|SocialismToday Socialist Party magazine|
Testing time for modern physics
PHYSICS IS BACK in the news, with daily press stories of astronomical discoveries and the completion of the $8 billion Large Hadron Collider (LHC) laboratory, a collaboration between 20 European nations. New Scientist magazine sells 100,000 copies in Britain each week, and the numbers applying for physics courses in British universities have increased for the first time for many years. So, what is the state of physics today? GEOFF JONES reports.
MARXISTS HAVE ALWAYS welcomed scientific progress. Karl Marx and Friedrich Engels had the keenest interest in the development of science in their day, and aimed to use the scientific method to analyse society. ‘Truth is concrete’ was their slogan. Marx spent years of his life in the British Museum poring over government statistics to test his models of capitalist development. Engels kept up with the latest scientific discoveries and interpreted them in terms of Marxist theory.
Today, Marxists have an easier task in some ways. There are shelves full of popular books and articles on physics. But there is often a problem sorting out what is correct from what is plain wrong and, after that, what is readable from what is not. Of all the books on the foundations of modern physics, two recent publications, Brian Greene’s The Fabric of the Cosmos, and Lee Smolin’s The Trouble with Physics, stand out as brilliant and readable (though difficult) complementary reports on the state of physics at the beginning of the 21st century.
Before we can talk about physics, we have to be sure we understand how physics works. Or, more generally, how do we look at things scientifically? First and obviously, we start from the evidence of our senses, using instruments as extensions of our senses, things we can measure. Second, we try to make a pattern of that evidence – the first patterns that people recognised were most likely the rising and setting of the sun and the progress of seasons. Out of that pattern comes an explanation, a theory, although this may not be a scientific theory in our sense (eg the idea that the sun is a horseman driving a flaming chariot across the heavens once a day). Science, as 16th century scientists realised, involved using that theory to expand our knowledge – to predict the consequences of some new, untried experiment. A good example is the well-known tale of Galileo dropping two spheres of different mass from the top of the tower of Pisa to see if they hit the ground at the same time. If the result is as predicted, the theory is strengthened. If not, it has to be re-examined. At bottom, the progress of science is a continual debate between theory and experiment.
No theory is perfect. There will always be ‘rogue’ observations which do not seem to fit (and ‘rogue’ scientists who do not accept it). But, in general, if the vast majority of existing experimental evidence can be explained and, most important, if the theory can be used to expand our knowledge, that theory is generally taken as the best approximation available at the time. At its strongest, a theory can coagulate into a generally accepted model of reality which scientists ‘take as read’. At any particular time most scientists work within the bounds of that model and apply it. For example, physicists devising new lasers and basing themselves on theories of solid state physics developed in the 1950s and 1960s.
SOME ‘SOCIOLOGISTS’ OF science see such a consensus as a reactionary structure where the ‘priests’ at the top impart the ‘right’ message to the faithful below. But this is incorrect. In principle, any theory, no matter how well rooted, is always open to challenge. Odd results that do not square with theory almost always occur. Mostly these can be ‘put aside’ for study at a later time, or can be used to ‘tweak’ the theory to make it fit.
But after a time the tweaks pile up. By analogy, you could build a simple rectangular garden shed. Over the years, as garden jobs multiply, bits have had to be added on for tool stores, a hole for a stovepipe has been knocked in the roof, felt tacked over one corner to keep the rain out, a compost bin fastened to one side. The shed has become a mess. In the same way, a theory with too many odd bits added to accommodate strange results looks a mess.
At some point an alternative is proposed – in our analogy, knocking down the old shed and building a new one. The proposer has to justify the new picture by showing how it simplifies and expands the explanations given by the old theory.
That process is not simple or easy, and may well involve conflict with established groups in society (as Galileo discovered when he challenged the prevailing orthodoxy of a universe centred around the earth). It may require courage and soul searching for one or many scientists. It is not going too far to describe the establishment of a new theory as a scientific revolution. And like a political revolution it may be long drawn out, untidy and end in a way unexpected by the people who started it.
We saw such a revolution in the first third of the 20th century. At the end of the 19th century, physicists had good reason to be pleased with themselves. As they saw it, most of the basic rules of what we now call ‘classical physics’ had been well established, apart from a few anomalies. But within a few years those anomalies produced a revolution in the physicist’s view of the world. That revolution looked in two separate directions: to the world of the very large and to the world of the very small.
Relativity & quantum mechanics
FOR TWO CENTURIES the mechanical motion of matter had been described by the dynamical equations first formulated by Isaac Newton. These equations describe bodies – snooker balls, planets, stars, etc – moving in well defined paths against a background of infinite space which formed an unchanging framework to which all measurements of position and time could be referred.
