Georges-Henri Lemaitre and the Birth of the Universe

Meet the Jesuit Priest who discovered the Big Bang Theory

Big Bang
This graphic shows the evolution of the universe, and particularly the massive galaxies it contains, since the formation event of the cosmos, called the Big Bang. NASA/Niels Bohr Institute/STScI

Georges-Henri Lemaitre was the first scientist to figure out the basics of how our universe was created. His ideas led to the theory of the "Big Bang", which began the expansion of the universe and influenced the creation of the first stars and galaxies. His work was once ridiculed, but the name "Big Bang" stuck and today this theory of the first moments of our universe is a major part of astronomy and cosmology studies.

Lemaitre was born in Charleroi, Belgium on July 17, 1894. He studied humanities at a Jesuit school before entering the civil engineering school of the Catholic University of Leuven at the age of 17. When war broke out in Europe in 1914, he put his education on hold to volunteer in the Belgian army. He was awarded the Military Cross with palms.

Troubled by his war experiences, Lemaitre resumed his studies. He studied physics and mathematics and prepared for the priesthood. He earned a doctorate in 1920 from the Université Catholique de Louvain (UCL) and moved on to the Malines seminary. He was ordained as a priest in 1923. 

The Curious Priest

Georges-Henri Lemaitre had an insatiable curiosity about the natural world and how the objects and events we observe came into being. During his seminary years, he discovered Einstein's theory of relativity. After his ordination, he studied at the University of Cambridge's solar physics laboratory (1923–24) and then at Massachusetts Institute of Technology (MIT) in Massachusetts. His studies introduced him to the works of American astronomers Edwin P. Hubble and Harlow Shapley, both of whom studied the expanding universe.

In 1927, Lemaitre accepted a full-time position at UCL and released a paper that focused the astronomy world's attention on him. It was called Un 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 (radial velocity: Velocity along the line of sight toward or away from the observer) of extragalactic nebulae).

His Explosive Theory Gains Ground

Lemaitre's paper explained the expanding universe in a new way, and within the framework of the General Theory of Relativity. Initially, many scientists—including Albert Einstein himself—were skeptical. However, further studies by Edwin Hubble seemed to prove the theory. Initially called the "Big Bang Theory" by its critics, scientists adopted the name because it seemed to work well with the events that occurred in the beginning of the universe. Even Einstein was won over, standing and applauding at a Lemaitre seminar, saying "This is the most beautiful and satisfactory explanation of creation to which I have ever listened."

Georges-Henri Lemaitre continued to make advances in science the rest of his life. He studied cosmic rays and worked on the three-body problem. This is a classical problem in physics where the positions, masses, and velocities of three bodies in space are used to figure out their motions. His published works include Discussion sur l'évolution de l'univers (1933; Discussion on the Evolution of the Universe) and L'Hypothèse de L atoms primitif (1946; Hypothesis of the Primeval Atom).

On March 17, 1934, he received the Francqui Prize, the highest Belgian scientific award, from King Léopold III, for his work on the expanding universe. In 1936, he was elected a member of the Pontifical Academy of Sciences, where he became the president in March 1960, remaining so until his death in 1966. He was also named prelate in 1960. In 1941, he was elected member of the Royal Academy of Sciences and Arts of Belgium. In 1941, he was elected member of the Royal Academy of Sciences and Arts of Belgium. In 1950, he was given the decennial prize for applied sciences for the period 1933-1942. In 1953 he received the very first Eddington Medal award of the Royal Astronomical Society.

Revised and edited by Carolyn Collins Petersen.