The Milky Way’s Neighborhood

What were the Shapley-Curtis debates of 1920?

During the first two decades of the twentieth century, Harlow Shapley believed that the Milky Way was the only major galaxy in the universe. Other scientists, such as Heber Curtis (1872–1942), thought that the “spiral nebulae” were in fact galaxies like our own. To bring light to this very important scientific question of the time, a series of scientific debates were held in Washington, D.C., in 1920 between Shapley and Curtis. Each person laid out the scientific issue in his own way and compared the evidence of one position versus the other. In the end, Harlow Shapley was wrong and Heber Curtis was right: the Milky Way is indeed one galaxy among billions in the universe. Even though Shapley was wrong, he still is considered a great scientist today.


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