Before Lemaître, the cosmos was assumed to be eternal and unchanging. He proved otherwise — with mathematics, with courage, and with a priest's willingness to follow truth wherever it led.
In 1927, working from Einstein's field equations of general relativity, Georges Lemaître derived what is now known as Hubble's Law — two years before Edwin Hubble published his own observational confirmation. Lemaître showed mathematically that the universe must be expanding, and that this expansion implied a beginning.
Einstein initially dismissed the idea, telling Lemaître: 'Your calculations are correct, but your physics is abominable.' It would take six more years — and Hubble's telescope — before the world caught up with what Lemaître had already proved on paper.
"Your calculations are correct, but your physics is abominable."
Annales de la Société Scientifique de Bruxelles
Derived the expanding universe from Einstein's field equations and proposed what would become Hubble's Law — two years before Hubble's observational paper. Initially published in French, it was largely overlooked until 1931.
Nature
Proposed the 'hypothesis of the primeval atom' — the idea that the universe began as a single quantum of energy that exploded outward. This is the first scientific formulation of what would later be called the Big Bang.
Lectures, California Institute of Technology
A series of lectures delivered in California, attended by Einstein, in which Lemaître presented the full theoretical framework of the expanding universe. Einstein stood and applauded at the conclusion.
Book — E. P. Dutton & Co.
Lemaître's full account of his cosmological theory for a general audience. He described the universe as beginning from a single primeval atom — a 'day without yesterday' — and expanding ever since.
Lemaître was the first to derive mathematically that the universe is not static but expanding — a conclusion that followed directly from Einstein's general relativity. He also proposed the first observational method to measure this expansion using galaxy redshifts.
In 1931, Lemaître proposed that the universe began as a single, extraordinarily dense quantum — the 'primeval atom' — which exploded and expanded into everything we observe. This is the first scientific statement of what we now call the Big Bang.
Lemaître derived the linear relationship between a galaxy's distance and its recession velocity — the law now named after Edwin Hubble — two years before Hubble's 1929 paper. The International Astronomical Union formally recognised Lemaître's priority in 2018.
Lemaître proposed that cosmic rays — high-energy particles striking Earth from space — were the remnants of the original primeval atom explosion. Though this specific hypothesis was later revised, it was a remarkably prescient attempt to connect the origin of the universe to observable phenomena.
When Pope Pius XII suggested in 1951 that the Big Bang confirmed the biblical account of creation, Lemaître firmly and publicly disagreed. He insisted that science and theology operated on separate planes — that his theory was physics, not theology, and should be evaluated as such.
In 1964, Penzias and Wilson detected the cosmic microwave background radiation — the faint thermal echo of the Big Bang that Lemaître had predicted. Lemaître learned of this discovery in the final weeks of his life in 1966. The universe had kept its secret for thirty-five years.
Derives the expanding universe and Hubble's Law from Einstein's equations
Edwin Hubble publishes observational confirmation — Lemaître's priority goes unrecognised for decades
Proposes the 'primeval atom' hypothesis in Nature — the first Big Bang theory
Einstein attends Lemaître's California lectures and publicly endorses the theory
Publishes The Primeval Atom, his full cosmological account for a general audience
Rejects Pope Pius XII's attempt to link the Big Bang to Genesis — insisting on the independence of science
Penzias and Wilson detect the cosmic microwave background — confirming the Big Bang
Lemaître learns of the CMB discovery weeks before his death on June 20
International Astronomical Union formally renames Hubble's Law to the Hubble–Lemaître Law
CONFIRMED 1964
The cosmic microwave background radiation — the faint thermal echo of the Big Bang — was detected by Penzias and Wilson, confirming what Lemaître had predicted 33 years earlier.
The evolution of the world can be compared to a display of fireworks that has just ended — some few red wisps, ashes and smoke. Standing on a well-chilled cinder, we see the slow fading of the suns, and we try to recall the vanished brilliance of the origin of the worlds.