No. 10 - Shapley/Curtis debate

Back in 1920, when it happened, this debate was so big that astronomers know it simply as "the Great Debate." And, like a political debate, this one happened on a single day, with a room full of people.

The Smithsonian Institution was the host for the debate, with Harlow Shapley arguing that the Milky Way galaxy was the center of the universe, with all other galaxies a part of the Milky Way; Heber Curtis, on the other hand, believed the Milky Way was just one of many galaxies.

Nowadays, sixth-grade students and anyone who's ever watched a planetarium show knows that Curtis was more right about the nature of our universe...but Shapley may have been more right about the nature of our galaxy, placing our sun at the outskirts of the Milky Way, while Curtis placed it dead center. It's nice when everyone gets to say they were right about something.