Georges Lemaītre - Scientist of the Day

Georges Lemaītre, a Belgian priest and astronomer, was born July 17, 1894. It is often said that Edwin Hubble, in 1929, announced that the universe is expanding, certainly one of the great cosmological discoveries of the century. Except that Hubble didn’t proclaim any such thing. What Hubble discovered was that more distant galaxies have a larger red-shift than closer galaxies, which one might interpret as the result of an expanding universe, but Hubble did not do so. The man who first proposed the expansion of the universe was Lemaītre, in a paper of 1927, and he did so on no observational evidence at all, arguing instead that Einstein’s equations of general relativity were more compatible with an expanding universe than with a static one. When the relationship between galactic distances and their red-shifts was discovered, it was Lemaītre, not Hubble, who saw the important implication—that the universe must be expanding. And in 1931, when Lemaītre’s work finally became known to English cosmologists, Lemaītre further proposed that the universe must have had a beginning in time as an incredibly dense “primaeval atom”, and the expansion is the result of the explosion of that condensed atom. In our terminology, Lemaītre was the originator of the idea of the Big Bang. It is still common in popular literature to credit Hubble with the expanding universe and George Gamow for the Big Bang idea, but Lemaītre is increasingly getting his due as the originator of both concepts. In 1933, there were several photographs taken of Lemaītre with Einstein, on the occasion of their joint visit to the United States; we see one of them above. Einstein was not too impressed with Lemaītre in 1927, but by 1933 he had come to embrace the expansion of the universe as the only viable solution of his equations of general relativity.

The other image shows the dust jacket of the 1st English edition of Lemaītre’s Primeval Atom (1950).

Dr. William B. Ashworth, Jr., Consultant for the History of Science, Linda Hall Library and Associate Professor, Department of History, University of Missouri-Kansas City