This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 |
http://www.nytimes.com/2010/07/13/science/13gravity.html —Preceding unsigned comment added by 71.251.222.38 ( talk) 11:33, 13 July 2010 (UTC)
"Also, a specific microscopic model has been proposed that indeed leads to entropic gravity emerging" The 'indeed' bothers me. 68.225.192.99 ( talk) 09:30, 9 August 2010 (UTC)
I'm turning the "attention needed" parameter on in the infobox, as I believe this article needs attention from the WP:Physics community. Specifically, the "Informal Explanation" section, fairly recently added, needs attention from an expert. At the moment, it's definitely grammatically flawed, isn't written in proper MoS style, and doesn't actually do a great job of explaining the concept any more "simply" than the intro at the top. I'm happy to do edits on the section to improve the grammar and readability, but I don't want to do so if the underlying quality of the explanation isn't worth the effort. I'm vaguely familiar with the holographic principle, but not in any great detail--I stopped physics in the middle of undergraduate QM (with the exception of some "pop" books on the subject and reading here on WP)--so I'd love for an expert to take a look first and cleanup the physics before I cleanup the writing. Thanks for your help! Qwyrxian ( talk) 11:52, 25 August 2010 (UTC)
I'm wondering if this page should be moved to "Entropic gravity" -- that seems to be the name coming into usage for this theory. Also, this page really needs the attention of an expert right now. Danski14 (talk) 22:40, 5 September 2010 (UTC)
Articles describing early theoretical work should be accompanied by a section outlining critiques and factual or logical arguments. —Preceding unsigned comment added by 76.204.18.32 ( talk) 19:25, 22 September 2010 (UTC)
If there was a preprint of the paper on January 6 2010, when will be the official publication? Xenan ( talk) 20:59, 17 September 2010 (UTC)
I tried to improve at least the wording on the informal explanation, but it's still not very good. Is this kind of thing normal in other complex scientific articles? While I was writing it, it "felt" bad, like I was doing OR instead of relying on what reliable sources have said. I'm now tempted to agree with deleting the section, unless we can find an "informal explanation" somewhere else and then summarize it. Is there a "Holographic Theory for Dummies" book? Is there anyone else who thinks it should be kept? If not, I'm willing to just take it all out, despite my earlier objections. Qwyrxian ( talk) 01:16, 12 October 2010 (UTC)
I have just made some edits to the article reflecting the fact that this proposal seems to be completely ruled out by experiment. From what I can tell, the arguments, especially the ones based on neutron interference experiments, seem completely robust. I dont see any way of escaping them, but feel free to discuss if anyone has an argument to the contrary. Isocliff ( talk) 21:06, 18 September 2011 (UTC)
Can we have at least some attmept at an explanation for the idea behind this theory? I find it difficult to see how gravity could arise thermodynamically. For example, gravity tends to destabilise density perturbations in the universe as denser regions of the interstellar medium collapse into compact objects like starts, planets and black holes. Entropy, on the other hand, tends to equilibrate density perturbations in order to achieve a system with the largest number of microstates. — Preceding unsigned comment added by 92.27.55.215 ( talk) 20:46, 18 May 2012 (UTC)
After detailed discussion with Sanpitch, I completely rewrote the criticism section. Arguments against entropic gravity that claim that one can experimentally falsify it are very hard to motivate since entropic gravity, as a handwaving argument, essentially just re-interprets general relativity (and in approximation Newtonian gravity). Since GR does not violate any of the precision tests that it has been subjected to, it is not clear why entropic gravity should, as it leads to the same conclusion, that Einstein's equations are the macroscopic equations of motion of space-time. The main paper that makes such a claim (based on an obscure analysis of neutron interference experiments in a framework that is not suitable to include post-Newtian models of gravity) has, in my opinion, extremely serious flaws and should't be cited.
There are, however, some fairly straight forward formal arguments that limit the scope of entropic gravity quite severely. Matt Visser's paper shows that Verlinde's hand waving argument for the derivation of Newtonian gravity as an entropic force only works under very limited assumptions. His more detailed analysis mostly eliminates entropic forces as sources of conservative forces in the setting of classical mechanics and is suggestive that Verlinde's initial handwaving argument is too naive, by far.
That, all by itself, is not a particularly large hurdle for entropic gravity as a possible explanation of gravity, since Newtonian gravity, (i.e. the notion that gravity can be understood as a potential), had always been merely shoehorned into classical mechanics. In a sense the naive treatment of Newtonian gravity by Verlinde himself seems to give credence to his own opinion that we need to learn to deal with gravity in a different way and listen much more carefully to what we already know about its detailed nature as a phenomenon that is deeply tied into space and time itself.
In the wake of Verlinde's paper multiple authors have made additional derivations of modified versions of general relativity. In response, Tower Wang has analyzed a wide class of such models for consistency with energy-momentum tensor conservation and the ability to derive a homogeneous and isotropic solution for the global universe from them. He concluded that the local conservation and the global homogeneity/isotropy demands put very strong limits on the types of models that can be derived from an entropic gravity formalism. This, again, is a double edged result for entropic gravity. On one hand, it strongly favors general relativity as a very special theory that can not be easily modified without serious consequences. On the other hand, it also limits entropic gravity to a narrow subset of physically possible models of gravity.
