On Saturday, April 20, 2019 at 4:14:27 PM UTC-5, [email protected] wrote: > > > > On Friday, April 19, 2019 at 2:53:00 AM UTC-6, Bruno Marchal wrote: >> >> >> On 19 Apr 2019, at 04:08, [email protected] wrote: >> >> >> >> On Thursday, April 18, 2019 at 6:53:33 PM UTC-6, Brent wrote: >>> >>> Sorry, I don't remember what, if anything, I intended to text. >>> >>> I'm not expert on how Einstein arrived at his famous field equations. I >>> know that he insisted on them being tensor equations so that they would >>> have the same form in all coordinate systems. That may sound like a >>> mathematical technicality, but it is really to ensure that the things in >>> the equation, the tensors, could have a physical interpretation. He also >>> limited himself to second order differentials, probably as a matter of >>> simplicity. And he excluded torsion, but I don't know why. And of course >>> he knew it had to reproduce Newtonian gravity in the weak/slow limit. >>> >>> Brent >>> >> >> Here's a link which might help; >> >> https://arxiv.org/pdf/1608.05752.pdf >> >> >> >> Yes. That is helpful. >> >> The following (long!) video can also help (well, it did help me) >> >> https://www.youtube.com/watch?v=foRPKAKZWx8 >> >> >> Bruno >> > > *I've been viewing this video. I don't see how he established that the > metric tensor is a correction for curved spacetime. AG * > >> >>
The physicists' vocabulary can be baffling (at least it is to me). I think the basic thing though is that the Einstein Field Equations (EFE) is not - in a sense - absolute. EFE is relative. Once one has established a coordinate system/metric (c-sys1) for "the world" independently, then EFE(c-sys1) provides a recipe for making predictions within c-sys1. Change c-sys1 to c-sys2, and EFE(c-sys2) calculates predictions in c-sys2. There is no absolute c-sys for "the world". - pt -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
