars increasing the metallicity of a given locality within a galaxy, e.g. the central bulge region of our Galaxy has likely seen far more star formation than regions at the periphery of the Milky Way. For temperatures of 1000-2000 K carbon monoxide is stable, so that most of the C and O atoms are bound in this form. However, many stars are either oxygen- or carbon-rich, resulting in the preferential formation of dust particles that are either oxides or solid carbon grains. Grains may grow further by accretion of atoms and molecules from the ISM, although, as mentioned above, timescales are likely to be unacceptably long unless the gas density n ≥ 10³ cm^-3, which is the case in cold molecular clouds.

If dust grains have icy mantles, these will evaporate if the grains are heated sufficiently, for example when a clump of denser gas in a molecular cloud contracts to form a prestellar core. Refractory materials such as hydrocarbons, graphite or silicates are very durable, as evidenced by the presence of rocky planets and even ourselves in the Solar System. However, sputtering by high-speed atoms can knock lattice atoms out of a grain and lead to its eventual destruction. Energetic supernovae (∼ 10⁴³ J) can set up shocks that disrupt the ISM and either destroy or reduce the size of dust grains.

Dust grains also play a role in the evolution of interstellar gas clouds. Depending on their energy (4-14 eV), ultraviolet (UV) photons can heat either the gas or dust in a molecular cloud. For UV (or visible light) photons with an energy less than the work function of a typical dust grain (W ∼ 5 eV), the radiation is absorbed by the grain, and then re-emitted in the infrared. As grains are not perfect radiators they achieve a temperature above the microwave background (2.7 K) of between 14-45 K, depending on the material. Higher energy UV photons eject electrons from grains via the photoelectric effect, where each released electron will carry several eV of energy, which will heat the gas via subsequent collisions. Dust can also act as a sink for energy, when higher temperature atoms or molecules (e.g. at 100 K) stick to lower temperature grains, where the energy difference is lost from the gas, and the grain subsequently radiates the energy away.

For star formation to occur in molecular clouds, there has to be a mechanism for removing the additional kinetic energy that is converted from gravitational potential energy when denser clumps in a cloud undergo collapse. Various molecular species, particularly CO, radiate effectively via collisional excitations, thereby cooling the cloud. However, the formation of molecules in the first place, even H₂ the most common, are difficult to explain with just gas phase reactions. Two body atomic collisions offer little opportunity for radiative stabilisation, with around only one in 10⁵ collisions producing a molecule. Interstellar densities make the possibility of a third body, that could remove some energy, even more unlikely. Added to this, UV photodissociation and various chemical reactions effectively destroy molecules on short timescales (∼300 yr), although it should be noted that once enough basic molecules exist (and are replenished), more complex species can form through chemical reactions.

Fig. 3: Expanding halo of light around V838 Monocerotis. The illumination of interstellar dust comes from the red supergiant star at the middle of the image, which gave off a pulse of light two years before the image was taken. Credits: NASA, the Hubble Heritage Team (AURA/STScI) and ESA.

It is self-evident that a mechanism for molecular formation does exist, as dense clouds consist primarily of molecular hydrogen, as well as over 100 other molecules. The surface of dust grains are believed to be the sites where H₂ can form, with the minimum requirement that one H atom is retained at the surface long enough for a second H atom to arrive and locate the first. In the vicinity of a grain, long-range van der Waals forces between an H atom and all the atoms of the grain create a potential well for the infalling H atom, which on collision becomes bound to the surface, due to some energy being transferred to the grain lattice. The atom may then move laterally across the surface before becoming bound at a particular site in the lattice. Subsequent movement to other bound lattice sites is achieved by the quantum-mechanical penetration of the barrier between sites. Simple calculations indicate that an H atom can be retained long enough at a grain's surface for a second atom to arrive and be met by the first atom. Upon formation H₂ is ejected from the grain, due to the large amount of energy released when the two H atoms combine. For other atoms and radicals, binding energies for grain surfaces are larger than for hydrogen, so if this catalysis works for H, it is likely to work for other molecules such as H₂O, CH₄ and NH₃. In denser regions ice mantles can also form on dust grains via two different processes. Water ice most likely forms when free oxygen atoms arriving at a grain surface successively combine with H atoms, forming H₂O molecules that are mostly retained. In this scenario, it is likely that the H atoms arrive at the grain's surface after the O atom, since two H atoms on the surface will find one another, react and desorb as H₂ before an O atom arrives. In contrast, solid CO forms by means of simple freeze-out on the cold dust.

