Temperature of the Heat Death of the Universe?

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Discussion Overview

The discussion revolves around the temperature of the heat death of the universe, exploring concepts related to energy, particle behavior, and entropy in the context of an expanding universe. Participants question how to calculate the temperature at heat death, the implications of energy being zero, and the nature of particles present at that state.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants inquire about calculating the temperature of the heat death based on the total energy in the universe, suggesting that in an expanding universe, this temperature may approach zero.
  • There is a discussion on whether all particles will have the same velocity at heat death, with some asserting that energy, not velocities, will be uniform.
  • One participant expresses uncertainty about the presence of energy in the form of mass at heat death, speculating that there may not be any energy available to do work.
  • Another participant mentions that massless particles, like photons, always travel at the speed of light, while massive particles have energy dependent on their mass and velocity, leading to different velocities in thermal equilibrium.
  • There is a suggestion that all matter might exist as photons at the heat death of the universe, prompting further inquiry into this idea.
  • A link to an external resource is provided for additional information on the future of an expanding universe.

Areas of Agreement / Disagreement

Participants express differing views on the nature of temperature and energy at heat death, with no consensus reached on the specifics of particle behavior or the implications of energy being zero.

Contextual Notes

Participants reference concepts such as entropy and thermal equilibrium, but there are unresolved assumptions regarding the definitions of temperature and energy in this context.

Alutoe
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Is there a way to calculate the temperature of the heat death of the universe based on the total amount of energy currently in the universe. And if the total amount of energy in the universe is zero (compose dof equal and opposite parts) is it possible for the parts to cancel each other out and return to a state of non-existence? Furthermore, I have heard that when the heat death of the universe happens everything will be at the exact same temperature, that is the velocity of all particles will be the same. But do we have a clue as to what type of particles will be around? Also, if everything is at the exact same temperature would that mean the universe could all be in a super fluid state?
 
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Alutoe said:
Is there a way to calculate the temperature of the heat death of the universe based on the total amount of energy currently in the universe.

In an expanding universe, which we think we live in, the temperature of heat death, if it ever occurs, will be zero.

Furthermore, I have heard that when the heat death of the universe happens everything will be at the exact same temperature, that is the velocity of all particles will be the same.

Energies, not velocities.
 
voko said:
In an expanding universe, which we think we live in, the temperature of heat death, if it ever occurs, will be zero.

Thank you, can you tell me where you know this from or a good direction to search into get the finer details of the idea?



voko said:
Energies, not velocities.

What I was saying was that the energy, and temperature (meaning the velocity) of all particles will be the same at the point when entropy is at a maximum. But that's even wishy-washey since they shouldn't have any velocity or energy available to do work. An interesting question now is will there still be energy present in the form of mass? My instinct says there would not be.
 
Alutoe said:
Thank you, can you tell me where you know this from or a good direction to search into get the finer details of the idea?

Energy is constant, so its density is ever thinner as the expansion continues.

What I was saying was that the energy, and temperature (meaning the velocity) of all particles will be the same at the point when entropy is at a maximum.

Massless particles, such as photons, always move at the speed of light, no matter what their energy. Energy of massive particles depends on their mass and their velocity, so particles with different masses in thermal equilibrium must have different velocities. Except, of course, the equilibrium at 0 K, where all massive particles must freeze into cosmic microwave background - which will become a misnomer, because it will not be microwave, but infinite-length-wave.
 
voko said:
Massless particles, such as photons, always move at the speed of light, no matter what their energy. Energy of massive particles depends on their mass and their velocity, so particles with different masses in thermal equilibrium must have different velocities. Except, of course, the equilibrium at 0 K, where all massive particles must freeze into cosmic microwave background - which will become a misnomer, because it will not be microwave, but infinite-length-wave.

Yes but what I'm also wondering or thinking is that all matter should be in the same form at the heat death of the universe (photons), do you know anything about this?
 

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