Does gravity defy the 2nd Law?

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Discussion Overview

The discussion revolves around the relationship between gravity, thermodynamics, and entropy, specifically questioning whether gravity can defy the second law of thermodynamics in the context of star formation from a diffuse gas cloud. Participants explore theoretical scenarios involving isolated systems and the implications of gravitational collapse on entropy.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants propose that gravity can lead to a burning star from a diffuse gas cloud, questioning if this defies the second law of thermodynamics.
  • Others argue that the second law holds for isolated systems and that significant entropy is removed from the system through radiation during star formation.
  • A participant questions whether a star formed from an isolated container of gas would ever collapse due to the inability to radiate energy.
  • There is a discussion about whether a burning star represents a higher entropy state than the original gas cloud, with some asserting that it does due to higher temperature and phase space considerations.
  • Some participants present analogies involving charged objects to illustrate concepts of entropy and energy transformation, raising questions about the nature of charge and its relation to entropy.
  • Concerns are raised about the implications of gravitational collapse in a contracting universe and whether stars could form under such conditions.
  • A participant emphasizes the quantitative nature of entropy and critiques qualitative interpretations, highlighting the importance of considering emitted radiation in the analysis.
  • Confusion arises regarding the conditions under which gravitational collapse occurs, with differing views on the necessity of energy dissipation for collapse to happen.

Areas of Agreement / Disagreement

Participants express multiple competing views on the relationship between gravity, entropy, and the second law of thermodynamics. The discussion remains unresolved, with no consensus on whether gravity can defy the second law or the conditions necessary for gravitational collapse.

Contextual Notes

Participants highlight limitations in defining systems as isolated and the complexities of quantifying entropy in various scenarios. The discussion also touches on the role of radiation and energy dissipation in gravitational processes.

  • #31
Perhaps an image is worth more than 100 words. This is my intuitive picture

Gravity and 2nd Law.JPG
 
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  • #32
Gerinski said:
I never stated that the cloud of gas could or could not radiate, that came only in some of the answers such as Anorlunda's.
You are the one who put it in the container, from which it can't radiate.
Personally, even now I do not see why such a gravitationally coalescing cloud of gas could not radiate to its immediate environment in the rest of the container.
What "rest of the container? Isn't it filled completely with a gas?

How does your scenario apply to the real universe? Why are we even talking about it? What game are we playing here?
 
Last edited:
  • #33
Gerinski said:
I never stated that the cloud of gas could or could not radiate
Gerinski said:
Because of the impossibility to radiate

In general, if you are going to do that, it's best to do it somewhere where your previous messages are not stored.

And I'm done here.
 
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  • #34
The answer was given by @Demystifier in post #6: the wrong assumption is that entropy has been reduced.

Time to close the thread. Thanks to all that participated.
 
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