When astronomers first encountered dust in the ISM, it was an irritating phenomenon that obscured and interfered with stellar observations. However, understanding the role of dust in cosmic processes has become one of the most fruitful endeavours in modern astronomy. Fuller treatments on the role of dust in the ISM can be found in:
The physics of the interstellar medium, J. E. Dyson and D. A. Williams, IoP Publishing, 1997;
The dusty universe, A. Evans, J. Wiley, 1994;
Dust and chemistry in astronomy, T. J. Millar and D. A. Williams, IoP Publishing, 1993;
Dust in the galactic environment, D. C. B. Whittet, IoP Publishing, 1992.

Gulliver's Travels and Kepler's Mistaken Ingenuity

by Keith Lambkin

This intriguing popular science tale illustrates how the physics of Kepler's third law of planetary motion influenced the thinking of Jonathan Swift's epic novel 'Gulliver's Travels'¹. Exploring the relationships and physics discoveries of Galileo Galilei, Johannes Kepler and Jonathan Swift, a proposal is set forth to explain one of the most puzzling passages in 'Gulliver's Travels' and to attempt to find out if Swift really knew the planet Mars had two moons, over 150 years before they were officially discovered. I first came across the following tale in the excellent book by Derek York, 'In Search of Lost Time'². Since then I have found numerous references and opinions on this tale^3,4 and developed some of my own. Using Derek York's book as a primary source and supplementing facts from other sources (included in the references) I put together a presentation. The aim of this presentation was to promote interest in physics through the use of mathematics, influential characters and humour. This presentation won the Institute of Physics Young Physics Conference Post Graduate lecture competition 2005 (Dublin, Ireland) and was later presented at the International Conference of Physics Students 2006 (Bucharest, Romania). This is the tale...

Gulliver's Travels - the epic story by the Irish author Jonathan Swift - was first published in 1726. After adventures in Lilliput (a land of little people) and Brobdingnag (a land of giants), the central character, Gulliver, finds himself in LaPuta, a land inhabited by highly intelligent people. It is at this stage of the book (Part III:III:IX) the following 'puzzling' passage appears... "Certain astrologers... have likewise discovered two lesser stars, or satellites, which revolve about Mars, whereof the innermost is distance from the centre of the primary planet exactly three of it's diameters, and the outermost five; the former revolves in the space of ten hours, and the latter in twenty-one and a half..."

Swift's "two lesser stars, or satellites, which revolve about Mars" are quite obviously a reference to the two moons of Mars, Phobos and Deimos. Although Swift's numbers for the moons' orbital distances and diameters are not completely correct, they are in the right range, differing by approximately 30% from their true values. But here is the puzzle; the two moons of Mars were discovered by Asaph Hall, at the US Naval Observatory, Washington DC in 1877. But this is 151 years after the first publication of Gulliver's Travels. So the question is, did Jonathan Swift just guess Mars had two moons or did he have some scientific insight into his choice, and if so, what?

Immanuel Velikovsky (1895-1979), a Russian psychiatrist, believed he knew the answer. In his well read book 'Worlds in Collision' (1930) Velikovsky claims "The collision between major planets... brought about a birth of comets... at least one of these comets in historical times became a planet (Venus)" ⁵. He apparently believed that approximately 3000 years ago, out of the belly of Jupiter came forth a comet which hurtled its way through the solar system. This comet narrowly missed Mars (then lying in an inner orbit between the Earth and the Sun) but passed close enough to pull away its atmosphere and send the planet into a highly elliptical orbit around the sun. The comet itself became trapped in the sun's gravitational field and eventually settled down into what we now know as the planet Venus. At this time Mars, during its highly elliptical orbit, passed close to the Earth on a number of occasions. So close in fact that people could not only see Mars and its two moons, but were also able to make detailed observations of the two moons' approximate sizes and periods. These observations, Velikovsky believed, were recorded in an ancient manuscript. Swift managed to get his hands on this ancient manuscript, hence find out Mars had two moons, but unfortunately this manuscript is now lost!

