Does the entropy of the universe as a whole change?

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Discussion Overview

The discussion revolves around the concept of entropy in the universe as a whole, exploring whether the universe can change states, the implications of its expansion, and the relationship between gravity and entropy. Participants consider theoretical and conceptual aspects of thermodynamics as applied to the universe.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions whether the universe can change states or break into pieces, suggesting that if it did not change, its entropy would remain constant.
  • Another participant argues against the idea of the universe breaking into pieces, stating that the universe encompasses everything and thus cannot cease to be the universe.
  • There is a consideration of the universe's expansion and the role of gravity, with one participant proposing that gravity might counteract the entropy associated with expansion.
  • A later reply challenges the idea of gravity overcoming expansion, referencing dark energy and the acceleration of the universe's expansion.
  • One participant introduces the concept of wave functions and information conservation, questioning what would cause the wave function of the universe to collapse if it interacts only with itself.
  • Another participant responds that the wave function need not collapse entirely and discusses the strong anthropic principle, noting that entropy in the universe is always increasing.
  • There is a discussion on the difficulty of applying thermodynamic principles to the universe as a whole, emphasizing the need for reference to causal contact and the differing perspectives of observers.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the nature of the universe, entropy, and the effects of gravity and dark energy. The discussion remains unresolved, with no consensus reached on the implications of these concepts.

Contextual Notes

Limitations include the dependence on definitions of the universe and causal contact, as well as unresolved questions about the application of thermodynamic principles to the universe as a whole.

friend
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Does the universe as a whole ever change from being the universe as a whole? Does it ever break into pieces and cease being the universe?

And if anything (like the universe) never changed its state, wouldn't that mean its entropy never changed? Are there any constant thermodynamic properties that can be assigned to the universe as a whole?
 
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No. Why would you expect the universe to "break into pieces". Besides "universe" means "everything there is, so the pieces would STILL be the universe (but it's still a non-starter).
 
I'm thinking of how the universe may be getting bigger at the same time gravity is drawing things together. Wouldn't gravity have a tendency to counteract the entropy of expansion?
 
friend said:
I'm thinking of how the universe may be getting bigger at the same time gravity is drawing things together. Wouldn't gravity have a tendency to counteract the entropy of expansion?
I have no idea what you mean. Dark Energy (whatever it is) has made it so that no only is the universe expanding, the rate of expansion is accelerating. Gravity was overcome some 5 billion years ago. Your late.
 
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Or, as I understand it, wave functions are unitary and conserve information. So if we were to write a wave function for the entire universe, what else besides the universe would the universe interact with to collapse the entire universe? If nothing, then the information content of the universe would remain constant, right?
 
The wave function of the entire universe need not collapse all. The portion of the universe which is in causal contact with you collapses via interacting with you, hence, you observe a universe that is comparable with your existence. This is called the "strong anthropic principal". It is by no means a widely agreed upon principal but it is something you might be interested in learning about.

Entropy of the universe is always increasing.

Thermodynamic principals are a bit hard to apply to the universe as a whole. If you define the universe as everything that is in causal contact then the universe consists of everything within a certain radius of a chosen object. Your universe and my universe are different because each of us is at the center of a slightly different sphere. Discussing the universe as a whole cannot be done without reference to the things within it, such as a high red-shift galaxy for example. But if we discus a high red-shift galaxy we have to acknowledge that, being in the center of a different sphere, it is in causal contact with things that we are not, and not in causal contact with things that we are.
 

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