‘Great Debate’ Glossary
Glossary Cepheid: A type of variable star used to determine distance. Shapley used a relation between the period of variation of this type of star and its absolute magnitude to calibrate distances to globular clusters during the `Great Debate.’ Curtis disputed these distances. Cepheids are used today as reliable distance estimators. Curtis: Heber D. Curtis. […] The post ‘Great Debate’ Glossary…
The term "Great Debate" refers to a heated discussion between astronomers Heber D. Curtis and Harlow Shapley in 1920. This debate centered around the nature of our Milky Way galaxy and the spiral nebulae observed in the sky. Curtis argued that our galaxy was small, the sun was near its center, and spiral nebulae were actually other galaxies similar to our own.
Shapley, on the other hand, believed our galaxy was vast, with our sun situated far from its center, and he did not believe spiral nebulae were external galaxies. Both Curtis and Shapley were proven wrong on their larger claims, but Shapley's assertion regarding the sun's position was correct. After the resolution of the debate, the term "galaxy" was adopted to refer to our own Milky Way, and "universe" began to signify the cosmos beyond the Milky Way.
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