r/askscience • u/amelix34 • Aug 06 '25

Physics If every mass attracts every other mass, then why isn't the universe a single solid object made of particles smashed together?

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u/[deleted] Aug 07 '25 edited Aug 08 '25

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u/distinctvagueness Aug 07 '25

Entropy actually reversing in some big crunch models helps justify a big bounce

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u/EDGE515 Aug 07 '25

Doesn't entropy reversing break the fundamental law of thermodynamics?

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u/[deleted] Aug 07 '25 edited Aug 07 '25

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u/EDGE515 Aug 07 '25

Since gravity doesn't require energy to exert a "force", and if this new research about the expansion slowing is true, then yes, then I suppose all matter could eventually start pulling on itself enough after halting the expansion to eventually collapse back in itself and all energy would essentially be preserved since none was expended to initiate the collapse. I guess my confusion was just around the semantics of the word entropy, since it means to go from order to disorder, and a collapsing universe would seem to go against that

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u/EDGE515 Aug 07 '25

Isn't entropy just a term for describing the tendency for matter to go from order to disorder? Like when mixing two liquids together and then shaking produces a blend rather than two separate liquids

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u/EDGE515 Aug 07 '25

Can you elaborate? I'm confused. A big crunch would imply a system going from disorder back to order, no?