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A comment on Why is there a normal galaxy sitting at the edge of the Universe?. Parent comment

Re:Why is there a normal galaxy sitting at the edge of the U... by chowells on Wednesday September 09, 2020 @02:50PM (#24424366)
Not in practice. In practice, this provides a very tiny force pulling subatomic particles apart in an atom's nucleus, or pulling atoms away from each other in a molecule, or pulling a celestial body's molecules away from each other. It makes no difference at all, because that force is absolutely dwarfed by the strong nuclear force, electromagnetism, or gravity, respectively. Systems that are coupled together by those forces, up to and including galaxies, are impacted only very minutely by this expansion.

For the expansion to have a significant impact on relative distances, the distances involved have to be so extreme that there's no real other interaction between the objects you're measuring from.

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Re:Why is there a normal galaxy sitting at the edge of the U... by hashmymustache on Wednesday September 09, 2020 @04:36PM (#24425629)
Does that expansion provide potential energy by creating space between attractive bodies? If so how do you account for conservation of energy?
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Re:Why is there a normal galaxy sitting at the edge of the U... by chowells on Wednesday September 09, 2020 @05:34PM (#24426181)
Yes, it will create some additional potential energy.

That doesn't contradict strict conservation of energy - it just adds another energy source that has to be accounted for when balancing everything.

It might contradict the aphorism "energy is never created or destroyed", but I'm not sure that was ever science.

It's more fun to think about it in terms of thermodynamics. Can that extra energy be used to reverse the second law of thermodynamics? I'm guessing not - it's so diffuse that it's probably impossible to use it to reduce entropy. The math for actually doing those calculations is well beyond what I know, though, so I'll just say that one's no more than a guess.

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Re:Why is there a normal galaxy sitting at the edge of the U... by mekkkkkk on Thursday September 10, 2020 @04:30AM (#24430128)
Great explanation! Thanks.
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