Edwin Hubble resolves the Shapely-Curtis debate by finding Cepheids in Andromeda

Between 1922 and 1923 Edwin Powell Hubble (20th November, 1889 - 28th September, 1953), an American astronomer, identified Cepheid variables in the Andromeda Nebula, proving that there were galaxies outside our own. Up until this point the idea of there being galaxies outside the Milky Way had. . .

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