WELCOME TO FUSION

Hello, and a very warm welcome from us, the Committee, to all members of the new Physics Society of the Open University.

Our aim is to bring you the latest news on what Milton Keynes is up to and give you the chance for a pro-active role in FUSION - we value your views on the articles you will see in the newsletters; let us have your opinion on scientific theory both old and new. We welcome material both serious and fun: devise a quiz, a crossword, puzzles, amusing drawings... tell us what you would like to see here, and make a contribution, your input makes the difference!

We will not take it for granted that all of you have easy Internet access, but for those who can, visit us at www.oufusion.org.uk for committee profiles, news and our feedback forum. Our quarterly newsletter will include the main interests on the website, plus regular features on the latest discoveries in physics, essential reviews on OU courses, book synopses, events we are organising and reports on those already done (tell us where you would like to go!), a history of physics through the ages and articles contributed by you, our members.

So we hope you find the following pages interesting and look forward to hearing from you!

Tina Heaton - Editor

QUANTA AND CONTINUUM

Physocs (not a typo)

As well as local Institute of Physics lectures, there may be other physics-based events going on in your area. If you live near a university which teaches physics, it will probably have a physics society as well. On the FUSION web site there are links to the web sites of physics societies we have managed to find out about, and on these sites you will find lists of their forthcoming events.

OK, many of these have a strongly alcoholic theme, but there are also some very interesting lectures and trips - recent examples from just three of the physocs listed include Nanotechnology, Creation and Decay at the Edge of Nuclear Existence, and Ancient Astronomy & Modern Science.

We are hoping to establish formal agreements with these societies so that we can attend one another's events, but in the meantime, if you turn up I am sure you won't be turned away! If you do not have internet access, contact Jim Grozier and he will provide details of what's going on in your area.

Be 'Alert' - your Society needs...

For those of you who are also members of the Institute of Physics, you can receive Alerts by email on up to the minute developments in Physics. Just register at their website on www.physics.org. So now there's no excuse. Just don't use them in your TMA's without a reference, or the tutors will get really confused.

Wanted: OU physics graduates!

In a recent email to an OU staff tutor, Chris Carpenter, the Head of Public Relations at Culham Science Centre - the UK's top fusion research centre and home of JET - 'expressed the hope that there could be closer links between the fusion and plasma physics expertise at Culham and mainstream university physics departments', in which he included the OU. He reminded us of the regular visits between Culham and OU residential schools in the past. Culham are apparently always on the lookout for new graduate physicists and value the added maturity of OU graduates.

The less you know, the more money you make

This can be proved, as follows:

Postulate 1: Knowledge is Power.

Postulate 2: Time is Money.

(here's the physics)

Postulate 3: Power = Work/Time.

Substituting for Power and Time from (1) and (2) into (3), we obtain

Knowledge = Work/Money.

Solving for Money, this becomes

Money = Work/Knowledge.

Thus as knowledge approaches zero, money approaches infinity, regardless of the work done. Q.E.D.

Gobbledegook

Physics is an ideal breeding-ground for incomprehensible gobbledegook. Well, OK, we know SOMEONE understands it, although... maybe even those who think up the stuff are tempted from the straight-and-narrow of simple, literal explanation in favour of the aesthetics of the thing (in other words, why use 10 short words when you can have 50 long, complicated ones?)

Here's an example culled from the postgraduate prospectus of a certain university:

Gaugino condensation models for the non-perturbative superpotential in string theory naturally generate (non-universal) soft supersymmetry breaking terms, and these in turn can lead to flavour changing neutral currents.

Have you come across anything like this? Maybe you know an even better (or worse) example? If so, please share it with us!

Uffs and Puffs

Faraday's Law is inscribed on a signpost on a cycle track near Budleigh Salterton in Devon.

Electron Spin

1st Atom: I've just lost an electron!

2nd Atom: Are you sure?

1st Atom: I'm positive!

Heroes and Zeros

HEROES

'A philosopher once said, "It is necessary for the very existence of science that the same conditions always produce the same results." Well they don't!'

Richard Feynman, The Character of Physical Law (1965).

