The universe is expanding
Galaxies are receding, and the cosmos has a history.
- When
- —
- Duration
- 2 years
- Known to
- ± 1 year
- Era
- Industrial, Holocene
Lemaître, a Belgian priest and physicist, derives an expanding universe from general relativity in 1927 and proposes it began from a primeval atom. Hubble publishes the observational relation between distance and recession velocity in 1929, building on Henrietta Leavitt's period-luminosity law for Cepheid variables. The universe stops being static and eternal and acquires an age — which is the question the entire first half of this timeline answers.