The Primeval Atom Hypothesis
Georges Lemaître · 1931
"A Belgian priest-physicist proposed, years before Hubble's data was fully digested, that the universe began from a single, extremely dense 'primeval atom' that has been expanding and cooling ever since — the first real formulation of what became the Big Bang theory."
The Big Bang wasn't Hubble's idea. In 1927, a Catholic priest who also held a physics doctorate proposed the universe expanded from an initial dense state — before most physicists, including Einstein at first, took it seriously.
Lemaître combined Einstein's general relativity equations with the idea of an expanding universe to argue that running expansion backward implies a beginning — a single, extremely compact 'primeval atom' that has been unpacking into the universe we observe ever since. Einstein reportedly told him at first that his physics was correct but his cosmology was 'abominable,' since a universe with a beginning raised uncomfortable philosophical and theological questions many scientists preferred to avoid. Hubble's 1929 observations gave Lemaître's proposal the empirical backing it needed, and the discovery of the cosmic microwave background decades later confirmed it further. Ironically, the term 'Big Bang' was coined by astronomer Fred Hoyle, a rival who intended it as mockery of a theory he didn't believe — the name stuck anyway.
What was significant about Lemaître's 'primeval atom' proposal relative to Hubble's later observations?
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The explanation above is written with AI assistance. These are the originals — go to them to check it.
- A Homogeneous Universe of Constant Mass and Increasing RadiusAnnales de la Société Scientifique de Bruxelles, 1927 (English translation 1931, MNRAS)
Hubble's Law and the Expanding Universe
"Distant galaxies are receding from us at speeds proportional to their distance — the first hard observational evidence that the universe itself is expanding, which run backward in time implies it began from a single point."