B Is the Accelerating Expansion of the Universe Wasting Energy?

mister i
Messages
19
Reaction score
7
This is my first (non-professional) post: It seems accepted that space is "created" (otherwise the expansion of the universe would exceed the speed of light). We are talking about "creation" (!!). The question would be: does current physics tell us if this represents a waste of energy for the universe? (which would be different from the energy of the vacuum, which is the energy that exists within space, but not its creation, for me they are different things)
 
Physics news on Phys.org
mister i said:
It seems accepted that space is "created"
I don't think that's accurate.
mister i said:
otherwise the expansion of the universe would exceed the speed of light
The expansion of space, to the extent that's really a thing, does not have a single speed. It is quantified by the Hubble constant, and comparing this to the speed of light is like asking if a kilogram is more than a meter. It doesn't make sense.
mister i said:
does current physics tell us if this represents a waste of energy for the universe?
I don't think there's a meaningful question to answer here - you can't define the total energy of the universe in a way anyone can agree on, so whether or not it is changing isn't answerable.
 
mister i said:
We are talking about "creation" (!!).
No, we're not.

mister i said:
The question would be: does current physics tell us if this represents a waste of energy for the universe?
No energy is expended for the universe to expand. The matter in the expanding universe is in free fall.
 
Ibix said:
The expansion of space, to the extent that's really a thing, does not have a single speed. It is quantified by the Hubble constant, and comparing this to the speed of light is like asking if a kilogram is more than a meter. It doesn't make sense.
here talks about acceleration and velocity: https://en.wikipedia.org/wiki/Accelerating_expansion_of_the_universe
 
mister i said:
here talks about acceleration and velocity: https://en.wikipedia.org/wiki/Accelerating_expansion_of_the_universe
And, as it says, the key quantities are the scale parameter ##a## and its derivatives and the Hubble constant. Individual galaxies have a velocity (although there are caveats), but this is not limited to be below ##c## and does not characterise the expansion.
 
From $$0 = \delta(g^{\alpha\mu}g_{\mu\nu}) = g^{\alpha\mu} \delta g_{\mu\nu} + g_{\mu\nu} \delta g^{\alpha\mu}$$ we have $$g^{\alpha\mu} \delta g_{\mu\nu} = -g_{\mu\nu} \delta g^{\alpha\mu} \,\, . $$ Multiply both sides by ##g_{\alpha\beta}## to get $$\delta g_{\beta\nu} = -g_{\alpha\beta} g_{\mu\nu} \delta g^{\alpha\mu} \qquad(*)$$ (This is Dirac's eq. (26.9) in "GTR".) On the other hand, the variation ##\delta g^{\alpha\mu} = \bar{g}^{\alpha\mu} - g^{\alpha\mu}## should be a tensor...
OK, so this has bugged me for a while about the equivalence principle and the black hole information paradox. If black holes "evaporate" via Hawking radiation, then they cannot exist forever. So, from my external perspective, watching the person fall in, they slow down, freeze, and redshift to "nothing," but never cross the event horizon. Does the equivalence principle say my perspective is valid? If it does, is it possible that that person really never crossed the event horizon? The...
Back
Top