by C. P. Snow
It was a fitting departure for one of the two greatest minds that natural science has ever known. There had not been a scientist of that stature since Newton’s death in 1727. Perhaps to lesser and frailer mortals it brings Einstein nearer to common earth to know that in those last years he once lost his temper. Not about the profoundest problems of physics and philosophy; not about the possibilities of mass annihilation; but about something much closer to a personal quarrel.
He was very angry, abusively angry, when Max Born, one of his oldest and most cherished colleagues, said that he intended to return to Germany for his years of retirement. Einstein couldn’t understand or tolerate this. To go and live among those murderers who had slaughtered millions of ‘our people’!
For the only time traceable in all Einstein’s correspondence, his magnanimity, kindness, even his courtesy deserted him. He had once said that he had no ties at all, not to a nationality, a state, an institution, even a group of friends or family. He was a solitary and all he belonged to was the human race. In old age there was an exception, but one which was discernible much earlier. It is necessary to repeat he wasn’t a believing Jew. He had no God except perhaps Spinoza’s impersonal God of the cosmos: but in some sense deeper than reason he had come to belong to his people, that is the Jewish people.
Born was upset by the tone of those letters, since he revered Einstein above all men. Einstein would not relent. Nothing in this life, or in the space-time of the universe, would make him forget or forgive the ‘final solution’.
It was in his old humane spirit that he issued his warning about world peril, and went on working at his equations the day before he died. (He had an aneurysm, had known for years that death was imminent and thought nothing of it – what was mortality in this universe?)
Others, not so far above the battle as Einstein, accepted more passionately that he was right about the H-bomb. Science had made it possible for the human race to commit suicide. How wide this feeling of fatality spread, no one really knew. But it was there.
9: The Younger Masters
MEANWHILE, particle physics – to a new generation of practitioners still the central subject in physics – was negating the prophecies of its decline. The war had transformed the scale of nuclear experiments. When Cockcroft built his first accelerator, in 1932, it could fit into a small laboratory. Ten years later, the tracks needed to accelerate particles could barely be fitted into an Olympic stadium. That was only the beginning. The cost of experimental research in particle physics rose beyond the financial powers of any European university. The Cavendish gave up the nuclear research which had won it fame. Only government institutes, such as Dubna in Russia, Harwell in England, could afford the new equipment. Rutherford’s apparatus had cost a few hundred pounds, Cockcroft’s not much more: now the budgets ran into many millions. Experimental nuclear research, and more than half of all the experimental research in the world, of any kind whatever, could be done only in America.
In pure science, America had become by far the greatest force on earth. Great universities, including Stanford, Berkeley, MIT and Princeton, could combine with government agencies to build major nuclear apparatuses. Young scientists went to America as once they had gone to the three European plinths of physics, Cambridge, Göttingen, Copenhagen.
That change, though, was more logistic than vital. Scientists go where they can do their work, and don’t repine much about the locality. It is possible that there was a slight loss in the intimate exchange of ideas, though as long as Niels Bohr lived theoreticians still spent longish spells in the cosiness of Copenhagen, and the tradition lasted when his son Aage took over. Otherwise physicists became extravagantly mobile, and their old-fashioned seniors grumbled that they were usually in the air – literally rather than figuratively. No one minded. The subject had its own dynamics, and the young were indifferent to the old customs. They were taking over, and science has always been ruthless with the old.
The old, the great men of the 1920s and 1930s, were in fact passing from the scene. Rutherford had died – of a curious medical accident – at sixty-six, in 1937. Einstein survived until 1956, Bohr till 1962, both dying in their late seventies. Like many of their near contemporaries, they didn’t cease from trying to promote international agreements about the nuclear bomb – not to much avail, except for scientific debates in organizations like Pugwash. Fermi died of cancer in his fifties, a major loss, his splendid mind unimpaired and now taking a world view. He died a modern scientist’s version of a stoical Roman death, taking notes about his disease until very near the end. Oppenheimer also died relatively young – at sixty-two – and also of cancer. Pauli, Schrödinger, Broglie, didn’t live into old age. Heinsenberg, who had become head of what once had been called the Kaiser Wilhelm Institute, reached his seventies, as did the Cavendish stars, Cockcroft and Blackett.
