On 3/20/2019 10:21 PM, [email protected] wrote:
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]
(orarXiv: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]
(orarXiv: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, *
No, it comes from the energy source that is providing the acceleration.
In the LHC protons are accelerated by EM fields which are powered by big
generators. So that's the source of the energy they radiate. It's
interesting that Grundler claims they radiate because the EM fields act
on the charge of the proton but NOT on the field of the proton. I'm not
sure I buy that, though it may be a heuristic way to look at the problem.
*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
*
It's unclear what case you're asking about. Free falling is not
accelerating in GR. Sitting still on the Earth is accelerating in
spacetime. So you need to say whether the charge you're considering is
on a geodesic or not AND whether the observer is on a geodesic or is
stationary relative to the charge or is on some non-geodesic different
from the charge.
Brent
--
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.
For more options, visit 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.