Perhaps today's science community would have little trouble dismissing Velikovsky's theory as mere fantasy, so let us look at another possible solution to the two moon problem. Johannes Kepler⁶ (1571 - 1630) was conceived on 16th May 1571 at 4:37am⁷. Now, if his parents kept records like that how did they expect their son to grow up to be anything but a scientist! He grew up in a time surrounded by witchcraft and astrology and is probably best know today for Kepler's laws of gravitational motion.

Introducing another great scientist of Kepler's era, Galileo Galilei (1564 - 1642) had been announcing a series of spectacular astronomical discoveries with his telescope. Now it is important to note that Galileo did not invent the telescope, although he did make his own. A man by the name of Thomas Harriett was making detailed maps of the moon in Oxford with his own telescope in 1609 before Galileo had made his first⁸. Galileo was however the first to publish results based on his telescopic observations and hence became associated with the telescope itself. Although not always just, the academic credit generally goes to those who publish results first, as is the case today.

As with many telescopic astronomical observations of the time, initial discoveries came fast but verifications of discoveries took months or even years. The prudent Galileo, knowing well the trade off between publishing first and the time delay to verify results, devised an ingenious system. He would announce his potential discovery in a (Latin) statement, scramble all the letters up into an anagram and send this anagram to his rivals, without spending potentially wasteful time trying to verify his results. If his discovery turned out to be true (i.e. verified by someone else) Galileo would then release the key to unscramble the anagram and hence claim the discovery as his own. Similarly, if the discovery turned out to be false, he would never release the key and hence no one would be any the wiser.

In 1610, Galileo discovered using his telescope what he thought were two moons of Saturn, (they later in fact turned out to be the rings of Saturn). And he wrote: "I have observed the highest planet (Saturn) in triplet" well in truth he wrote this in Latin which is "Altissimum planetam tergenimum observavi" and then scrambled this up into the anagram: SMAISMRMILMEPOETALEUMIBUNENUGTTAVRIAS Now, Kepler got his hands on this algorithm and knowing Galileo had a telescope, was intrigued to determine what Galileo had discovered. Using great ingenuity, Kepler managed to decode this anagram, or at least he thought he had. He unscrambled the letters to form the following Latin phrase: "Salve umbistineum geminatum Martia proles", which Koestler in his book 'The Sleepwalkers'⁹ translates as "Hail burning twin, offspring of Mars". Kepler believed that Galileo had discovered two moons around Mars. This was great news to Kepler because he was a big fan of geometry in the solar system. He knew that Venus had no moons, the Earth one; for Mars to have two, with Jupiter four, created the series 0,1,2,4... which fitted in perfectly with his geometric outlook of the planetary system. Granted, the letters of his unscrambled version didn't perfectly match the anagram, but Kepler was convinced that he had decrypted Galileo's anagram.

Now to pose another question, could the idea of Swift's "two lesser stars, or satellites" have originated form Kepler's "twin, offspring of Mars"? Perhaps, but in order to give any credibility to this connection, a link must be shown proving that Swift knew of Kepler and his writings.

First, let us take a quick look at Kepler's 3rd Law of planetary motion. It states: The square of the period of any orbital body is proportional to the cube of the semi-major axis of its orbit. Mathematically this can be expressed as

T²/R³ = 4π²/GM,

where T = period (time for one complete revolution), R = orbital distance (distance between the centre of mass of each body), G = universal gravitational constant (6.67 × 10^-11 N m² kg^-2), and M = the mass of the larger (centred) body.

Basically what the equation is saying is that the property period squared over the distance cubed in any closed system is equal to a constant. Or alternatively, that period squared is proportional to the distance cubed. Taking a brief example of the Earth going around the Sun; T = 365.25 days, R = 1 AU (astronomical unit) then T²/R³ = 133407 units^*. Compare this to Mars going around the Sun where Mars has a period T = 686.98 days, R = 1.52 AU this gives T²/R³ = 133410 units^*. To all intents and purposes the same number (differing only by a fraction of a percent). The equation works.

