This article is about the Belgian physicist and priest. For the spacecraft, seeGeorges Lemaître ATV. For the American physician, seeGeorge D. LeMaitre. For the professional road bicycle racer, seeGeorges Lemaire.
Lemaître was a professor of physics at Louvain from 1927 until his retirement in 1964. A pioneer in the use ofcomputers in physics research, in the 1930s he showed, withManuel Sandoval Vallarta of MIT, thatcosmic rays are deflected by theEarth's magnetic field and must therefore carryelectric charge. Lemaître also argued in favor of including a positivecosmological constant in the Einstein field equations, both for conceptual reasons and to help reconcile theage of the universe inferred from the Hubble–Lemaître law with the ages of the oldest stars and the abundances ofradionuclides.[8]
Georges Lemaître was born inCharleroi, Belgium, the eldest of four children of Joseph Lemaître, a prosperous industrialist who owned a glassworks factory,[11] and Margueritenée Lannoy, who was the daughter of a brewer.[12] Georges was educated at theCollège du Sacré-Cœur, a grammar school in Charleroi run by theJesuits.[11] In 1910, after a fire destroyed the glassworks, the family moved toBrussels, where Joseph had found a new position as manager for the French bankSociété Générale. Georges then became a pupil at another Jesuit school,St. Michael's College.[11] Although he had expressed his interest in pursuing a religious vocation, his father convinced him to attend university first and to train as amining engineer.[citation needed]
Georges Lemaître (left) and his younger brother Jacques (right) in uniform after they volunteered for the Belgian Army on 7 August 1914
In 1911, Lemaître began to study engineering at theCatholic University of Louvain. In 1914, after the outbreak ofWorld War I, Lemaître interrupted his studies to volunteer for theBelgian army. He participated in theBattle of the Yser, in which the Belgians succeeded in halting theGerman advance. When the army transferred him from the infantry to artillery, Lemaître was sent to complete a course onballistics. His prospects of promotion toofficer rank were dashed after he was marked down forinsubordination as a result of pointing out to the instructor a mathematical error in the official artillery manual.[11] However, at the end of hostilities he received the BelgianWar Cross with bronze palm,[13] one of only five rank-and-file troops to receive that award from the hands of KingAlbert I.[11]
Lemaître was an admirer of the French Catholic writerLéon Bloy.[14] During a leave from his military service in World War I, Lemaître visited Bloy inBourg-la-Reine, near Paris, where Bloy was living in a house that had belonged to his late friend and fellow writerCharles Péguy.[14] On that occasion, Lemaître shared with Bloy an essay entitledLes trois premières paroles de Dieu ("The First Three Words of God"), in which he attempted to reconcile theGenesis creation narrative with modern science.[14] Bloy, however, was unimpressed and advised Lemaître to grow more familiar with the works of theChurch Fathers.[15] This experience may have contributed to Lemaître's abandonment of the "concordist" effort to reconcile theological and scientific knowledge at a common intellectual level.[16] Years later, Einstein questioned Lemaître on the idea of concordism. Lemaître opposed the idea that faith and science are opposed, but also acknowledged that concordism was invalid, arguing, "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"[17]
Lemaître had considered joining the Jesuits or theBenedictines, but finally decided to prepare instead for thediocesanpriesthood.[20] Between 1920 and 1923 he was a student at theMaison Saint-Rombaut, theseminary for "late vocations" (i.e., mature students for the priesthood) of theArchdiocese of Mechelen. It was during his spare time at the seminary that Lemaître learned thegeneral theory of relativity. He wasordained as a priest on 22 September 1923 by Cardinal Mercier.[21][22] As a diocesan priest inFrench-speaking Belgium, he was known as "Abbé Lemaître".