In 1905, Albert Einstein, studying the propagation of light, put forward the revolutionary idea that such a unique unchanging background could not exist – that measurements of time and distance were dependent on the motion of the person or machine making the measurements. Time and space each have an objective existence but only together can they be considered as an absolute entity – unitary space-time (at least within our universe). This came to be known as the principle of relativity, although Einstein did not like the phrase, believing (correctly) that it would lead to much sloppy thinking. Later, Einstein extended his theory to solve one of the problems Newton left unanswered: what were gravitational forces? In the general theory of relativity, mass has the property of being able to distort space-time, hence producing what we experience as gravitational attraction. Einstein’s theories were almost as violently contested as Galileo’s but the weight of experimental evidence accumulated over the last half century has made the Einstein picture of the universe generally accepted.
At the same time as Einstein was developing his theories, new experimental techniques, such as the ability to produce high vacuums, made it possible to study the structure of atoms, previously thought to be the indivisible building blocks of nature. In 1898, JJ Thompson demonstrated the existence of electrons – tiny charged particles ejected from atoms. In 1911, using experimental apparatus which was a distant (and very much cheaper) ancestor of the Large Hadron Collider, Ernest Rutherford and his group in Manchester found the astounding result that an atom, rather than being a solid lump of matter with electrons scattered inside, consisted mostly of empty space with nearly all its mass concentrated in a tiny nucleus. There was no way this result could be squared with theories of classical mechanics and electromagnetism. It formed the starting point for a whole new view of the world: quantum mechanics.
The theory of quantum mechanics was developed in the 1930s primarily by Werner Heisenberg (a German), Erwin Schrödinger (an Austrian) and Paul Dirac (an Englishman). It replaced the classical picture of well-defined particles moving in well-defined orbits with a much fuzzier one. Heisenberg’s well-known uncertainty principle stated that, at any one moment, it was impossible to measure precisely both the position and speed of a particle. More than that, in an experiment where one of a number of possible outcomes could occur, it seemed that quantum mechanics could only predict the probability of each one, rather than saying definitely that one rather another would be seen. Even simple experiments produced results that made no sense in classical terms but could be predicted perfectly using quantum mechanics. For example, a school experiment uses a simple TV cathode ray tube. A stream of electrons gives a pattern of light on the CRT screen after passing through a screen with two parallel slits pierced in it. The result – a pattern of light and dark bands – is inexplicable in classical terms. However, quantum mechanics gives a perfect prediction of the result, but implies that, either each electron travelled somehow through both slits at the same time; or if, as common sense suggests, the electron travelled only through one slit, it must somehow ‘know’ that the other slit exists! So there was no way in which the classical picture of the electron as a tiny snooker ball could correspond to reality. And what applied to electrons must surely apply to atoms and to bodies made out of atoms!
FROM THE 1930s, the problem of what this implied for the meaning of ‘reality’ worried leading physicists (especially Einstein). But when it came to analysing and predicting the behaviour of atoms and molecules, quantum mechanics proved astoundingly successful. The attitude of most physicists was (and is): ‘What the hell, it works’.
Quantum mechanics, despite its bizarre implications, is arguably the most successful theory in the history of physics. The whole of today’s electronics, communications, IT and computing technology has been a result of its application. What is more, in the last 70 years, no experimental evidence has clashed with its predictions. In fact, quite the reverse. In the 1930s, Einstein and two co-workers, Nathan Rosen and Boris Podolsky, thought up an experiment which would demonstrate that either quantum mechanics was incorrect or that two particles separated by kilometres, or even light years, would have to be instantaneously connected together in some inexplicable way. In the 1980s, technological developments enabled that experiment actually to be carried out. The quantum mechanical prediction was vindicated, throwing into even higher relief the question of what ‘reality’ means.
But quantum mechanics made it possible for physicists to dig deeper into the structure of matter. Forty years of work has established what we know as the standard model of fundamental particle physics: the existence of two families of particles (quarks and leptons) held together by four forces (electromagnetic, strong, weak and gravitation) which form the basis of all matter as we know it.
This is the situation at the beginning of the 21st century. Relativity theory and quantum mechanics have separately revolutionised the way we see the universe. But it is not possible to mesh the two theories. In fact, applying one to the other produces meaningless results. Unifying the two theories, producing one overarching theory which accommodates both, remains an unachieved goal. The two books, The Fabric of the Cosmos, and The Trouble with Physics, encapsulate the triumphs of physics in the 20th century and the challenge lying before it.
