I frequently encounter statements that indicate that the expansion of space occurs everywhere except where galaxy clusters/groups or galaxies themselves are gravitationally bound. This statement seems to correctly indicate that space expansion does not drive such bound systems apart, but it implies what I believe to be an incorrect concept. That is, to my understanding the mechanisms driving space expansion are not absent within gravitationally bound systems, they are just small compared to other forces. If space expansion somehow turned off within such systems and, its characteristics would be even more bizarre than they already are. Is it more correct to say that space expansion occurs everywhere, including within gravitationally bound systems and, for that matter, within chemically bound molecules, within atoms, etc.? My non-expert understanding is that, in these systems, gravity (and other bonds) overwhelm space expansion and the net effect is that they contract (or at least do not expand) despite the expansion of space, but that whatever is driving space expansion is operative at all scales so far as we know.
It's not space that's expanding-it's spacetime. That's the important point. Regarding gravitationally bound systems, this statement refers to the Newtonian approximation. There do exist systems that remain bound, when the spacetime geometry changes with time, in particular consistent with an expanding Universe and there exist systems that become unbound, although this may take a very long time.
I have the same doubts. Expansion a la Hubble is considered only over extremly large distances
For shorter distances perhaps one cannot detect it as being too small, or that
it really does not exist within a bound system.
Stams answer is equally evasive.
From second to second, time expands, and time is part of space-time, isn't it?
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