Extreme longevity, though, was not an occupational feature of major scientists, as it has often been of visual artists and musicians. Of the heroic era of the 1930s the most eminent practitioners now living (1980) are Kapitsa in his middle eighties, and Dirac relatively juvenile at seventy-eight. There are, of course, plenty of men who were quite young but influential in the making of the first fission bombs, and still actively at work.
The roll-call of mortality, however, hasn’t affected the march of physics. It would be astonishing if it had. Some great men seem irreplaceable. There has been only one Einstein, perhaps only one Bohr. They defy the statistical laws. But in general, the amount of scientific talent in the world must be about the same in any period, and the same applies to anything short of the most abnormal genius. As scientific education spreads to larger numbers of the world’s population, as now in China, the number of available talents will increase. The only question is whether the intellectual situation (and other situations too) will give those talents the fullest possible opportunity to flourish. It may be that the circumstances of the 1920s and 1930s were abnormally propitious. Physicists today may not have the same extraordinary opportunity, and it may not have happened before in the history of science. That has been argued by observers of detachment and historical sense.
The argument is well meant; there may be a little in it, but not much. No one would think of doubting that contemporary theoreticians such as Richard Feynman, Murray Gell-Mann, Abdus Salam, Yuval Ne-eman, Freeman Dyson, would have done spectacular work if born just before 1900 and in their prime in the mid 1920s. All that is certain. It is also possible, or even probable, that they might have found it slightly easier to arrive at major conceptions, and formulations, overnight. That is open to reflection. Having said that, one has said about all that is valid on the good or bad luck of being born in 1940 rather than 1900.
The test is, what is felt inside the situation by the contemporary theorists themselves. They show the same creative satisfaction as their forerunners half a century ago. They are as confident. The great problems are showing themselves more difficult than was once thought – all the better. As Rutherford in one letter encouraged Bohr, no one can expect to clear up the whole of physics in a week, and one ought to feel grateful that the enterprise looks like going on for ever.
That has been the view of the toughest-minded physicists of the century. They have enjoyed recalling that Lord Kelvin, the great nineteenth-century classical physicist, announced around 1904 that physics had now come to an end – presumably with himself. Whereas Rabi, asked recently what branch of science he would now devote himself to, if starting today as a young man (the answer expected was probably molecular biology), said with his customary robustness, ‘Nuclear physics, of course.’
The present leaders would cheerfully say the same. The theoreticians might add that their recent work hasn’t yet been widely assimilated, even among fellow professionals. There has been a longer time-lag than in the assimilation of quantum mechanics. That doesn’t matter. Their juniors will make the exposition clearer. All scientific exposition comes to look straightforward within a g
eneration. Richard Feynman is a major scientific figure and that is already recognized.
Feynman has performed one of the great intellectual syntheses, which lives under the general title of quantum electrodynamics. With scientists’ addiction to hilarity, it is usually called QED. It is perhaps not an accident that Einstein’s paper on the Special Theory of Relativity was originally called ‘On the Electrodynamics of Moving Bodies’. Feynman’s is a generalization on the same scale but looking at the subject from a different point of view.
Einstein had used Maxwell’s laws of electromagnetism to investigate the properties of a moving body. He found the well-known bizarre effects of relativity: a moving body becomes shortened; its mass increases; its clocks run slower. Feynman was interested in the details of electromagnetic force itself. In QED, the electric repulsion is not caused by ‘action at a distance’, or by a ‘field’ distorting space and time – the path that Einstein was trying to follow in his later years. Electrical and magnetic forces are the result of charged particles exchanging entities called photons. These are in fact none other than the units of radiation, the quanta, that Planck and Einstein had discovered at the turn of the century. Here, however, they are not acting as particles of radiation. They are exchanged so quickly that scientists cannot ever detect them passing from one body to another – Heisenberg’s Uncertainty Principle ensures that. But they do produce a force.
