Temperature of the Heat Death of the Universe?

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SUMMARY

The temperature of the heat death of the universe is theorized to be zero Kelvin, as all particles will reach thermal equilibrium at this state. In an expanding universe, energy density decreases, leading to a scenario where all particles, including massless photons, will exhibit the same energy and velocity. The discussion emphasizes that at maximum entropy, all matter may transition into a form dominated by massless particles, fundamentally altering the nature of the universe. Key references include concepts from thermodynamics and cosmology, particularly regarding the cosmic microwave background and particle behavior at absolute zero.

PREREQUISITES
  • Understanding of thermodynamics and entropy
  • Familiarity with cosmology and the expanding universe model
  • Knowledge of particle physics, particularly massless particles and their properties
  • Basic grasp of the cosmic microwave background radiation
NEXT STEPS
  • Research the implications of maximum entropy in thermodynamics
  • Study the behavior of massless particles in thermal equilibrium
  • Explore the concept of cosmic microwave background and its evolution
  • Investigate the theories surrounding the future of an expanding universe
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Astronomers, physicists, and students of cosmology interested in the long-term fate of the universe and the principles of thermodynamics and particle physics.

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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