heyuhua
Registered Senior Member
I've provided several examples.
It's not an either/or, silly!
Galaxies are being separated by expansion AND some are merging.
The expansion of the universe is an AVERAGE. All galaxies have motion with respect to each other.
As I have said, even if there was a so-called merger, it was extremely rare and cannot be the mechanism of galaxy formation. That is to say, if galaxies come from merger, then merger will be a common phenomenon, and the conclusion of cosmic expansion cannot be established.