Now, let us look at the rest of the passage from Gulliver's Travels which was started above. It continues:

"...so that the squares of the periodical times are very near in the same proportion with the cubes of their distance from the centre of Mars, which evidently shows them to be governed by the same law of gravitation that influences the other heavenly bodies."

Here Swift is making a direct reference to Kepler's 3rd Law. Let us substitute Swift's values for the periods and distances of his two moons orbiting Mars. The innermost moon (Phobos) has T = 10 hours and R = 3 Mars diameters, which gives T²/R³ = 3.704 units†. The outermost moon (Deimos) has T = 21.5 hours and R = 5 Mars diameters, which gives T²/R³ = 3.698 units†. To all intents and purposes the same number (differing only by a fraction of a percent). Swift did know of Kepler's writings.

At this point Velikovsky is well within his right to jump back into the tale claiming Swift proves his (what seems outrageous) theory. "The reason your moons obey Kepler's Law is because they came from his previously mentioned lost manuscript. This manuscript contained recorded observations of actual moons (as Mars was closely passing by Earth in its highly elliptical orbit!) and actual moons would obey Kepler's laws because that is the way moons behave." One has to admit, however unlikely, that this is a good argument. Good, but with one small flaw. In 1726 when Gulliver's Travels was first published, the mass of Mars was not known. What has that got to do with anything one might ask. Let us look at the following example.

The right hand side of our equation contains all constants, with M being the mass of Mars in this case. Substituting in the true mass of Mars as known today (0.64 × 1024 kg) we get a constant of 22.22 units†. Using the value that Swift used for the mass of Mars we get from above a constant equal approximately 3.7 units† as seen previously. But these constants differ by over 600%. Sorry Velikovsky, real moons can't deviate from nature by 600%. Your argument is invalid. Swift knew of Kepler's writings and yes Swift's values equalled the same constant but they equalled the wrong constant. Swift guessed the mass of Mars to make his values work.

So in summary, how could Swift have known about Phobos and Deimos? He could have guessed, it would have been a pretty amazing guess but perhaps a guess none the less. He may have had psychic powers or maybe the Martians told him! He may have got the idea from another writer or philosopher from that era. Voltaire (1694-1778) a French philosopher of the time had mentioned he believed that Mars had two moons, but more so for artistic reasons than scientific ones¹⁰. Swift may have learnt of the two moons from Velikovsky's ancient lost manuscript. Or maybe, Swift's "two lesser stars, or satellites" could actually have been Kepler's 'twin, offspring of Mars', which were actually Galileo's 'two moons of Saturn', which were actually the 'rings of Saturn'?

Therefore to conclude, did Jonathan Swift just guess Mars had two moons or did he have some scientific insight into his choice, and if so what? As to the answer, well, you decide!

* Days²/AU³. † Hours²/Mars Diameters³.

Keith Lambkin works at University College Dublin in Ireland.

References

1. Gulliver's Travels, Jonathan Swift, (numerous publishers, numerous years).
2. In Search of Lost Time, Derek York, Institute of Physics Publishing, 1997.
3. Ringside seat: sometimes, in science as in boxing, you want to be up close; sometimes you want to keep your distance, Neil deGrasse Tyson, Natural History, Oct 2004.
4. Galileo's Anagrams and the Moons of Mars, www.mathpages.com/home/kmath151.htm.
5. Worlds in Collision, Immanuel Velikovsky, (numerous publishers, numerous years).
6. A Short Biography of Kepler, NASA, kepler.nasa.gov/johannes.
7. The Decline of Astrology and The Christian Cult, www.esoterism.ro/english/declin-astrology.php.
8. The Irrepressible Galileo Galilei, Deborah Houlding, www.skyscript.co.uk/galileo.html.
9. The Sleepwalkers, Arthur Koestler and Herbert Butterfield, Penguin, 1964.
10. The Mysterious Moons of Mars, Lee Krystek, 1997, www.unmuseum.org/marsmoon.htm.