ZEROS

The CERN Summer Student Programme is a once-in-a-lifetime opportunity to work at the world-famous research centre, learning about particle physics, meeting other physics students and physicists from all over Europe and working with them on cutting-edge experiments. But only if you're under 27, because CERN operates an 'under-27s only' policy. We contacted them to ask why, but have not yet had a reply... in the United States, ageism has been illegal since 1967.

Your Letters

Well, we have not had many yet! But we are sure that you will put that right for the next issue of FUSION. Send your pithy pieces by pigeon, snail or email to any of the addresses at the foot of page 8.

From FirstClass, OUSA Physics

Russell Corbyn writes: 'Schrödinger put forward that everything, something and nothing all occur at the same time (it's just a case of working out which time, what events and the relativity of it to others)'.

Casey Jones replies: 'My cat offered a view on something like this - "I don't know whether your alive when I'm in the box, but when I get out you're a dead-man"'.

Fusion by email

If you would like to receive FUSION as a full colour Acrobat PDF file, please send an email to Paul Ruffle (editor@oufusion.org.uk) and he will add you to our emailing list.

Shock Discovery Rocks 90-year-old Theory

Scientists are concerned that the General Theory of Relativity may collapse in on itself if it is found to contain only the amount of mathematics that they have so far detected. They estimate that there would have to be about 10 times as much maths hidden in it somewhere to achieve a flat, self-sustaining theory. This 'missing maths' may be in a different form from that which we are used to, and may include all sorts of exotic concepts not known in Milton Keynes, such as tensors and manifolds. Alternatively, it is possible that there is a massive black hole at the centre of the theory, into which the maths is disappearing, only to re-emerge in another universe as sociology or French literature (continued on page 357).

REVISION WEEKENDS

M500 Society

Aston University, Birmingham

14-16 September 2001

Jeremy Humphries tells us that they have plenty of spaces for S207. The tutor for S207, Ian Saunders, is one of the best we have come across. So if you are studying S207 don't miss an excellent opportunity to prepare for the exam. There has been a respectable take up for SM355, but there is room for more as M500 have two tutors available for SM355 - Mike Thorpe and Gordon Worrall.

For full details and an application form send an SAE to: Jeremy Humphries, M500 Week-end Organizer, 36 Penmanor, Finstall, Bromsgrove B60 3BZ. Tel: 01527 836571. Email: jeremy.humphries@virgin.net. Web: http://freespace.virgin.net/ jeremy.humphries/sept.htm.

Chemistry Society

York University

28-30 September 2001

Hello, I am on the committee for the OU Chemistry Society. I'm sure that some of you may have heard of us. What you may not be aware of is that the Chemistry Society organises a revision weekend each year at York University. Although this event does cover all the chemistry courses there is also provision for S207 and S281. In addition, I have asked if we could cover SM355 this year and the answer is YES, provided that there is a minimum of 15 students.

The weekend is held from Friday evening on the 28 September to Sunday afternoon on the 30 September and costs £140 for standard accommodation or £165 for en-suite accommodation. This covers all tuition, accommodation and meals for the weekend.

If anyone is interested in SM355, could they let me know either by email (kmy6@student.open.ac.uk) or by mail to Kathie Yeowell, 4 Bevil Court, Hoddesdon, Herts, EN11 9LX. If sufficient people are interested I will circulate the booking forms and get things organised.

If however you are interested in S207 or S281, then this can be booked direct by sending a (non-returnable) deposit of £25 with two stamped addressed envelopes to: Carole Arnold, 51 Paddock Lane, Halifax, HX2 0NT. Please make cheques payable to the Open University Chemistry Society.

I'd like to take the opportunity to wish FUSION every success.

Kathie Yeowell

Wot - No Quarks?

Many of us are eagerly looking forward to the introduction of a brand-new astrophysics course, S381 - The Energetic Universe in 2002, and also the new 'decoupled' summer school for SMT356 - Electromagnetism. However, even with the new additions it will still not be possible to clock up 360 points entirely in physics courses, which is why there is still no named degree in the subject. And there are still areas of the standard physics curriculum which are not covered by the OU. Last November, a student asked 'Why is there no OU particle physics course?' on the S357 conference on FirstClass. This prompted several replies, the general consensus of which was that there ought to be one. But how do we go about getting one? And what exactly does creating a new course involve?

