<p>This question presupposes that you agree that the heat death of the universe is eventually gonna happen, in some far distant future.</p>
<p>I'm trying to understand what the different <em>stages</em> of the heat death would be (much like evolution on the main sequence). I believe energy from fusion will be one of the first forms of energy to be exhausted, and was thinking that gravitational might be one of the last.</p>
<p>A relevant question: <a href="https://astronomy.stackexchange.com/questions/7950/hulse-taylor-binary-pulsar-what-is-the-rate-of-mass-energy-loss-from-the-sourc">Hulse-Taylor binary pulsar - what is the rate of mass/energy loss from the source?</a></p>
<p>When would this (theoretical) free energy finally be exhausted?</p>
<p>An estimate within 3 orders of magnitude, scoped to our current understanding of the composition and size of the observable universe would suffice</p>

CC BY-SA 4.0
2024-12-10T06:24:33.400Z
If you're looking at the far future, at a time when there are no stars, then you're looking well beyond the time when interesting chemistry will occur.  No chemistry means no biology and no life. That said, if this is part of [worldbuilding.se] you may get a more useful response there.
James K
CC BY-SA 4.0
2024-12-10T14:31:35.473Z
If I modified the scope of the question to remove the civilization aspect, just looking at it from a pure thermodynamics perspective, would that be more relevant/answerable?
ijustlovemath
CC BY-SA 4.0
2024-12-10T22:07:55.230Z
To be honest, I'm not really sure what you mean by "gravitational energy"  The energy released when two bodies fall towards one another? It's not really a source of energy.  Or do you mean the energy released as a gas cloud contracts?  That's not right since in this distant future there are no gas clouds....
James K
CC BY-SA 4.0
2024-12-11T13:32:09.617Z
When two black holes or it each other, energy is slowly bled away from the system by the means of gravitational waves. These waves do carry some form of energy, since the orbits decay (albeit slowly) over time. Thermodynamically that is a form of free energy, is it not?
ijustlovemath
CC BY-SA 4.0
2024-12-11T13:32:40.560Z
A recent paper about binary pulsars which investigates this: https://arxiv.org/abs/1906.07568
ijustlovemath
CC BY-SA 4.0
2024-12-12T00:49:32.243Z
Hm. This has an interesting angle. Maybe have a look at [Do gravitational waves carry energy?](https://physics.stackexchange.com/q/387525/329416)
Greg Burghardt
CC BY-SA 4.0
2024-12-12T00:52:55.570Z
Not all that interesting. Black holes can be a source of energy thanks to for example Penrose process. Gravitational waves are like least useful thing in the universe in this respect. I guess that's why OP thought about them, like there would be nothing else, in some future, which is hardly likely.
Mithoron
CC BY-SA 4.0
2024-12-12T03:19:50.803Z
I'm just looking to understand the order of magnitude timescales at which different forms of energy would reach maximum entropy! Sorry if that wasn't clear
ijustlovemath
CC BY-SA 4.0
2024-12-14T23:01:38.453Z
I'm not seeing how background gravitational waves could become a better source of energy than background photos, ever.
Mithoron
CC BY-SA 4.0
2024-12-14T23:32:34.977Z
I am not asking about the *quality* or *usability* of the energy, more the *timescale in which it exists at all*
ijustlovemath
<supernova><gravitational-waves><heat><thermodynamics>
How long will gravitational energy be around after the last supernova?
ijustlovemath
# How long will gravitational energy be around after the last supernova?

(Asked by: username_0 on 2024-12-10)

This question presupposes that you agree that the heat death of the universe is eventually gonna happen, in some far distant future.

I'm trying to understand what the different *stages* of the heat death would be (much like evolution on the main sequence). I believe energy from fusion will be one of the first forms of energy to be exhausted, and was thinking that gravitational might be one of the last.

A relevant question: [Hulse-Taylor binary pulsar - what is the rate of mass/energy loss from the source?](https://astronomy.stackexchange.com/questions/7950/hulse-taylor-binary-pulsar-what-is-the-rate-of-mass-energy-loss-from-the-sourc)

When would this (theoretical) free energy finally be exhausted?

An estimate within 3 orders of magnitude, scoped to our current understanding of the composition and size of the observable universe would suffice

**Tags:** supernova, gravitational-waves, heat, thermodynamics
> **Comments:**
> **username_1**: If you're looking at the far future, at a time when there are no stars, then you're looking well beyond the time when interesting chemistry will occur.  No chemistry means no biology and no life. That said, if this is part of [worldbuilding.se] you may get a more useful response there.  
> **username_0**: If I modified the scope of the question to remove the civilization aspect, just looking at it from a pure thermodynamics perspective, would that be more relevant/answerable?  
> **username_1**: To be honest, I'm not really sure what you mean by "gravitational energy"  The energy released when two bodies fall towards one another? It's not really a source of energy.  Or do you mean the energy released as a gas cloud contracts?  That's not right since in this distant future there are no gas clouds....  
> **username_0**: When two black holes or it each other, energy is slowly bled away from the system by the means of gravitational waves. These waves do carry some form of energy, since the orbits decay (albeit slowly) over time. Thermodynamically that is a form of free energy, is it not?  
> **username_0**: A recent paper about binary pulsars which investigates this: https://arxiv.org/abs/1906.07568  
> **username_2**: Hm. This has an interesting angle. Maybe have a look at [Do gravitational waves carry energy?](https://physics.stackexchange.com/q/387525/329416)  
> **username_3**: Not all that interesting. Black holes can be a source of energy thanks to for example Penrose process. Gravitational waves are like least useful thing in the universe in this respect. I guess that's why OP thought about them, like there would be nothing else, in some future, which is hardly likely.  
> **username_0**: I'm just looking to understand the order of magnitude timescales at which different forms of energy would reach maximum entropy! Sorry if that wasn't clear  
> **username_3**: I'm not seeing how background gravitational waves could become a better source of energy than background photos, ever.  
> **username_0**: I am not asking about the *quality* or *usability* of the energy, more the *timescale in which it exists at all*  

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