Shapley's Big Galaxy
Since interstellar absorption dimmed the stars, Shapley assumed the
globular clusters were farther away than they really are. Shapley's
estimate of the size of our galaxy was so large he believed the Milky
Way comprised most of the universe.
In 1924, Edwin Hubble discovered Cepheid variables in the Andromeda
Nebula, and proved Andromeda was an external galaxy larger than the
Milky Way. Shapley's Big Galaxy theory had to yield to the new
findings.
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