His model of an expanding Universe (1927) was superior to that of W. de Sitter in that it took into account mass, gravitation, and the curvature of space. Similar models had been proposed in the early 1920s by the Russian mathematician Alexander Alexandrovich Friedmann (1888–1925). Lemaître argued further (1931) that the quantum theory supported an origin in the explosion of a ‘primeval atom’ or ‘cosmic egg’ into which was originally concentrated all mass and energy. As modified by A. S. Eddington, Lemaître’s model provided the springboard for G. Gamow’s Big Bang theory.