Einstein on the Run Read online

Instead of particles of matter, Einstein imagined regions of very intense field – rather like knots in the even grain of a piece of wood. In The Evolution of Physics, he and his collaborator, Leopold Infeld, wrote in 1938:

  Could we not reject the concept of matter and build a pure field physics? What impresses our senses as matter is really a great concentration of energy into a comparatively small space. We could regard matter as the regions in space where the field is extremely strong. . . . A stone thrown is, from this point of view, a changing field. . . . There would be no place, in our new physics, for both field and matter, field being the only reality. This new view is suggested by the great achievements of field physics, by our success in expressing the laws of electricity, magnetism, gravitation in the form of structure laws and finally by the equivalence of mass and energy. Our ultimate problem would be to modify our field laws in such a way that they would not break down for regions in which the energy is enormously concentrated.

  With each successive attempt, Einstein’s unified field theory became more purely mathematical and less based on the real world. He had started his scientific life in the 1890s by imagining himself chasing a light ray, and had invented general relativity by wondering how gravity would feel if he jumped off a rooftop, but now he progressively lost interest in such physical ideas. Perhaps his flawed thinking in the 1930 ‘thought’ experiment on quantum mechanics with the photon and the box was suggestive, in that the flaw lay in his failure to consider the physical method of measurement; by idealising the experiment too much, he overlooked a key element (as spotted by a triumphant Bohr).

  During the 1930s, Einstein seems to have lost interest in the fundamental advances that were being made in physics. The discovery of the positron, the first known ‘anti-matter’ particle, in 1932/33 made little impact on his work – which was ironic given that Dirac had predicted its existence in 1928 by applying special relativity to the quantum mechanics of the electron (though Einstein did admire Dirac’s mathematics). And the same happened with the discovery of the neutron in 1932 and the muon in 1936, which heralded the discovery of many other nuclear particles. The richness of the newly discovered subatomic world – each particle with its mass, spin, charge, quantum number and other features – did not emerge from Einstein’s new field equations. Despite the importance of his 1905 equation E = mc2 in understanding nuclear fission (discovered in 1938), he showed no serious interest in the emerging new model of the nuclear forces.

  According to the physicist Steven Weinberg, a Nobel laureate who played a key part in the ‘electroweak’ theory of the 1960s and 1970s that unified electromagnetism with the weak interactions of the nucleus, one of Einstein’s approaches to a unified field theory lives on, in much-modified form, in today’s string theory. But of the other approach, the extension of general relativity to a non-symmetric metric, ‘no trace remains in current research’. Einstein’s three decades of endless calculation after 1925 have left little behind except manuscripts. Although physicists may honour his final search for its sheer faith in the possibility of unification – as is evident in the continuing search for a ‘theory of everything’ – his specific ideas were first ignored and then forgotten, in signal contrast with his work on relativity and quantum theory.

  So why did Einstein stick with his search, one may well ask? Part of the reason may have been the stubbornness of an ageing physicist past his intellectual prime: a widely held criticism that Einstein himself joked about to Born and others. In addition, there was his sense of duty to physics. Einstein told a physicist who expressed regret at his efforts that although he knew the chance of success was very slight, he felt obliged to try. ‘He himself had established his name; his position was assured, and so he could afford to take the risk of failure. A young man with his way to make in the world could not afford to take a risk by which he might lose a great career.’ Yet, the main reason Einstein persisted was probably the one that fired his exchanges with Born. Not only had Einstein always been drawn to the deepest questions in physics, he was also philosophically convinced that reality was determined by laws, not by chance, and that these laws made physical reality independent of the human mind. God does not play dice – he was certain.

  Perhaps the clearest expression of this conviction came in Einstein’s meeting with Rabindranath Tagore in Germany in 1930 not long before the Solvay Congress. Tagore, though best known as a poet (for which he won the Nobel prize in 1913), a song composer, a philosopher, and as a spiritual leader and fighter for India’s freedom beside Mahatma Gandhi, was also interested in science. But Tagore’s philosophical position was quite opposed to Einstein’s. Their 1930 conversation, soon published in the New York Times, shines a bright light on Einstein’s philosophical position and throws it into sharp relief.

