Georges Lemaître: The Priest, the Primeval Atom, and the Big Bang

Georges Lemaître was a Belgian priest who liked red wine, made his students laugh, and is known as the father of the Big Bang theory.

Over the weekend I found myself listening to an online sermon from Holy Trinity Brussels. The preacher introduced Belgian priest and physicist Georges Lemaître. He rightly celebrated Lemaître as one of the architects of what we now call the Big Bang theory. That was enough to remind me I really must add him to my ever-growing list of Famous Belgians.

The sermon itself, though, left me a little flat. The preacher invoked Lemaître’s work on the Big Bang and black holes to defend belief in the resurrection of Jesus, grouping all three together as “singularities”. These are moments where normal physics breaks down. He suggested that all three therefore belong to the same category of extraordinary event.

I think that’s a shaky argument. The Big Bang and black holes are accepted science because they emerge from empirical observation, mathematical modelling, and decades of testing and revision. The resurrection is believed on the basis of faith, theology, and ancient testimony.

Calling them all “singularities” doesn’t bridge that gap, it just borrows scientific language to lend credibility to a claim that operates by entirely different rules. The two things aren’t in the same ballpark as far as evidence goes, and treating them as if they are doesn’t strengthen the case for either.

But that’s enough of that. Lemaître himself was famously insistent that science and faith should be kept in separate lanes. So I’ll take his advice, set the sermon aside, and explore one of Belgium’s most remarkable and underappreciated figures.

A mind that couldn’t stay still

Georges Henri Joseph Édouard Lemaître was born in Charleroi on 17 July 1894, the eldest of four children. His family were devout Catholics. By the age of nine, young Georges had already decided he wanted to be a priest. But his father had other ideas, and so Georges dutifully enrolled at the Catholic University of Louvain to study civil engineering.

Then came the First World War.

In 1914, Lemaître interrupted his studies to volunteer for the Belgian army. He served as an artillery officer and witnessed the first poison gas attack in history. The experience left him shaken but not broken. His comrades apparently marvelled at his ability to disconnect mentally from the horror around him and bury himself in physics books whenever he got a moment’s peace.

His prospects of promotion to officer rank were dashed after he was marked down for insubordination as a result of pointing out to the instructor a mathematical error in the official artillery manual.

At the end of hostilities, he received the Belgian War Cross with bronze palm. He was one of only five rank-and-file troops to receive that award directly from King Albert I. Then he went back to university, swapped engineering for mathematics, and never looked back.

Priest and physicist

After completing his doctorate in mathematics in 1920, Georges Lemaître entered the seminary. He was ordained as a priest on 22 September 1923 by Cardinal Mercier. Ten days later he was on a boat to England.

At Cambridge, Lemaître was a research associate in astronomy and worked with the eminent astrophysicist Arthur Eddington, who introduced him to modern cosmology, stellar astronomy, and numerical analysis. From Cambridge he crossed the Atlantic to Harvard and then MIT, where he met some of the leading astronomers of the day. These included men who were beginning to observe something strange and significant about the galaxies.

The universe, it appeared, was moving.

The day without yesterday

Back in Belgium in 1925, Lemaître threw himself into the question that was quietly upending physics. In 1927, he proposed that the universe is indeed expanding. He published his findings in a Belgian scientific journal that, with a certain irony, almost nobody outside Belgium read. Einstein himself told him: “Your calculations are correct, but your physics is abominable.”

Lemaître filed that away and pressed on.

By 1931, he had gone further. He suggested that the expansion of the universe began from a state of enormous density, which he called “the Primeval Atom.”

If everything is expanding outwards, he reasoned, then wind it back far enough and you arrive at a single, impossibly dense point; a moment of beginning. He called it, with a poet’s instinct, “a day without yesterday.”

It was a staggering idea. Many astronomers at the time were still uncomfortable with the idea that the universe is expanding. That the entire observable universe of galaxies began with a bang seemed preposterous. Even Einstein took years to come around. But when he finally did (at a lecture in California in 1933, where Lemaître presented his theory) Einstein stood up and applauded, reportedly saying it was “the most beautiful and satisfying explanation of creation” he had ever heard.

He also predicted that there should be observable radiation left over from the Big Bang explosion; an afterglow of the beginning. Shortly before his death, Lemaître learned that Arno Penzias and Robert Wilson had discovered the cosmic microwave background radiation, the first and still most important observational evidence in support of the Big Bang.

Lemaître died in 1966 knowing he’d been right all along.

The man behind the theory

What makes Lemaître so endearing is that his greatness sat lightly on him. He enjoyed company and was a fun person to be around, always laughing, smiling and joking. He enjoyed drinking red wine and eating good food. In his later years, just like the universe, his body expanded with the passage of time.

He was also careful about keeping his faith and his science separate. When Pope Pius XII tried to use the Big Bang theory as confirmation of the Biblical creation story, Lemaître was reportedly horrified, and later convinced the Pope not to make any further public statements linking the theory to religious doctrine. He believed science and religion asked different kinds of questions, and mixing them up helped neither.

Lemaître served as President of the Pontifical Academy of Sciences from 1960 until his death in 1966. He was, to the end, both things at once: priest and physicist, believer and scientist, a man who saw no contradiction in that at all.

Honours and legacy of Georges Lemaître

The recognition came in waves, not always at the right time. In 1934, he received the Francqui Prize, presented to him by King Léopold III. It was the highest scientific honour Belgium could bestow. In 1936, Pope Pius XI inducted him into the Pontifical Academy of Sciences, and in 1951 he became the first recipient of the Eddington Medal from the Royal Astronomical Society.

Posthumously, the honours have only grown. There is a crater on the Moon named after him, as well as the asteroid (1565) Lemaître. The ESA’s fifth Automated Transfer Vehicle, launched to the International Space Station in 2014, was named Georges Lemaître. In 2018, the International Astronomical Union officially renamed Hubble’s Law as the Hubble-Lemaître Law, finally giving him credit for the discovery that had, for decades, gone largely to Hubble’s name.

Georges Lemaître’s Belgium

You can still walk in his footsteps. In Leuven, his sculpted bronze bust, displaying his wiry spectacles and stiff collar, is mounted on a plinth in the courtyard of the College van Premonstreit, which once housed the Physics Institute of KU Leuven. His living and working quarters in Heilige-Geestcollege (Holy Ghost College) are also there, where in 1958 he proudly carried one of the first computers in Belgium up to his attic.

In neighbouring Louvain-la-Neuve, his statue stands at the Catholic University’s Place des Sciences, chalk in hand in front of a copper blackboard etched with a swoosh of atoms. A 21-mile cycling route – the Big Bang Route – connects the two university towns where he lectured, marked with QR-coded signposts telling his story along the way.

It’s a fittingly quiet tribute to a quietly extraordinary man. No thunder, no fanfare, just a bicycle path through the Belgian countryside, tracing the outline of a life that changed how we understand everything.

Here’s my profile of another outstanding Belgian scientist: Nobel Prize for Physics (2026) winner Francis Halzen!

Denzil Walton

I created Discovering Belgium in 2011 to share the country’s hidden stories, fascinating places, and remarkable people. Through articles, photography, and audio walks, I share discoveries that reveal Belgium beyond the obvious. Hope you enjoy this site.