> On 21 Apr 2019, at 08:07, Philip Thrift <[email protected]> wrote: > > > > 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 <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 > <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”.
Right. Like there is no absolute universal machine for the mindscape, including the world. Physics is not just coordinate independent, it is observer independent, and even more deeply (with mechanism) universal machine independent. That’s why we can use arithmetic, or combinator, or any Turing complete theory, any “phi_i”, for the ontology for the “theory of everything”. Bruno > > - 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] > <mailto:[email protected]>. > To post to this group, send email to [email protected] > <mailto:[email protected]>. > Visit this group at https://groups.google.com/group/everything-list > <https://groups.google.com/group/everything-list>. > For more options, visit https://groups.google.com/d/optout > <https://groups.google.com/d/optout>. -- 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.