It remains to be seen if future work can narrow these results down further to either a unique theory of space-time (which may very well turn out to be GR), or, if entropic gravity will, eventually, be completely eliminated on formal grounds. StillFascinated ( talk) 06:40, 16 February 2013 (UTC)
Article is biased by criticism without adequate opposite point of view. Also it is low quality overall. I don't have time do rewrite it, but I will add some response to criticism to balance a little. wp:npov
If you are completely unfamiliar with the topic please don't edit with 'common sense approach'. -- Asterixf2 ( talk) 18:48, 10 March 2016 (UTC)
My personal judgment of 1001.0785v1 from a quick look is that Verlinde doesn't clearly state what space-time or alternative to space-time he starts off with. If space-time is emergent, then it has to be emergent from something. It would be OK to start off with just an abstract set, but things have to be defined clearly if this is to be more than just an heuristic essay. You cannot assume what you are trying to derive. Anyway, this is just my personal judgment and irrelevant for the article itself (unless i publish it somewhere in a reliable source :P).
What's more important is that most of the material should be shifted from the top down to some sections below which try to present the topic. The lead section (introduction) should then be just a condensed version of the actual content. Shifting material down the page is easy. Writing a short, NPOV summary is more difficult - which is why i'm leaving someone else to do it :P. Boud ( talk) 09:04, 1 October 2010 (UTC)
So if between elements occasionally information is lost from the collection, is that 'entropic gravity'? Or are we talking about something else? 178.255.168.77 ( talk) 21:22, 4 May 2016 (UTC) PS is there a better way of editing this stuff than in a text editor and with these stupid tildes and wotnot?
Should we mention Verlindes 2016 formulation as "Emergent gravity". Seems to improve and explains MOND. New Scientist reports on an experimental test of EG and says it passes without resorting to free parameters. EG: Emergent Gravity and the Dark Universe Verlinde 2016, Brouwers test : First test of Verlinde's theory of Emergent Gravity using Weak Gravitational Lensing measurements Brouwer 2016, NS news item : First test of rival to Einstein’s gravity kills off dark matter. Whereas MOND explains galactic rotations, EG seems to also explain galactic clusters that MOND had problems with (and provides an explanation/mechanism for MOND). - Rod57 ( talk) 10:27, 9 January 2017 (UTC)
This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
Archive 1 |
http://www.nytimes.com/2010/07/13/science/13gravity.html —Preceding unsigned comment added by 71.251.222.38 ( talk) 11:33, 13 July 2010 (UTC)
"Also, a specific microscopic model has been proposed that indeed leads to entropic gravity emerging" The 'indeed' bothers me. 68.225.192.99 ( talk) 09:30, 9 August 2010 (UTC)
I'm turning the "attention needed" parameter on in the infobox, as I believe this article needs attention from the WP:Physics community. Specifically, the "Informal Explanation" section, fairly recently added, needs attention from an expert. At the moment, it's definitely grammatically flawed, isn't written in proper MoS style, and doesn't actually do a great job of explaining the concept any more "simply" than the intro at the top. I'm happy to do edits on the section to improve the grammar and readability, but I don't want to do so if the underlying quality of the explanation isn't worth the effort. I'm vaguely familiar with the holographic principle, but not in any great detail--I stopped physics in the middle of undergraduate QM (with the exception of some "pop" books on the subject and reading here on WP)--so I'd love for an expert to take a look first and cleanup the physics before I cleanup the writing. Thanks for your help! Qwyrxian ( talk) 11:52, 25 August 2010 (UTC)
I'm wondering if this page should be moved to "Entropic gravity" -- that seems to be the name coming into usage for this theory. Also, this page really needs the attention of an expert right now. Danski14 (talk) 22:40, 5 September 2010 (UTC)
Articles describing early theoretical work should be accompanied by a section outlining critiques and factual or logical arguments. —Preceding unsigned comment added by 76.204.18.32 ( talk) 19:25, 22 September 2010 (UTC)
If there was a preprint of the paper on January 6 2010, when will be the official publication? Xenan ( talk) 20:59, 17 September 2010 (UTC)
I tried to improve at least the wording on the informal explanation, but it's still not very good. Is this kind of thing normal in other complex scientific articles? While I was writing it, it "felt" bad, like I was doing OR instead of relying on what reliable sources have said. I'm now tempted to agree with deleting the section, unless we can find an "informal explanation" somewhere else and then summarize it. Is there a "Holographic Theory for Dummies" book? Is there anyone else who thinks it should be kept? If not, I'm willing to just take it all out, despite my earlier objections. Qwyrxian ( talk) 01:16, 12 October 2010 (UTC)
I have just made some edits to the article reflecting the fact that this proposal seems to be completely ruled out by experiment. From what I can tell, the arguments, especially the ones based on neutron interference experiments, seem completely robust. I dont see any way of escaping them, but feel free to discuss if anyone has an argument to the contrary. Isocliff ( talk) 21:06, 18 September 2011 (UTC)
Can we have at least some attmept at an explanation for the idea behind this theory? I find it difficult to see how gravity could arise thermodynamically. For example, gravity tends to destabilise density perturbations in the universe as denser regions of the interstellar medium collapse into compact objects like starts, planets and black holes. Entropy, on the other hand, tends to equilibrate density perturbations in order to achieve a system with the largest number of microstates. — Preceding unsigned comment added by 92.27.55.215 ( talk) 20:46, 18 May 2012 (UTC)
After detailed discussion with Sanpitch, I completely rewrote the criticism section. Arguments against entropic gravity that claim that one can experimentally falsify it are very hard to motivate since entropic gravity, as a handwaving argument, essentially just re-interprets general relativity (and in approximation Newtonian gravity). Since GR does not violate any of the precision tests that it has been subjected to, it is not clear why entropic gravity should, as it leads to the same conclusion, that Einstein's equations are the macroscopic equations of motion of space-time. The main paper that makes such a claim (based on an obscure analysis of neutron interference experiments in a framework that is not suitable to include post-Newtian models of gravity) has, in my opinion, extremely serious flaws and should't be cited.
