Mechanical Energy - Self energy of Universe

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Discussion Overview

The discussion revolves around the concept of the total mechanical energy, specifically the self-energy of the universe in the context of its expansion, as understood through general relativity. Participants explore the implications of the universe's expansion and its associated energy, particularly focusing on the observable universe.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant inquires about the total mechanical energy of the universe due to its expansion, seeking an equation and numerical value.
  • Another participant argues that there is no meaningful way to express the expansion of space as a kinetic object of objects within it.
  • There is a suggestion that the total size of the universe is unknown and could potentially be infinite, with a focus on the observable universe.
  • A participant expresses confusion regarding a previous claim about the nature of the universe's expansion and seeks clarification on energy associated with it.
  • Discussion includes the average energy density of regular matter, dark matter, and dark energy as relevant to the observable universe.
  • It is noted that while there is a kinetic energy value mentioned in an article, it describes a different process than those associated with the universe's expansion.
  • Another participant mentions that energy is not defined on global scales in general relativity.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the nature of energy associated with the universe's expansion. Multiple competing views are presented regarding the definition and implications of energy in this context.

Contextual Notes

Limitations include the ambiguity surrounding the definitions of energy in general relativity, the unknown total size of the universe, and the distinction between different types of energy associated with cosmic processes.

Philosopha
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What is the total mechanical energy (self energy) of the universe that is due to the fact that it expands, taken the big bang as the origin - on the basis of general relativity?

If anyone could supply me with the equation and number (what size is it in kgm2/s2) I would be very thankful.
 
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There is no meaningful way to express the expansion of space as a kinetic object of objects inside.

Unrelated to that, the total size of the universe is unknown (it could even be infinite). You can ask for the observable universe.
 
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Thx, that is what I had thought was the standart view, but someone whom I thought would know for sure made me believe differently ... that was why I asked this question. All good. Thx.
 
Last edited:
mfb said:
There is no meaningful way to express the expansion of space as a kinetic object of objects inside.

Unrelated to that, the total size of the universe is unknown (it could even be infinite). You can ask for the observable universe.

What can I ask for the observable universe? Considering there is no meaningful way to express the expansion as a kinetic object.
The observable universe is what I'm after. So is there any energy associated with its expansion or not? - Because I was told there is just the way I did it is wrong...

Thx in advance
 
Last edited:
Philosopha said:
What can I ask for the observable universe? Considering there is no meaningful way to express the expansion as a kinetic object.
The average energy density (for regular matter, dark matter and dark energy) is an interesting number.

The cosmic energy inventory

The observable universe is what I'm after. So is there any energy associated with its expansion or not? - Because I was told there is just the way I did it is wrong...
You can associate the acceleration of the expansion with an energy density (dark energy). You do not have to, however.
 
You will notice in the article MFB posted there is a kinetic energy value, however that energy describes a different process than those associated with expansion see section 2.10
 
Thank you both, and thank you very much for the paper. Will have a good read. The acceleration -DE context sounds exactly what I stumbeled across.
 
Energy is not defined in GR on global scales.
 
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