The present volume, set in the turbulent post-World War I period, finds Einstein awaiting news of the 1919 British eclipse expedition to test the general relativistic prediction of the deflection of starlight by the sun. With the expedition's success, he becomes the first science celebrity of our age. Deeply interested in the other, stellar redshift test of his theory, Einstein supports astronomers engaged in experimental work on the issue. Piqued by early suggestions of a unified field theory, he ponders how to unify gravitation and electromagnetic field theory and also works to resolve...

The first half of this volume presents a substantial amount of heretofore unavailable correspondence. From among family letters closed for twenty years after the death of Margot Einstein, who donated them to the Albert Einstein Archives in Jerusalem, the volume presents, for the first time, letters written by Einstein's sons, the adolescent Hans Albert and little Eduard, and numerous letters written by Einstein to his cousin and future second wife Elsa Einstein. Combined with newly available correspondence with his close friend Heinrich Zangger, this supplementary correspondence provides...

The more than one thousand letters and several dozen writings included in this volume cover the years immediately before the final formulation of new quantum mechanics. The discovery of the Compton effect in 1923 vindicates Einstein's light quantum hypothesis. Niels Bohr still criticizes Einstein's conception of light quanta and advances an alternative theory, but Walther Bothe and Hans Geiger perform a difficult experiment that decides in favor of Einstein's theory. At the same time, Satyendranath Bose sends a new quantum theoretical derivation of Planck's law to Einstein and he discovers...