There are, however, some fairly straight forward formal arguments that limit the scope of entropic gravity quite severely. Matt Visser's paper shows that Verlinde's hand waving argument for the derivation of Newtonian gravity as an entropic force only works under very limited assumptions. His more detailed analysis mostly eliminates entropic forces as sources of conservative forces in the setting of classical mechanics and is suggestive that Verlinde's initial handwaving argument is too naive, by far.
That, all by itself, is not a particularly large hurdle for entropic gravity as a possible explanation of gravity, since Newtonian gravity, (i.e. the notion that gravity can be understood as a potential), had always been merely shoehorned into classical mechanics. In a sense the naive treatment of Newtonian gravity by Verlinde himself seems to give credence to his own opinion that we need to learn to deal with gravity in a different way and listen much more carefully to what we already know about its detailed nature as a phenomenon that is deeply tied into space and time itself.
In the wake of Verlinde's paper multiple authors have made additional derivations of modified versions of general relativity. In response, Tower Wang has analyzed a wide class of such models for consistency with energy-momentum tensor conservation and the ability to derive a homogeneous and isotropic solution for the global universe from them. He concluded that the local conservation and the global homogeneity/isotropy demands put very strong limits on the types of models that can be derived from an entropic gravity formalism. This, again, is a double edged result for entropic gravity. On one hand, it strongly favors general relativity as a very special theory that can not be easily modified without serious consequences. On the other hand, it also limits entropic gravity to a narrow subset of physically possible models of gravity.
It remains to be seen if future work can narrow these results down further to either a unique theory of space-time (which may very well turn out to be GR), or, if entropic gravity will, eventually, be completely eliminated on formal grounds. StillFascinated ( talk) 06:40, 16 February 2013 (UTC)
Article is biased by criticism without adequate opposite point of view. Also it is low quality overall. I don't have time do rewrite it, but I will add some response to criticism to balance a little. wp:npov
If you are completely unfamiliar with the topic please don't edit with 'common sense approach'. -- Asterixf2 ( talk) 18:48, 10 March 2016 (UTC)
My personal judgment of 1001.0785v1 from a quick look is that Verlinde doesn't clearly state what space-time or alternative to space-time he starts off with. If space-time is emergent, then it has to be emergent from something. It would be OK to start off with just an abstract set, but things have to be defined clearly if this is to be more than just an heuristic essay. You cannot assume what you are trying to derive. Anyway, this is just my personal judgment and irrelevant for the article itself (unless i publish it somewhere in a reliable source :P).
What's more important is that most of the material should be shifted from the top down to some sections below which try to present the topic. The lead section (introduction) should then be just a condensed version of the actual content. Shifting material down the page is easy. Writing a short, NPOV summary is more difficult - which is why i'm leaving someone else to do it :P. Boud ( talk) 09:04, 1 October 2010 (UTC)
So if between elements occasionally information is lost from the collection, is that 'entropic gravity'? Or are we talking about something else? 178.255.168.77 ( talk) 21:22, 4 May 2016 (UTC) PS is there a better way of editing this stuff than in a text editor and with these stupid tildes and wotnot?
Should we mention Verlindes 2016 formulation as "Emergent gravity". Seems to improve and explains MOND. New Scientist reports on an experimental test of EG and says it passes without resorting to free parameters. EG: Emergent Gravity and the Dark Universe Verlinde 2016, Brouwers test : First test of Verlinde's theory of Emergent Gravity using Weak Gravitational Lensing measurements Brouwer 2016, NS news item : First test of rival to Einstein’s gravity kills off dark matter. Whereas MOND explains galactic rotations, EG seems to also explain galactic clusters that MOND had problems with (and provides an explanation/mechanism for MOND). - Rod57 ( talk) 10:27, 9 January 2017 (UTC)