Gravitating particles and entropy

In summary, the concept of entropy in a system of gravitating particles is complex and can be interpreted in different ways. While the overall entropy of the universe always increases, locally it may appear to decrease due to the effects of gravity. However, this decrease is temporary and reversible, and the ultimate state of the system is one of maximum entropy.
  • #1
Student100
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<Moderator's note: this is a spin-off from another thread>

Matter isn't spreading out because of gravitational attractions between matter. If you took a bunch of gravitating particles and sealed them in container, the highest state of entropy is one where all the particles coalesce, which would be counter to the highest state being spread out. If that's what you mean, but I'm not sure I fully understand your argument.

You still have the opportunity, assuming you don't get banned for spamming this thread in the other forum. You do need solid references when discussing something "basic" when counter to what's currently accepted.
 
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  • #2
Student100 said:
... the highest state of entropy is one where all the particles coalesce...
I think this is exactly backwards.
 
  • #3
DaveC426913 said:
I think this is exactly backwards.

Hrmm, I don't believe so.
I02-35-entropy2.jpg


But, I certainty could be wrong.
 
  • #4
a) shows that a dispersed gas is highest entropy.
 
  • #5
DaveC426913 said:
a) shows that a dispersed gas is highest entropy.

I think you missed the gravitating particles before the quote. =)
 
  • #6
Student100 said:
I think you missed the gravitating particles before the quote. =)
I didn't.
I think you are reading too much into the graph.

I see the entropy timeline applying to the top series, but not the bottom series. Without explanatory context, the interpretation is ambiguous (for all I know the bottom series is a personal pet theory of the author's,)

But I'd be interested in clarifying the intended meaning of the diagram, and then its provenance and veracity.

Here's a PF thread describing the ultimate increase in entropy.

https://www.physicsforums.com/threads/can-gravity-decrease-entropy.224800/#post-1875395

Maybe this should be split off. It's off-topic.
 
  • #7
DaveC426913 said:
I didn't.
I think you are reading too much into the graph.

I see the entropy timeline applying to the top series, but not the bottom series. Without explanatory context, the interpretation is ambiguous (for all I know the bottom series is a personal pet theory of the author's,)

But I'd be interested in clarifying the intended meaning of the diagram, and then its provenance and veracity.

Here's a PF thread describing the ultimate increase in entropy.

https://www.physicsforums.com/threads/can-gravity-decrease-entropy.224800/#post-1875395

Maybe this should be split off. It's off-topic.
http://math.ucr.edu/home/baez/entropy.html

Is a pretty good discussion on the topic. It's a lot more complicated than what I said above or the figure, but as far as I understand it, it's physically sound.

Edit: I see you already linked to a topic here, that links to the link above as well.
 
  • #8
It seems to suggest the gravity only temporarily and locally reduces entropy (like energy from the sun does for Earth.) but that, ultimately, the entropy of the universe goes up.
 
  • #9
Student100 said:
<Moderator's note: this is a spin-off from another thread>

Matter isn't spreading out because of gravitational attractions between matter. If you took a bunch of gravitating particles and sealed them in container, the highest state of entropy is one where all the particles coalesce, which would be counter to the highest state being spread out. If that's what you mean, but I'm not sure I fully understand your argument.

You still have the opportunity, assuming you don't get banned for spamming this thread in the other forum. You do need solid references when discussing something "basic" when counter to what's currently accepted.

I appreciate this discussion point, however I wasnt referring to entropy of gravitating particles or matter. I was referring to for example, a single particle which somehow contains a large sum of energy without exploding. That its energy should spread out with the intensity of an atomic blast, should it be released from these bounds. That somehow energy from the big bang could somehow be restrained to form a particle in the first instance, but then also to persist for billions of years, longer... I enjoy these conversations and learn through them, but this thread is going to be locked soon or deleted. So what a grand waste of time this place is
 
  • #10
The tread that spun this off has been closed as well. This place is stifling. This forum is in a battle against entropy, in a bid to keep things tidy tidy. Sterile more like.

I like you people, but stop talking to me please. I'm trying to leave
 
  • #11
DaveC426913 said:
It seems to suggest the gravity only temporarily and locally reduces entropy (like energy from the sun does for Earth.) but that, ultimately, the entropy of the universe goes up.

