'The Happiest Thought of my Life'
Musz es sein? Es musz sein.
The February 17, 1921, issue of Nature is almost completely devoted to relativity. It appeared at a time when 'in two cases predicted [by general relativity] phenomena for which no satisfactory alternative explanation is forthcoming have been confirmed by observation, and the third is still a subject of inquiry' [L1] The first two phenomena are the precession of the perihelion of Mercury and the bending of light by the sun. Both effects had been calculated by Einstein in 1915. The first agreed very well indeed with long-known observations. The second had waited until 1919 for confirmation. The third was the red shift of radiation, the experimental magnitude of which was still under advisement in 1921.
This issue of Nature appeared at a time when Einstein was already recognized as a world figure, not only by the physics community but by the public at large. Its opening article is by Einstein and begins, 'There is something attractive in presenting the evolution of a sequence of ideas in as brief a form as possible . . .' [E1]. There follow papers by Dyson and Crommelin, the astronomers, by jeans, Lorentz, Lodge, and Eddington, the physicists, and by Hermann Weyl, the mathematician. Also included are the inevitable philosophical contributions. This issue of the journal had been long in coming. The plan for it was conceived a few weeks after the historic November 6, 1919, joint meeting of the Royal Society and the Royal Astronomical Society in London, at which the results of the May 1919 eclipse expeditions had been reported as being in agreement with Einstein's theory. In that same month, Einstein had been approached for a contribution to Nature [L2]. It was he who by his efforts to be 'as brief as possible' caused much delay. In January 1920 his article was almost ready 'but has become so long that I doubt very much whether it can appear in Nature' [E2]. It did not. His short paper which eventually did appear [E1] is quite different from his original manuscript, entitled 'Grundgedanken und Methoden der Relativitätstheorie in ihrer Entwicklung dargestellt.' That paper was never published but has survived. The