FUSION contacted Barrie Jones, the Head of Physics and Astronomy at the OU, who acknowledged that there are 'holes' in the curriculum, specifically in the areas of thermodynamics, statistical physics, nuclear physics, and the applications of quantum physics, as well as particle physics. Sadly, it all comes down to cost. Preparing a new OU course costs money, and in order to justify expenditure there has to be a sufficient demand. Although some courses (such as S281, which is soon to be rewritten) attract large numbers, others have low student populations and, overall, the OU makes a net loss on 3rd level physics courses.

The pion-muon death cycle - a double anniversary (photo courtesy of CERN).

'Physics is not sufficiently popular a subject to attract the numbers of students that could support a more complete set of courses at level 3', says Dr Jones. S381, like two of the three existing level 3 courses, is being written around a set book, and this is cheaper than starting from scratch, but once you move outside the popular areas of astronomy and astrophysics, such economies alone are incapable of balancing the books.

It is not all doom and gloom, however. Barrie Jones points out that S381 will 'introduce some new physics', and one might hazard a guess that that would include some nuclear and particle physics. Furthermore, there are plans for a new 30 point project course at level 3, which will give students an opportunity to concentrate on one of the 'missing' subject areas; it may be available in 2004. As for named degrees, the Physics Department is lobbying hard for Physics & Mathematics and Physics & Astronomy degrees to be introduced in the near future.

In the meantime - what subjects would YOU like added to the University's physics portfolio? Let us know, and we will pass your comments on. And for the real particle physics junkies, there is a very good website at http://hepweb.rl.ac.uk/ppuk which will keep you busy for a while.

Jim Grozier

Optical Tweezers - Moving Matter with Light

A very brief introduction by David McGloin

Light is a strange sort of thing. In its everyday form it is a vital part of our sense of vision and it's perhaps not something we give much thought to. It is an ethereal, almost abstract thing that physically we can't quite grasp. Light does, however, have a physical presence. Though it is massless it does have a momentum. This momentum was famously ascribed to light by de Broglie by the equation p=h/* where * is the wavelength of the light and h is Planck's constant.

If we put in some numbers to this equation we can see why light has no discernible physical impact: h is of the order of 10^-34Js and * is of the order of 500nm (500x10^-9m) and so the momentum of a single photon of light is ~ 10^-27kgm/s. Not very much! Even if you consider all the light that is continually bombarding your body, you will agree (from experience if not from the maths) that you don't feel a thing. The momentum of light can play an appreciable part, however.

Light is able to act on atoms. When light is absorbed or emitted by an atom then the atom will receive a kick, in one direction or another, due to the momentum the light possesses. Momentum has to be preserved after all. This phenomenon is the basis of the laser cooling of atoms, resulting in temperatures of a fraction of a degree Kelvin.

Light can also be made to act on macroscopic particles, albeit small ones. Such systems are called optical tweezers and they use a focused laser beam to pick up and manipulate objects such as silica spheres, biological samples and more recently to manipulate nanomachines. So how do they work? If we consider a silica sphere that sits in the path of a laser beam, as shown in the figure, then we can see that the laser is refracted as it passes through the sphere. Put simply we can say that the beam direction is changed due to the action of the sphere.

Now, if we remember Newton's second law, which states that the force acting on a body is equal to the rate of change of momentum of that body then we can see that if the momentum of a body changes then a force must be acting on it. The momentum of a body changes if the direction of the body alters, since momentum is a vector quantity. Hence as the light passes through the sphere and has its direction changed a force must be present, since the light possesses momentum. The way in which the forces act on the sphere are shown in the figure. The trick with optical tweezers is to arrange for the laser beam to be focused so that the momentum transferred is just enough to counteract gravity. (There are also other forces present, as some of the light is reflected off the sphere, but we'll ignore them here). Note that the sphere is pulled by the laser toward the centre of the focus (the point of highest laser intensity). The forces involved are tiny, of the order of pico-Newtons (10^-12N).

