1. What was the Shapley–Curtis debate all about? Was a winner declared at the end of the debate? Whose ideas turned out to be correct? 2. How did Edwin Hubble prove that M31 is not a nebula in our...

1. What was the Shapley–Curtis debate all about? Was a winner declared at the end of the debate? Whose ideas turned out to be correct?

2. How did Edwin Hubble prove that M31 is not a nebula in our Milky Way Galaxy?

3. What observations led Harlow Shapley to conclude that we are not at the center of the Galaxy?