(1894–1966) Belgian astronomer and cosmologist
Lemaître was born at Charleroi in Belgium. After serving in World War I, he studied at the University of Louvain in Belgium from where he graduated in 1920. He then attended a seminary at Mailines, becoming ordained as a Roman Catholic priest in 1923. Before taking up an appointment at the University of Louvain in 1925, he spent a year at Cambridge, England, where he worked with Arthur Eddington, and a year in America where he worked at the Harvard College Observatory and the Massachusetts Institute of Technology. He remained at Louvain for the whole of his career, being made professor of astronomy in 1927.
Lemaître was one of the propounders of the big-bang theory of the origin of the universe. Einstein's theory of general relativity, announced in 1916, had led to various cosmological models, including Einstein's own model of a static universe. Lemaître in 1927 (and, independently, Alexander Friedmann in 1922) discovered a family of solutions to Einstein's field equations of relativity that described not a static but an expanding universe. This idea of an expanding universe was demonstrated experimentally in 1929 by Edwin Hubble who was unaware of the work of Lemaître and Friedmann. Lemaître's model of the universe received little notice until Eddington arranged for it to be translated and reprinted in the Monthly Notices of the Royal Astronomical Society in 1931. It was not only the idea of an expanding universe which was so important in Lemaître's work, on which others were soon working, but also his attempt to think of the cause and beginning of the expansion.
If matter is everywhere receding, it would seem natural to suppose that in the distant past it was closer together. If we go far enough back, argued Lemaître, we reach the ‘primal atom’, a time at which the entire universe was in an extremely compact and compressed state. He spoke of some instability being produced by radioactive decay of the primal atom that was sufficient to cause an immense explosion that initiated the expansion.
This big-bang model did not fit too well with the available time scales of the 1930s. Nor did Lemaître provide enough mathematical detail to attract serious cosmologists. Its importance today is due more to the revival and revision it received at the hands of George Gamow in 1946.
Subjects: Astronomy and Astrophysics.