Figure 1. The optical tweezers in action. The incoming light is focused down to a tight spot and the forces that act on the sphere are such that the centre moves towards this focus. The 'F's in the diagram indicate the forces on the sphere.

So what are the tweezers used for? Well, as you might imagine they are used for manipulating small objects. Biologists use them to manipulate cells, large molecules and the like with unprecedented precision by shining the laser through a microscope and then viewing the samples on a video camera. One interesting application in this area is the measurement of forces on molecules. For instance two tweezers can be used to draw out a strand of DNA and then the recoil can be studied as the tweezers are turned off. Tweezers are also the basis for a more esoteric part of the molecular manipulation toolkit known as optical spanners. These devices use special kinds of laser beams to impart angular momentum to the particles and hence they are able to rotate.

The thing that has always fascinated me about this subject is that it is light, that magical, ethereal quantity that manifests itself in such a physical, macroscopic way.

A starting point for resources on Optical Tweezers and Spanners on the web can be found at: http://www.physics.gla.ac.uk/~aoneil/otworld.htm. For questions or other information David McGloin can be contacted at: dm11@genie.co.uk.

S357 - Space, Time and Cosmology

- a student's perspective

This third level course makes different demands of the student than other physics courses at this level. Other offerings, such as Quantum Mechanics or Electromagnetism have a high level of mathematical content, and assessment generally involves use of these mathematical skills attained through the course. But with S357, one needs to demonstrate a thorough understanding of, and to draw conclusions from, the physics taught. Usually two essays are required in assessment - and there is an essay component in the exam (not compulsory in 2000).

The course material is divided into four blocks, accompanied by videos, tapes, glossaries and a mathematics guide. The glossaries are more than just a dictionary of terms - they assist the student with concise summaries of concepts, and form a very useful compare and contrast function.

Block 1.

Is in effect a revision of Newtonian mechanics at the level covered by the foundation course S103 and some of the second level physics course. For those students who have already covered this material - it can be somewhat repetitive and motivation can slip a bit here. Although it's necessary to cover this material - to understand the need for Special Relativity - I would have thought that just a couple of units would have sufficed - there is a lot of other material to cover in the subsequent blocks.

Block 2

Opens with a brief introduction to Electromagnetism (again revision if you've already taken the electromagnetism course) and uses Maxwell's equations to question physics knowledge as it stood at that time - either Newton was wrong or something else was needed - Enter Einstein, Special Relativity and the Lorentz transformation equations (very simple - I am relatively hopeless at maths; -) We are introduced here to the Lorentz interval and Spacetime diagrams - which don't appear at this stage of the course to be that relevant.

Block 3

This is the first of the heavier loaded blocks - it's difficult to realise that one should start on this earlier than advertised! (OU - a change in the timetable might help here?) Here we study the General Theory of Relativity. It introduces the use of geodesics and metric theory (a substitute for tensor calculus?), to model GR and its effects. If only I knew then what I now know - the language in the unit does not explain clearly that metric theory is just a way of using 'general' equations by substitution of parameters for different scenarios. Instead the material uses what is perfectly correct language for the physics community but which actually confuses the student used to the semantics of other OU physics courses. The block finishes with a unit on Black Holes - brilliant for sceptics like me - makes you want to take up the subject at a higher level - so you can prove it wrong!

Block 4

AKA the cosmology block. This is popular with the astronomy students. It covers Big Bang theory and the large scale structure of the universe and is so interesting I read it again after the exam. Another good block for the sceptics out there - this student had to really suspend credibility for a while. This is not a criticism - it is the best way to learn - trying to prove the authors wrong!

Overall

A very interesting and attainable course - great to arouse interest in the subjects covered, and makes you want to take cosmology to post graduate level just to satisfy yourself that it really is all true. The main complaint is the uneven work-load, but this could be corrected by timetabling the TMA's differently.

Norrette Moore

'Well, either we've found the Higgs boson, or Fred's just put the kettle on'

Surrey Space Centre

A few weeks ago myself and around 20 others visited the Surrey Space Centre in Guildford. We had a two hour presentation from Dr Craig Underwood, an academic from the University of Surrey who works in the centre (there are also around twenty other staff, some of whom are also academics and some of whom are engineers).

