On Monday, July 6, 2020 at 5:29:51 AM UTC-6, John Clark wrote: > > On Mon, Jul 6, 2020 at 2:36 AM Alan Grayson <[email protected] > <javascript:>> wrote: > > *> For laws of physics to exist, they must be independent of coordinate >> system.* > > > That statement *IS* the Equivalence Principle, >
In every text that I've seen the EP is specifically related to gravity, and for good reason; namely, it is conditioned by "locally". In a gravitational field, two bodies allowed to fall free, do NOT take parallel paths. Each falls to the center of mass of the gravitating body. My statement above is NOT the EP. It's a general statement of the requirements of a law of physics. AG > it's just using different language, and Einstein passionately thought it > was true, but there were some instances where it didn't seem to be. For > example, if there was no limit on how fast you could move and the speed of > causality was infinite then you could move at the speed of light alongside > a light beam and if you looked at the light beam you would see that it > consisted of a unmoving standing wave of electric and magnetic fields; but > that's *NOT* what Maxwell's equations says it should ever look like. So > Maxwell's equation, a very important law of physics, would NOT be > independent of the coordinate system. > Before Einstein's 1905 paper, it was known that ME's are invariant under the LT. They predicted c for the SoL, but didn't specifically indicate in which coordinate system this would be true. They suggested it would be true in ANY coordinate system, and gave Einstein a clue about the invariance of the SoL for SR. AG > > Einstein was just about the only one who was bothered by this and so he > worked on the problem and in 1905 he found the solution, at least for > Maxwell's equations, he found a way to make them true regardless of the > coordinate system. > As previously stated, before 1905 it was known that ME's are invariant under the LT. In his 1905 paper, Einstein didn't modify ME's; he just modified Newtonian mechanics to make mechanics invariant under the LT. AG But doing the same thing for gravity was far far more difficult, he > concentrated on the problem for 10 years after that so hard he got sick, > lost 60 pounds and nearly died, but eventually he found a tensor to > describe how objects move through space-time and a tensor to describe how > mass curved space-time. And so with those tensors gravity became > independent of the coordinate system too > > *> I don't see what the EP has to do with this, * > > > I do. > > John K Clark > -- 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 view this discussion on the web visit https://groups.google.com/d/msgid/everything-list/61fb55d7-2a63-4dc8-a9ca-5afd6fa53fb9o%40googlegroups.com.
