All Questions
Tagged with space-expansion thermodynamics
53
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Does the expansion of the universe cause the universe reach maximum entropy faster than a non expanding universe?
I've seen Does an expanding universe cool down?
So I understand an expanding universe cools down, my question is, does an expanding universe reach maximum entropy faster than a non-expanding universe?
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Why is the First Law of Thermodynamic related to Fluid Equation?
In Cosmology, there is a equation called Fluid Equation:
$$\dot{{\varepsilon}}+3\frac{\dot{a}}{a}(\varepsilon+P)=0.$$
It is derived by taking time derivative of the First Law of Thermodynamic:
$\dot{E}...
- 411
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Friedmann fluid equation in the non-relativistic case
The Friedmann fluid equation I am referring to is:
$$ a\frac{d\rho}{da} = -3(\rho+P) .$$
In the non-relativistic (low temperature) case for an ideal gas universe (representing matter), I know that the ...
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What causes a big rip?
If dark energy has $w<-1$ you get the Big rip scenario, where dark energy becomes more and more powerful until it eventually rips all matter apart. Why does this occur? Why does having $w<-1$ ...
- 2,908
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Could entropy ever be reversed in the universe with infinite time?
In the far future there will be most likely a point where a maximal state of entropy will be reached in the universe where no more useful work could be done and no structures would form, reaching a ...
- 2,462
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Why is it surprising that the universe was in an extraordinarily low-entropy state right after the big bang? [duplicate]
So I don't understand why it's surprising that the universe in an extraordinarily low-entropy state right after the big bang?
The way I see it the second law of thermodynamics forbids almost anything ...
- 1,389
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Is the universe getting hotter? Brighter?
Due to their fusion processes every star is radiating massive amounts of photons and (to a lesser extent) neutrinos. Are all of these getting absorbed in matter over time, warming it, or is the total ...
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Kinetic energy and collisions in cosmology? [duplicate]
Objects in space time can move due to the expansion of spacetime itself (where objects that are sufficiently far apart would recede from each other due to the Hubble flow) and peculiar motions (which ...
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Will interstellar helium condense to a liquid as space expands and cools?
Intergalactic space is 2.7K (https://en.wikipedia.org/wiki/Outer_space) Interstellar space is a little warmer. My understanding is that these will decrease over time.
The phase diagrams of helium I ...
- 488
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Thermodynamical argument in cosmology
I'm interested in the following question: What could we say about the thermodynamical properties of the Universe, using thermodynamics alone (without using general relativity), assuming that the ...
- 7,592
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Does thermal expansion and expending a solid object depends on processes? [duplicate]
As we know that for a rod of length $l_o$ if we increase the temprature by $2T$, the final length of the rod will be,
$$l_{f_1}=l_o(1+2\alpha T)$$
Where as if we first increase to T and then stop,
$$l=...
- 165
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What's wrong with this thermodynamics argument on the cosmological constant?
I'm puzzled by the following thermodynamics argument on the cosmological constant interpreted as a perfect fluid of pressure $p = -\, \rho$. I start considering a simple fluid of local energy density ...
- 7,592
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Avoiding heat death in an accelerated expanding universe?
Would there be any way to avoid heat death in an accelerated expanding universe?
https://en.m.wikipedia.org/wiki/Heat_death_of_the_universe
Is the heat death of the universe completely unavoidable in ...
- 2,462
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Cosmological perturbations and energy in an expanding universe?
I was reading an interesting book from cosmomogist Viatcheslav Mukhanov Physical Foundations of Cosmology and I had a specific question about it:
It is usually said that energy conservation is ...
- 2,462
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Energy harvesting in expanding universe? [closed]
There has been much discussion (in Physics Stack Exchange for instance) about how could we (theoretically) extract energy from the accelerated expansion of the universe.
However, the only ...
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