Einstein on the Run Read online

  Once again, he heard from Murray. ‘I fully understand your action, and even feel the strongest sympathy with it, but I hope and believe that you are wrong,’ Murray wrote.

  I believe that the right line would have been for a number of us to say that it was impossible for the Committee on Intellectual Cooperation to function while the French were refusing to submit their case to arbitration and were creating practically a state of war in Europe. I believe that some other members of the committee would have been willing to take that line. The committee itself consists largely of people who have nothing particular to do with the League and are not, I fear, permeated with the League spirit.

  Einstein stuck to his guns, so to speak, with reluctance. He told Murray in his reply: ‘the League functions as a tool of those nations which, at this stage of history, happen to be the dominant powers. Thus, the League not only fails to uphold justice but actually undermines the faith of men of goodwill who believe in the possibility of creating a supranational organisation.’

  But when Murray, with the unanimous support of the com-mittee, tried to lure Einstein back a year or so after his 1923 resignation, he was again open to discussion. He assured Murray: ‘I do not hesitate to tell you that my closest and most enlightened friends were the ones who expressed the deepest regret over my resignation. I myself have slowly come to feel that I was influenced more by a passing mood of disillusionment than by clear thinking.’ Certainly, thus far the League had often failed; yet in such challenging times as these he recognised that the League was the institution that offered the greatest likelihood of effective action if its members were to strive honestly for international reconciliation.

  Einstein re-joined the committee in June 1924 and remained a member, formally speaking, until 1932. But it has to be said that he was never an assiduous attender of its discussions, or an enthusiast for them, because he found the committee to be trapped between France’s desire for political domination and Germany’s desire to restore its political respectability.

  Perhaps the only committee project that really caught Einstein’s imagination was its commitment to encouraging and publishing ‘an exchange of letters between leaders of thought, on the lines of those which have always taken place at the great epochs of European history’. From this emerged a pamphlet, Why War?, based on Einstein’s own exchange with Sigmund Freud in 1932. It attempted to answer his opening question to Freud, ‘Is there any way of delivering mankind from the menace of war?’, and his concluding question, ‘Is it possible to control man’s mental evolution so as to make him proof against the psychosis of hate and destructiveness?’ On which Einstein commented provocatively, bearing in mind his own exposure to the behaviour of German academics during the First World War: ‘Here I am thinking by no means only of the so-called uncultured masses. Experience proves that it is rather the so-called “intelligentsia” that is most apt to yield to these disastrous collective suggestions,’ because, he said, ‘the intellectual has no direct contact with life in the raw but encounters it in its easiest, synthetic form – upon the printed page.’

  Why War? was published by the League of Nations Inter-national Institute of Intellectual Cooperation in 1933 – ironically the year in which the Nazis seized power in Germany – with the active help of some German intellectuals, including physicists such as Lenard, and the silent cooperation of others, such as Planck.

  Probably, Einstein’s growing disillusionment with the League of Nations was what kindled his belief in militant pacifism. Dislike of war had been implicit in his childhood in Germany; hatred of it explicit in some of his statements during and after the First World War, including his participation in the ‘Manifesto to the Europeans’ published in 1917. However, he did not actually ally himself with war resistance movements until the later years of the 1920s.

  In early 1928, he told the Women’s International League for Peace and Freedom, which had arranged a conference on gas warfare to be held in Geneva simultaneously with a meeting of the League of Nations Disarmament Commission:

  It seems to me an utterly futile task to prescribe rules and limitations for the conduct of war. War is not a game; hence, one cannot wage war by rules as one would in playing games. Our fight must be directed against war itself. The masses of people can most effectively fight the institution of war by establishing, in time of peace, an organisation for absolute refusal of military service. The efforts made in this direction in England and Germany appear rather promising.

  That same month, Einstein accepted election to the board of directors of the German League for Human Rights, which was then the leading pacifist movement in Germany.

  Later in 1928, he sent a message to the No More War Movement in London, the British section of War Resisters’ International, which was more emphatic than his earlier message:

  I am convinced that the international movement to refuse participation in any kind of war service is one of the most encouraging developments of our time. Every thoughtful, well-meaning and conscientious human being should assume, in time of peace, the solemn and unconditional obligation not to participate in any war, for any reason, or to lend support of any kind, whether direct or indirect.

  Finally, in 1930, he made his most pungent statement about militarism in an article, ‘The World as I See It’, which soon became a key text on Einstein the humanitarian:

  I feel only contempt for those who can take pleasure marching in rank and file to the strains of a band. Surely, such men were given their great brain by mistake; the spinal cord would have amply sufficed. This shameful stain on civilisation should be wiped out as soon as possible. Heroism on command, senseless violence and all the loathsome nonsense that goes by the name of patriotism – how passionately I despise them! How vile and contemptible war seems to me! I would rather be torn limb from limb than take part in such an ugly business.

