Expanding universe and thermodynamics

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The discussion centers on the implications of the universe's expansion on bound systems like atoms and solar systems. Participants clarify that while space is expanding, this expansion does not affect gravitationally bound systems, which remain stable due to local interactions. The concept of energy release due to "falling in" of matter within these systems is challenged, with explanations emphasizing that the effects of expansion are negligible at small scales. The conversation also touches on the complexities of general relativity and the nature of space as a framework rather than a tangible entity. Ultimately, the consensus is that while expansion occurs, it does not impact the stability of bound structures or their energy dynamics.
  • #31
PeterDonis said:
That's because the thermodynamic budgetry you are used to is based on an underlying assumption of time translation invariance (which someone mentioned in a previous post). The expansion of the universe breaks time translation invariance; that means the thermodynamic budgetry you learned no longer holds in the form you learned it. There are ways of constructing a modified budgetry, but it still has limitations.

This article by Sean Carroll is worth reading in this connection:

http://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/
Excellent link, PeterDonis. Directly addresses the question.
 

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