Science Revision Weekend 2006

by Digby Tarvin

This year saw the presentation of the third Science Revision Weekend organized jointly by Fusion and the OU Chemistry Society.

The revision weekend was held from the 29th of September to the 1st of October, and was notable this year for being the first to be held at the Yarnfield Park Training and Conference Centre in Staffordshire.

The new venue proved very popular as both the accommodation and the teaching facilities were far superior to those available at the former University of York venue, and the more favourable prices and conditions allowed us to keep the registration fees below the level that would have been required by the ever increasing costs at the old venue.

The only problem associated with the new venue was a location not easily accessed by public transport on weekends, which we endeavoured to alleviate by providing a complimentary coach to the nearest railway and bus stations. But even this provision failed to make every students journey painless, as one of the pubs used as a landmark in the description of how to get there changed its name at the last minute, and track work on Sunday meant that students planning to travel home from one of the stations were faced with a replacement bus service and greatly extended journey time.

During the weekend 19 tutors provided tuition for 14 of Open University's science subjects, with an average of 18 students in each class.

The weekend commenced with a post registration dinner on the Friday evening, followed by the first teaching session from 20:00 till 21:30. On Saturday classes started again at 9:00am following a hearty breakfast, and carried on through the day with breaks for morning and afternoon tea/coffee as well as lunch and dinner.

On Saturday evening there was some respite from the mental exertions of the day and a chance to rekindle any wilting enthusiasm for study as we were treated to presentations by the heads of the OU Physics and Chemistry departments (Professor Braithwaite and Dr. David Roberts respectively) followed by the inaugural Science Revision Weekend Guest Lecture given by the renowned author, journalist and TV producer Simon Singh.

Simon's talk, entitled 'Big Bang', was a lively and accessible coverage of the history, reasoning and experimental evidence behind our current theory explaining the origin and evolution of our Universe. His unique perspective ranged from the the early theories of Georges Lemaître and the competing steady state theories, to the current conclusions drawn from Hubble's red shift observations and the detection of cosmic background radiation, and included less familiar topics such as the influence of female computers and the relevance of satanic messages hidden in Led Zeppelin songs.

The presentation included demonstrations of effects ranging from Doppler shift to electrified gherkins, with nerdy musical accompaniment by the Chromatics and the Satanic Led Zeppelin piece.

The subjects and numbers of students attending were as follows:

Subject	Minimum	Maximum
S204	9	11
S207	24	32
S216	10	12
S205	22	22
S282	8	13
S283	4	9
S269	21	26
S328	23	27
S342	14	24
S343	18	30
S377	11	17
S381	23	28
SD329	9	14
SMT359	27	32

If you are interested in attending the Science Revision Weekend next year, keep an eye on the Fusion web site events page or the revision weekend web site at www.sciencerevision.org.uk for announcements.

Café Scientifique

by Jim Grozier

Some readers will already be familiar with the Café Scientifique movement; many will probably be unaware of it as yet, and given the hectic life that most OU students live, many of those who have heard of it may not have had a chance to try it out. However, with a Café in or near most large towns in the UK, and several new ones springing up each year, it is a phenomenon that is definitely in the ascendant.

Café Scientifique is a cross between a scientific lecture and a political debate, but it takes place in the sort of venue where you wouldn't expect to find either. Dubbed as "Science for the Sociable", Café Scientifique (or CS for short) is to be found in cafés, bars, bookshops, arts centres etc, and its mission is "to take science away from the bum-numbing chairs of the classroom and into big, fluffy sofas". The idea is that an invited speaker gives a short (20-30 minutes) talk on a scientific subject, and then there is a prolonged period of questions and discussion over a drink or two and maybe some food. There are about 40 Cafés Scientifiques in the UK, a similar number in the USA and Canada, and smaller numbers in a dozen or more other countries, including France.

More than France? Well, yes, because despite its name, CS is a British invention, although it was based on a French idea - the "Café Philosophique" movement which was started up in 1992 by the philosopher Marc Sautet. It was reading Sautet's obituary in 1998 that inspired Duncan Dallas to set up the very first CS in Leeds. It's still going strong, and has since been joined by many others. (See www.cafescientifique.org to find a café near you).

