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So I know that we do not know the sum of all energy in the universe, but why can we not just estimate with the following logic? (That I assume has some fatal flaw preventing anyone from guessing the total energy of the universe with it)

Since the universe is considered uniform by some (if you zoom out a lot) could we take an average piece of the universe, guess how many of those pieces there are in the universe, and then multiply the chunk’s energy by how many of them we think could exist?

Qmechanic
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ACertainArchangel
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    Related: https://physics.stackexchange.com/q/2838/2451 , https://physics.stackexchange.com/q/10309/2451 and links therein. – Qmechanic Feb 28 '22 at 05:25

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IF the universe is infinite, and it also satisfies approximately the homogeneous characteristic, THEN the sum of all energy is also INFINITE.

IF the universe is finite, and it also satisfies approximately the homogeneous characteristic, THEN the sum of all energy is UNKNOWN because the volume of the finite universe is not known.

However, the relevant equation is known, but you may not be interested in the math.

Buzz
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This has been done. This energy density is called the critical density and is about 5 GeV/$c^2$ per cubic meter (i.e. 5 proton masses per cubic meter or or $10^{-26}$kg/m$^3$). So, I do not understand why you write that we did not know the sum of all energy in the universe.

rfl
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  • Mmm… I asked a question about the ratio of potential and kinetic energy in the universe and someone said that we don’t know the sum of all energy in the universe. I suppose this person was mistaken? – ACertainArchangel Feb 28 '22 at 22:01
  • Also can we multiply the energy of 5 proton masses by our guess of the number of cubic meters in the universe to get its total energy and does this include potential? – ACertainArchangel Feb 28 '22 at 22:04