From The Telegraph:
In this extract from Quantum, shortlisted for the BBC Samuel Johnson Prize for non-fiction, Manjit Kumar delves into one of the greatest controversies in the history of physics
Paul Ehrenfest was in tears. He had made his decision. Soon he would attend the week-long gathering where many of those responsible for the quantum revolution would try to understand the meaning of what they had wrought. There he would have to tell his old friend Albert Einstein that he had chosen to side with Niels Bohr. Ehrenfest, the 34-year-old Austrian professor of theoretical physics at Leiden University in Holland, was convinced that the atomic realm was as strange and ethereal as Bohr argued.
In a note to Einstein as they sat around the conference table, Ehrenfest scribbled: ‘Don’t laugh! There is a special section in purgatory for professors of quantum theory, where they will be obliged to listen to lectures on classical physics ten hours every day.’ ‘I laugh only at their naivete,’ Einstein replied. ‘Who knows who would have the [last] laugh in a few years?’ For him it was no laughing matter, for at stake was the very nature of reality and the soul of physics. The photograph of those gathered at the fifth Solvay conference on ‘Electrons and Photons’, held in Brussels from 24 to 29 October 1927, encapsulates the story of the most dramatic period in the history of physics. With seventeen of the 29 invited eventually earning a Nobel Prize, the conference was one of the most spectacular meetings of minds ever held. It marked the end of a golden age of physics, an era of scientific creativity unparalleled since the scientific revolution in the seventeenth century led by Galileo and Newton.