Quantum_ Einstein, Bohr and the Great Debate About the Nature of Reality - Manjit Kumar [142]
After several days, Heisenberg later recalled, 'Bohr, Pauli and I – knew that we could now be sure of our ground, and Einstein understood that the new interpretation of quantum mechanics cannot be refuted so simply'.56 But Einstein refused to yield. Even if it failed to capture the essence of his rejection of the Copenhagen interpretation, he would say, 'God does not play dice'. 'But still, it cannot be for us to tell God, how he is to run the world', replied Bohr on one occasion.57 'Einstein, I am ashamed of you,' said Paul Ehrenfest only half-joking, 'you are arguing against the new quantum theory just as your opponents argue about relativity theory.'58
The only impartial witness to the private encounters between Einstein and Bohr at Solvay 1927 was Ehrenfest. 'Einstein's attitude gave rise to ardent discussions within a small circle, in which Ehrenfest, who through the years had been a close friend of us both,' recalled Bohr, 'took part in a most active and helpful way.'59 A few days after the conference ended, Ehrenfest wrote a letter to his students at Leiden University vividly describing the goings-on in Brussels: 'Bohr towering completely over everybody. At first not understood at all (Born was also there), then step by step defeating everybody. Naturally once again the awful Bohr incantation terminology. (Poor Lorentz as interpreter between the British and the French who were absolutely unable to understand each other. Summarizing Bohr. And Bohr responding with polite despair.) Every night at 1 a.m. Bohr came into my room just to say ONE SINGLE WORD to me, until 3 a.m. It was delightful for me to be present during the conversations between Bohr and Einstein. Like a game of chess. Einstein all the time with new examples. … to break the UNCERTAINTY RELATION. Bohr from out of the philosophical smoke clouds constantly searching for the tools to crush one example after the other. Einstein like a jack-in-the-box, jumping out fresh every morning. Oh, that was priceless. But I am almost without reservation pro Bohr and contra Einstein.'60 However, Ehrenfest admitted 'that he would not be able to find relief in his own mind before concord with Einstein was reached'.61
At Solvay 1927 the discussions with Einstein were conducted, Bohr said later, in 'a most humorous spirit'.62 Yet he noted wistfully, 'a certain difference in attitude and outlook remained, since with his mastery for coordinating apparently contrasting experiences without abandoning continuity and causality, Einstein was perhaps more reluctant to renounce such ideals than someone for whom renunciation in this respect appeared to be the only way to proceed with the immediate task of coordinating the multifarious evidence regarding atomic phenomena, which accumulated from day to day in the exploration of this new field of knowledge.'63 It was Einstein's very successes, implied Bohr, that kept him anchored in the past.
The fifth Solvay conference ended with Bohr, in the minds of those gathered in Brussels, having successfully argued for the logical consistency of the Copenhagen interpretation, but failing to convince Einstein that it was the only possible interpretation of what was a 'complete', closed theory. On his journey home, Einstein travelled to Paris with a small group that included de Broglie. 'Carry on', he told the French prince as they parted company. 'You are on the right road.'64 But de Broglie, disheartened at the lack of support in Brussels, would soon recant and accept the Copenhagen interpretation. When Einstein reached Berlin he was exhausted and subdued. Within a fortnight he wrote to Arnold Sommerfeld that quantum mechanics 'may be a correct theory of the statistical laws, but it is an inadequate conception of individual elementary processes'.65
While Paul Langevin later said that 'the confusion of ideas reached its zenith' at Solvay 1927, for Heisenberg this meeting of minds was the decisive turning point in establishing the correctness of the Copenhagen interpretation.66 'I am satisfied in every respect with the scientific results',