Lemaître a propus primul ceea ce cunoaștem drept teoria Big Bang asupra originii Universului, pe care el a denumit-o „ipoteza atomului inițial” sau „Oul Cosmic”.[24]
Preotul născut la Charleroi a fost primul cercetător care a prezis prin calcule matematice cu 20 de ani mai înainte teoria că universul nu este static, ci este în continuă expansiune. Această dovadă a venit două decenii mai târziu în anul 1965 când Penzias și Wilson descopereau prin telescoape performante ecourile exploziei primordiale, adică a conceptului de Big Bang în forma cunoscută astăzi.
Lemaître însuși și-a descris teoria sa ca „oul cosmic care explodează în momentul creației”. Aceasta a devenit mai bine cunoscută sub numele de „teoria Big Bang”, un termen peiorativ inventat de Fred Hoyle. Cu toate acestea, Lemaître, ca preot, credea că Universul și deci și Pământul au fost create de către Dumnezeu.[25]
Big Bang-ul este compatibil cu crearea lumii din nimic,[26] idee susținută de creștinism începând cu secolul al II-lea d.Hr. și adoptată de iudaism.[27] Fizicienii atei s-au opus inițial din acest motiv adoptării teoriei.[28]
În 1951 papa Pius al XII-lea a declarat că teoria lui Lemaître validează științific catolicismul. Totuși, Lemaître s-a opus acestei proclamații, afirmând că teoria este neutră și că nu este nici legătură și nici contradicție între religie și teoria sa.[29][30] Când Lemaître și Daniel O'Connell, consilierul științific al papei, l-au sfătuit pe papă să nu mai menționeze cosmogonia în public, el a fost de acord.[31] Deși era catolic convins, autorul teoriei era contra amestecării științei cu religia,[32] deși credea că cele două domenii ale experienței umane nu se aflau în conflict.[33]
^Howson, Colin (). Objecting to God. Cambridge University Press. p. 92. ISBN9781139498562. Nor is the agreement conincidental, according to a substantial constituency of religious apologists, who regard the inflationary Big Bang model as direct evidence for God. John Lennox, a mathematician at the University of Oxford, tells us that 'even if the non-believers don't like it, the Big Bang fits in exactly with the Christan narrative of creation'. ... William Lane Craig is another who claims that the Biblical account is corroborated by Big Bang cosmology. Lane Craig also claims that there is a prior proof that there is a God who created this universe.|access-date= necesită |url= (ajutor)
^May, Gerhard (). Creatio ex nihilo [Creation from nothing]. Continuum International. p. xii. ISBN978-0-567-08356-2. Accesat în . If we look into the early Christian sources, it becomes apparent that the thesis of creatio ex nihilo in its full and proper sense, as an ontological statement, only appeared when it was intended, in opposition to the idea of world-formation from unoriginate matter, to give expression to the omnipotence, freedom and uniqueness of God.
^Kragh, Helge. Cosmology and Controversy: The Historical Development of Two Theories of the Universe. Princeton University Press. 1999. pg 259. 'The atheist Bonnor rejected big-bang theory for largely the same reasons as Hoyle did; among these, that it lent support to divine creation. "The underlying motive is, of course, to bring in God as creator," Bonnor stated.'
^Peter T. Landsberg (). Seeking Ultimates: An Intuitive Guide to Physics, Second Edition. CRC Press. p. 236. ISBN9780750306577. Indeed the attempt in 1951 by Pope Pius XII to look forward to a time when creation would be established by science, was resented by several physicists, notably by George Gamow and even George Lemaitre, a member of the Pontifical Academy.
^Steven Soter and Neil deGrasse Tyson (). „Georges Lemaître, Father of the Big Bang”. COSMIC HORIZONS: ASTRONOMY AT THE CUTTING EDGE. American Museum of Natural History. Accesat în . It is tempting to think that Lemaître’s deeply-held religious beliefs might have led him to the notion of a beginning of time. After all, the Judeo-Christian tradition had propagated a similar idea for millennia. Yet Lemaître clearly insisted that there was neither a connection nor a conflict between his religion and his science. Rather he kept them entirely separate, treating them as different, parallel interpretations of the world, both of which he believed with personal conviction. Indeed, when Pope Pius XII referred to the new theory of the origin of the universe as a scientific validation of the Catholic faith, Lemaître was rather alarmed.Mentenanță CS1: Utilizează parametrul autori (link)
^Simon Singh (). Big Bang. HarperCollins UK. p. 362. ISBN9780007375509. Lemaître was determined to discourage the Pope from making proclamations about cosmology, partly to halt the embarrassment that was being caused to supporters of the Big Bang, but also to avoid any potential difficulties for the Church. ...Lemaître contacted Daniel O'Connell, director of the Vatican Observatory and the Pope's science advisor, and suggested that together they try to persuade the Pope to keep quiet on cosmology. The Pope was surprisingly compliant and agreed to the request - the Big Bang would no longer be a matter suitable for Papal addresses.
^Simon Singh (). Big Bang. HarperCollins UK. p. 362. ISBN9780007375509. It was Lemaître's firm belief that scientific endeavour should stand isolated from the religious realm. With specific regard to his Big Bang theory, he commented: 'As far as I can see, such a theory remains entirely outside any metaphysical or religious question.' Lemaître had always been careful to keep his parallel careers in cosmology and theology on separate tracks, in the belief that one led him to a clearer comprehension of the material world, while the other led to a greater understanding of the spiritual realm... ...Not surprisingly, he was frustrated and annoyed by the Pope's deliberate mixing of theology and cosmology. One student who saw Lemaître upon his return from hearing the Pope's address to the Academy recalled him 'storming into class...his usual jocularity entirely missing'.
