Lemaître

Georges Lemaître was a Belgian priest, astronomer, and physicist who proposed that the universe is expanding and that cosmological evolution follows the laws of general relativity, ideas that laid the groundwork for what would become the Big Bang theory. He is often regarded as one of the founders of modern cosmology for connecting Einstein’s theory of gravitation with observational cosmology.

Born in Charleroi in 1894, Lemaître studied at the Catholic University of Leuven, where he was ordained as a priest and pursued advanced work in physics and astronomy. In 1927 he published a seminal paper in which he showed that the equations of general relativity admitted expanding-universe solutions. He proposed a model described as “a universe of constant mass and expanding radius,” arguing that galaxies recede from one another as a consequence of this cosmic expansion, a view compatible with the redshift observations already accumulating from distant galaxies.

In 1931 he further proposed the primeval-atom hypothesis, suggesting that the universe began from a single extremely dense and hot state and has been expanding ever since. This early hot-origin idea anticipated the conceptual framework of the Big Bang.

Lemaître spent much of his career as a professor at the Catholic University of Leuven and remained committed to a view of science that could harmonize with his religious faith. His cosmological work, alongside observational advances in the mid-20th century, helped establish the prevailing scientific understanding of an expanding, evolving universe.