Heber D. Curtis. Participant in the `Great Debate' in 1920. Curtis argued that our Galaxy was small, the sun was near the center, and spiral nebulae were other galaxies similar to our own. Both Curtis and Shapley were incorrect on the first point (Curtis guessed too small, Shapley too large), and Curtis was also incorrect on the second point. That Curtis was correct in the last point has changed mankind's view of our place in the universe.