This chapter discusses the historical impact of the advent of general relativity, in 1916, on British physicists and astronomers, and, at a personal level, its effect on Eddington's life. In this way I prepare for the next chapter in which I shall show that the intellectual effect of the general theory on Eddington was to accentuate certain philosophical ideas which he already had. These ideas take us some way along the road to understand the mystery described in Chapter 1.

The genesis of general relativity

We left Eddington reinstalled in Cambridge in 1914, clearing up his earlier astronomical work and just about to begin the investigation directed towards the understanding of the mechanism of the Cepheid variables. By that time the dust was beginning to settle on Einstein's 1905 paper in which the concept of time had been so strikingly changed. The Cambridge aether-theorists were working their way towards reconciliation but, doubtless, were more concerned in 1914 with the international disaster that was to sweep away the comforts of the long Edwardian summer. Then in 1915–16 there appeared a new paper by Einstein (Einstein 1916) which followed up his earlier one by changing completely the concept of space. This is usually described as Einstein's successful attempt to extend the idea of relativity to include gravitation. The problem of gravitation was considered particularly important because special relativity seemed to give a privileged position to the other well-known field theory, electromagnetism. The Lorentz transformations left Maxwell's equations unchanged. Yet in some ways gravitation was the more fundamental field because of its universal action.