On Wednesday, March 20, 2019 at 12:51:18 PM UTC-6, Brent wrote: > > > > On 3/20/2019 3:07 AM, [email protected] <javascript:> wrote: > > > > On Tuesday, March 19, 2019 at 7:23:29 PM UTC-6, Brent wrote: >> >> >> >> On 3/19/2019 9:32 AM, John Clark wrote: >> >> On Tue, Mar 19, 2019 at 4:50 AM <[email protected]> wrote: >> >> * > I suppose Einstein started with the motivation of finding a general >>> transformation from one accelerating frame to another, and later gave up on >>> this project and settled for a theory of gravity. Is this true? TIA, AG* >> >> >> Einstein's breakthrough, what he called "the happiest thought of my life" >> was when he realized a man in a falling elevator will not feel gravity but >> a man in a accelerating elevator will. In other words an accelerating frame >> and gravity are the same thing, that's why it's called the Equivalence >> Principle. >> >> >> I wonder if Einstein ever considered whether a charged particle in the >> falling radiate would radiate? >> >> Brent >> > > Because of your typos, at first I thought you were joking. Well, maybe it > was a joke, but for me it sounds like a damned good question. I surmise > that a charged particle accelerating due to gravity does NOT radiate > energy, but why? AG > > > Sorry about the typos. Yes, it does seem paradoxical. Here's a paper > that purports to solve the problem. > > The radiation of a uniformly accelerated charge is beyond the horizon: a > simple derivation > Camila de Almeida > <https://arxiv.org/search/physics?searchtype=author&query=de+Almeida%2C+C> > , Alberto Saa > <https://arxiv.org/search/physics?searchtype=author&query=Saa%2C+A> > (Submitted on 6 Jun 2005 (v1 <https://arxiv.org/abs/physics/0506049v1>), > last revised 2 Dec 2005 (this version, v5)) > > We show, by exploring some elementary consequences of the covariance of > Maxwell's equations under general coordinate transformations, that, despite > inertial observers can indeed detect electromagnetic radiation emitted from > a uniformly accelerated charge, comoving observers will see only a static > electric field. This simple analysis can help understanding one of the most > celebrated paradoxes of last century. > > Comments: Revtex, 6 pages, 2 figures. v2: Some small corrections. v3: > Citation of a earlier paper included. v4: Some stylistic changes. v5: Final > version to appear in AJP > Subjects: Classical Physics (physics.class-ph); General Relativity and > Quantum Cosmology (gr-qc) > Journal reference: Am.J.Phys. 74 (2006) 154-158 > DOI: 10.1119/1.2162548 > <https://arxiv.org/ct?url=https%3A%2F%2Fdx.doi.org%2F10.1119%252F1.2162548&v=623983a0> > > Cite as: arXiv:physics/0506049 <https://arxiv.org/abs/physics/0506049> > [physics.class-ph] > (or arXiv:physics/0506049v5 <https://arxiv.org/abs/physics/0506049v5> > [physics.class-ph] for this version) > And another paper that looks at possible experimental evidence. > > Electrical charges in gravitational fields, and Einstein's equivalence > principle > Gerold Gründler > <https://arxiv.org/search/physics?searchtype=author&query=Gr%C3%BCndler%2C+G> > (Submitted on 14 Sep 2015 (v1 <https://arxiv.org/abs/1509.08757v1>), last > revised 12 Oct 2015 (this version, v3)) > > According to Larmor's formula, accelerated electric charges radiate > electromagnetic waves. Hence charges should radiate, if they are in free > fall in gravitational fields, and they should not radiate if they are > supported at rest in gravitational fields. But according to Einstein's > equivalence principle, charges in free fall should not radiate, while > charges supported at rest in gravitational fields should radiate. In this > article we point out indirect experimental evidence, indicating that the > equivalence principle is correct, while the traditional interpretation of > Larmor's formula must be amended. > > Subjects: General Physics (physics.gen-ph) > Cite as: arXiv:1509.08757 <https://arxiv.org/abs/1509.08757> > [physics.gen-ph] > (or arXiv:1509.08757v3 <https://arxiv.org/abs/1509.08757v3> > [physics.gen-ph] for this version) > However, I don't find them entirely convincing. We know that double > stars, which are orbiting one another in free-fall, radiate gravitational > waves. Are we to suppose that if one or both of them had an electrical > charge that there would be no EM radiation? > > Brent >
*If we go back to classical E&M, where does the EM radiation come from which is emitted for accelerating particles? It can't come from the self field of, say, an electron, since that would imply loss of mass or charge of the electron, which is never claimed. So it must come from the EM field causing the acceleration. Now if we go to the case of gravity without any EM source fields, and we still get EM radiation due to the acceleration, where does it come from? AG * -- 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.