  ‘There are two different conceptions about the nature of the universe – the world as a unity dependent on humanity, and the world as reality independent of the human factor,’ said Einstein. Tagore responded: ‘This world is a human world – the scientific view of it is also that of the scientific man. Therefore, the world apart from us does not exist; it is a relative world, depending for its reality upon our consciousness.’

  ‘Truth, then, or beauty, is not independent of man?’ asked Einstein. ‘No,’ replied Tagore. ‘If there were no human beings any more, the Apollo Belvedere no longer would be beautiful?’ queried Einstein. ‘No,’ said Tagore. ‘I agree with regard to this conception of beauty, but not with regard to truth,’ said Einstein. ‘Why not? Truth is realised through men,’ asked Tagore. ‘I cannot prove that my conception is right, but that is my religion,’ said Einstein firmly.

  Then he became concrete: ‘The mind acknowledges realities outside of it, independent of it. For instance, nobody may be in this house, yet that table remains where it is.’ ‘Yes,’ said Tagore, ‘it remains outside the individual mind, but not the universal mind. The table is that which is perceptible by some kind of consciousness we possess.’

  ‘If nobody were in the house the table would exist all the same, but this is already illegitimate from your point of view, because we cannot explain what it means, that the table is there, independently of us. . . . We attribute to truth a superhuman objectivity,’ said Einstein. ‘In any case, if there be any truth absolutely unrelated to humanity, then for us it is absolutely non-existing,’ replied Tagore.

  ‘Then I am more religious than you are!’ exclaimed Einstein.

  Bohr’s view of reality – and the views of some other quantum physicists – had more in common here with Tagore’s view than with Einstein’s. For quantum mechanics maintains, like Tagore, that reality is dependent on the observer. In science, said Einstein, ‘we ought to be concerned solely with what nature does’. Bohr, however, insisted that it was ‘wrong to think that the task of physics is to find out how nature is. Physics concerns what we can say about nature.’

  Soon after his conversation with Tagore, in a seventieth birthday message for him, Einstein wrote: ‘Man defends himself from being regarded as an impotent object in the course of the Universe. But should the lawfuless of events, such as unveils itself more or less clearly in inorganic nature, cease to function in front of the activities in our brain?’ From an early age Einstein had believed human free will to be an illusion. He had a gut belief in the existence of a supreme law-giver – called God, if you will (as Einstein often did). Somehow this belief in determinism coexisted with his extreme individualism and exceptionally strong ethical values. ‘I have never been able to understand Einstein in this matter,’ wrote Born.

  COSMOLOGY AND THE EXPANDING UNIVERSE

  Interestingly, Einstein’s resistance to the new discoveries in quantum mechanics at the subatomic level was not paralleled by a comparable resistance to equally revolutionary new discoveries in cosmology in the far reaches of the universe during the same period. In fact, Einstein would apply general relativity, following the theory’s confirmation by English astronomers in 1919, to a
spate of radical new American astronomical observations made in the late 1920s.

  In the history of cosmology, the fifteen years from 1917 to 1932 are reminiscent of the early seventeenth century, when Galileo’s telescope provided astronomical evidence for the Copernican solar system and Kepler reformulated the planetary orbits as ellipses. ‘Theory fed on observation, observation fed on theory, and in the end science ended up much grander and more powerful than before. This time around, astronomers recognised the Milky Way as one of countless galaxies strewn through a vast and dynamic universe, each one composed of many billions of stars,’ wrote a former NASA space scientist, Corey Powell, in his study of Einstein, cosmology and religion. ‘And the cosmologists were ready to make sense of it all, to demonstrate they could explain our place among the fleeting galaxies as readily as their ancestors had put the Earth in motion among the planets.’