The talk was very interesting, especially as I have become used to such things being at a level where the general public can understand, but here I found that we were told more about the science behind the satellites and the amazing things that they allow us to do.

We were shown pictures of the hole in the ozone layer above Antarctica, from a satellite built by the Centre in conjunction with the Chilean government, who understandably are interested in the progression of the hole towards their territory. We were also shown how, theoretically, one satellite could be sent up to bring another down.

Over the last two decades the Surrey Space Centre has sent up around 21 satellites - some with the help of scientists from countries such as Chile, Turkey, China, Korea and the Philippines, whose governments were purchasing the satellites.

After the talk we went to see the 'mission control' room, with the inevitable map of the world complete with tracks of the satellites plotted across it (just like in all those James Bond movies). Interestingly, the room is unmanned; if a satellite needs assistance it sends a text message to the engineer on his mobile phone. Now that's what I call technology.

We also saw the PICOSAT satellite which is currently being prepared. It is a cube with sides of about a foot, amazing that such a small thing will be launched into space and will send down meaningful information to us about our world.

We hope to arrange another visit to the centre some time next year. In the meantime if you are interested you could visit their website at www.sstl.co.uk, or read the visit report of one of the young scientists in our group on the FUSION web site. Sarah Jane is only eleven years old but she seems to have gleaned more from the visit than I did!

Eleanor Cowan

Protoplanetary Migration

During a recent visit to the OU campus at Milton Keynes, three of your Officers attended a talk by Dr Frederic Masset (Service d'Astrophysique, CEA Saclay, Paris) as part of the series of weekly Physics & Astronomy Colloquia.

62 extra-solar planets or exoplanets have so far been detected orbiting stars other than our sun.

One of the surprising things about these discoveries is that giant planets as big as, or bigger than, Jupiter have been found orbiting very close to the star, where, according to current theories, they could not have condensed out of the disc of matter surrounding the star, because it is too hot. So how did they get there?

Dr Masset has done extensive computer simulations of the growth of planets out of the disc, and has shown that the effect of the disc material on a planet which forms at, say, the radius of Jupiter (5 astronomical units) produces a torque (the differential Lindblad torque) which can cause migration of the planet towards the star. This can, under certain circumstances, be balanced by a corotational torque exerted by matter trapped in the planet's orbit by its gravity, halting the migration. He has also modelled a two-giant system which shows that planets similar in mass to Jupiter and Saturn might reach an equilibrium and not migrate towards the star.

This talk, while not aimed specifically at students, was accessible to anyone familiar with the concepts of torque, angular momentum and gravity, and included some very high quality visual simulations.

For details of future Colloquia see the OU Physics Department's web site (or the FUSION web site under Links, then Seminar Programs) or ring 01908 653229. Jim Grozier

The Secret of Anti-Gravity!

Question:

If you drop a buttered piece of bread, it will always drop butter side down. But when you drop a cat it will always land on its feet. What would happen if you took a piece of buttered bread, strapped it on the back of a cat (butter side up) and dropped both?

Answer:

Even if you are too lazy to do the experiment yourself you should be able to deduce the obvious result. The well known Laws of Butterology demand that the butter must always hit the ground, and the equally strict Laws of Feline Aerodynamics demand that the cat cannot land on its back.

If the combined construct were to land, nature would have no way to resolve this paradox. Therefore it simply does not fall. That's right! You have discovered the secret of antigravity!

A buttered cat will, when released, quickly move to a height where the forces of cat-twisting and butter repulsion are in equilibrium. This equilibrium point can be modified by scraping off some of the butter - providing lift, or removing some of the cat's limbs, allowing descent.

Most of the civilized species of the Universe already use this principle to drive their ships within planetary systems. The loud humming heard by most sighters of UFOs is, in fact, the purring of several hundred cats. The one obvious danger, of course, arises if the cats manage to eat the bread off their backs. In this case they will instantly plummet.

Naturally the cats will land on their feet but this generally doesn't do them much good, since right after they make their landing several tons of red-hot starship and irritated aliens crash on top of them.