  Einstein speaks at a Jewish fundraising dinner at the Savoy Hotel, London, October 1930, along with George Bernard Shaw (on the right). Between them sits Lord Lionel Rothschild, a leading British Jew. In his speech, Shaw counted Einstein among the ‘makers of universes’, in the company of Pythagoras, Ptolemy, Aristotle, Copernicus, Kepler, Galileo and Newton.

  And that same year, at a meeting in New York, he declared himself a militant pacifist in a speech – the so-called ‘Two-per-cent speech’ – which quickly became a symbol for the international pacifist movement, both figuratively and literally, in the form of pacifist lapel buttons with the legend ‘2%’. He said: ‘Even if only two per cent of those assigned to perform military service should announce their refusal to fight, as well as urge means other than war of settling international disputes, governments would be powerless, they would not dare send such a large number of people to jail.’

  Soon afterwards, Bertrand Russell publicly welcomed this speech. But in a private letter to the secretary of War Resisters’ International, Russell warned: ‘The next war will, I think be more fierce than the war which as yet is still called “Great”, and I think governments would have no hesitation in shooting the pacifist two per cent.’

  The rise to political power of Nazism in Germany in 1933 put Einstein the militant pacifist in an extremely awkward position, in which he would feel forced to change his mind about military service. But before coming to that turbulent period of his life, let us revisit his science. In the late 1920s, at the same time as he embraced militant pacifism, Einstein became a militant critic of the theory of quantum mechanics, developed from work done by his scientific friends and colleagues in Britain, Germany and several other countries inspired by Einstein’s original quantum theory of 1905.

  Quantum mechanics is certainly imposing. But an inner voice tells me that it is not yet the real thing. The theory says a lot, but does not really bring us any closer to the secret of the ‘old one’. I, at any rate, am convinced He is not playing at dice.

  Letter from Einstein to Max Born, December 1926

  From his original paper on the photoelectr
ic effect in 1905 until his death in 1955, Einstein thought about the physical significance of quantisation in physics without coming to any firm conclusions – as vividly demonstrated in his many exchanges with one of the founders of quantum mechanics, Born, which began in Germany around 1925 and continued between the United States and Britain after Einstein and Born emigrated in 1933. As early as 1911, Einstein told Besso (who had crucially helped him with special relativity in 1905): ‘I no longer ask whether these quanta really exist. Nor do I try to construct them any longer, for I now know that my brain cannot get through in this way. But I rummage through the consequences as carefully as possible so as to learn about the range of applicability of this conception.’ In 1922, he told Ehrenfest: ‘I suppose it’s a good thing that I have so much to distract me, else the quantum problem would have long got me into a lunatic asylum. . . . How miserable the theoretical physicist is in the face of nature, and in the face of his students.’ And in later life, he told another physicist, Otto Stern, a fellow Nobel laureate like Born: ‘I have thought a hundred times as much about the quantum problem as I have about general relativity theory.’

  Some of the issues it threw up are still very much with us more than a century after Einstein’s first paper. Unlike relativity, quantum theory still provokes fierce debate. Indeed, physicists are fond of quoting provocative comments about the mysteriousness of quantum theory from its pioneers, such as this one from Richard Feynman, a founder of the powerful theory of quantum electrodynamics in the 1940s and 1950s, who wrote in 1967: ‘I think I can safely say that nobody understands quantum mechanics.’ In 2018, Carlo Rovelli, a founder of the (as yet unproven) theory of loop quantum gravity, admitted: ‘The strange landscape of the physics of relativity . . . becomes even more alien when we consider quanta and the quantum properties of space and of time.’

  EVOLUTION OF THE QUANTUM CONCEPT

  There were two main phases of Einstein’s role in the quantum story. The first ran from 1905, the date of his paper assuming the existence of light quanta (later called photons), to the mid-1920s, when his assumption was unequivocally validated by the experiments of Arthur Compton showing that X-rays were waves scattered by the free electrons in metal foil according to quantum rules. During this first phase, now known as the period of the ‘old’ quantum theory, Einstein maintained – almost alone – that light itself was quantised, while making major contributions to physics by employing this hypothesis. This is not to say that quantum concepts were not seriously discussed by others then; they certainly were, as in Planck’s 1900 theory of the absorption and emission of black-body radiation and Niels Bohr’s 1913 solar-system model of the atom, based on the nuclear model of Rutherford. But Einstein’s light quanta were considered too radical for polite scientific society. In 1922, they were evaded in Einstein’s Nobel prize citation, which referred instead to his ‘services to theoretical physics and especially for his discovery of the law of the photoelectric effect’; and the same happened the following year when the Nobel prize was given to Robert Millikan partly for his experimental confirmation of the same law. During this first phase ‘it was the law that was accepted, not the photon’, the physicist Andrew Whitaker stressed in his historical study, Einstein, Bohr and the Quantum Dilemma. ‘Einstein’s initial conception of the photon was no less than an act of genius, and his perseverance with it, despite the negative response and his own misgivings over the relation between the wave and particle concepts, showed great determination and courage.’

