Submitted by Tank_AT t3_11r2ae9 in askscience
araujoms t1_jcaj9kq wrote
Reply to comment by Aseyhe in Does space expansion occur uniformly in all directions and dimensions? by Tank_AT
Of course it is linked to the cosmic expansion rate, it is the very thing that is making the expansion rate accelerate!
Aseyhe t1_jcb1zf4 wrote
Dark energy's gravity accelerates cosmic expansion. Dark energy also induces small-scale gravitational repulsion. However, we cannot say that cosmic expansion induces small-scale gravitational repulsion, because the two are not directly linked.
That is the claim in the top-level comment: that cosmic expansion does not have a local dynamical influence. This claim remains correct.
araujoms t1_jcb3ioi wrote
Of course cosmic expansion does not induce small-scale gravitational repulsion, it's the other way around. It's incomprehensible how can you say that they are not directly linked.
I think you are focussing too much on correcting the misconception that the inertial expansion of the universe is somehow a force pulling things apart, so much that you are ignoring the fact that the cosmological constant is a force pulling things apart that in fact causes the cosmic expansion to accelerate.
Aseyhe t1_jcb4c5l wrote
I'm addressing expansion of space because that's the topic of the question. I am confused as to why you think I should answer a different question.
(Regardless, it would seem to me that the appropriate course for you would be to make a separate answer, rather than to falsely claim that the existing answer is incorrect!)
araujoms t1_jcb5ryj wrote
Because you are so emphatic in your answer that expansion is not a force that one gets the impression that no such force exists. For example, you quote > You shouldn’t think of galaxies as being pulled apart by some kind of expanding space
and > there is no local effect on particle dynamics from the global expansion of the universe: the tendency to separate is a kinematic initial condition, and once this is removed, all memory of the expansion is lost.
While both sentences are technically correct, a lay person will incorrectly conclude that no local repulsive force exists. I don't think this is good science communication.
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