Could entropy be reversed eventually in the far future?

In summary: Yes, because then there would be no cosmological horizon and the "amount of universe" that was accessible would increase without bound.
  • #1
Suekdccia
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TL;DR Summary
Could entropy be reversed eventually with infinite time in the far future?
In the far future there will be most likely a point where a maximal state of entropy will be reached in the universe and after the last black hole evaporates there could be no more structures and no more work could be done.

According to the Poincaré recurrence theorem for a closed universe there could be a reversal of entropy in long-term periods. However in a flat universe with an accelerated expansion it is not so clear that this theorem holds.

However, are there any other mechanisms through which entropy could be ever reversed eventually after reaching heat death? Perhaps something related with quantum fluctuations?
 
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  • #2
"Could entropy be reversed" makes no sense. Entropy is a thermodynamic quantity. Could temperature be reversed? Could heat capacity be reversed?
 
  • #3
Suekdccia said:
In the far future there will be most likely a point where a maximal state of entropy will be reached in the universe
Not if the universe keeps expanding. There is no maximum entropy in a universe that expands forever.
 
  • #4
PeterDonis said:
Not if the universe keeps expanding. There is no maximum entropy in a universe that expands forever.
Isn't it assymtotic to a maximum.
In the far distant future with very few particles around the entropy of the cosmic event horizon predominates.
Presently the universe has a physical deficit from the maximum.
 
  • #5
256bits said:
In the far distant future with very few particles around the entropy of the cosmic event horizon predominates.
Ah, that's right, in the presence of a cosmological constant things will asymptote to de Sitter spacetime in the far future, which has a constant finite entropy for any given region.
 
  • #6
PeterDonis said:
Ah, that's right, in the presence of a cosmological constant things will asymptote to de Sitter spacetime in the far future, which has a constant finite entropy for any given region.
Would temperature drop to 0K in such universe?
 
  • #7
Suekdccia said:
Would temperature drop to 0K in such universe?
No, it would only drop to the horizon temperature, which is a finite value that depends on the value of the cosmological constant.
 
  • #8
PeterDonis said:
No, it would only drop to the horizon temperature, which is a finite value that depends on the value of the cosmological constant.
Also, here it seems to indicate a mechanism through which new structures could form black holes even after the last one evaporates with denisty perturbations (https://arxiv.org/abs/astro-ph/9701131), see F.1. and VI. D. (Even for an open universe, the question of reaching heat death seems open)
 
  • #9
PeterDonis said:
No, it would only drop to the horizon temperature, which is a finite value that depends on the value of the cosmological constant.
Also, if the cosmological constant vanished, would we be again in the case whwre maximal entropy is never reached?
 
  • #10
Suekdccia said:
if the cosmological constant vanished, would we be again in the case whwre maximal entropy is never reached?
Yes, because then there would be no cosmological horizon and the "amount of universe" that was accessible would increase without bound.
 

FAQ: Could entropy be reversed eventually in the far future?

What is entropy and why is it important in physics?

Entropy is a measure of the disorder or randomness in a system. It is a central concept in the second law of thermodynamics, which states that the total entropy of an isolated system can never decrease over time. This law implies that natural processes tend to move towards a state of maximum disorder or equilibrium. Entropy is important because it helps explain why certain processes are irreversible and provides insight into the direction of time.

Is it theoretically possible to reverse entropy?

In theory, reversing entropy is not prohibited by the laws of physics, but it is extraordinarily unlikely. The second law of thermodynamics suggests that while local decreases in entropy can occur (such as in living organisms or certain engineered systems), the overall entropy of an isolated system will increase. Reversing entropy on a macroscopic scale would require conditions or mechanisms that are currently beyond our understanding and capability.

Could advanced technology in the far future reverse entropy?

While it's a fascinating idea, reversing entropy would require manipulating an enormous amount of information and energy with extreme precision. Advanced technology might be able to create localized decreases in entropy or manage entropy more effectively, but reversing it on a universal scale remains speculative. Such technology would need to overcome fundamental physical limitations that we don't yet fully understand.

What role does the concept of a "heat death" of the universe play in this discussion?

The "heat death" of the universe refers to a state in which the universe has reached maximum entropy, and all energy is evenly distributed, leaving no gradients to perform work. In this state, all processes would cease, and the universe would be in thermodynamic equilibrium. This concept underscores the challenge of reversing entropy because it represents the ultimate end state predicted by the second law of thermodynamics.

Are there any scientific theories or hypotheses that suggest entropy could be reversed?

Some speculative theories, such as those involving cyclic models of the universe or certain interpretations of quantum mechanics, suggest scenarios where entropy might decrease under specific conditions. However, these ideas are highly theoretical and not widely accepted within the scientific community. Currently, there is no empirical evidence to support the possibility of reversing entropy on a universal scale.

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