First English language edition, first impression, of Lemaître's popular book on what would become known as the Big Bang theory. First published as L'Hypothese de l'Atome Primitif in the same year. A very attractive copy, uncommon in the dust jacket.

Georges Lemaître (1894-1966) was a Belgian Catholic priest who earned his PhD in physics at MIT in 1927 and worked with Arthur Eddington and Harlow Shapley. That same year he published a paper in the Proceedings of the Scientific Society of Brussels positing a solution to Einstein's equations of general relativity that predicted an expanding universe. Though the paper initially received little attention, Lemaître realised that his solution tallied with Edwin Hubble's new discoveries about galaxies, and in 1930 he and Eddington had an English translation published.

'Together with Hubble's observations, Lemaître's paper convinced the majority of astronomers that the universe was indeed expanding, and this revolutionized the study of cosmology. A year later, Lemaître explored the logical consequences of an expanding universe and boldly proposed that it must have originated at a finite point in time. If the universe is expanding, he reasoned, it was smaller in the past, and extrapolation back in time should lead to an epoch when all the matter in the universe was packed together in an extremely dense state. Appealing to the new quantum theory of matter, Lemaître argued that the physical universe was initially a single particle - the "primeval atom" as he called it - which disintegrated in an explosion, giving rise to space and time and the expansion of the universe that continues to this day. This idea marked the birth of what we now know as Big Bang cosmology' (Sother & deGrasse Tyson, Cosmic Horizons, American Museum of Natural History).

First edition; 8vo; later pencilled note to the rear free endpaper, very light spotting to the edges of the text block, contents faintly toned; original green cloth, titles to spine in silver, spine a little rolled, cloth fresh, an excellent copy in the price-clipped, lightly rubbed, and toned jacket with a few small spots and nicks, and two very short closed tears; 186 pp.