Talk:Theoretical motivation for general relativity

The name of the article should not have changed. MP  (talk) 17:23, 24 February 2006 (UTC)


 * I must agree with this. It does not cover the true foundations at all. --EMS | Talk 01:59, 27 February 2006 (UTC)


 * I changed the name to "Theoretical motivation for general relativity." Complexica 17:43, 10 August 2006 (UTC)

The section entitled "Principle of least action in general relativity" has multiple errors and needs to be corrected.
 * (1) Most obviously world line and geodesic are each defined very awkwardly in terms of themselves.
 * (2) The principle of least action doesn't "state" anything about the world line as the text erroneously suggests, although perhaps the world line is defined in terms of an "action" in the sense that term is used in the phrase "the principle of least action".
 * (3) The statement that the "shortest world line" is the geodesic ..." is completely unintelligible to me. It does not seem to agree with other definitions in Wikipedia of world line or geodesic.
 * (4) The reference to the Lagrangian density cannot be right in this context, assuming the referenced article to be correct. The referenced article says :Lagrangian density refers to an integrand used when integrating over all spacetime (volume element d4x), and I infer Lagrangian, unadorned, refers to an integrand over a timelike path (time elment dt) in spacetime.
 * (5) The reference to "orbiting particle" and "the earth" are unduly restrictive, suggesting the definition of the action is fundamentally about objects orbiting the earth, which it is not. I think it is simply about world lines of test particles (think "objects of negligible mass").

I would fix the problems, but I'm not enough of an expert to do it. If I figure out how to fix it, I will. It looks to me like I will have to look outside Wiki for the correct information as some other articles in Wiki also seem a little fuzzy. Thinkor (talk) 22:21, 24 December 2009 (UTC)