Feynman extended this concept until the theory could explain all the remaining puzzles in electricity and magnetism. QED, for example, predicts with amazing accuracy the strength of the electron’s magnetic field, a quantity that simpler theories had invariably got wrong. The theory needed much heavier mathematical machinery than anything in the Special Theory of Relativity, some contributed by one of Feynman’s collaborators, Freeman Dyson. Dyson is English-born, a man of formidable mathematical powers combined with a whirling imagination. Englishmen might like to say that he is a credit to English education: but he would have been a credit to any education anywhere, that kind of gift being too irrepressible to subdue.
The full importance of quantum electrodynamics has not yet been seen in perspective. The statements are accepted, but at present they look bizarre. Feynman himself looks a little bizarre by comparison with his immediate seniors. Most of them, not all, gave an external appearance of gravitas. Kapitsa, with cheek and psychological subtlety, penetrated Rutherford’s façade, but no one else dared to. Bohr was not only a paterfamilias at home but a father figure to anyone around him. Nearly all the others were reasonably stately personages. Of course, some of them had their private troubles and frailties, sexual, even financial, but those didn’t obtrude as with a similar assembly of artists. The percentage of stable marriages among scientists has been abnormally high.
Feynman has his own style, and a very different one from Rutherford’s or Bohr’s. To an extent, it is a style shared by some of his contemporaries. But essentially it is Feynman’s own. He would grin at himself if guilty of stately behaviour. He is a showman, and enjoys it. Since he enjoys it, he is not inclined to suppress it. He is a dashing performer. There have been a number of fine and eloquent expositors of science. W L Bragg was a splendid lecturer. Feynman is also a splendid lecturer, but in a distinctly different tone, rather as though Groucho Marx was suddenly standing in for a great scientist.
Here we ought to remember that sober-minded observers, such as the philosopher Samuel Alexander, knowing both Rutherford and Einstein when young though already world-famous, decided that Rutherford behaved like a rowdy boy and Einstein like a merry boy. The latter statement is the more interesting, in view of the moral weight that Einstein carried in later life. It may have accrued to him as life darkened him, though even in old age he could burst into bouts of jollity. It will be interesting for young men to meet Feynman in his later years.
All those capable of judging say that the theory of quantum electrodynamics is beautiful – a favourite term of theoreticians’ praise. In the same spirit, the present theory of sub-atomic particles strikes those inside the situation as beautiful. Outsiders, with appropriate humility, might suggest that it is a fairly rococo kind of beauty.
The memory returns to Heisenberg, in the early 1920s, going for a solitary stroll through the grounds of Bohr’s institute, and brooding over the question – can nature be all that absurd? Thirty or forty years later, Heisenberg’s successors could have been thinking that nature might not be all that absurd but was singularly lacking in economy. The great new particle accelerators in the United States – giant descendants of Cockcroft’s accelerator – propelled sub-atomic particles to higher and higher energies. (Although none can travel as fast as light, the closer they get to that limiting speed, the more energy they have.) These high energy bullets were creating many new, different species of sub-atomic particles when they hit any kind of target. The comparative simplicity of a universe consisting of only three types of particles, protons, electrons, neutrons, had disappeared. These new-found particles existed only for a fraction of a second, but their existence was incontrovertible. All were heavier than the electron, most heavier even than the proton, and they came with different masses and with different charges. Nearly all physicists believed – and still believe – as a matter of intuition or faith, that there must, in the very long run, be elegance and harmony in nature. A few heretics, like the immensely talented Edward Bullard, have always been convinced that this is a man-made or anthropomorphic delusion. For nearly everyone else, though, there had in the end, so they felt, to be elegance and harmony. In this new medley of particles, where had the elegance and harmony gone?
