Talk:Scalar theories of gravitation

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This article was nominated for deletion on 2005-11-07. The result of the discussion was keep. An archived record of this discussion can be found here.

Contents

[edit] Comments on the earlier article, Scalar gravitation

Note: following an AfD, this article was moved and completely rewritten; the following comments in this section apply to the old article, not to the present one, which is completely different. For comments on the new article, start here.---CH 01:57, 3 December 2005 (UTC)


[edit] This article is misleading, inaccurate, and appears to violate WP:NOR

The fact that this article is by an anonymous editor and cites a "web-book" by one Paul Bird, rather than a reputable textbook, or research papers published in a reputable journal, should raise a red flag. The IP address 62.137.136.136 is registered to a company called Energis UK, which provides dialup access to customers in the UK. The website which hosts the cited web-book is apparently provided by a company called Tiscali UK Limited, which provides web hosting services for customers in the UK. While this is prima facie weak evidence, wiki-experienced users will understand immediately why I suspect that the anonymous editor is none other than Paul Bird.

In fact, while Bird (?) presents his theory as a supposedly viable alternative to classical relativistic theories of gravitation studied in the scientific literature, scalar theories are not viable as fundamental theories of gravitation, although they can be useful pedagogically. See for example the standard textbook by Gravitation by Misner, Thorne, and Wheeler, and then see the interesting paper by Watt and Misner, Relativistic Scalar Gravity.

One specific thing I noticed which is somewhat comical: the author gives a solution for his field equation (in this case, it reduces to the usual wave equation in polar spherical coordinates) a + b / r in the form 1 − 2m / r, i.e. with suggestively chosen/named values for the undetermined constants, and then claims in the next section that the alleged fact that the mass parameter m falls out is remarkable evidence of the theory's veracity! Of course, on the basis of the description here, it was the author himself who arranged for the parameter m to appear so "miraculously". Anyone familiar with differential equations or physical theories will take the point immediately (and probably have a chuckle), but unfortunately, the general public is unlikely to be sufficiently sophisticated mathematically to spot this absurdity for what it is.

Another obvious problem is that Bird calls his theory "relativistic", but the metric does not appear in his action, so presumably he does not have in mind a metric scalar theory of gravitation, and his "action" suggests he intends some kind of flat background scalar theory, but he doesn't even appear to realize that these points require qualification. Similarly for his putative force law, which appears without any discussion, much less attempted justification.

In short, on the basis of the description here, this constitutes unpublishable dreck and should not be presented in the WP as a viable physical theory.---CH (talk) 00:35, 7 November 2005 (UTC)

Special Relativity does not need a metric in the sense of a variable metric which is different for each point in space-time to define the curvature of space-time because special relativity is not about curved space-time. Of course you can write the flat space-time metric explicitly if you want to but this is by no means necessary. I fear that some of the comments expressed in this discussion are by interested amateurs who do not really know a lot of mathematics or physics, but like to think they do.

—Preceding unsigned comment added by 62.137.135.52 (talk • contribs) (dialup IP in London, registered to Energis UK, an ISP headquartered in Leeds) 12:31, 10 November 2005

[edit] Response to criticisms

In response to the criticisms by Hillman I have made changes to the article to make clear

  • The results of Scalar Gravity are not compatible with current experimental results
  • The theory satifies Special Relativity (which does not need a metric) but not General Relativity
  • This is not Paul Bird's original theory but a theory considered by many including Einstein before he arrived at General Relativity. There is no reason to hide this historical and interesting fact.
  • Hillman concedes that Scalar Gravity theories can be useful and hence this is good reason to have an article on Wikipedia about them.
  • The value, m, results from the fact that the source term of the wave equation is the mass-energy field and that the 2 is convential (see General Relativity) in order that the theory reduces to Newtonian physics without redefining the constants. This is well known standard practice.

Finally I object to the word drek which is 'inflamatory' and should not be used on Wikipedia.

—The preceding unsigned comment was added by 62.137.135.0 (talk • contribs) 18:26, 7 November 2005 (UTC)

I guess the article would be more acceptable if it made clear that this is just a toy model (assuming that is the case), which is perhaps being studied to get some kind of feeling, but which is not being considered as a possible alternative to general relativity. Bird's web page does at least give the impression that he thinks of it as a viable physical theory, and that seems to be an extremely rare, perhaps unique, opinion.
Furthermore, provide more references, for instance for the fact that the theory was considered by Einstein, or for the four-derivative form, and the guess that that's renormalisable. If it is a theory considered by many, then that shouldn't be hard.
There are some more problems, in that it pretends in the introduction that there is a single theory of scalar gravity, while there seem to be more, and that it presupposes a lot of knowledge without mentioning it.
Finally, a caveat: I am not a physicist. -- Jitse Niesen (talk) 19:24, 7 November 2005 (UTC)
This anon's comments only help to impeach him/her. Perhaps the most egregous is the odd assertion that SR does not "need" a metric. SR very much is a metric theory, albeit one without a gravitational field. Also, while it is true that scalar gravity was "considered by Einstein", the researcher who did much of the early work on "scalar gravity" theories was Gunnar Nordström. Finally, as shown in this arXiv article of scalar gavity (which BTW looks to me like a good starting point for rewriting this article), the field equations (and probably also the metrics) given in the current article are not at all the ones the Nordtröm experimented with. --EMS | Talk 05:44, 10 November 2005 (UTC)
P.S. I find this editor's objections to the use of the word "drek" to hardly be worthy of support. While perhaps more direct than is preferable, it certainly gets the point across about the unsuitability of this article as written by this anon. --EMS | Talk 05:44, 10 November 2005 (UTC)

[edit] Article rewritten

I assume that I need not elaborate on the deficiencies of the previous version which led to this. Suffice it to say that I suggest that the new version be kept but renamed to scalar theories of gravitation as described above and in the AfD page. --EMS | Talk 04:53, 12 November 2005 (UTC)

Ed, good job. (I'm still officially on break, just dropped by to check for messages.) ---CH 01:58, 3 December 2005 (UTC)

[edit] Article needs more work

This article still needs a lot of work, although it might be useful to postpone revision until more good articles on specific theories are available in WP. Some problems I noticed:

  1. the section of Nordström's theory and Einstein (should probably be Einstein-Grossmann) scalar theory say nothing not said more clearly in Nordström's theory of gravitation. That article isn't perfect either, of course, and it would be good to have a comparable article on the Einstein-Grossman theory as part of the history of science project, linked to the articles on hole argument and the article on Nordström's theory.
  2. the last section is veering off into a list of classical theories of gravitation, including an obscure scalar-tensor theory of Zee which apparently is not available on-line (and is probably insufficiently notable).

HTH ---CH 21:36, 17 April 2006 (UTC)

Hmm... just noticed that both those problems date right back to the version of 09:10, 13 November 2005 by our London anon, this time using 62.137.134.78 (again, dialup from London to the ISP Energis UK). ---CH 21:45, 17 April 2006 (UTC)