Jun 20 – Msgr Georges LeMaitre, (1894-1966), Priest, Physicist, Father of the “Big Bang” Theory

Not a saint, yet, but a personal and professional hero of mine.


Monsignor Georges Henri Joseph Édouard Lemaître (July 17, 1894 – June 20, 1966) was a Belgian Roman Catholic priest, honorary prelate, professor of physics and astronomer at the Catholic University of Leuven.

Lemaître proposed what became known as the Big Bang theory of the origin of the Universe, which he called his ‘hypothesis of the primeval atom’.

Lemaitre was a pioneer in applying Einstein’s theory of general relativity to cosmology. He introduced the theoretical Hubble’s law in 1927 as a generic phenomena in relativistic cosmology. In 1931, he published his primeval atom theory in Nature. At the time, Einstein had expressed skepticism about Lemaître’s 1927 paper.

But it is Lemaître’s theory that changed the course of science.  Lemaître worked with astronomers and designed his theory to explain the observed redshift of galaxies, have testable implications, the linear relation beween distances and velocities, and to be in accord with observations of the time.

Lemaître proposed his theory at an opportune time, since Edwin Hubble would soon publish his velocity-distance relation that strongly supported an expanding universe and, consequently, the Big Bang theory. In fact, Lemaître’s 1927 paper derived what became known as Hubble’s Law, two years before Hubble did so, and provided an estimate of the numerical value of the constant. However, the data used by Lemaitre do not allow him to prove that there was an actual linear relation, a result achieved by Hubble.

Because Lemaître spent his entire career in Europe, his contributions are not as well known in the United States (USA) as those of Hubble or Einstein, men well known in the USA by virtue of residing there.

Lemaître recognized expanding solutions within relativistic cosmologies. Lemaître is the first one to propose that the expansion is the explanation for the redshift of galaxies. He further concluded that an initial “creation-like” event must have occurred.

Einstein at first dismissed, privately, Lemaître out of hand, saying that not all mathematics leads to correct theories. After Hubble’s discovery was published, Einstein quickly and publicly endorsed Lemaître’s theory, helping both the theory and its proposer get fast recognition.


In 1933, Lemaître found an important inhomogeneous solution of Einstein’s field equations describing a spherical dust cloud, the Lemaitre-Tolman metric.

At the end of his life, he was devoted more and more to numerical calculation. He was in fact a remarkable algebraicist and arithmetical calculator. Since 1930, he used the most powerful calculating machines of the time like the Mercedes. In 1958, he introduced at the University a Burroughs E 101, the University’s first electronic computer. Lemaître kept a strong interest in the development of computers and, even more, in the problems of language and programming. This interest grew with age until it absorbed him almost completely.

In 1951 Pope Pius XII took the position that the scientific theory of the Big Bang confirmed the biblical creation story. This apparently caused great embarrassment, even to horror, for Lemaitre, who met with the Pope very soon after to caution the Holy Father on drawing parallels between a scientific theory and the book of Genesis.  The Pope appointed LeMaitre to the Pontifical Academy of the Sciences.  John XXIII made him its president.

Georges LeMaitre, after having received numerous scientific awards in the latter part of his career for his work, died on June 20, 1966, shortly after having learned of the discovery of cosmic microwave background radiation, which provided further evidence for his intuitions about the birth of the Universe.

“We can compare space-time to an open, conic cup…The bottom of the cup is the origin of atomic disintegration; it is the first instant at the bottom of space-time, the now which has no yesterday because, yesterday, there was no space.”
-Msgr Georges LeMaitre, The Primeval Atom


Technically yours, 🙂

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