Scientists are currently working day and night with hundreds of buttered cats, dropping them from various heights to see if they do indeed float. As with most experimental work, they are only having partial success, with the current fatality rate being 46 percent.

Recycled by kind permission of the University of Warwick Physics Society Newsletter 'Dark Matter'.

SCIENCE HISTORY

Ptolemy & Copernicus:

Geocentricity & Heliocentricity

In 1543 scientific Europe was presented with a radical new theory for the structure of the Universe - De Revolutionibus Orbium Colestium (Concerning the Revolutions of the Heavenly Bodies). That theory was Nicolas Copernicus's Heliocentric Universe, which turned the then accepted Ptolemaic Geocentric model on its head, placing the Sun, not the Earth, at the centre of Creation.

An Earth-Centred Universe

The achievement of Claudius Ptolemy (c100 - 170) lay in his ability to, as a mathematician, adequately predict the planets' positions whilst maintaining the Greek belief in an ordered and balanced Universe; that being that each planet moved along a circular orbit at a constant speed. However, a problem that had dodged both cosmologists and philosophers for many centuries was the apparent retrograde motion of Mars, Jupiter and Saturn. Occasionally the daily motion of these planets across the sky appeared to halt and then proceed in the opposite direction.

Ptolemy attempted to explain this by suggesting that each planet revolved on the edge of a circle (Epicycle) and that the centre of each Epicycle in turn revolved around the Earth on a path called the Deferent.

Using this model Ptolemy could make reasonably accurate predictions of the planets' positions, and because the entire concept intertwined so neatly with the Church's teaching that the Earth and its inhabitants were the centre of God's Creation, the theory of Geocentricity became an article of faith and immune to scientific scrutiny for 1400 years - that is until the Renaissance and Nicolas Copernicus.

Heliocentricity

The works of the ancient Greek philosophers such as Plato were widely available during the Renaissance, both in their original form, for those who could read Greek, and also translated into Latin for general usage in universities. Nicolas Copernicus, studying at Krakow University in Poland, exposed to such papers and inspired by the questioning of long-held beliefs, prompted by the Reformation spreading from Western Europe, recognised many deficiencies in the Ptolemaic model. He felt that any model of planetary motion must account for observations made and associated trigonometrical calculations. The Ptolemaic model fell down on a number of occasions in this respect. In addition to this, the Renaissance movement required simplicity and elegance, not complicated systems of circles within circles. In fact over the many centuries since Ptolemy, many extra epicycles had been added in an effort to make Geocentricity agree with observation.

The revival of Neoplatonism urged Copernicus to hold the Sun and God in the same awe: God created life and the Sun gives us light and warmth essential to life and is God's creation. Would it not therefore be truer to faith to place the Sun at the centre of the Universe rather than the Earth?

This idea of Heliocentricity was not new, and had first been hinted at many centuries earlier by the Greek philosopher, Heraclides, who had claimed that the Earth rotated daily on its axis. Aristarchus had also suggested Heliocentricity, with the background stars an enormous distance away, accounting for their consistency in brightness.

In the Copernican system the Universe is centred around the Sun, with the planets and background stars orbiting in perfectly circular paths. In addition the Earth rotates daily on its own axis, which accounts for the changing seasons. Making the Universe Heliocentric removed the largest of the Ptolemaic Epicycles and neatly explained the apparent retrograde motion of Mars, Jupiter and Saturn as being an optical illusion caused by the Earth passing by one of these planets and the planet appearing to move backwards against the stars. The theory also explained why Mercury and Venus never appeared more than a certain distance from the Sun, due to their solar orbits falling within the Earth's.

Heliocentricity allowed a new ordering of the planets according to their periods of revolution; unlike Ptolemy's Universe, the greater the radius of a planet's orbit the greater time the planet takes to make one orbit around the Sun.

But Copernicus' model was not without its problems. He clung to the Classical idea that the planets move in circular orbits and at constant speeds (and therefore like Ptolemy he had to devise a system of circles within circles to predict position with reasonable accuracy).

Nor did he actually conclusively prove that the Earth orbited the Sun. The first direct evidence of that came much later, from the work of Sir Isaac Newton and his laws of motion.

Tina Heaton