Category talk:General relativity

Name changes, new categories

Hi all, I have been trying to improve the organization of these pages. No, I don't like the present top of this page either. I am trying stuff out and right now this is the best I can do. I feel that Category:Lorentzian manifolds is not really a parent of Category:General relativity nor vice versa, hence my playing around with "see also". Is there some Wikipedia convention is cases like this to make the two equally venerable but closely related categories parents of each other? If so, this might be a better solution.

Some of you might already have noticed that I have

• gathered articles on various tests of gtr into a new subcategory, "Tests of general relativity",
• gathered articles on various famous coordinate charts into a new subcategory, "Coordinate charts in general relativity",
• gathered articles on various exact solutions into a new subcategory, "Exact solutions in general relativity", and renamed the article "Exact solutions of Einstein's field equations" to "Exact solutions in general relativity" (yes, the article has the same name as the category, but after thinking about it, I think this actually has advantages; after all, we have an article called "General relativity" and a category of the same name).

I also moved the "General relativity" category a subcategory of "Theories of gravitation", and made articles on related theories like "Einstein-Cartan gravity" belong to this category. So, gtr has been "demoted" to just another theory of gravitation, but it is so far the only one which has a category of its own, as befits its extraordinary interest and importance.

(Note: following someone's suggestion, I removed the redundant remarks about certain pages I want to delete.)

Is this a feature or a bug?

While doing the work described above, I noticed that under "Articles in this category", several articles are listed after an asterisk. I also see that "Event horizon" and "Gravitational lens" are listed at the end, after a curly brace. I suspect this might reflect some broken wikicode, but haven't figured out what is causing this.

See Template_talk:General_relativity --EMS | Talk 22:19, 27 July 2005 (UTC)

Reversion of comment by Techguru

Hi, Techguru, thanks for your interest in these pages. Einstein said "everything should be made as simple as possible, but no simpler". I feel that the comment you added to the little introductory blurb on this category page, "simply put relativity is stating that time is relative to the observer", was too simple. Much too simple. That's why I removed it. By the way, you typed the first letter of your sentence immediately after the period of the preceding sentence, and you omitted (I think) a comma after "simply put", so in future edits you may want to be more careful about punctuation.---CH (talk) 18:13, 5 August 2005 (UTC)

Intro is too big.

I think that the intro has gotten too big. The goal is to explain what this category is about, not to document GR itself. (After all, we have the general relativity article for that.) I would like to shorten it back to about 3 medium length sentences or perhaps 4 short sentences. However, I do not see a good way to do that just yet. (What I am considering doing is pruing everything starting with "In this theory ...". I notice that doing so removes some of my own verbage, but I guess that says something about the utility of that verbage.) --EMS | Talk 19:03, 7 August 2005 (UTC)

Recategorizations

Hi all, I think it is important to distinguish between

1. concepts which belong to general relativity itself, such as
   • ADM energy
   • Birkhoff's theorem
   • Einstein field equation
   • Einstein-Hilbert action
   • Einstein tensor (defined more generally, but very closely associated with this theory)
   • Frame fields in general relativity (since on frames in gtr, not frames in Lorentzian manifolds)
   • Numerical relativity
   • Penrose-Hawking singularity theorems
   • Petrov classification
   • Regge calculus
   • Segre classification (sort of)
   • Weak-field approximation, plus billions and billions of forthcoming articles, e.g. on Initial value formulations and ADM formulation,
2. concepts which involve Lorentzian manifolds, such as
   • Christoffel symbols
   • Asymptotically flat spacetime
   • Einstein notation
   • Geodesic deviation equation
   • Geodesic (general relativity) (needs to be renamed!)
   • Ricci decomposition
   • Spacetime symmetries
   • Spherically symmetric spacetime
   • Static spacetime
   • Stationary spacetime,plus some articles I've already moved to a new category.

Note that the new category Category:Lorentzian manifolds concerns concepts concerning Lorentzian manifolds (four dimensional psuedo-Riemannian manifolds with 1+3 signature), including their interpretation as spacetimes.

Many articles are misnamed, e.g. Gravitational singularity should probably be Curvature singularity, in which case it should perhaps be in the new category.

Some others are a bit iffy:

• Geometrized unit system (I'd be inclined to keep it here)

Thoughts? ---CH (talk) 12:08, 2 September 2005 (UTC)