Quantum_ Einstein, Bohr and the Great Debate About the Nature of Reality - Manjit Kumar [91]
Kronig later recalled that as he read Pauli's letter to Landé his 'curiosity was aroused'.47 Pauli had outlined the need to label every electron inside an atom with a unique set of four quantum numbers and its consequences. Immediately Kronig began thinking about the possible physical interpretation of the fourth quantum number, and came up with the idea of an electron rotating about its axis. He was quick to appreciate the difficulties attached to such a spinning electron. However, finding it 'a fascinating idea', Kronig spent the rest of the day developing the theory and doing the mathematics.48 He had worked out much of what Uhlenbeck and Goudsmit would announce in November. When he explained his findings to Landé, both men were impatient for Pauli to arrive and give his seal of approval. Kronig was taken aback when Pauli ridiculed the notion of electron spin: 'That is surely quite a clever idea, but nature is not like that.'49 So fervent had Pauli been in rejecting the proposal, Landé tried to soften the blow: 'Yes, if Pauli says so, then it is not like that.'50 Dejected, Kronig abandoned the idea.
Unable to contain his anger when electron spin was quickly embraced, in March 1926 Kronig wrote to Bohr's assistant Hendrik Kramers. He reminded Kramers that he had been the first to suggest electron spin and had not published because of Pauli's derisive reaction. 'In future I shall trust my own judgement more and that of others less', he lamented, having learnt the lesson too late.51 Disturbed by Kronig's letter, Kramers showed it to Bohr. No doubt remembering his own dismissal of electron spin when Kronig had discussed it with him and others during his stay in Copenhagen, Bohr wrote to express his 'consternation and deep regret'.52 'I should not have mentioned the matter at all if it were not to take a fling at the physicists of the preaching variety, who are always so damned sure of, and inflated with, the correctness of their own opinion', replied Kronig.53
Despite feeling robbed, Kronig was sensitive enough to ask Bohr not to mention the whole sorry affair in public, since 'Goudsmit and Uhlenbeck would hardly be very happy about it'.54 He knew they were entirely blameless. However, both Goudsmit and Uhlenbeck became aware of what had happened. Uhlenbeck later openly acknowledged that he and Goudsmit 'were clearly not the first to propose a quantized rotation of the electron, and there is no doubt that Ralph Kronig anticipated what certainly was the main part of our ideas in the spring of 1925, and that he was discouraged mainly by Pauli from publishing his results'.55 It was proof, a physicist told Goudsmit, 'that the infallibility of the Deity does not extend to his self-styled vicar on earth'.56
In private, Bohr believed that Kronig 'was a fool'.57 If he was convinced of the correctness of his idea, then he should have published no matter what others thought. 'Publish or perish' is a rule not to be forgotten in science. In his heart, Kronig must have reached a similar conclusion. His initial outburst of bitterness towards Pauli amid the disappointment of missing out on electron spin had dissipated by the end of 1927. At only 28, Pauli was appointed professor of theoretical physics at the ETH in Zurich. He asked Kronig, who was once again spending time in Copenhagen, to become his assistant. 'Every time I say something, contradict me with detailed arguments', Pauli wrote to Kronig after he accepted the offer.58
By March 1926 the problems that had led Pauli to reject electron spin had all been resolved. 'Now there is nothing else I can do than to capitulate completely', he wrote to Bohr.59 Years later, most physicists assumed that Goudsmit and Uhlenbeck had received the Nobel Prize – after all, electron spin was one of the