Talk:Geometrodynamics

Gosh, I tried to add a comment here an hour so so ago, but apparently it didn't take.

I was trying to say that I just added to the article some citations to print books which I think rather decisively show that the article as it stands mischaracterizes the state of geometrodynamics. First, in two books coauthored by Wheeler and published in 1973, 1995 respectively, he uses Einstein geometrodynamics as a synonym for general relativity, which has certainly never become anabandoned domain of physics! Second, one article in the book edited by Butterfield is on quantum geometrodynamics, which is very much alive.

So I think this article needs to be thoroughly rewritten. If no-one objects (is anyone but me "watching" this page?), I'd like to do that in the next week or so.

I'm watching now, :) --MarSch 13:24, 24 Jun 2005 (UTC)

Thanks, MarSch. I will get some of those books, refresh my memory, and try to rewrite the article in the next few days. --CH (talk) 1 July 2005 03:47 (UTC)

You say [Wheeler] "uses Einstein geometrodynamics as a synonym for general relativity". That was my understanding as well, so I was also disconcerted by the article's claim of abandonment. If you do write something to straighten it out, it would be great. GangofOne 20:37, 19 July 2005 (UTC)

Gosh, I'm agreeing with GangofOne! What a strange world. --Pjacobi 20:44, July 19, 2005 (UTC)

Geometrodynamics and GR

MTW's opening scene-setting chapter is called "Geometrodynamics in brief", I think that Wheeler seems to be referring to geometrodynamics as an ongoing research project or concept or "work in progress" rather than a specific finished theory – like the principle of relativity, or the principle of equivalence, individual attempts at implementing the idea can fail without invalidating the basic idea.

Wheeler, A journey into gravity and spacetime (1990) pp.118,

"Einstein's 1915 battle-tested and still-standard law of geometrodynamics, his famous field equation."

But going back to MTW's Gravitation (which calls its introductory chapter, "Geometrodynamics in brief"), we find this:

W.K. Clifford, 1870/1879/1882, quoted in MTW Gravitation, section 44.3 pp1202-1203

“I hold the fact (1) That small portions of space are in fact of a nature analogous to hills on a surface which is on average flat; namely, that ordinary laws of geometry are not valid on them. (2) That this property of being curved or distorted is continually being passed from one portion of space to another after the manner of a wave (3) That this variation in the curvature of space is what really happens in that phenomenon which we call the motion of matter, whether ponderable or etherial. (4) That in the physical world nothing else takes place but this variation, subject (possibly) to the law of continuity.”

MTW continues:

“Ask if there is a sense in which one can speak of a particle constructed out of geometry. Or rephrase the question in updated language: “Is a particle a geometrodynamic exiton?” What else is there out of which to build a particle except geometry itself?

The Clifford-Einstein space theory of matter has not been forgotten in recent years. …

Wheeler (1962, again quoted on pp.1202)

“the vision of Riemann, Clifford and Einstein, of a purely geometric basis for physics, today has come to a higher state of development, and offers richer prospects – and presents deeper problems – than ever before.”

Why General Relativity Needs To Be Modified

General Relativity has proven to be satisfactory for most purposes. The exception occurs in cases of high energy and short distances where Quantum Mechanics cannot be ignored. Quite a lot has been published by research groups attempting to join GR with QM. Examples are causal set theory, loop quantum gravity, twistor theory, noncommutative geometry, and string theory. Robert J. Low of Coventry University remarked in a recent discussion on Research Gate "Everybody who knows enough about it to understand the question expects GR to break down at very high energies." Topological Geometrodynamics or TGD has been developed by a theoretical physicist in Finland Matti Pitkänen for about 40 years as one of the many attempts to modify GR for high energy. TGD has become associated with Scale Relativity of Laurent Nottale, and Squeezed Coherentstates in the high energy range. Astrojed (talk) 19:32, 16 August 2017 (UTC)

Compatibility

Of course, the penalty associated with taking Clifford's approach literally, and applying curvature arguments to conventional mechanics, is that the familiar flat-spacetime physics of special relativity no longer seems to appear anywhere in the description: If all moving-body problems can be described purely in terms of curvature, we have velocity-dependent curvature, and since SR's relationships are a special-case solution for flat spacetime, we no longer have the standard SR equations of motion and Doppler relationships, but … Something Else. Lose the crutch of Euclidean geometry, and we are left looking at a big scary blank page. Its the "total rewrite" option.

So, in that sense GMD does not seem to be the same thing as current GR.

