Was the Big Bang first proposed by a priest?

What did Lemaître propose, and what did Hubble add?

Lemaître was born in Charleroi, Belgium, in 1894. He served as an artillery officer in the First World War, studied physics, and was ordained a priest in 1923. He then studied with the English astronomer Arthur Eddington and visited most of the major centers of astronomy in the United States. In 1925 he became a professor at the Catholic University of Louvain, according to the American Museum of Natural History.

In 1927 he published a paper in French in the Annales de la Société Scientifique de Bruxelles. Working from Einstein’s theory of gravity, he found a universe that grows with time. He worked out that light from distant galaxies should be shifted toward the red (a redshift) in proportion to their distance. Then he used published data to estimate how fast the universe expands. The International Astronomical Union’s 2018 resolution notes that he had rediscovered Friedmann’s math, and that the paper’s language and little-known journal left it largely unnoticed.

Einstein was not impressed at first. At a 1927 physics conference in Brussels, he reportedly told Lemaître that his math was correct but his physics was “abominable.” In 1930 Lemaître reminded Eddington of the paper, and Eddington arranged an English translation, which appeared in 1931. A letter uncovered in 2011 shows that Lemaître made the translation himself and chose to leave out his own estimate of the expansion rate.

Meanwhile Edwin Hubble, at Mount Wilson Observatory in California, published a short 1929 paper based on 24 nearby galaxies. It showed that the farther away a galaxy is, the faster it moves away from us. Most of the speeds came from the astronomer Vesto Slipher; the distances were Hubble’s. As Neta Bahcall of Princeton University explains in a 2015 commentary, Hubble did not link his result to the expanding-universe math, but his paper convinced the scientific community. His distances were too small by a factor of about seven, yet the pattern held.

In 1931 Lemaître went further. Eddington had written that, philosophically, the notion of a beginning was “repugnant” to him. In a one-page letter to Nature, Lemaître replied that, in his view, quantum theory suggests “a beginning of the world very different from the present order of Nature.” Run time backward, he reasoned, and all the universe’s energy ends up packed into a few quanta, or even one. Others, including George Gamow, later built this into the modern Big Bang theory, which differs from his primeval atom in many ways. Shortly before he died in 1966, Lemaître learned of the discovery of the cosmic microwave background, which the museum calls the most important observational evidence for the Big Bang.

In 2018 the International Astronomical Union put this history on record. Of the 4,060 members who voted, 78% backed a resolution recommending that the expansion of the universe be called the Hubble–Lemaître law. The resolution does not formally rename the law. It praised Lemaître’s “intellectual integrity,” which, it said, made him value the progress of science more than his own visibility.

How did Lemaître fit science and faith together?

Lemaître told the New York Times that he saw “two paths leading to truth” and decided to follow both, according to the UCLouvain archives. At Louvain he studied the philosophy of Thomas Aquinas alongside science, and it helped him keep two ideas apart. One is the physical beginning of the universe, which science can study. The other is Creation, a question for theology: God’s act of bringing the world into existence. Aquinas taught that the world’s having a beginning is “an object of faith, but not of demonstration or science.” He also warned believers against weak arguments for faith, which give unbelievers a reason to laugh (Summa Theologiae I, q. 46, a. 2).

Lemaître did not start there. During and after the First World War, he wrote a text trying to link the first words of Genesis with science. Over the years he left that approach behind. In 1936 he said that “the supreme Being can never be reduced to a scientific hypothesis,” and that a Christian scientist has the same tools as a colleague who does not believe, as Mariano Artigas records for the University of Navarra. His faith stayed deep: the archives describe yearly silent retreats and notebooks where prayers sit next to equations. The Catholic Catechism today teaches that faith and reason can never truly conflict, since God “cannot deny himself, nor can truth ever contradict truth” (paragraph 159).

What is the strongest objection?

Objections come from both directions.

From the side of faith, some believers see the Big Bang as pointing to creation. Pope Pius XII made that case to the Pontifical Academy of Sciences on November 22, 1951. He cited Hubble’s galaxies and other clues to a beginning in time, and said science seemed to have become a witness to the primordial “Fiat Lux.” He concluded: “Creation, therefore, in time, and therefore, a Creator; and consequently, God!” Yet in the same address, he said these facts were not conclusive arguments for creation in time; on that point, he said, such arguments come from revelation alone. The facts still awaited further investigation and confirmation, and the theories needed new developments.

Lemaître was troubled, the Louvain archives say. His theory was not yet settled or widely accepted. In his view, the speech blurred the physical beginning with Creation. And as a member of the academy, he feared critics would say he shared that view. The pope never named him, and his speech to the International Astronomical Union on September 7, 1952, did not mention the primeval atom. Artigas writes that Lemaître had spoken beforehand with Father Daniel O’Connell, director of the Vatican Observatory; the Louvain archives call that only a possibility. Lemaître held no grudge. In 1963 he said the pope had spoken on ground proper to him.

From the skeptical side, the worry ran the other way. Einstein came to accept that the universe expands, but, Artigas writes, the primeval atom reminded him too much of creation. Fred Hoyle, a rival who favored an eternal universe, accused Lemaître of concordism, that is, of shaping science to match religion. At a 1958 physics congress in Brussels, Lemaître answered that his theory stays completely outside any metaphysical or religious question. It leaves the materialist free to deny any transcendent being, he said, and for the believer it rules out any attempt at familiarity with God.

What do people often get wrong?

• “Hubble found the expanding universe on his own.” Hubble’s 1929 data were decisive, but Lemaître had derived the expansion and estimated its rate two years earlier. That is one reason the International Astronomical Union now recommends the name Hubble–Lemaître law.
• “Lemaître made up the Big Bang to back up the Bible.” He argued as a physicist, and he spent his career keeping physics and theology distinct.
• “The Church fought the Big Bang.” Lemaître joined the Pontifical Academy of Sciences in 1936 and became its president in 1960, and the pope’s 1951 speech praised the new cosmology.
• “He named it the Big Bang.” According to the Louvain archives, the name came from rivals who used it on the BBC to belittle his idea.

Where can people of faith and skeptics agree?

• Evidence decides the physics. The expanding universe won support through data, and the Big Bang through later evidence such as the microwave background, not because of who proposed them.
• The science leaves the God question open. In Lemaître’s words, the theory leaves the materialist free to deny any transcendent being. For the believer, he said in 1936, God can never be reduced to a scientific hypothesis.
• Faith and science can share one life. Our story Science and Faith: Enemies, Strangers, or Partners? and our answer Can someone love science and still believe in God? explore how many people do both.
• Nobody gains from weak arguments. Aquinas warned against them, and Lemaître did not want faith tied to a theory that was still unsettled. Science deals in evidence rather than final answers, as we explain in our answer on what science can and cannot settle.

How can you check this yourself?

• Read the 1931 letter. Lemaître’s note in Nature is one page long, and his key sentence is in the first paragraph.
• Read the vote. The IAU’s press release gives the numbers, and its background file lists the key papers behind the resolution.
• Read the pope’s own words. The Pontifical Academy of Sciences posts the 1951 address in English.
• Follow the science forward. Our answers on whether time began at the Big Bang and how old the universe is pick up where Lemaître left off.

The answer stays the same. A Catholic priest proposed the ideas that grew into the Big Bang, and he insisted they stand or fall as physics.