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Can Milky Way and Andromeda collision reconcile with an Expanding Universe with galaxies spreading away from each other like "raisins in a loaf"? (lemmy.dbzer0.com)

submitted 6 months ago* (last edited 6 months ago) by Melatonin@lemmy.dbzer0.com to c/asklemmy@lemmy.ml

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I understand that our local galaxy group is considered "gravitationally bound" and therefore exempt from the expansion from each other ((, but we don't seem to have other galaxies collected into their own "local groups" of gravitationally bound clusters, so are we saying we're somehow unique? Is there a trick of perception taking place?)) <---edit:this is wrong

I found this quote in the Wikipedia article on the Expansion of the universe.

While objects cannot move faster than light, this limitation applies only with respect to local reference frames and does not limit the recession rates of cosmologically distant objects.

It seems to me that if we can perceive at cosmological distance something that cannot exist, perhaps we are falsely observing an expanding universe. Maybe everything IS gravitationally bound and we're just seeing expansion because... Relativity?

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[–] FriendBesto@lemmy.ml 1 points 6 months ago

Gravitational pull in local clusters of galaxies can exist and even contradict larger clusters or the universe as a whole, just in a smaller scale. The passage of time is also localised due to gravitational intensity, too. We know the universe is not expanding at the same rate in different places, as well.

This can happen in sets of complex systems of systems. In your query it somewhat analogous to if you were throwing a ball northbound at 100km/h in a train moving southbound at 50km/h. On a planet circling its star at 107,800 km/h in a total different direction. While the star drags the earth along with other planets in its own orbit in a different direction.