Talk:Maxwell's equations in curved spacetime

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[edit] spacetime is dynamic

It's true that general relativity dictates that spacetime be dynamic. But nowhere in this article is any use made of that assumption. It seems pretty irrelevant, so I'm removing it. And adding something to the intro to suggest that we actually still have the same equations. -lethe ^{talk +} 22:15, 5 April 2006 (UTC)

OK, I understand now why the intro wants to mention that spacetime is dynamic, and why it is relevant. The fact that spacetime must get a curvature from the electromagnetic field means that there is no such thing as Maxwell's equations in flat spacetime. I don't think the intro made that clear before (I didn't realize that's what it was saying, for example), and I've tried to improve that.

The intro still had problems though: the equations presented in this article are not really a generalization of Maxwell's equations, unless you restrict the meaning of the phrase "Maxwell's equations" to mean only that form of the equations you learned as an undergraduate. Introducing an explicit metric dependence is useful even when you want to do Maxwell's equations in spherical coordinates on flat spacetime. It is the first step towards a coordinate independent formulation. Once you do have your coordinate independent formulation, you see that actually, Maxwell's equations are exactly the same in curved spacetime. I've rewritten the intro to try to reflect this view. -lethe ^{talk +} 16:37, 6 April 2006 (UTC)

I knew there were some iffy issues regarding generalisation, approximations etc. of Max. Eq.'s. I didn't want to mention them right at the start of the article, as that's not where these technical issues belong. But your rewriting of the intro. is good - you've worked well around these issues whilst keeping the important points where they should be. MP (talk) 09:52, 7 April 2006 (UTC)

[edit] formatting

I didn't like some of your formatting changed, Mpatel. For starters, the Manual of style suggests (and I agree) that we shouldn't start a sentence with a math symbol (you start one clause with a *). Also, I really don't like inline tex, so I'm changing that back. Finally, you changed the equation from *d*F = j to d*F = *j. As far as I can tell, one of these equations must be wrong by a minus sign, since *²=–1 on two forms in any spacetime with signature 1. I thought that the first equation was the proper one, but I'm not positive. I guess I'd like to get straight on that. -lethe ^{talk +} 17:35, 8 April 2006 (UTC)

[edit] Black hole lensing gif

It should be common sense that a 10 mb picture shouldn't be on the front page. I don't really care to start an edit war over it.