Lemaître, Georges Henri Joseph Édouard (1894-1966)

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Lemaître with Albert Einstein. Source: Kragh, Helen, "Georges Lemaître, een boegbeeld van de kosmologie",p. 123.

Cosmologist and priest, born on 17 July 1894 in Charleroi and died in Leuven on 20 June 1966. Lemaître was the designer of a model of the expansion of the universe from a primitive atom, and is therefore called the "father of the big bang".

Biography

Lemaître attended Latin-Greek at the Collège du Sacré-Coeur in Charleroi. After a preparatory year of mathematics and physics at the Collège Saint-Michel, he enrolled at the University of Leuven in 1911 to study Engineering and Philosophy. On 25 July 1913, he became a candidate in engineering sciences. He completed his first Ph.D on 21 July 1914. However, when World War I broke out, Lemaître was forced to interrupt his studies . He volunteered for army service and became an artillery adjutant. After the war, in April 1919, the young man resumed his studies, but also enrolled in the candidature course in mathematics and physics. On 27 November 1919, he obtained his baccalaureate in thomistic philosophy. Finally, on 31 July 1920, he also obtained his doctorate in mathematics and physics. His supervisor was Charles-Jean de La Vallée Poussin. In October the same year, Lemaître entered the seminary in Mechelen. On 22 September 1923, he received his priestly ordination.

In 1923, Lemaître was one of the lucky ones who was able to study in England and the USA through funds from the Belgian government and the Commission for Relief in Belgium. At Cambridge University, the young priest joined the team of Arthur Eddington (1882-1944) as a student researcher. After a year, he moved from Cambridge in England to the American Massachusetts, where Lemaître, until 1925, prepared a doctorate at the Institute of Technology (M.I.T) on "The gravitational field in a fluid sphere of uniform invariant density according to the theory of relativity". For this, he received the Ph.D. degree in physics in July 1927. During his stay in America, Lemaître also worked for a time as an intern at the Harvard observatory and visited other observatories. He also met Edwin Hubble there. At the California Institute of Technology, he met Robert Millikan, one of the pioneers in cosmic ray research. At the Lowell Observatory in Flagstaff, Arizona, he met Vesto Slipher, who had observed a redshift in the spectra of most spiral nebulae. After his return, Lemaître was appointed part-time lecturer and then full professor at the University of Leuven. There, the triple doctor taught relativity, history of mathematics and natural sciences and mathematical methodology. It was in Leuven that he worked on his hypothesis of the dynamical and expanding universe on which he published in 1927 his later famous article Un Univers homogène de masse constante et de rayon croissant rendant compte de la vitesse radiale des nébuleuses extragalactique.

Despite his appointment in Leuven, Lemaître stayed in the United States several more times during the 1930s. A first stay, from August 1932 to February 1933, was funded by the C.R.B. Initially Lemaître stayed at Harvard College Observatory and at M.I.T, but after Christmas 1932 he moved to Pasadena to work at the California Institute of Technology. Here he met Albert Einstein (1879-1955). After a brief stay in Leuven, Lemaître was a visiting professor at the Catholic University of America in Washington from September 1933 to March 1934 . There he lectured on the astronomical applications of relativity. From September 1934 to June 1935, the Belgian priest stayed at the School of Mathematics at Princeton's Institute of Advanced Studies, where Einstein had a permanent residence. In February 1938, Lemaître returned to America once more, this time as a visiting professor in the Department of Mathematics at the University of Notre Dame du Lac in Indiana. On the eve of World War II, he was back in Leuven.

World War II interrupted Lemaître's intense international contacts. He and his family tried to flee, an attempt that failed. Because of the damage to his house caused by a bombardment, Lemaître was forced to move to Brussels. The University of Leuven resumed teaching at the end of June 1940. However, the presence of students from the ULB - the Brussels university had closed its doors in November 1941 - caused religious tensions. An intervention by Lemaître with the rector ensured that these students were exempted from the usual religious obligations.

In 1964, Lemaître was granted emeritus status. At the end of that year, he suffered a heart attack. Afterwards, his health remained very precarious.