At the seminary, Lemaître joined theFraternité sacerdotale des Amis de Jésus ("Priestly fraternity of the Friends of Jesus"), which had been created by Cardinal Mercier to promote the spiritual life of select diocesan priests and which was established canonically by his successor, CardinalJozef-Ernest van Roey. As a member of the fraternity, Lemaître tookvows ofchastity, poverty, and obedience, as well as specialvotum immolationis ("vow of immolation") promising complete submission to the person of Christ. In the spirit of the fraternity, Lemaître did not discuss his involvement with theAmis de Jésus outside of the group, but he regularly made silent retreats in a house calledRegina Pacis ("Queen of Peace") inSchilde, nearAntwerp, and also undertook translations of themystical works ofJohn of Ruusbroec.[23]
A young Georges Lemaître in clerical dress, early 1920s
In 1922, Lemaître applied to the Belgian Ministry of Sciences and Arts for a travel bursary. As part of that application, he submitted a thesis on the astronomical implications of general relativity that included a demonstration that the most general form of theEinstein field equations included acosmological constant term. The jury awarded Lemaître a prize of 8,000Belgian francs.[11]
Cardinal Mercier supported Lemaître's scientific work and helped him to obtain further financial support for a two-year visit to Great Britain and the United States.[11] Only ten days after his ordination, Lemaître left Belgium to take up residence at St Edmund's House, then a community of Catholic priests studying for degrees at theUniversity of Cambridge and which would later becomeSt Edmund's College. At Cambridge, Lemaître was a research associate in astronomy and worked with the eminent astrophysicistArthur Eddington, who introduced Lemaître to moderncosmology,stellar astronomy, andnumerical analysis.[11]
On his return to Belgium in 1925, Lemaître became a part-time lecturer at theCatholic University of Louvain and began working on a report that was finally published in 1927 in theAnnales de la Société Scientifique de Bruxelles ("Annals of the Scientific Society of Brussels"), under the titleUn Univers homogène de masse constante et de rayon croissant rendant compte de la vitesse radiale des nébuleuses extragalactiques ("A homogeneous Universe of constant mass and growing radius accounting for the radial velocity of extragalactic nebulae").[3] There he developed (independently of the earlier work ofAlexander Friedmann) the argument that the equations ofAlbert Einstein'sgeneral theory of relativity implied that the Universe is not static (seeFriedmann equations). Lemaître connected this prediction to what he argued was a simple relation of proportionality between the averagerecessional velocity of galaxies and their distance to the Earth.
This 1927 paper had little impact because theAnnales de la Société Scientifique de Bruxelles were not widely read by astronomers or physicists outside of Belgium. Moreover, the initial state that Lemaître proposed for the Universe in this 1927 paper was Einstein's model of a static universe with acosmological constant,[25] but at this time, Einstein insisted that only a static picture of the universe was physically acceptable. Lemaître later recalled Einstein saying to him: "vos calculs sont corrects, mais votre physique est abominable" ("your calculations are correct, but your physics is abominable").[26]
Also in 1927, Lemaître returned to MIT to defend his doctoral dissertation onThe gravitational field in a fluid sphere of uniform invariant density according to the theory of relativity.[27] Upon obtaining that second doctorate, Lemaître's was appointedordinary professor at the Catholic University of Louvain.
According to theBig Bang theory, theuniverse emerged from an extremely dense and hot state (singularity).Space itself has been expanding ever since, carryinggalaxies with it, like raisins in a rising loaf of bread. The graphic scheme above is an artist's conception illustrating the expansion of a portion of a flat universe.