  At the beginning of this period, in 1917, Einstein set about applying general relativity to the universe as a whole. Com-paratively uninformed about the latest empirical work in astronomy, his primary interest was not to construct a cosmological model from observations, but rather to build ‘a spacious castle in the air’ (as he told the astronomer Willem de Sitter), in order to test his theory. Much to his surprise, and even dismay, general relativity predicted the cosmos to be dynamic, not static: either expanding or contracting over time. Since Einstein knew of no astronomical evidence for such movement, he added a term to his existing field equations of relativity, intended to counteract the attractive influence of gravity and thereby stabilise the universe, making it static and therefore eternal, as he thought it should be. Known as the ‘cosmological constant’, it allowed Einstein to predict a cosmos that was both static and finite, with a radius and average density of matter that could be calculated from first principles rather than from astronomical observations. But he admitted in his published paper that the new term was ‘not justified by our actual knowledge of gravitation’ and was ‘necessary only for the purpose of making possible a quasi-static distribution of matter, as required by the fact of the small velocities of the stars’. In other words, the cosmological constant was something of a fudge factor.

  Now, however, other theoreticians entered the picture by exploring different relativistic models of the cosmos. A physicist and mathematician, Alexander Friedmann, proposed that non-static models of the universe should be considered. In 1922–24, Friedmann, using Einstein’s field equations, derived a whole class of dynamic cosmic models. Soon after, a theoretical physicist and Catholic priest, Georges Lemaître, treated emerging astronomical observations of a systematic recession of distant galaxies as evidence of an expansion of space on the largest scales. He postulated an origin of the universe in a ‘primeval atom’: the first conception of what would become the Big Bang model that dominates cosmology today. Unaware of Friedmann’s work, Lemaître demonstrated how such a cosmic expansion could be derived from Einstein’s field equations. But when Einstein was made aware of the work of both Friedmann and Lemaître, he could not accept their cosmic models. In a discussion with Lemaître in 1927, Einstein said he regarded theoretical models of an expanding universe as ‘totally abominable’.

  In 1929, new observations compelled him to change this view. The American astronomer Edwin Hubble with his assistant Milton Humason, working with the advanced telescope at the Mount Wilson Observatory in California, observed a linear relation between the recession velocity of distant galaxies and their radial distance. ‘Many theorists saw the phenomenon as possible evidence for an expansion of space, and set about constructing relativistic models of an expanding universe similar to those of Friedmann and Lemaître,’ according to physicist Cormac O’Raifeartaigh. ‘In all these theories, it was assumed that the average density of matter in the universe would decrease as space expanded – what is known as an “evolving” universe.’

  After Einstein had seen the astronomical evidence for expansion with his own eyes on a visit to the Mount Wilson Observatory in 1931, he too published papers with ‘evolving’ universes: one on his own in 1931, and another with de Sitter in 1932. In both cases, Einstein abandoned his 1917 cosmological constant on the grounds that the constant was now redundant. In later years, he even supposedly referred to the cosmological constant as the ‘biggest blunder’ of his life (according to the cosmologist George Gamow). But, ironically, evidence from the late twentieth century restored the need for the cosmological constant. It now appears to be connected with the fact that the expansion of the universe is accelerating. The possibility of a cosmological constant ‘did not go away so easily’, wrote Weinberg in 1993.

  Einstein in 1915 operated under the assumption that the field equations should be chosen to be as simple as possible. The experience of the past three quarters of a century has taught us to distrust such assumptions; we generally find that any complication in our theories that is not forbidden by some symmetry or other fundamental principle actually occurs. It is thus not enough to say that a cosmological constant is an unnecessary complication. Simplicity, like everything else, must be explained.

  As Einstein disarmingly remarked the year before his death, while commenting on the life and work of Eddington and the many conflicting theories of the origin of the universe, ‘Every man has his own cosmology and who can say that his own theory is right!’

  His own ‘evolving universe’ paper was published in Berlin in April 1931. A week or two later, he set off for Oxford to give three public lectures about relativity, including current references to cosmology and the unified field theory. Being Einstein, he would not shy away from presenting his latest scientific thinking. How much of this theorising even his physicist host, Professor Lindemann, would be capable of understanding was highly questionable. Without doubt, however, Einstein’s second major visit to England would expand both his own universe and that of an ancient university.