Lemaître became a member of the Société scientifique de Bruxelles during his seminary days. He also became a member of Les Amis de Jésus, a fraternity for priests. On 27 July 1935, he became an honorary canon at the Saint Rombouts Chapter in Mechelen. In 1933, Lemaître became corresponding member of the Académie royale des Sciences et Belles-Lettres de Bruxelles and ordinary member in 1941. In 1949, he became director of the Class of Sciences. On 1 June 1937, he became a founding member of the Pontifical Academy of Sciences in Rome. He was president of this institute from 27 March 1960 until his death. He bacame a member of the Royal Astronomical Society of London on 9 June 1939. He was a Grand Officer in the Order of Leopold.

Works

The young Lemaître had a strong interest in Einstein's theory of relativity, which was not very well-known in the Belgian physics community at the time. Théophile De Donder was the only one who studied the theory. His school therefore had an important influence on Lemaître. He also studied several publications by Henri Henri Louis Vanderlinden including La gravifique. In the 1920s and 1930s, Georges Lemaître had spent much time abroad and had established close friendships with Einstein, Dirac, Schrödinger, Hubble, Shapley, Eddington, Tolman and Russell. He did not create a school of cosmology, but he left a long-lasting mark on Belgian science through his collaborators and students. Louis Bouckaert and Charles Manneback were students of his.

Physical cosmology, the expanding universe and the Big Bang

Georges Lemaître was a pioneer in modern physical cosmology. He formulated his theory of the expanding universe in 1927 with the article Un Univers homogène de masse constante et de rayon croissant rendant compte de la vitesse radiale des nébuleuses extragalactiques. In it, he also calculated the constant at which the expansion occurred. His theorem was initially rejected by Einstein, who stuck to his own static model of the universe. Lemaître's article was initially little noticed by his colleagues. The turnaround came only in 1930 when Hubble's observations provided evidence for the expanding universe. This forced theoretical astronomy to accept that the universe was not static, as had been assumed until then. With the 1927 (re)discovery of Lemaître's theory, cosmology underwent an irreversible paradigm shift. Lemaître became instantly world-renowned.

Lemaître, Georges, Évolutions temporelles du rayon de l’Univers en fonction de la constante cosmologique pour un espace de courbure positive, 1927, Archives de l'Université catholique de Louvain, Archives Georges Lemaître, BE A4006 FG LEM-836.
Source: UCL Archives

In doing so, Lemaître was the first to propose in 1931, in the framework of Einstein's general theory of relativity, a model of the expansion of the universe from a much smaller and hotter volume in which mass and energy - what Lemaître called a 'cosmic egg' - are concentrated. It is a model in which the universe has a finite age and was created by an expansion of a primordial atom, in the distant past. In doing so, Lemaître also estimated that the age of the universe had to be between 10 and 20 billion years. Here, Lemaître introduced quantum physics into astrophysics, his vision being very closely aligned with Niels Bohr's quantum physics. This contribution was the basis of the Big Bang theory, which he successfully elaborated even further in the article L'univers en expansion. From then on, Lemaître also gained international recognition. His theory came to be known as the "big bang" theory. However, it also inflamed the debate between religion and science. As a priest, Lemaître was forced time and again to point out the distinction between his scientific work and his faith. He himself did not want his big bang hypothesis to be played off against the theological understanding of creation.

Lemaître was also interested in cosmic rays and from 1933 to 1955 devoted some 15 articles to the study of their orbits in the Earth's magnetic field.

After his death, the role Lemaître played in the development of the new view of the universe was underexposed for a long time. The hypotheses of the expanding universe and the constant (the "Hubble constant") were subsequently attributed to Hubble. Outside Leuven, Lemaître's cosmological theories received very little attention in the Belgian scientific community for a long time. Only since the 1980s has his name reappeared in this history of science and his pioneering work has been increasingly recognised.
In 2018 Hubble's law was renamed to the Hubble-Lemaître law by the International Astronomical Union in recognition of the work Lemaître had done.

