1920: The Shapley-Curtis Debate The Evidence

• Shapley:

  • If spiral nebulae were galaxies the size of our own, then the novae we see associated with them must be 15,000 times brighter than nearby novae. It’s more logical that they are nearby objects (less than 20,000 light years away) with normal novae.
  • Globular clusters form a sphere 300,000 light years in diameter centered 50,000 light years away from here. So the sun isn’t in the center.

Notes: