Talk:Alternatives to general relativity

message: Welcome to a new Wikipedia page. I started it after finding that Wikipedia articles on gravity and alternatives to General Relativity were a complete mess, with several excellent articles (eg. on Brans-Dicke), many substandard entries, and nothing like a proper index.
As I write this the page is still under construction. I've still to add the rest of the equations, a big table of PPN results, add footnotes, add all the cross-references within, from and to the article, and fix the glaringly obvious faults.
So please don't edit the page until 2 Sept 2006. After that, go for it!
Mollwollfumble 01:09, 25 August 2006 (UTC)
replies: text: My advice is to keep plugging away on this article.  In both content and title it is much better than classical theories of gravitation.  --EMS | Talk 03:12, 31 August 2006 (UTC)
thread_title:  new Wikipedia page 

message: Hi there. I would really like to see this article improve, as it has the potential to be a very good article indeed. That's not to say it's not a good artile at the moment. I would say that, overall, most (all ?) of the important information is already present in the article (good work Mollwollfumble!). The only question is one of making the article much better (by Wikipedia's rigorous standards). I would like to suggest the following improvements/points for discussion:
* The 'Classification of theories' (section 4.1) should come before the 'Early theories' section (number 3).
* Having thus classified the theories, is it better to group the theories in chronological order or by type (bimetric theories, scalar theories etc...) ? My preference is by type; this should be discussed though.
* The 'Testing of alternatives to GR' section could be split of into another article. Thoughts ?
* There should perhaps be main article links to the articles that describe the theories in more detail (as there is for the 'Testing of alternatives to GR' section) - this is mainly for better and more consistent presentation. 
These are just a few ideas off the top of my head that I felt should be worth discussing to improve the article. Mollwollfumble, you have done some very good work in presenting details of Lagrangians etc... and finding all those references. I hope more editors will be encouraged to help improve this article. Thanks for reading this. MP   (talk) 20:00, 1 April 2007 (UTC)
thread_title:  Suggestions for improvement 

message: The section for Process Physics, under "Other Modern Theories", seems to have been removed for the reason that it has not been published in well-known notable journals. May I suggest you read Process Physics, including it's talk section, and reconsider whether it belongs here or not. There are several scientific articles referenced on that page which would definitely be worth a look.
I personally think it at least needs to be mentioned as an alternative theory, with a link to the main article. I'll leave it up to you as to what you want to do with this. Bill Killed The Unicorns
: As far as I see, process physics is in the category "fringe physics" and the "Fringe subjects without critical scientific evaluation". Ok, I'm also interested in alternative theories, but what do you think is happening if every non-mainstream theory, which is not published in reputable sources, will be included in the article? For example, look at Heim theory and so on. --D.H 09:19, 4 May 2007 (UTC)
thread_title: Process Physics

message: I've transferred the following text from Talk:General relativity/WIP#Alternatives to general relativity; that section has been considerably shortened, but the removed info. (i.e. the following text) may still be useful for this article:
*Nordström's theory of gravitation (1913) was one of the earliest metric theories (an aspect brought out by Einstein and Fokker in 1914). Nordström soon abandoned his theory in favor of general relativity on theoretical grounds, but this theory, which is a scalar theory, and which features a notion of prior geometry, does not predict any light bending, so it is solidly incompatible with observation.
*Alfred North Whitehead formulated an alternative theory of gravity that was regarded as a viable contender for several decades, until Clifford Will noticed in 1971 that it predicts grossly incorrect behavior for the ocean tides.
*George David Birkhoff's (1943) yields the same predictions for the classical four solar system tests as general relativity, but unfortunately requires sound waves to travel at the speed of light. Thus, like Whitehead's theory, it was never a viable theory after all, despite making an initially good impression on many experts.
*Like Nordström's theory, the gravitation theory of Wei-Tou Ni (1971) features a notion of prior geometry, but Will soon showed that it is not fully compatible with observation and experiment.
*The Brans-Dicke theory and the Rosen bimetric theory are two alternatives to general relativity which have been around for a very long time and which have also withstood many tests. However, they are less elegant and more complicated than general relativity, in several senses.
*There have been many attempts to formulate consistent theories which combine gravity and electromagnetism. The first of these, Weyl's gauge theory of gravitation, was immediately shot down (on a postcard) by Einstein himself, who pointed out to Hermann Weyl that in his theory, hydrogen atoms would have variable size, which they do not. Another early attempt, the original Kaluza-Klein theory, at first seemed to unify general relativity with classical electromagnetism, but is no longer regarded as successful for that purpose. Both these theories have turned out to be historically important for other reasons: Weyl's idea of gauge invariance survived and in fact is omnipresent in modern physics, while Kaluza's idea of compact extra dimensions has been resurrected in the modern notion of a braneworld.
*The Fierz-Pauli spin-two theory was an optimistic attempt to quantize general relativity, but it turned out to be internally inconsistent. Pascual Jordan's work toward fixing these problems eventually motivated the Brans-Dicke theory, and also influenced Richard Feynman's unsuccessful attempts to quantize gravity.
*Einstein-Cartan theory includes torsion terms, so it is not a metric theory in the strict sense.
*Teleparallel gravity goes further and replaces connections with nonzero curvature (but vanishing torsion) by ones with nonzero torsion (but vanishing curvature).
*The Nonsymmetric Gravitational Theory (NGT) of John W. Moffat is a dark horse in the race.
MP (talk•contribs) 20:58, 29 November 2007 (UTC)
thread_title:  Transported text 