In 1929, the US astronomerEdwin Hubble published a paper in theProceedings of the National Academy of Sciences of the United States of America showing, based on better and more abundant data than what Lemaître had had at his disposal in 1927, that, in the average, galaxies recede at a velocity proportional to their distance from the observer. Although Hubble himself did not interpret that result in terms of an expanding Universe, his work attracted widespread attention and soon convinced many experts, including Einstein, that the Universe is not static. The proportionality between distance and recessional velocity for galaxies has since been commonly known as "Hubble's law", but in 2018 theInternational Astronomical Union (IAU) adopted a resolution recommending that it be referred to as the "Hubble-Lemaître law".[2]
In 1931, an English translation of Lemaître's 1927 report appeared in theMonthly Notices of the Royal Astronomical Society, with a commentary byArthur Eddington that characterized Lemaître's work as a "brilliant solution" to the outstanding problems of cosmology and a response by Lemaître to Eddington's comments.[28] This English translation, however, omitted Lemaître's estimate of the "Hubble constant" for reasons that remained unclear for many years.[29] The issue was clarified in 2011 byMario Livio: Lemaître himself removed those paragraphs when he prepared the English translation, opting instead to cite the stronger results that Hubble had published in 1929.[5]
In March 1931 Lemaître wrote a brief report in which he proposed that the universe expanded from a single initialquantum, which he called the "primeval atom". This was published inNature,[6] and later that year Lemaître participated in a public colloquium on "The Evolution of the Universe" held in London on 29 September 1931 to mark the centenary of theBritish Association for the Advancement of Science.[30]
Lemaître and Einstein met on four occasions: in 1927 inBrussels, at the time of aSolvay Conference; in 1932 in Belgium, at the time of a cycle of conferences in Brussels; in California in January 1933;[35] and in 1935 atPrinceton. In 1933 at theCalifornia Institute of Technology, after Lemaître presented his theory, Einstein stood up, applauded, and is reported to have said, "This is the most beautiful and satisfactory explanation of creation to which I have ever listened."[36] However, there is disagreement over the reporting of this quote in the newspapers of the time, and it may be that Einstein was not referring to the "primordial atom" theory as a whole, but only to Lemaître's proposal thatcosmic rays could be "fossils" of the primordial decay.
Lemaître argued that cosmic rays could be a "fossil radiation" produced by the decay of the primeval atom. Much of his work in the 1930s was focused on cosmic rays. In 1946, Lemaître published a book onL'Hypothèse de l'Atome Primitif ("The Primeval Atom Hypothesis"), which was translated into Spanish in the same year and into English in 1950. The astronomerFred Hoyle introduced the term "Big Bang" in a 1949 BBC radio broadcast to refer to cosmological theories such as Lemaître's, according to which the Universe has a beginning in time.[37][38] Hoyle remained throughout his life an opponent of such "Big Bang" theories, advocating instead asteady-state model of an eternal Universe.
In 1948, theoreticiansRalph Alpher,Robert Herman, andGeorge Gamow predicted a different form of "fossil radiation" based on the Big Bang model, now known as thecosmic microwave background (CMB). The CMB was produced when the contents of the expanding Universe cooled sufficiently that they became transparent toelectromagnetic radiation. In 1965, shortly before his death, Lemaître learned from his assistantOdon Godart of therecent discovery of the CMB by radio astronomersArno Penzias andRobert Wilson. That discovery convinced most experts of the scientific validity of the Big Bang.
Lemaître maintained throughout his career that theEinstein field equations should incorporate a positivecosmological constant () term. His reasoning was based on both theoretical and empirical considerations. Lemaître argued in 1958 that "if some extension of relativity towards a broader field, such asquantum theory, has to be achieved the superfluous term shall be very much welcomed".[39] He also held that theaccelerating expansion of the universe induced by could help to reconcile theage of the universe deduced from theHubble-Lemaître law with the ages of the oldest stars and the observed abundances ofradionuclides.[8] Lemaître argued for a positive cosmological constant both in print and in correspondence with Einstein, who was skeptical about the reality of such a term after abandoning hismodel of a static universe in the early 1930s.[8] TheNobel Prize in Physics for 2011 was awarded toSaul Perlmutter,Brian P. Schmidt, andAdam G. Riess for establishing the reality of the universe's accelerating expansion, based on extensive surveys ofType Ia supernovae used as astronomical "standard candles". In the scientific background for that prize, the Royal Swedish Academy of Sciences credited Lemaître with the idea that such an acceleration is driven byvacuum energy, also modernly called in this contextdark energy.[40]
Lemaître viewed his work as a scientist as neither supporting nor contradicting any truths of the Catholic faith, and he was strongly opposed to making any arguments that mixed science with religion,[22] although he held that the two were not in conflict.[41] He was always anxious that his work on cosmology should be judged on purely scientific criteria.