Café Scientifique is run on a shoestring by willing volunteers. Although grants have been obtained in some cases, the bread-and-butter work gets done for love, and a hat passed round every month pays for speakers' expenses. There are very few, if any, rules; it is a virtual organisation in the truest sense of the term. Some organisers are a little "purist" and discourage the use of visual aids such as PowerPoint, on the basis that "anything that smacks of a lecture is a big no-no", while others - myself included - are happy for any sort of presentation, high-tech or not, and recognise that many scientific concepts - such as climate change - are difficult to convey to the uninitiated and the sceptical without the use of graphs or other illustrations.

Most people who have experienced Café Scientifique would agree that it is the discussion aspect that is the most important. It is not simply a lecture with an extended period of questions; the whole point of it is to get the public to engage with science, and to express their point of view so that it becomes a two-way exchange of information, and not just an "expert" talking down to the uninitiated. In our Brighton CS sessions, a very valuable member of the audience is a teacher friend who knows very little about science but is keen to learn, and is also very ready to ask "What's in it for the housewife?" To date, she hasn't actually asked this question at a CS event in so many words (although she frequently hurls it at me in private) but she and others have certainly conveyed to several of our speakers that "we" are not prepared to simply swallow it all unquestioningly.

I took over as organiser of the Brighton branch in the summer of 2005, after the original person who had shepherded it through its first two years had to give up in order to concentrate on her day job. Our venue is a seafront bar with splendid sea views, nice food and a fantastic atmosphere. And what's more, they let us have the place for nothing, so that we only have to find the money for speakers' expenses and hiring PA equipment. Luckily, we also have the services of a very talented chairperson, and so my role is very much a "behind the scenes" one, mainly consisting of finding and booking speakers, sending out mailings and flyers, and liaising with the venue. This was a challenge at first - particularly identifying possible speakers, and persuading them to come and talk to us - but now, with most of the next session booked up, I can afford to relax and just enjoy it.

In the last year, we have had sessions on consciousness, taste and smell, life in the universe, intellectual property, nuclear fusion, the ethical implications of scientific research, microgeneration (generating your own power), psycho-somatic illnesses, and dating (no, not THAT sort!) Our audiences have varied in number from 30 to 60, and we have had some lively discussions. Particularly memorable occasions were when, during the microgeneration session, someone in the audience turned out to be actually doing it, and our academic expert willingly gave the floor to them; also when the nuclear fusion speaker brought in some equipment and announced that he was going to do a demonstration - which turned out to be just the effect of magnets on plasma, not the whole works, but was still very much appreciated! We also had a speaker who, in another life, had been a folk singer, and responded to the very last question - "can you give us a song?" by doing just that! In fact, on another occasion when we had been discussing some pretty depressing issues, someone suggested that we all finish with a few choruses of "Always Look On The Bright Side of Life" - so we did.

Do try out your local Café if you have one. And if you find yourself going regularly - or perhaps you already do - you might like to offer to help. I can assure you that any such offer will be very gratefully received!

Come along - join the fun!

So it's goodbye to HIM ...

by Jim Grozier

Paul Ruffle is leaving the Fusion committee after nearly six years, to take up an exciting new job at an observatory in the USA.

I first met Paul at the Young Physicists' Conference in Chester in November 2000, and was very glad that he was there, if only because it meant I was only the second oldest person there (by about a month!) Six weeks later, he and I were among the five founder members of Fusion, who launched the society at its inaugural meeting at the University of Westminster on 13 January 2001. For most of the ensuing six years, Paul has looked after the Fusion newsletter and website, and chaired most of the meetings.

At that time, Paul was working as a self-employed graphic designer, and his skills in this field lent a very professional air to both the newsletter and the website. The newsletter has been warmly received by Fusion members anxious to break the isolation that comes with being an OU student, and the website has grown steadily into a goldmine of physics-related material of all sorts; both newsletter and website have won awards from Nexus, the student wing of the Institute of Physics.