message: In Einstein–Hilbert action, we see that the Einstein field equations follow from using a constant times the Scalar curvature as the gravitational Lagrangian. Suppose we just add a little bit of the square of the Riemann–Christoffel tensor, R^{\alpha}_{\beta \gamma \delta} R^{\mu}_{\nu \rho \sigma} g_{\alpha \mu} g^{\beta \nu} g^{\gamma \rho} g^{\delta \sigma} \,? Have any alternative theories like this been proposed or evaluated? JRSpriggs (talk) 18:22, 13 June 2008 (UTC)
replies: text: I should have said something about why one would want to do this. I was wondering how we could modify general relativity to eliminate the problem of singularities. If intense gravitational fields created anti-gravity (similar to the cosmological constant), then that might do it. Adding a term like the one I mentioned (if one gets the sign right) might do it, I hope. JRSpriggs (talk) 14:55, 15 June 2008 (UTC)
replies: text: I recently saw a mention of Einstein-Gauss-Bonnet gravity which apparently adds a small contribution for the square of the Riemann-Christoffel tensor and the square of the Ricci curvature and the square of the scalar curvature. I think that this article should cover EGB! JRSpriggs (talk) 06:42, 20 July 2008 (UTC)
replies: text:  just created an article on Gauss-Bonnet gravity. JRSpriggs (talk) 07:16, 4 July 2010 (UTC)
thread_title:  How about just tweaking the dependence of the action on the Riemann–Christoffel tensor? 

message: There is a new gravity theory that has been published. It passes all experimental tests of GR, and in addition a corporation is using the new theory as the basis for their alternative energy tests. This theory should really be listed on this page... even if it is just a link to the theory. The theory is called Gravity Theory Based on Mass-Energy Equivalence.  Gravityforce (talk) 22:54, 20 November 2008 (UTC)
thread_title:  New alternative gravity theory

message: I can't find the article for  J. W. Moffat.  Anybody know what it is listed under?
Moffat is of no help. FX (talk) 20:02, 4 February 2009 (UTC)
replies: text: Is John Moffat (physicist) the right one? - Eldereft (cont.) 20:24, 4 February 2009 (UTC)
thread_title:   J. W. Moffat? 

message: Which formula does Nasa find most accurate when calculating orbits etc?  —Preceding unsigned comment added by 86.135.98.182 (talk) 01:27, 9 April 2009 (UTC)
replies: text: I do not know what they do, but I would guess that they use Parameterized post-Newtonian formalism with parameters which match General Relativity itself. But the general relativistic corrections are probably small compared to the corrections needed to deal with the Sun, Moon, and planets, and mass concentrations in the Earth (e.g. mountains), and special relativity. JRSpriggs (talk) 04:07, 9 April 2009 (UTC)
thread_title:  Nasa 

message: In the section Alternatives to general relativity#Classification of theories, the various types of metric theories are supposed to be listed from simplest to most complex. However, bitensor (η,g) theories are listed before tensor (g) theories (including GR) even though they are more complex than GR. JRSpriggs (talk) 13:49, 14 March 2011 (UTC)
thread_title:  Bitensor are more complex than GR 

message: Text uses eta, table xi, for "check for preferred location effects".  At least I think that's the problem.
Too stupid to try to change it.
200.104.177.67 (talk) 20:05, 19 January 2013 (UTC)
replies: text: If you look at Parameterized post-Newtonian formalism, you will see that there are two different sets of parameters used. One of them includes η and the other ξ. Does that answer your question? JRSpriggs (talk) 22:26, 19 January 2013 (UTC)
thread_title:  Minor error 

message: They should not be. General relativity is understood to be theory that only works at distances large compared to the Planck length. To talk about general relativity or its alternatives is already to imply that we're talking about macroscopic distances, so an article about "alternatives to GR" should clearly mean theories that lead to different experimental consequences at observable scales. Quantum gravity theories/TOEs aren't "alternatives" to GR because GR doesn't make predictions for Planck-scale experiments. The rest of the text seems more or less wise to this fact, since I think they're only mentioned one other brief time. Im guessing this part of the lead should be rewrote to say something along the lines of what I just wrote. Isocliff (talk) 23:17, 26 April 2013 (UTC)
replies: text: The lead merely mentions them to make it clear that this article does not cover them, and provide links to articles that do. Is that not just what you are asking for? Perhaps you should read the whole lead more carefully. JRSpriggs (talk) 06:44, 27 April 2013 (UTC)
thread_title: Why are quantum gravity and TOE's part of the lead?

message: It seems to me that the article on Modified models of gravity should be merged into this article. The "Modified models of gravity" article is very short, doesn't really contain any information that's not found in "Alternatives to general relativity", and is not in fact a different topic. The worst part of having two separate articles is that readers of one aren't necessarily aware of the other's existence -- looking for the article on Modified Gravity I came first upon "Modified models of gravity" and have only recently discovered that this much more detailed article exists. HFD90 (talk) 02:13, 24 October 2014 (UTC)
replies: text: Yes, I agree and will do this soon if no one disagrees. Absolutelypuremilk (talk) 14:35, 6 December 2015 (UTC)
replies: text:  I have done this now Absolutelypuremilk (talk) 14:18, 14 December 2015 (UTC)
thread_title:  Merger proposal 

message: The article tries to cover two topics simultaneously: the historical alternatives to general relativity, and modern day modifications of general relativity. That's why the article's such a mess. Plus, since the article is defined itself so broadly, it lets people try and sneak in fringe theories which reject general relativity altogether. The article should be cleaned up and split into two new articles, Historical alternatives to general relativity, and Theories modifying general relativity. cnte (talk) 17:33, 22 March 2018 (UTC)
replies: text: Well, it is really a list of notable theories of gravity. It shows what the competition is or has been for GTR. I do not see the benefit of narrowing the focus as you are effectively suggesting. There will always be people trying to sneak in fringe ideas. Better here than in some other places. JRSpriggs (talk) 01:27, 23 March 2018 (UTC)
replies: text: It's not really a narrowing of focus. There's two different topics, the history of general relativity and the theories which people developed against it, and modern theories which attempt to modify general relativity. One's a topic about history, the other's a topic about modern theoretical physics, so they require different approaches and treatments. My suggestion *would* eliminate theories which outright contradict general relativity, but that's ridiculous. Wikipedia isn't the place for fringe theories, unless they're notable for some other reason, and they can always be included in a subsection. cnte (talk) 21:00, 23 March 2018 (UTC)
replies: text: Virtually all theories of gravity other than general relativity itself and those theories which include it as a special case (for certain values of their parameters) have already been disproven either by experiment or by showing that they are self-contradictory. So this article is really about those "fringe" theories. If you take them out, there is nothing left. And they should be covered by Wikipedia, so that readers can know what they are and why they were rejected. JRSpriggs (talk) 21:31, 23 March 2018 (UTC)
replies: text: Huh? As far as I know, theories which modify GR (to e.g., explain the dark force) still exist and are debated by physicists, not to mention string theory and loop gravity. They are not yet disproven, and these are qualitatively different from fringe theories which outright ignore parts of general relativity. And this is missing the point anyway, because the article still covers two different topics. Do historical alternatives to GR and modern modifications of GR really need to be crammed into the same article? On some level, they might be same thing, but from an encyclopedic point of view, they deserve separate treatment. cnte (talk) 08:53, 24 March 2018 (UTC)

text: Correct me if I am wrong, but no one knows how to calculate the perihelion  precession of Mercury or the deflection of light by the Sun from either string theory or loop gravity. If the theory cannot make a unique prediction which can be tested, then that amounts to failing the test. Maybe the theories can be patched up someday, but that has not happened yet. JRSpriggs (talk) 06:48, 25 March 2018 (UTC)
replies: text: String theory, LQG and whatever else is discussed have to reproduce general relativity in the limit of large distances. They all agree with the GR calculation for the perihelion precession of Mercury and similar tests of relativity. The differences appear where quantum mechanics becomes relevant (together with gravity). It is unclear how this region can be tested, but that doesn't mean it would be impossible. --mfb (talk) 08:42, 25 March 2018 (UTC)
replies: text: Their proponents want them to approach general relativity as \hbar \to 0, but can they prove that they do? JRSpriggs (talk) 01:08, 26 March 2018 (UTC)
thread_title:  Article split 

message: As far as I understand, loop quantum gravity seeks to merge relativistic effects with quantum mechanics, creating a theory that satisfies both. LQM doesn't compete with relativity; it accepts it as correct and synthesizes it with quantum mechanics. With this in mind, I don't quite see its relevance to this article, which concerns alternatives to the theory of relativity.  — Preceding unsigned comment added by Micah von stauffenberg (talk • contribs) 22:29, 12 December 2018 (UTC)
replies: text: Just like special relativity has classical mechanics as a limit LQG should have general relativity as a limit, but that is true for all alternatives discussed here: They all have to reproduce the predictions of general relativity where they have been tested. It is still a separate theory that tries to be more general. --mfb (talk) 15:05, 13 December 2018 (UTC)
thread_title:  LQM? 

message: I could not find any reference to Logunov's theory of relativistic gravity (RTG).
162.211.38.110 (talk) 16:51, 28 July 2020 (UTC)
replies: text: If you have any independent reliable sources describing Anatoly Logunov's theory and taking it seriously, please add a section to the article based on those sources. JRSpriggs (talk) 14:34, 29 July 2020 (UTC)
thread_title:  Logunov's theory?? 

message: For completeness the table of PPN parameters should have the parameters for Newton's theory at the top before the parameters for Einstein's theory. I believe that they would be all zeros. Does anyone have a reliable source to back that up? JRSpriggs (talk) 16:21, 4 September 2020 (UTC)
thread_title:  PPN parameters for Newton's gravity? 

message: Please see User:JRSpriggs/MOND. JRSpriggs (talk) 21:49, 19 March 2023 (UTC)
thread_title:  My suggestion 

message: https://zenodo.org/records/10035511
Significant enough for inclusion in this article? 
Mss1 = \frac{2\pi{R1}^3/3(1-cos(sin{^-}{^1}(R2/D)))}{\pi{R1}^3/3\cdot4}M1
Mss2 = \frac{2\pi{R2}^3/3(1-cos(sin{^-}{^1}(R1/D)))}{\pi{R2}^3/3\cdot4}M2
Then: 
F = (G\cdot{Mss1})\cdot(G\cdot{Mss2})
Where:
G = 1.13832865e−9
F = Gravitational force (N)
M1 = Mass of body 1(kg)
M2 = Mass of body 2(kg)
Mss1 = Effective mass of body 1 (kg)
Mss2 = Effective mass of body 2 (kg)
D = Distance between bodies (m) 
R1 = Radius of body 1 (m)
R2 = Radius of body 2 (m)
The theory basically dispenses with dark matter, general relativity, Newton’s law on gravity and the use of the inverse square. It also explains gravitational waves classically. 
The oracle 2015 (talk) 23:17, 13 December 2023 (UTC)
thread_title:  Effective Mass Theory of Gravity