I'm not so sure this is correct. The expansion is not said to simply "stop" at the boundary of galaxies, but it becomes so small at this scale as to be insignificant and undetectable. Even galaxies in local clusters are not appreciably separating from one another due to cosmic expansion. Out in the hugely vast distances between the galaxy clusters - that's where the cosmic expansion becomes detectable, and it's difficult to appreciate just how hugely vast these distances are.

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