  Doctoral ceremony in large hall. Serious, but not wholly accurate speech in Latin. Then my last lecture at Rhodes House on the mathematical methods of field theory. The dean slept wonderfully in the first row. Frightfully well-behaved and friendly audience. Afternoon nap at Lindemann’s. Meal in college and finally pacifist students in cute old private house. Great political maturity among the Englishmen. How pitiful are our students by comparison!

  Comment by Einstein about a day in Oxford in his travel diary, May 1931

  In the 1920s, England had taken Einstein to its heart, following his initial burst of scientific fame in 1919 and his first personal visit to Manchester and London in 1921. In 1924, George Bernard Shaw – who had met Einstein (a decided fan of Shaw’s work) at the house of Lord Haldane – privately informed him that ‘You are the only sort of man in whose existence I see much hope for this deplorable world’, while frankly admitting his own inability to understand Einstein’s theory. In 1925, Bertrand Russell (for whose book Political Ideals Einstein had written an enthusiastic introduction to its German edition in 1922) published an introductory book, The ABC of Relativity. Russell kicked off with this come-on: ‘Everybody knows that Einstein did something astonishing, but very few people know exactly what it was that he did.’ At the same time the poet Sir John Squire remarked epigrammatically, in extending two classic lines about Newton written by Alexander Pope in 1730:

  Nature, and Nature’s laws lay hid in night.

  God said, Let Newton be! and all was light.

  It did not last: the Devil howling ‘Ho!

  Let Einstein be!’ restored the status quo.

  In 1925, the Royal Society awarded Einstein its highest honour, the Copley Medal, which had been given to Faraday in 1838. The Society’s secretary, Sir James Jeans, while officially informing Einstein, added a personal touch: ‘I think you are the youngest recipient in the two hundred years or so since it has been awarded; in any case if you are not, I think you ought to be.’

  By 1930, according to Shaw, Einstein belonged to the pantheon of the immortals. Speaking at a public dinner in London
for a Jewish cause where Einstein was the guest of honour, Shaw counted him among the ‘makers of universes’, in the company of Pythagoras, Ptolemy, Aristotle, Copernicus, Kepler, Galileo and Newton – ‘not makers of empires’. He added: ‘and when they have made those universes their hands are unstained by the blood of any human being on earth’. (A humble Einstein responded: ‘I, personally, thank you for the unforgettable words which you have addressed to my mythical namesake, who has made my life so burdensome, who, in spite of his awkwardness and respectable dimension, is, after all, a very harmless fellow.’)

  Einstein near the Sheldonian Theatre, Oxford, during his doctoral ceremony, May 1931. The public oration about Einstein, given in Latin, failed to translate ‘relativity’ or to mention Isaac Newton.

  INTRODUCING FREDERICK LINDEMANN

  On 1 May 1931, Lindemann’s chauffeured Rolls Royce collected Einstein from the docks at Southampton when his passenger liner arrived from Hamburg. But instead of heading straight for Oxford in the car, Lindemann broke the journey at Winchester so that Einstein could see the town’s wonderful Gothic cathedral and also pay a surprise visit to the cloistered seclusion of its notably intellectual boys’ public school, Winchester College, founded in 1382, which has the longest unbroken history of any school in England.

  Here, however, Professor Lindemann encountered a problem: the school porter refused to admit him and his guest on the grounds that the school was closed because the boys were at work. Attempts to persuade the porter to make an exception for Albert Einstein failed – no matter how many names of Lindemann’s eminent friends, including the prime minister’s, he dropped. Finally, Lindemann said he had a message to give to a boy, John Griffiths, from his mathematician–physicist father in Oxford, who worked with Lindemann at the Clarendon Laboratory. This recommendation worked the necessary magic, and a passing junior boy was sent to find Griffiths, who now takes up the story (as he recalled in the school’s magazine, The Trusty Servant, half a century later).