Internal energy and total heat of universe

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SUMMARY

The discussion centers on the principles of thermodynamics as they apply to the universe, specifically addressing the conservation of energy. It is established that while energy is neither created nor destroyed (dU = 0), the concept of energy conservation does not hold at cosmological scales. The universe's expansion does not imply work being done on a vacuum, as no vacuum exists in standard cosmological models. Therefore, the assertion that heat is continuously added to the universe is incorrect.

PREREQUISITES
  • Understanding of thermodynamic principles, specifically the first law of thermodynamics.
  • Familiarity with the concept of internal energy (U) and work (W) in thermodynamics.
  • Knowledge of cosmological models and their implications on energy conservation.
  • Basic grasp of general relativity and its relationship to energy definitions in the universe.
NEXT STEPS
  • Research the implications of the first law of thermodynamics in cosmology.
  • Study the concept of energy conservation in general relativity.
  • Examine different cosmological models and their treatment of vacuum and energy.
  • Learn about the role of dark energy in the expansion of the universe.
USEFUL FOR

Students of physics, particularly those studying thermodynamics and cosmology, as well as researchers exploring the implications of energy conservation in the universe.

CuriousBanker
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Hello. I am starting to learn about thermodynamics. (i'm going to use lower case "d" for delta)

Energy is neither created nor destroyed. So dU = 0 for the universe as a whole.

If the universe is constantly expanding, then it must be doing work on the vacuum around it, right? So W is a positive number

dU = Q - W
0 = Q - a positive number

So Q is a positive number.

So heat is being added to the universe constantly.

Is this correct?
 
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CuriousBanker said:
Hello. I am starting to learn about thermodynamics. (i'm going to use lower case "d" for delta)

Energy is neither created nor destroyed. So dU = 0 for the universe as a whole.

If the universe is constantly expanding, then it must be doing work on the vacuum around it, right? So W is a positive number

dU = Q - W
0 = Q - a positive number

So Q is a positive number.

So heat is being added to the universe constantly.

Is this correct?
Energy is not conserved at cosmological scales

http://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/
 
CuriousBanker said:
Energy is neither created nor destroyed. So dU = 0 for the universe as a whole.
Unfortunately, the energy of the universe is not a well defined quantity. http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_gr.html

A globally conserved energy is only defined for a class of spacetimes that does not include the usual model of the universe.

CuriousBanker said:
If the universe is constantly expanding, then it must be doing work on the vacuum around it, right?
There is no vacuum around the universe in the usual cosmological models.
 
CuriousBanker said:
must be doing work on the vacuum around it, right?
Dale said:
There is no vacuum around the universe in the usual cosmological models.

And if there were, the universe would not be doing work on the vacuum.
 
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