Einstein as a Transitional Figure: The Birth of Wave Mechanics

Abstract We now leave the period of the old quantum theory and turn to the time of transition, during which matter waves were being discussed by a tiny group of physicists at a time when matter wave mechanics had not yet been discovered. This period begins in September 1923 with two brief communications by Louis de Broglie to the French Academy of Sciences [Bl, B2]. It ends in January 1926 with Schroedinger’s first paper on wave mechanics [S1). The main purpose of this chapter is to stress Einstein’s key role in these developments, his influence on de Broglie, de Broglie’s subsequent influence on him, and, finally, the influence of both on Schroedinger. Neither directly nor indirectly did Einstein contribute to an equally fundamental development that preceded Schroedinger’s discovery of wave mechanics: the discovery of matrix mechanics by Heisenberg [H1]. Therefore, I shall have no occasion in this book to comment in any detail on Heisenberg’s major achievements.