The Great Debate
  A hundred years ago (1920) in the auditorium of the Smithsonian Institution's
U.S. National Museum there were two lectures under the auspices of the George
Ellery Hale Lecture series, what has come to be called the 'Great Debate'. In
the debate, Harlow Shapley and Heber Curtis argued over the 'Scale of the
Universe'. Curtis argued that the Universe is composed of many galaxies like
our own and they are relatively small. Shapley argued that the Universe was
composed of only one big Galaxy. In Shapley's model, our Sun was far from the
center of this great island Universe.