Some of the most powerful of the new generation of theoreticians weren’t defeated, notably Murray Gell-Mann and his colleague Yuval Ne-eman. Yes, there was an underlying harmony and an underlying beauty, but it needed new concepts and new mathematics to read it. The new mathematics which Gell-Mann introduced was more unfamiliar than the matrix algebra which had founded quantum mechanics, and was more difficult for physicists to domesticate. If experience is any guide, that domestication will duly happen.
The new mathematical tool that Gell-Mann introduced to physics was called ‘group theory’. As had happened with quantum mechanics and matrix theory, the mathematical structure had been around for a century. It had been formulated by a young French mathematician, Evariste Galois, who wrote out his ideas the night before he was due to take part in a duel. Galois was killed. But his ideas lived on, eventually to form the basis of our current understanding of the particles from which the universe is built up.
Gell-Mann noticed certain patterns amongst the newly discovered particles, when their properties were displayed on a graph. They seemed to fall into certain families, or groups. Galois’ group theory applied exactly to this kind of mathematical set-up. Although other physicists were sceptical about Gell-Mann’s patterns, he pointed out that the theory indicated a hole, a place in the pattern which should be occupied by a particle with certain properties. In 1964, experimenters at Brookhaven National Laboratory discovered this particle. Gell-Mann was right. The fundamental particles do form families.
Group theory was a stronger tool than this, though. It laid down rules governing the relationships in the family groups: how you would need to alter one particle to turn it into another of the same family or pattern. Gell-Mann found that this mathematical device, which evidently worked so well, corresponded to a simple physical interpretation. The ‘fundamental particles’ produced in the particle accelerators are composite. They are made up of smaller entities, which Gell-Mann called ‘quarks’ – apparently before he detected that peculiarly unsuitable word in Finnegan’s Wake. Gell-Mann is deeply cultivated, an enthusiastic linguist, one of the cleverest men of the century as well as one of the deepest conceptual thinkers; but like nature itself he hasn’t much taste for classical austerity.
Quarks are very curious entities, if entity is the right word. They come either in twos or threes, the latter cutting across the
grain of nearly all natural phenomena. Three quarks make up one proton. Quarks are not individually detectable by experimental means: they exist, but in the formal world of the new equations. They exhibit various phases of behaviour in those equations, to which theoreticians have attached terms of discrimination, such as colour, flavour, charm. These terms mean nothing except as labels in the equations themselves.
There has been nothing quite like this array of concepts in theoretical physics, or in any other branch of science before. It presents some absorbing problems in epistemology. If Einstein and Bohr were still alive, that great debate of theirs would take on another lease of existence. Theory has reached a climactic point – this is the present climax, and not the final one, of a series of revolutions which began in 1900 with Planck and his quantum of radiation, climbed up to the heights of Einstein and Bohr, consolidated itself with Dirac and Heisenberg, as always in science drawing in many minds along the way, and is now expressed by Gell-Mann, Ne-eman, Salam, and a dozen others.
Those who have contributed to this intellectual edifice – it is not a rhetorical flourish to say with a cool mind that it is the major intellectual achievement of our century, and will be so regarded by our successors – have come from nearly all countries, different forms of society, different ethnic stocks. The names in this account tell their own story. There have been Americans, Russians, Germans, French, Italians, British, Japanese. A statistically disproportionate number are of Jewish origin.
There is someone who ranks with the most eminent who should be mentioned. This is Abdus Salam, who has over the past twenty-five years been a leader in the theoretical developments just discussed. Salam was born in a peasant home in a Pakistani village. He managed to get a place in the government college at Lahore. Conceptual and mathematical ability is easy to detect at a very early age, and in Salam’s case some enlightened administrator apparently did so. After Lahore, he was despatched to Cambridge, studied with Dirac, and since then has had a creative career of continuous brilliance.