Expanding universe and thermodynamics

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SUMMARY

The discussion centers on the implications of the universe's expansion on bound systems, such as atoms and solar systems. Participants clarify that while space is expanding, this expansion does not affect the size of bound systems due to local gravitational interactions. The concept of energy release from "falling in" of matter within these systems is debated, with consensus indicating that dark energy's effects are negligible at small scales. The conversation highlights the distinction between cosmological expansion and local gravitational forces, emphasizing the need for a nuanced understanding of general relativity.

PREREQUISITES
  • Understanding of general relativity and its implications on spacetime.
  • Familiarity with the concepts of dark energy and dark matter.
  • Knowledge of metric expansion of space and its effects on cosmic structures.
  • Basic principles of gravitational interactions in bound systems.
NEXT STEPS
  • Research "metric expansion of space" to understand its implications on cosmic structures.
  • Study "general relativity" to grasp how it affects energy conservation in expanding universes.
  • Explore the role of "dark energy" in cosmic expansion and its negligible effects on local scales.
  • Investigate "differential geometry" and "metric tensors" for a deeper mathematical understanding of spacetime.
USEFUL FOR

Astronomers, physicists, cosmologists, and anyone interested in the dynamics of the universe and the interplay between expansion and gravitational forces.

  • #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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