  Then in 1925–26, the beginning of the second phase of quantum theory, along came quantum mechanics, originated by Werner Heisenberg (from Germany) and Erwin Schrödinger (from Austria), together with Bohr (from Denmark), Born (from Germany), Louis de Broglie (from France), Paul Dirac (from England) and others – but not Einstein. Once again he stood almost alone. In this phase of the quantum revolution, from 1926 until his death, Einstein was profoundly sceptical about his colleagues’ new interpretation of physical reality in terms of probability, indeterminacy and uncertainty – which did not prevent it from quickly becoming the orthodoxy it remains today, not only in physics and chemistry but throughout science. In Einstein’s view, however successful quantum theory might be in describing natural phenomena, it remained incomplete, like gravitational theory before the invention of general relativity. As Einstein wrote of Newton in 1933, ‘the tremendous practical success of his doctrines may well have prevented him and the physicists of the eighteenth and nineteenth centuries from recognising the fictitious character of the foundation of the system’. He believed that the same would eventually prove true of the quantum theory.

  Three comments from pivotal figures in twentieth-century science, each of them close to Einstein, give a fair picture of the deep resistance to his 1905 theory of quantised light in the days of the old quantum theory. In 1910, the physical chemist Nernst called Einstein’s quantum hypothesis ‘probably the strangest thing ever thought up. If correct, it opens entirely new roads for so-called ether physics and for all molecular theories. If false, it will remain “a beautiful memory” for all times.’ To Nernst, the hypothesis apparently looked alluring but illicit. Hence his decision to convene the first Solvay Congress in Brussels in 1911 in order to discuss the implications of the quantum hypothesis, at which Einstein gave the concluding address. Less sympathetic was Planck, who was of course a theoretical physicist like Einstein. Planck had greeted special relativity in 1905 as the work of a new Copernicus, but he was embarrassed by the intellectual offspring of his own quantum theory of black-body radiation. In 1913, when fulsomely recommending Einstein for membership of the Prussian Academy in Berlin, Planck nonetheless felt obliged to add a gentle apology for his distinguished protégé’s subversive quantum notion: ‘That sometimes, as for instance in his hypothesis of light quanta, he may have gone overboard in his speculations should not be held against him too much, for without occasional venture or risk no genuine innovation can be accomplished even in the most exact sciences.’ Least sympathetic of all was the American experimental physicist Millikan, who in 1909 had first measured the charge on the electron in his classic oil-drop experiment. In 1916, Millikan bluntly called Einstein’s quantum theory ‘wholly untenable’, a ‘bold, not to say reckless, hypothesis’, in two published scientific papers. What is particularly pointed about this criticism is that Millikan had just spent ten years in his laboratory testing the predictions of Einstein’s 1905 equation for the photoelectric effect and reluctantly confirmed its striking accuracy. Even so, Millikan refused to accept Einstein’s theoretical explanation of his own laboratory results, because to have allowed the existence of light quanta would have appeared an absolute contradiction to the ruling wave concept of light.

  The earliest of Einstein’s applications of the quantum hypo-thesis (after the photoelectric effect), which he published in 1907, was not directly to do with light quanta. It concerned the solid state.

  In the 1820s, two physicists, Pierre Dulong and Alexis Petit, had experimented with heating various metallic elements such as copper, nickel and gold, and had discovered an interesting and useful rule, the so-called Dulong and Petit law. It states that the amount of energy required to increase the temperature of 1 kilogram of a substance by 1 degree Centigrade – known as its specific heat capacity – is inversely proportional to its atomic weight (more accurately, its relative atomic mass). The greater the atomic weight of an element, the smaller its specific heat capacity; multiplied together, the atomic weight and the specific heat equalled a constant value across a number of different substances, as measured by Dulong and Petit. Their law was thus good evidence for the atomic structure of matter and also suggested the surprising fact that the atoms of a range of different elements had exactly the same capacity for heat regardless of their atomic weight.

  But as Einstein had been aware since his student days, Dulong and Petit’s law worked well only at high temperatures and only with certain elements, not with others. At low temperature
s the specific heat capacity fell and the law was not obeyed; and for diamond (carbon), boron and silicon, the specific heat was found to be much too low even at room temperature.

  Einstein sought a quantum explanation of these specific heat anomalies. According to the kinetic theory, which explains Brownian movement in liquids and gases (as noted by Einstein in 1905), the atoms in solids must absorb heat by vibrating more vigorously on their crystal lattices, in the same way that atoms in liquids and gases zip around with higher velocities at higher temperatures. But suppose the fixed atoms in a solid oscillated not in a continuous manner but in a quantised way, such that they could increase their energy of vibration only in steps, not continuously? In other words, suppose the vibrations could take only discrete energy values. Einstein further assumed that the magnitude of the quantised energies could be calculated from Planck’s simple quantum equation linking energy and frequency (here the frequency of atomic vibration). On this basis his calculation gave a remarkably accurate account of the general behaviour of simple solids. As Einstein predicted in his 1907 paper: ‘If Planck’s theory of radiation goes to the heart of the matter, then we must also expect to find contradictions between the present kinetic theory and experiment in other areas of the theory of heat – contradictions that can be resolved by following this new path.’