Talk:Alternatives to general relativity
From Wikipedia, the free encyclopedia
 |
This article is within the scope of WikiProject Physics, which collaborates on articles related to physics. |
| B | This article has been rated as B-Class on the assessment scale. |
| ??? | This article has not yet received an importance rating within physics. |
|
Help with this template This article has been rated but has no comments. If appropriate, please review the article and leave comments here to identify the strengths and weaknesses of the article and what work it will need. |
|
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)
- 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)
[edit] Suggestions for improvement
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)
[edit] Process Physics
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)
You make a good point, but since the article is "Alternatives to general relativity" it would be a bit biased to exclude some just becuase they don't have as much evidence behind them as some of the others mentioned here. Perhaps a better alternative would be to add a section entitled "other theories" or something like that, and then list there links to all other alternative theories, including those that have too little evidence behind them to merit a detailed explanation in this article. And then if one particular theory gets some better evidence to support it, it will be a reasonably simple process to add a new section to this article where it does get a detailed explanation. Bill Killed The Unicorns 02:50, 11 May 2007 (UTC)
[edit] Transported text
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,[citation needed] 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.
