The universe is expanding
From one galaxy to billions, in five years
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Until 1924 it was an open dispute whether the Milky Way was the whole universe. Hubble settled it by finding Cepheid variables in Andromeda and applying Leavitt's relation to them. Five years later he showed that redshift increases with distance — what is now called Hubble's law. A universe that is expanding must have been smaller before, and that is the starting point of all Big Bang cosmology. Georges Lemaître had published the same relation two years earlier, in French, in a little-read journal.
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On Mount Wilson in California stood the world's largest telescope. Edwin Hubble used it to show two things: that the faint smudges astronomers had seen were other galaxies far beyond our own, and that they are all moving away from us — the further off, the faster. The universe is getting bigger.
Sources
- Hubble, PNAS 15 (1929) — «A Relation between Distance and Radial Velocity among Extra-Galactic Nebulae»
- Lemaître, Annales de la Société Scientifique de Bruxelles 47 (1927)
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Report a correctionPart of Terra Saga — the story of Earth on a timeline. terrasaga.org ·