This is good and bad: If a full GMD model is not SR-compliant, it doesn’t fit our usual definition of a "credible" classical theory, which might lead some theorists to decide that the GMD idea is discredited … but since it seems that the current "credibility" criteria only pass theories that are incapable of recreating Hawking radiation effects, perhaps any theory that s going to have to deal with the black hole information paradox needs to fail these criteria to have a chance of working. ErkDemon 00:46, 29 August 2005 (UTC)

I added some more info on Einstein's Gemometrodymanics, just the summary of the basics..

(unsigned and undated comment added by 69.106.75.129)

Thanks, but I think you missed the point of that paragraph, whihc is to very briefly describe a specific formulation of general relativity, the ADM initial value formulation. Possibly this paragraph can be further improved once we have better articles on that, but in any case the quotation you used--- which is due to John Archibald Wheeler-- is already mentioned (with attribution) in more appropriate places elsewhere in the Wikipedia).---CH (talk) 15:28, 2 October 2005 (UTC)

New version

I just completely rewrote the article. I think the new version is accurate and NPOV, but this is complicated stuff and without articles on ADM, superspace, and all that to refer to, it is not really possible to truly explain the full context for Wheeler's ideas. I also added some more citations. The Ph.D. thesis of Anderson is particularly useful for learning about how Wheeler's ideas evolved and how Butterfield, Isham, and their students have taken up baton. I hope everyone is now happy!---CH (talk) 14:22, 29 August 2005 (UTC)

* Much better than the original, cheers! ErkDemon 23:24, 30 August 2005 (UTC)

I've just stumbled across this page. IMHO it still needs a complete rewrite. There is no mention of the actual essence of geometrodynamics, i.e., the formulation of general relativity as a theory based on a configuration space of three-metrics modulo three-dimensional diffeomorphisms. This area is actually quite far from dead, and some very interesting work has been done over the past year or so. If nobody objects, I would like to try to add in considerably more relevant tecnhical details.

81.107.35.121 (talk · contribs)

This could be helpful if you cite reliable sources (preferably using appropriate [templates]), assuming that you can minimize any conflict of interest from over-citing your own papers and that you avoid WP:NOR by citing review articles in mainstream journals like Rev. Mod. Phys or Living Reviews where possible. Please keep in mind that while we aim high, this is a general encyclopedia, not RMP, so try to choose your citations wisely. While registering is optional, we have a problem with shills making POV-pushing edits, so I would find it very helpful if you register and provide a bit of information (ideally, a real name) so that we can easily verify your expertise and assure ourselves that you are not pushing some peculiar point of view (see this for a recent bad example which you don't want to follow!). Be assured that in the spirit of WP:AGF we do recognize that anyone with sufficient expertise to improve my version will probably have published in this area, so we can cut some slack vis a vis writing about your own contribs; what really matters is to keep it unbiased. TIA ---CH 06:44, 19 June 2006 (UTC)

Students beware

I extensively rewrote the August 2006 version of this article and had been monitoring it for bad edits, but I am leaving the WP and am now abandoning this article to its fate.

Just wanted to provide notice that I am only responsible (in part) for the last version I edited; see User:Hillman/Archive. I emphatically do not vouch for anything you might see in more recent versions. Given past history, I have some reason to believe that at least some future versions are likely to present slanted information, misinformation, or disinformation. Beware also of external links to other websites, which may well present a misleading account of this topic.

Good luck in your search for information, regardless!---CH 23:54, 30 June 2006 (UTC)

Thank you sir. I bow to a superior Jedi.

Seriously,

-- HelviticaBold 02:20, 1 March 2012 (UTC)

Clifford link

Before the International Congress for Logic, Methodology, and Philosophy of Science in 1960 Wheeler began by quoting William Kingdon Clifford's "Space theory of Matter" of 1870.

Can we get links in the references to those two? Crasshopper (talk) 07:31, 19 September 2011 (UTC)

You have a MAJOR mistake (vaguness is a mistake in encyclopedias; a complete reality I never elaborated; but I used the poetic word)

You philosophically and unmathematically claimed: completely in terms of geometry. (and not in terms of entropic geometry - and then we have to create the missing page)

Emotional words are wrongly put in science.

Usually geometry is static/non-evolving.

In geometrodynamics geometry is entropic; everchanging and evolving (series of calculations that do not stop).

Fix your vague mistake. — Preceding unsigned comment added by 2A02:587:4104:B0C1:41A3:E72B:1F52:909C (talk) 00:20, 13 July 2020 (UTC)