Quantum_ Einstein, Bohr and the Great Debate About the Nature of Reality - Manjit Kumar [107]
As the years passed, Schrödinger began to wonder if he would ever make a major contribution that would establish him among the first rank of contemporary physicists. At the beginning of 1925 he was 37, long having celebrated the 30th birthday that was said to be the watershed in the creative life of a theorist. Doubts over his worth as a physicist were compounded by a marriage in trouble because of affairs on both sides. By the end of the year Schrödinger's marriage was shakier than ever, but he made the breakthrough that would ensure his place in the pantheon of physics.
Schrödinger was taking an ever more active interest in the latest developments in atomic and quantum physics. In October 1925, he read a paper that Einstein had written earlier in the year. A footnote that flagged up Louis de Broglie's thesis on wave-particle duality caught his eye. As with most footnotes, virtually everyone ignored it. Intrigued by Einstein's stamp of approval, Schrödinger set about acquiring a copy of the thesis, unaware that papers by the French prince had been in print for nearly two years. A couple of weeks later, on 3 November, he wrote to Einstein: 'A few days ago I read with the greatest interest the ingenious thesis of de Broglie, which I finally got hold of.'9
Others were also beginning to take note, but in the absence of any experimental support, few were as receptive to de Broglie's ideas as Einstein and Schrödinger. In Zurich, every fortnight, physicists from the university got together with those from the Eidgenossische Technische Hochschule (ETH), for a joint colloquium. Pieter Debye, the ETH professor of physics, ran the meetings and asked Schrödinger to give a talk on de Broglie's work. In the eyes of his colleagues, Schrödinger was an accomplished and versatile theoretician who had made solid but unremarkable contributions in his 40-odd papers that spanned areas as diverse as radioactivity, statistical physics, general relativity and colour theory. Among these were a number of well-received review articles that demonstrated his ability to absorb, analyse and organise the work of others.
On 23 November Felix Bloch, a 21-year-old student, was present when 'Schrödinger gave a beautifully clear account of how de Broglie associated a wave with a particle and how he could obtain the quantization rules of Niels Bohr and Sommerfeld by demanding that an integer number of waves should be fitted along a stationary orbit'.10 With no experimental confirmation of wave-particle duality, which would come in 1927, Debye found it all far-fetched and 'rather childish'.11 The physics of a wave – any wave, from sound to electromagnetic, even a wave travelling along a violin string – has an equation that describes it. In what Schrödinger had outlined there was no 'wave equation'; de Broglie had never tried to derive one for his matter waves. Nor had Einstein after he read the French prince's thesis. Debye's point 'sounded quite trivial and did not seem to make a great impression', Bloch still remembered 50 years later.12
Schrödinger knew that Debye was right: 'You cannot have waves without a wave equation.'13 Almost at once he decided to find the missing equation for de Broglie's matter waves. After returning from his Christmas holiday, Schrödinger was able to announce at the next colloquium held early in the New Year: 'My colleague Debye suggested that one should have a wave equation; well, I have found one!'14 Between one meeting and the next, Schrödinger had taken de Broglie's nascent ideas and developed them into a fully-blown theory of quantum mechanics.
Schrödinger knew exactly where to start and what he had to do. De Broglie had tested his idea of wave-particle duality by reproducing the allowed electron orbits in the Bohr atom as those in which only a whole number of standing electron wavelengths could fit. Schrödinger knew that the elusive wave equation he sought would have to reproduce the three-dimensional model