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#1




entropy and gravitation
A smooth distribution corresponds to high entropy and a lumpy one to low
entropy if gravity is not involved. For example, air in a room has high entropy, but all the oxygen in one part and all the nitrogen in another part would correspond to low entropy. If gravity is involved, however, things are reversed: a lumpy distribution (e.g. everything in black holes) has a high entropy and a smooth distribution (e.g. the early universe) has a low entropy. Let's imagine the early universea smooth, lowentropy distributionand imagine gravity becoming weaker and weaker (by changing the gravitational constant). Can we make G arbitrarily small and the smooth distribution will still have low entropy? This seems strange: an ARBITRARILY SMALL G makes a smooth distribution have a low entropy. On the other hand, it seems strange that the entropy should change at some value of G. 
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#2




entropy and gravitation
On 30 May 2017 Phillip Helbig wrote:
it seems strange that the entropy should change at some value of G. For a while I thought thermodynamics was the most marvellous science, but now I think that "entropy" is just a fudge to fill in the gap after the enthalpy is measured. So who ever proved that "disorder" is a full explanation of socalled entropy? I had the same thoughts as Phil about the effects of scale on that interpretation (as well as how it is different in space than on a planet), but casting it in the light of the value of G is a new one. 
#3




entropy and gravitation
On 5/30/2017 6:55 AM, Phillip Helbig (undress to reply) wrote:
A smooth distribution corresponds to high entropy and a lumpy one to low entropy if gravity is not involved. For example, air in a room has high entropy, but all the oxygen in one part and all the nitrogen in another part would correspond to low entropy. If gravity is involved, however, things are reversed: a lumpy distribution (e.g. everything in black holes) has a high entropy But if everything is in one big black hole, and the black hole would need only mass and angular momentum and charge to describe it, then that would be extremely low entropy (and essentially we would have back the "ordinary" behavior you described first). So the difference is only in the entropy that is in the "soft supertranslation hair" (if that is the correct theory..) If the oxygen in one corner of the room would also have this extra entropy that black holes seem to have (for whatever reason), then the cases would be the same. Provided of course that before black hole formation occurs the normal behavior (lumpy distribution has lower entropy) is respected by gravity as it is by other forces. So the question is: would there still be a reason, in cases without black holes, to expect that gravity is different?  Jos 
#4




entropy and gravitation
In article , Jos Bergervoet
writes: But if everything is in one big black hole, and the black hole would need only mass and angular momentum and charge to describe it, then that would be extremely low entropy (and essentially we would have back the "ordinary" behavior you described first). The first clause doesn't really make sense, since if "everything" (presumably meaning all matter in the universe) were "in one big black hole", this would have to be something different than what is normally thought of as a black hole, e.g. a static solution in a background of Minkowski space. 
#6




entropy and gravitation
In article ,
Gerry Quinn writes: The smooth distribution always has the same entropy. Start with the smooth distribution and no gravity, and increase the gravitational constant. Now high entropy states start to become available that were not available withouy gravity. Sounds plausible. To put it another way, the 'clumpy' states in the nongravitational universe have lower entropy than the smooth state, but the clumpy states in the gravitational universe have higher entropy than the smooth state. Imagine a clumpy universe with no gravity. It has low entropy (lower than the smooth universe). Now G starts increasing from zero to, say, its current value (at which point the clumpy universe has a higher entropy than the smooth universe). At some value of G, the clumpy universe must have the same entropy as the smooth universe (which you say has the same entropy with or without gravity). So for this value of G, the entropy is independent of the clumpiness. Someone has made an error somewhere. 
#7




entropy and gravitation
In article ,
says... In article , Gerry Quinn writes: The smooth distribution always has the same entropy. Start with the smooth distribution and no gravity, and increase the gravitational constant. Now high entropy states start to become available that were not available withouy gravity. Sounds plausible. To put it another way, the 'clumpy' states in the nongravitational universe have lower entropy than the smooth state, but the clumpy states in the gravitational universe have higher entropy than the smooth state. Imagine a clumpy universe with no gravity. It has low entropy (lower than the smooth universe). Now G starts increasing from zero to, say, its current value (at which point the clumpy universe has a higher entropy than the smooth universe). At some value of G, the clumpy universe must have the same entropy as the smooth universe (which you say has the same entropy with or without gravity). So for this value of G, the entropy is independent of the clumpiness. Someone has made an error somewhere. Why should it not be independent of the clumpiness? Consider a smooth universe full of hydrogen, with nonzero density and no gravity. This universe is clumpy too, it's just that the clumps are mostly H2. You could make the same paradox by imagining a universe full of H atoms, and slowly turning on atomic interactions.  Gerry Quinn  This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus 
#8




entropy and gravitation
Le 30/05/2017 Ã* 06:55, Phillip Helbig (undress to reply) a Ã©crit :
Let's imagine the early universea smooth, lowentropy distributionand imagine gravity becoming weaker and weaker (by changing the gravitational constant). Can we make G arbitrarily small and the smooth distribution will still have low entropy? This seems strange: an ARBITRARILY SMALL G makes a smooth distribution have a low entropy. On the other hand, it seems strange that the entropy should change at some value of G. What about time? An aribtrarily small G will take an almost infinite time to manifest itself. Weaker gravity will EVENTUALLY get matter clumpy but if gravity is weak, it will take MUCH more time for gravity effects to manifest themselves. An arbitrarily small gravity will take arbitrarily long time to have any effect. Does the contradiction disappear if we take time into the picture? 
#9




entropy and gravitation
Dne 02/06/2017 v 09:04 jacobnavia napsal(a):
What about time? An aribtrarily small G will take an almost infinite time to manifest itself. Weaker gravity will EVENTUALLY get matter clumpy but if gravity is weak, it will take MUCH more time for gravity effects to manifest themselves. An arbitrarily small gravity will take arbitrarily long time to have any effect. Does the contradiction disappear if we take time into the picture? Thermodynamics generally does not care, what time it takes for a system to get into the preferred final state.  Poutnik ( The Pilgrim, Der Wanderer ) A wise man guards words he says, as they say about him more, than he says about the subject. 
#10




entropy and gravitation
In article ,
Gerry Quinn writes: To put it another way, the 'clumpy' states in the nongravitational universe have lower entropy than the smooth state, but the clumpy states in the gravitational universe have higher entropy than the smooth state. Imagine a clumpy universe with no gravity. It has low entropy (lower than the smooth universe). Now G starts increasing from zero to, say, its current value (at which point the clumpy universe has a higher entropy than the smooth universe). At some value of G, the clumpy universe must have the same entropy as the smooth universe (which you say has the same entropy with or without gravity). So for this value of G, the entropy is independent of the clumpiness. Someone has made an error somewhere. Why should it not be independent of the clumpiness? Because it's not. A room full of air with the same density everywhere has higher entropy than a room with all of the air squeezed into one corner. (In the case where gravity can be neglected. When gravity plays a role, then the clumpier distribution has higher entropy.) 
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