By the time he had completed his OU studies, however, Paul had given up the job and gained a PhD studentship in the astrophysics group at UMIST in Manchester, which he took up the day after his last OU exam! Four years, and lots of hard work, later he became Dr Paul Ruffle, and almost immediately landed a job at the National Radio Astronomy Observatory (NRAO) at Green Bank, West Virginia, USA. Paul will be providing support to astronomers using the 100 metre Green Bank Telescope, the world's largest fully steerable radio telescope, situated in a remote spot high up in the Appalachian Mountains.

Paul has done a huge amount for Fusion, and will be sorely missed. We wish him every success, and hope that he will stay in touch and send us some interesting articles for the newsletter.

And goodbye to HER ...

Lindsey Shaw Greening is also stepping down from the committee, to concentrate on the final year of her PhD. Lindsey joined the Committee in January 2005, and, in her role of OU LIaison Officer, has helped Fusion to achieve one of its original aims, which was to try to promote better communication between the student body and the Physics & Astronomy Department; until she arrived, no-one on the committee had any formal connection with the Department, as we were all either current or past undergraduates, and knew next to nothing about how it actually worked. Lindsey has provided invaluable "inside information" on such things as who is the best member of the Department to contact about various specific subjects, as well as departmental news; she helped to organise Fusion's Open Day activities in 2005, and also the lecture evening in November of that year, was instrumental in getting the first S207 Preparation Weekend off the ground in January 2006, and has done some valuable groundwork for our planned re-run of the Weekend Astronomy Event, which we are hoping to organise on the OU campus in the near future - as well as more mundane tasks such as booking rooms on campus for committee meetings.

A graduate of Warwick University, Lindsey joined the OU's binary star group to do a PhD in X-ray binary stars, looking for black hole binary stars in normal galaxies (such as the Milky Way and Andromeda). We wish her well in her studies and her future career.

... And hello to YOU?

It's FUN on the Fusion Committee!

With the departure of Paul and Lindsey, there are vacancies on the Committee for Newsletter Editor, Webmaster, and OU Liaison Officer, to add to the existing vacancy for Events Organiser; and we are always on the lookout for "officers without portfolio", aka ordinary committee members.

One thing not all Fusion members realise (as we can tell from some of the e-mails we get!) is that the people who run the society, as with all other OU societies, are just ordinary people, working for love, not money; and our society work has to compete with the demands of day jobs, study commitments and families. We don't get any help from the OU (although we do get financial support in the form of an annual payment which covers membership for Departmental staff and postgraduate students, as well as the cost of sending the newsletter to physics tutors). And since most of the current committee members have either graduated or are at an advanced point in their degrees, we feel there should be a greater proportion of relatively new students who can carry the society forward when we have moved on.

So - please don't think "oh, they're doing a good job, they don't need my help" - we DO need you, and hope you will decide to help out, even if you can only do a little - every little bit helps.

And besides, think of the benefits!

• Being on a society committee looks good on your CV.

• As well as the vacancies mentioned, there are committee posts that involve liaison with Nexus, and thus with physics students at other universities; and also with OUSA, including an opportunity to attend Societies Standing Committee meetings and OUSA Conference on behalf of the Society.

• Organising events, publishing the newsletter and keeping the website up-to-date - all for the benefit of the members - are very rewarding ways of spending your spare time; and it's FUN!

• Travel expenses for attending committee meetings are paid, and we either provide or pay for your lunch, and sometimes have a nice pub dinner afterwards. And if any of your Fusion activities involve an overnight stay (such as helping at a residential weekend event, or attending the AGM) the society will pay for it.

• You get to rub shoulders with some of the finest brains, and the nicest (and most modest) people in the country - US!

If you would like to find out more then join us for Fusion Day on 20th January, where you can meet the current committee and attend a Fusion AGM, and perhaps become a committee member yourself. (For more details of Fusion Day, see above). If you think you might like to join the committee but can't make the AGM, then write to Digby Tarvin at secretary@oufusion.org.uk. For obvious reasons, we would prefer a postgraduate student or junior faculty member at the OU for the post of OU Liaison Officer, but the other posts are open to all members.