Mathematical publications

After World War II, Lemaître's attention shifted to the problems of celestial bodies and numerical methods. He was instrumental in developing the Computer Centre at the University of Leuven. In 1958, he purchased the first computer for this university. He also contributed to mathematics, including on the theory of elliptic integrals, numerical analysis, elementary arithmetic and theoretical mechanics. His doctoral dissertation dealt with the approximation of functions of multiple change equals by polynomials. The study of the motion of three point masses subjected to Newton's law of gravitation led to a system of differential equations involving singularities corresponding to collisions between the bodies. The regularisation of this problem consists in the introduction of new coordinates that make the double shocks disappear. Such a coordinate system was introduced by Georges Lemaître between 1952 and 1954 and bears his name. He was also passionate about electronic calculators. He was interested in teaching basic calculation techniques and suggested the use of new numerals.

Lemaître received several awards and recognitions for his research. In 1934, he won the first Francqui Prize for the mathematical, physical and chemical sciences. In the same year, he was the first laureate of the Mendel Medal. On 30 May 1934, he received an honorary doctorate from McGill University (Montreal). On 10 June 1936, he was laureate of the Prix Janssen of the Société Astronomique de France. In 1950, he was awarded the Ten-Yearly Prize of the Belgian Government for Applied Mathematical Sciences for the period 1933-1942. In 1953 he received the first Eddington Medal, awarded by the Royal Astronomical Society.

Publications

• A selection of his publications and a list of his publications can found in: LEMAÎTRE, Georges. Georges Lemaître et l'Académie royale de Belgique: oeuvres choisies et notice biographique. Classe des sciences, Académie royale de Belgique, 1995.
• See also the Georges Lemaître Archives on the website of the UCL Archives.

Bibliography

• BRIEN, Paul, "Georges Lemaître", in: Florilège des sciences en Belgique pendant le 19^e et le début du 20^e, Brussel : Académie royale de Belgique Classe des sciences, 1968, 97-113.
• MANNEBACK, Charles, "Notice sur Monseigneur Georges Lemaître membre de l’Académie", in: Annuaire de l’Académie royale des Sciences, des Lettres et des Beaux-Arts de Belgique, 1974, 87-115.
• MANNEBACK, Charles, "Lemaître (Georges-Henri-Joseph-Édouard, Mgr", in: Biographie nationale, t. 38, col. 453-465.
• "G.Lemaître", in: Cent Wallons du siècle, Charleroi: Institut Jules Destrée, 1995.
• STOFFEL, Jean-François Stoffel (éd.), Georges Lemaître, savant et croyant. Actes du colloque tenu à Louvain-la-Neuve le 4 novembre 1994 [suivi de] La physique d'Einstein, texte inédit de Georges Lemaître, Turnhout : Brepols, 1996.
• LAMBERT, Dominique, "Monseigneur Georges Lemaître et le débat entre la cosmologie et la foi", in: Revue Théologique de Louvain, 28 (1997), 28-53 en 227-243.
• LUMINET, Jean-Pierre, L'invention du big bang, Parijs : Éditions du Seuil, 1997.
• LAMBERT, Dominique, Un atome d'univers, Brussel: éditions Lessius, éditions Racine, 2000.
• KRAGH, Helge, "Georges Lemaître, een boegbeeld van de kosmologie", in: Robert Halleux, Geert Vanpaemel, Jan Vandersmissen en Andrée Despy-Meyer (red.), Geschiedenis van de wetenschappen in België 1815-2000, Brussel: Dexia, 2001, vol. 2, 123-130.
• LAMBERT, Dominique, "Temps et Création. Quelques remarques à partir de la cosmologie de Georges Lemaître", in: Théophilyon, t.6, 2001, p. 375-393.
• "Lemaître, le père du Big Bang", in: Les génies de la sciences, avril 2007.
• ROMBAUT, Hans en WAELKENS, Christoffel, "Georges Lemaître", in: Nationaal Biografisch Woordenboek, vol.19, Brussel: Paleis der Academiën, 2009, kol. 585-609.
• NUSSBAUMER H., BIERI, L., Discovering the Expanding Universe, Cambridge University Press, 2009.
• LIVIO, Mario, "Mystery of the missing text solved", in: Nature, 479 (2011), 171–173.