What major cosmological debate involving Harlow Shapley and Heber Curtis was settled by Hubble's findings around 1924?

Answer

Whether the Milky Way was the entire universe

The Great Debate centered on whether faint nebulae were clouds within the Milky Way or separate 'island universes,' which Hubble confirmed by showing Andromeda was external.

What major cosmological debate involving Harlow Shapley and Heber Curtis was settled by Hubble's findings around 1924?
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