I think that would be a correct way to look it. The net entropy change due to coalescing gravitating particles is positive, irreversible due to inelastic collisions and the radiation of energy away from the local system, but can be viewed locally as a decrease in entropy since we're ignoring the transfer of information away from the local system.

In the figure above the particles coalesce into a black hole, in which the entropy would be related to the surface area of the event horizon. If the other set of particles also collapsed and those two black holes merged, the resulting surface area would have to be larger than either of the originals, and entropy would increase. Eventually, they would decay and the system would obtain equilibrium.

Maybe the easiest way to view this would be to look at the uniformity of the CMB I think. Neglecting gravity, the universe was already basically in the maximum state of entropy. However, with gravity, the gravitational entropy of the system was low.

It's not the easiest physics concepts to understand, and I don't understand it very well myself. It's also very easy to fall into misconceptions, like I think the other guy who spurred this thread did? Or that I'm probably doing.

I'm still going through the previous linked post and the links from @atyy. It's getting late and I should probably try to sleep. Hopefully someone with more knowledge on this sort of thing will reply. o_O
 
  • #12
Student100 said:
I think that would be a correct way to look it. The net entropy change due to coalescing gravitating particles is positive, irreversible due to inelastic collisions and the radiation of energy away from the local system, but can be viewed locally as a decrease in entropy since we're ignoring the transfer of information away from the local system.

In the figure above the particles coalesce into a black hole, in which the entropy would be related to the surface area of the event horizon. If the other set of particles also collapsed and those two black holes merged, the resulting surface area would have to be larger than either of the originals, and entropy would increase. Eventually, they would decay and the system would obtain equilibrium.

Maybe the easiest way to view this would be to look at the uniformity of the CMB I think. Neglecting gravity, the universe was already basically in the maximum state of entropy. However, with gravity, the gravitational entropy of the system was low.

It's not the easiest physics concepts to understand, and I don't understand it very well myself. It's also very easy to fall into misconceptions, like I think the other guy who spurred this thread did? Or that I'm probably doing.

I'm still going through the previous linked post and the links from @atyy. It's getting late and I should probably try to sleep. Hopefully someone with more knowledge on this sort of thing will reply. o_O

No, I didnt misconceive. I spoke on such a simple circumstance of entropy, not much room for confusion. Not like that whole black hole event horizon entropy tossed bs
 
  • #13
Timedial said:
I'm trying to leave
You keep SAYING that. I didn't realize it was so difficult.
 
  • #14
Timedial said:
I'm trying to leave

And yet you are still here. This is dragging on like a death scene from Bugs Bunny.
 
  • #15
Vanadium 50 said:
And yet you are still here. This is dragging on like a death scene from Bugs Bunny.
:biggrin:
 
  • #16
Haha still here. I tried to delete my account but apparently can't. Disabled email notifications
 

1. What are gravitating particles?

Gravitating particles are objects or entities that have mass and are attracted to each other by the force of gravity. Examples include planets, stars, and even galaxies.

2. How do gravitating particles affect entropy?

Gravitating particles play a crucial role in the increase of entropy in the universe. As they come together and form larger structures, such as galaxies or clusters of galaxies, their gravitational pull causes them to become more disordered, leading to an overall increase in entropy.

3. What is the relationship between gravity and entropy?

Gravity and entropy are closely linked, as gravity is responsible for the formation and movement of particles, which in turn affects the overall entropy of the system. The more massive and dense a system is, the stronger its gravitational pull, leading to a higher level of disorder and thus, a higher level of entropy.

4. Can gravitating particles violate the laws of thermodynamics?

No, gravitating particles do not violate the laws of thermodynamics, as they are subject to the same laws as any other physical system. The increase in entropy caused by gravitating particles is in accordance with the second law of thermodynamics, which states that the overall entropy of a closed system will increase over time.

5. How does the behavior of gravitating particles impact the formation of structures in the universe?

The behavior of gravitating particles is crucial in the formation of structures in the universe, such as galaxies, stars, and even planets. As particles come together under the force of gravity, they form larger and more complex structures, eventually leading to the formation of galaxies and other celestial bodies.

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