Prussia hired Einstein to think, not to teach. Within two years he gave its Academy a new law of gravity.

Newtonian gravity, treating light as particles, gives a deflection of 0.875″ for a ray grazing the edge of the sun. The field equations of November 1915 double it. Only a total eclipse, darkening the sun, would let anyone photograph the stars beside it and measure the shift.

The test fell to two British parties on 29 May 1919. Frank Dyson, the Astronomer Royal, coordinated them from England; Arthur Eddington went to Príncipe, off West Africa, and Charles Davidson and Andrew Crommelin to Sobral in Brazil. Not every plate agreed: the plates from the larger astrograph at Sobral were discounted because the stars were out of focus. The rest pointed to Einstein.

The eclipse plates had to be measured against photographs of the same stars taken at night, when the sun was elsewhere in the sky. The verdict came at a joint meeting of the Royal Society and the Royal Astronomical Society on 6 November 1919. The next day’s Times headline ran: “Revolution in Science” · “New Theory of the Universe” · “Newtonian Ideas Overthrown”.

In between, Einstein’s own life changed. He was divorced in February 1919, and married his cousin Elsa on 2 June 1919, four days after the eclipse.

In 1929 the city’s Magistrat decided to give Einstein a plot by the water for his 50th birthday. The plan fell apart in the city council, where conservatives and nationalists campaigned against him. Einstein declined any gift from Berlin and bought the plot, in Caputh, himself; the building permit came on 21 June 1929.

His architect was Konrad Wachsmann, 28 years old, who designed a prefabricated timber house. The Einsteins spent the summers of 1930 to 1932 there, sailing the Havel in his boat, the Tümmler. In the summer of 1933 the regime confiscated the house and the boat.

Einstein’s resignation, dated 28 March 1933, was noted by the Academy’s plenum on 30 March 1933. Two days later the Academy issued its statement: it had “no reason to regret Einstein’s withdrawal”. Lenard’s and Stark’s “Deutsche Physik” movement was already attacking relativity as “Jewish physics”.

The flat in the Haberlandstraße was searched by the SA several times that spring. Most of the furniture, his library and his papers were packed in the summer of 1933 and sent, with the help of the French embassy, to Paris and then to Princeton. The house itself was destroyed by bombs in the Second World War. On 24 March 1934 Germany stripped Einstein of his citizenship.