Georges Lemaître

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Lore & Background

Georges Lemaître was born in Charleroi, Belgium, the eldest of four children of Joseph Lemaître, a prosperous industrialist who owned a glassworks factory, and Marguerite née Lannoy, daughter of a brewer. He studied engineering at the Catholic University of Louvain starting in 1911, but interrupted his studies in 1914 to volunteer for the Belgian army during World War I. He participated in the Battle of the Yser and later received the Belgian War Cross with bronze palm from King Albert I. After the war, he abandoned engineering for physics and mathematics, earning his doctorate in science in 1920 with a thesis on the approximation of functions of several real variables. He was ordained a priest on 22 September 1923 by Cardinal Mercier. With Cardinal Mercier's support, he traveled to England, working with Arthur Eddington at the University of Cambridge in 1923–1924, and to the United States, working with Harlow Shapley at the Harvard College Observatory and at MIT in 1924–1925. Lemaître became a professor of physics at Louvain from 1927 until his retirement in 1964. He was a pioneer in using computers in physics research and, with Manuel Sandoval Vallarta of MIT, showed that cosmic rays are deflected by Earth's magnetic field and must carry electric charge. He also argued for including a positive cosmological constant in the Einstein field equations to help reconcile the age of the universe inferred from the Hubble–Lemaître law with the ages of the oldest stars and the abundances of radionuclides. Lemaître remained a secular priest of the Archdiocese of Mechelen until his death. He was made an honorary canon of St. Rumbold's Cathedral in 1935. In 1960, Pope John XXIII appointed him as Domestic Prelate, entitling him to be addressed as 'Monsignor,' and in that same year he was appointed president of the Pontifical Academy of Sciences, a post he occupied until his death. He received the first Eddington Medal of the Royal Astronomical Society in 1953 for his work on the expansion of the universe.

Reader's Guide

Georges Lemaître's significance lies in his foundational role in modern cosmology. He was the first to argue that the recession of galaxies is evidence of an expanding universe and to connect the observational Hubble–Lemaître law with the solution to the Einstein field equations for a homogenous and isotropic universe. His hypothesis of the primeval atom became the first formulation of the Big Bang theory. Lemaître also advanced astrophysics by demonstrating, with Manuel Sandoval Vallarta, that cosmic rays are deflected by Earth's magnetic field and must carry electric charge. He argued for including a positive cosmological constant in the Einstein field equations, both for conceptual reasons and to reconcile the age of the universe with the ages of stars and radionuclides. Lemaître opposed the idea that faith and science are opposed, but also acknowledged that concordism was invalid, stating: 'Should a priest reject relativity because it contains no authoritative exposition on the doctrine of the Trinity? Once you realize that the Bible does not purport to be a textbook of science, the old controversy between religion and science vanishes.' His legacy endures as a pioneer who combined rigorous scientific inquiry with his religious vocation.

Did You Know?

• Lemaître was one of only five rank-and-file troops to receive the Belgian War Cross with bronze palm from King Albert I after World War I.
• During a leave in World War I, Lemaître visited the French Catholic writer Léon Bloy and shared an essay attempting to reconcile Genesis with modern science; Bloy advised him to study the Church Fathers.
• Lemaître's 1927 paper on the expanding universe had little initial impact because the Annales de la Société Scientifique de Bruxelles were not widely read outside Belgium.
• Lemaître was a member of the Fraternité sacerdotale des Amis de Jésus, a priestly fraternity created by Cardinal Mercier, and took vows of chastity, poverty, obedience, and a special vow of immolation.
• In 1960, Pope John XXIII appointed Lemaître as Domestic Prelate, entitling him to be addressed as 'Monsignor,' and he served as president of the Pontifical Academy of Sciences from 1960 until his death.