Max Abraham (26.03.1875 - 16.11.1922) was a German theoretical physicist. He was born in Danzig (now Gdańsk). He graduated from the University of Berlin (1897), where he worked as an assistant to M. Planck. In 1900—09 he was professor at the University of Göttingen and in 1910—1914 at the University of Milan; after the war he was professor again in Milan, then in Stuttgart and Aachen.His research was in the field of mathematical physics, electrodynamics, electron theory and the theory of gravitation. He gave classical Maxwellian electrodynamics its finished modern form and did much towards the creation of electron theory. In 1902—1903 he formulated the first hypothesis about the structure of the electron, according to which the electron is a rigid sphere with a uniformly distributed charge. Starting from this model, Abraham was one of the first to introduce the concept of electromagnetic momentum, and he gave a formula for the way the electromagnetic mass of the electron depends on its velocity. In 1912 he proposed a theory of gravitation which generalises Newton's but does not take account of Einstein's equivalence principle.