Indeed, it seems that the science of today, by going back in one leap millions of centuries, has succeeded in being a witness to that primordialFiat Lux, when, out of nothing, there burst forth with matter a sea of light and radiation [... Thus modern science has confirmed] with the concreteness of physical proofs the contingency of the universe and the well-founded deduction that about that time the cosmos issued from the hand of the Creator.[42]
Lemaître was reportedly horrified by that intervention and was later able, with the assistance of FatherDaniel O'Connell, the director of theVatican Observatory, to convince the Pope not make any further public statements on religious or philosophical interpretations of matters concerningphysical cosmology.[43]
According to the theoretical physicist and Nobel laureatePaul Dirac,
Once when I was talking with Lemaître about [his cosmological theory] and feeling stimulated by the grandeur of the picture that he has given us, I told him that I thought cosmology was the branch of science that lies closest to religion. However Lemaîtredid not agree with me. After thinking it over he suggested psychology as lying closest to religion.[44]
Georges Lemaître and Andrée Bartholomé using a Burroughs E101 computer in the numerical research laboratory of the Catholic University of Louvain, May 1959 (Archives de l'Université catholique de Louvain)
WithManuel Sandoval Vallarta, whom he had met at MIT, Lemaître showed that the intensity ofcosmic rays varies with latitude because they are composed ofcharged particles and therefore are deflected by theEarth's magnetic field.[45] In their calculations, Lemaître and Vallarta made use of MIT's newdifferential analyzer computer, developed byVannevar Bush.[46] That work disproved the view, advocated among others by the Nobel laureateRobert Millikan, that cosmic rays were composed of high-energy photons. Lemaître and Vallarta also worked on a theory of primary cosmic radiation and applied it to their investigations of the Sun's magnetic field and the effects of the galaxy's rotation.
In 1933, Lemaître found an important inhomogeneous solution ofEinstein's field equations describing a spherical dust cloud, theLemaître–Tolman metric. He became increasingly interested in problems of numerical computation and in the 1930s began to use the most powerfulcalculator available at the time, the mechanicalMercedes-Euklid. In his only work inphysical chemistry, Lemaître collaborated in the numerical calculation of the energy levels of monodeuteroethyelene (a molecule ofethylene with one of itshydrogen atoms replaced bydeuterium).[47]
During theSecond Vatican Council of 1962–65, the pope asked Lemaître to serve on the 4th session of thePontifical Commission on Birth Control.[52] However, since his health made it impossible for him to travel to Rome —he suffered a heart attack in December 1964— Lemaître demurred. He told aDominican colleague, Père Henri de Riedmatten, that he thought it was dangerous for a mathematician to venture outside of his area of expertise.[53] Lemaître died on 20 June 1966, shortly after having learned of the discovery ofcosmic microwave background radiation, which provided solid experimental support for his theory of the Big Bang.[54]
Lemaître was strongly opposed to theLeuven Vlaams ("Flemish Leuven") movement that sought to make instruction at the Catholic University of Leuven monolingual inDutch. With the historianGérard Garitte, in 1962 Lemaître established theAssociation du corps académique et du personnel scientifique de l'Université de Louvain (ACAPSUL, "Association of the faculty and scientific personnel of the University of Louvain") to advocate for the continued use of the French language in that institution.[55] After Lemaître's death, theuniversity was separated into a Dutch-speaking institution,KU Leuven, and a French-speaking institution,UCLouvain, based in the planned town ofLouvain-la-Neuve ("New Leuven") that was built for that purpose just across thelanguage border inWalloon Brabant.
