One large Milky Way galaxy or many galaxies? 100 years ago, a young Edwin Hubble settled astronomy’s ‘Great Debate.’
In 1920, astronomers Harlow Shapley and Heber Curtis held a Great Debate. Shapley argued that the spiral nebulae were small and in the Milky Way, while Curtis took a more radical position that they ...
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Edwin Hubble
Edwin Powell Hubble is renowned for determining that there are other galaxies in the Universe beyond the Milky Way, and for observing that the universe is expanding at a constant rate. Hubble was ...
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Hubble finds proof that the universe is expanding
The two keys to Edwin Hubble's breakthrough discovery were forged by others in the 1910s. The first key, the period-luminosity scale discovered by Henrietta Leavitt, allowed astronomers to ...