THE FABRIC OF the Cosmos gives a brilliant sketch of the present state of fundamental physical theory. Brian Greene starts by discussing relativity theory and its implications for our view of space and time. This analysis cannot be bettered for the general reader. He goes on to outline the strange picture of reality given by quantum mechanics and describes what has appeared over the past 20 years to be the best candidate for a theory to unify quantum mechanics and relativity: superstring theory.
In the standard model, fundamental particles are seen as ‘point particles’ with no spatial dimensions. Superstring theory postulates that these ‘particles’ are in fact made up of tiny one-dimensional ‘strings’. The various ways in which these strings can vibrate (like the different vibrations of the strings on a guitar) account for the properties of the particles that we observe and the forces between them. Unlike earlier theories, this picture includes gravitational forces and meshes together general relativity and quantum theory.
But string theory faced – and still faces – major problems. First was the complexity of the mathematics involved and the fact that the strings had to vibrate not merely in our four space-time dimensions but in an eleven dimensional space-time where seven of the spatial dimensions are ‘curled over’ on themselves so that we do not observe them. Second was the fact that there appear to be a very large number of alternative solutions to the equations of string theory. Third and most important, at our present stage of technological development, it is impossible to test the theory.
To explain the last point, remember that the only way we can investigate the constituents of matter is by probing it in some way. Rutherford investigated the atom by shooting helium nuclei at a foil of gold atoms and seeing how they were deflected. To probe the atomic nucleus, particles of much higher energies are needed. In the 1940s and 1950s, cyclotrons or synchrotrons were built which accelerated electrons or protons to high energies before they smashed into atomic nuclei. The fragments resulting from such collisions enabled the identification and measurement of what we refer to as fundamental particles. At higher energies still, the structures of protons and neutrons could be investigated, giving rise to our present standard model. (The LHC is the latest generation of such particle accelerators.)
But to investigate superstring theory, accelerators are needed which produce particles with energies far, far in excess of what is technologically imaginable. Nevertheless, Greene expresses well the enthusiasm which string theorists felt that superstring theory was indeed the true overarching solution for all questions of the fundamental nature of matter.
Five great problems
COMPARED WITH GREENE’S book, Lee Smolin’s The Trouble with Physics gives a cool (and much less mathematically challenging) look at the state of physics at this moment. Although he worked on string theory, Smolin has come to the conclusion that an overwhelming emphasis on that approach has led to an impasse, which has meant that, over the last 20 years, there has been no significant development in theoretical physics comparable to that which took place in the first 30 years of the 20th century. Where Greene is happy to accept, and almost glorifies in, the bizarre way in which the development of quantum theory has brought into question the whole definition of reality as we understand it, Smolin sees this as a major problem.
Smolin categorises ‘five great problems’ facing physics at this time which he believes require a completely different theory or even a different sort of theory to cope with.
Two of these problems – the problem of combining general relativity and quantum theory, and the need for a theory which provides a unified explanation of the existence of the various particles and forces – are problems which superstring theory claims to answer. In reply, Smolin emphasises that until some experimental test of the theory can be devised, superstring theory cannot participate in the debate between experiment and theory which forms the basis of scientific progress.
A related problem is the fact that the values of the fundamental constants which make up the standard model of fundamental particle physics seem arbitrary and unrelated.
Fourthly, Smolin points out the fundamental scientific and philosophical problem in the foundation of quantum mechanics: what is ‘reality’? The view most commonly taught today is the so-called ‘Copenhagen interpretation’, named after the institute where Neils Bohr developed it, in opposition to Einstein’s views. Essentially, it states that until some measurement is made on it, a particle in the sense we mean it, does not exist. Quite obviously, this picture of some sort of ‘Matrix–style’ shadow universe has deep philosophical consequences directly contradictory to materialist ideology. But there is as yet no acceptable alternative – and most scientists adopt a pragmatic approach: ‘Despite the fact that quantum mechanics seems to have no basis in reality as we understand it, it works’.
Finally, Smolin discusses two purely experimental problems deriving from astronomical measurements: ‘dark matter’ and ‘dark energy’. Observation of the rotation of galaxies shows that the gravitation force holding them together is much larger than can be accounted for by the mass of the objects we can see (stars, dust clouds, etc). So it is necessary to assume that invisible dark matter makes up perhaps 70% of our galaxy. No-one knows what this consists of. Alternatively, our theory of gravitation needs modification. Second, measurements of the speed of recession of galaxies has shown that our universe is not merely expanding but that the expansion is accelerating and that there must be some unknown dark energy driving this process.
In Smolin’s view, these problems add up to a ‘crisis’ in physics comparable to that which faced classical physics at the end of the 19th century – a crisis which may require a whole new approach, possibly as different from present day quantum physics as quantum physics was from classical physics. Superstring theory may well form a part of such a new approach, but it may not.
