Great Debate on the scale of the universe
Great Debate on the scale of the universe
Overview
In April 1920 astronomers Harlow Shapley and Heber Curtis met at the National Academy of Sciences to debate the scale of the universe: whether the spiral nebulae were gas clouds inside a vast Milky Way or entire 'island universes' of stars. No data could settle the question that night, but the debate crystallised the decisive measurement needed — the distance to the nebulae. Hubble supplied that answer within five years, resolving the debate in favour of island universes.