In
astronomy, the
Great Debate, also called the
Shapley–Curtis Debate, was an influential
debate between the astronomers
Harlow Shapley and
Heber Curtis which concerned the nature of so-called
spiral nebulae and the
size of the universe. The basic issue under debate was whether distant nebulae were relatively small and lay within the outskirts of our
home galaxy or whether they were in fact independent galaxies, implying that they were exceedingly large and distant. The debate took place on 26 April 1920, in the
Baird auditorium of the
Smithsonian Museum of Natural History. The two scientists first presented independent technical papers about "The Scale of the Universe" during the day and then took part in a joint discussion that evening. Much of the lore of the Great Debate grew out of two papers published by Shapley and Curtis in the May 1921 issue of the
Bulletin of the National Research Council. The published papers each included counter arguments to the position advocated by the other scientist at the 1920 meeting.