In 2005, Lemaître was voted to the 61st place ofDe Grootste Belg ("The Greatest Belgian"), aFlemish television program on theVRT. In the same year he was voted to the 78th place by the audience of theLes plus grands Belges ("The Greatest Belgians"), a television show of theRTBF. Later, in December 2022, VRT recovered in its archives a lost 20-minute interview with Georges Lemaître in 1964, "a gem", says cosmologistThomas Hertog.[61][62] On 17 July 2018,Google Doodle celebrated Georges Lemaître's 124th birthday.[63] On 26 October 2018, an electronic vote among all members of theInternational Astronomical Union voted 78% to recommend changing the name of the Hubble law to theHubble–Lemaître law.[2][64]
"Un Univers homogène de masse constante et de rayon croissant rendant compte de la vitesse radiale des nébuleuses extra-galactiques".Annales de la Société Scientifique de Bruxelles (in French).47:49–59. 1927a.Bibcode:1927ASSB...47...49L.
^"Obituary: Georges Lemaitre".Physics Today.19 (9):119–121. September 1966.doi:10.1063/1.3048455.
^abc"The week in science: 26 October–1 November 2018".Nature.563 (7729):10–11. 31 October 2018.doi:10.1038/d41586-018-07180-9.PMID30382217.S2CID256770198.The International Astronomical Union recommends that the law should now be known as the Hubble–Lemaître law, to pay tribute to the Belgian priest and astronomer Georges Lemaître, who derived the speed–distance relationship two years earlier than did US astronomer Edwin Hubble.
^Da Re, Mattia; Hiraux, Françoise; Laduron, Clara; Mostaert, Camille."The Great War and a moderate concordism".Georges Lemaître, Father of the Big Bang theory. Retrieved4 June 2025.
^Lemaître G., "Quaternions et espace elliptique, (note présentée lors de la séance du 8 février 1948)",Acta Pontificiae Academiae Scientiarum, 1948,12(8), pp. 57-78
^De Maeseneer, Wim (31 December 2022)."Lang naar gezocht, eindelijk gevonden: VRT vindt interview uit 1964 terug met de Belg die de oerknal bedacht" [Long sought, finally found: VRT finds 1964 interview with Belgian who invented the Big Bang].vrtnws.be (in Dutch). Retrieved4 January 2023.VRT has recovered a lost interview with Georges Lemaître in its archives. He was interviewed about it in 1964 for the then BRT, but until recently it was thought that only a short excerpt of it had been preserved. Now the entire 20-minute interview has been recovered. "A gem," says cosmologist Thomas Hertog.
^Satya Gontcho A Gontcho; Jean-Baptiste Kikwaya Eluo; Gabor, Paul (2023). "Resurfaced 1964 VRT video interview of Georges Lemaître".arXiv:2301.07198 [physics.hist-ph].
Lambert, Dominique (1996). "Mgr Georges Lemaître et les "Amis de Jésus"".Revue Théologique de Louvain (in French).27 (3):309–343.doi:10.3406/thlou.1996.2836.ISSN0080-2654.
Lambert, Dominique (1997). "Monseigneur Georges Lemaître et le débat entre la cosmologie et la foi (à suivre)".Revue Théologique de Louvain (in French).28 (1):28–53.doi:10.3406/thlou.1997.2867.ISSN0080-2654.
Lambert, Dominique (2015). van Bibber, Karl (ed.).The Atom of the Universe: The Life and Work of Georges Lemaître. Translated by Ampleman, Luc. Copernicus Center Press.ISBN978-8378860716.
Berger, A.L., editor,The Big Bang and Georges Lemaître: Proceedings of a Symposium in honour of G. Lemaître fifty years after his initiation of Big-Bang Cosmology, Louvain-Ia-Neuve, Belgium, 10–13 October 1983 (Springer, 2013).
Cevasco, George A (1954). "The Universe and Abbe Lemaitre".Irish Monthly.83 (969).
Farrell, John,The Day Without Yesterday: Lemaître, Einstein and the Birth of Modern Cosmology (Basic Books, 2005),ISBN978-1560256601
Godart, Odon & Heller, Michal (1985)Cosmology of Lemaître, Pachart Publishing House.
McCrea, William H. (1970). "Cosmology Today: A Review of the State of the Science with Particular Emphasis on the Contributions of Georges Lemaître".American Scientist.58 (5).