Read together, the two books (which cover much of the same ground) form a fascinating double act. Greene shows an infectious enthusiasm and excitement with the forward progress of fundamental theory. Smolin, on the other hand, notes the progress of physics in fits and starts. A period of ‘calm’, when a theory is generally accepted and when the theory enables major developments to be made, is followed by a ‘revolutionary’ period, when a new, more comprehensive theory replaces it. He believes that the time for such a revolution is overdue. Obviously, such a revolution cannot be ‘forced’ like rhubarb but Smolin is concerned that the social structure of physics as organised today makes it less likely that such a theory will emerge.
Physics in capitalist society
THE FINAL PART of Smolin’s book discusses what he sees as the reason why the physical theory of the fundamental nature of the universe has got stuck in a rut over the last quarter century. There has been a huge concentration of work along the path of superstring theory without reference to any possible experimental verification. To Smolin this shows a failure to complete the revolution started at the beginning of the 20th century or to engage seriously with his ‘five great problems’. He recognises that physics research does not take place in a vacuum but tends to see the problem from inside. He makes a clear case that the way the ‘physics community’ is structured makes it almost inevitable that talented researchers who want a permanent job and career prospects will be forced to concentrate on ‘safe’ areas of research. Funding will only flow to those areas which senior professors think are most fruitful and which will enhance their prestige. Smolin’s arguments are based on his experience in the USA, but could probably be generalised. Smolin does not enlarge on the reasons for this and why, as he acknowledges, the situation is getting worse. For this, physics must be seen in the context of capitalist society as a whole.
The ‘physics community’ has always had its place and role in capitalist society. It is no accident that the huge leap forward in the funding of physics came on the back of World War II and the ‘cold war’. To an extent, the funding of the LHC was a product of competition between the ruling classes – and hence, the scientific establishments – of the EU and USA for leadership in this particular branch of physics.
It is also true that the ‘scientific establishment’ has always tended to be resistant to new theories. Einstein himself was refused a university post and developed his theories while working as a clerk in the patent office. But the situation has got worse in the past quarter century. University funding has become tied ever closer to the needs of big business sponsors or, at one remove, to what government and its advisors believe is ‘worth’ studying. Avenues of enquiry which do not seem to offer a quick payoff or which are regarded as likely to lead to a ‘dead end’ have been increasingly strangled. In 2003, the British physicist, Tony Leggett, won a Nobel Prize for work carried out in the 1980s. He says that today he would not have the freedom to follow that particular line of work.
A sclerotic system
IT IS THIS creeping sclerosis in the channels of communication and research that concerns Smolin. But this sclerosis is only symptomatic of an ideological attitude common to the whole ruling class. The belief by string theorists that their theory provides all the answers, and that any other line of enquiry is beneath contempt, mirrors that of the pundit Francis Fukuyama that ‘history has ended’, and that of the US neo-conservatives in their Project for the New American Century, that US capitalism represents the final, highest and finest state of society.
But as the 18th century US statesman John Adams put it: "Facts are stubborn things; and whatever may be our wishes… they cannot alter the state of facts and evidence". Just as the facts of the worsening situation in Iraq and the Middle East has reduced the confident perspectives of the neo-cons to a heap of smoking ash, so may the predictions of superstring theory disappear into a cloud of mathematical abstraction uncoupled from any relation to the real world.
Physics may be ripe for a revolution. It is no accident that revolutionary periods in society are mirrored in science and in the arts. The foundations of modern physical theory were laid in the first decade of the 20th century, a period of political and social upheaval. As we move into a new period of crisis for world capitalism, the crisis in physics that Smolin identifies may well start to be resolved. However that resolution takes place, it will change profoundly our picture of the universe we live in.
At the same time, as the constraints of capitalism are strangling the freedom of scientific research, the scientific method itself is being contested, not just by well-funded establishments dedicated to pushing anti-scientific beliefs such as that of ‘intelligent design’, but by a general mistrust of ‘science’ seen as a weapon of exploitation. Marxists have a duty to understand not just the latest developments in modern physics – at least in a basic form – but also the use of scientific method to produce such developments, and to be able to pick out what is science and what is mumbo-jumbo. Greene and Smolin approach from different angles our most basic picture of the universe. Taken together they give an insight into what the ‘scientific method’ really means.
The Fabric of the Cosmos, Brian Greene, Penguin Books, 2005, £9-99
The Trouble with Physics, Lee Smolin, Houghton Mifflin, 2006, £8-99
Both available from Socialist Books