[graham.d]

Yor_on, I don't think there is a problem regarding the difference in observation of em radiation between the comoving observer and a distant one (in the orbiting electron case). The issue is whether the electron is losing energy and its orbit decaying. This is a distinct measurable difference in how the electron will behave depending on the point of observation and would be a paradox. I am sure there is a fault in my reasoning somewhere, but I need to see, and be convinced, where it is.

I will read some of the references you cite later.

[Ron Hughes (OP)]

"Then a part of the radiating energy will be absorbed by the water and
will warm it up. On measuring the temperature of the water the observer will be to register the radiation."

I disagree with the writer's assumption. He is assuming that the electron will radiate in the accelerating laboratory (K) but to the observer in (K) it will not radiate. It will appear to radiate to the stationary observer in (K'). Conversely if the observer (K) can look at (K') then he will see the electron radiate. The equivalence principal is satisfied.

[Ron Hughes (OP)]

Have I missed something Graham? Why is it assumed that the orbiting electron's orbit will decay? Unless some force acts on it the orbit will be stable. As an aside, shortly I will post an explanation of why we see the photon as having both a magnetic and electric component at ninety degrees to each other. I will be busy for the rest of the weekend and will post Monday in the thread "The Photon".

[graham.d]

Ron, in order for em energy to flow away fron the star and orbiting electron, the energy has to come from somewhere. The energy from an accelerating charge is emitted as Bremsstrahlung radiation and is normally considered to be (literally) from the braking effect on the charge. If there is such radiation the electron orbit must decay I think. And, as far as I undestand, there has to be em radiation from an orbitting electron.

I should have said Larmor radiation rather than Bremsstrahlung.

[yor_on]

Yor_on, I don't think there is a problem regarding the difference in observation of em radiation between the comoving observer and a distant one (in the orbiting electron case). The issue is whether the electron is losing energy and its orbit decaying. This is a distinct measurable difference in how the electron will behave depending on the point of observation and would be a paradox. I am sure there is a fault in my reasoning somewhere, but I need to see, and be convinced, where it is.

I will read some of the references you cite later.

Well Graham, that is why I say I don't think it's possible. I can't find fault in your logic, presuming that the electron will accelerate the scenario is the same as mine I think? the far observer should both observe radiation and the electron 'breaking orbit' as I see it. But for the near observer, presuming that we can't observe the energy disappearing it will be as 'magic' if it is so. So the scenario seems too weird for me

Now, that's a thing to remember )

[Ron Hughes (OP)]

   Graham, you post is is basically the same as an orbiting electron in the hydrogen atom and produces a possible error in my own logic about how radiation is produced. For my idea to be correct then that electron must emit radiation with respect to all observers outside that system. I have not as yet looked for conformation of such radiation. I will endeavor to do so now.

[Ron Hughes (OP)]

So far everything I've read suggests that the electron is a wave. That being said it would mean the electron around the proton would not emit radiation and my original premise holds.

The electron orbiting a star does not lose energy with respect to the star. As far as the star is concerned the electron does not emit radiation. The electron only emits radiation with respect to an observer outside the system as suggested by GR.

[graham.d]

So far everything I've read suggests that the electron is a wave. That being said it would mean the electron around the proton would not emit radiation and my original premise holds.

The electron orbiting a star does not lose energy with respect to the star. As far as the star is concerned the electron does not emit radiation. The electron only emits radiation with respect to an observer outside the system as suggested by GR.

I am not sure about the star. It may depend on whether an observer is on the surface of the star and moving with respect to the orbiting charge. I think we established that we think a comoving observer in free fall with the charge would not see any radiation but that someone external to the system would see radiation. The question still is whether or not the orbit would decay. If energy is coming out as a result of the orbit then the orbit must decay - GR or not - a co-moving observer should also see this decay. That is the paradox. What are we missing here?

I am happy to consider electrons in atoms as a QM problem. You can replace the electron with a large charged body to avoid QM issues.

[Farsight]

An accelerated charged particle emits radiation with respect to a stationary observer but if the observer is accelerated along with the particle does the observer still detect the particle emitting radiation?

Yes. SoulSurfer mentioned a synchrotron. Here in the UK we have the "Diamond Light Source", see http://www.diamond.ac.uk/ which I've visited. They use dipole magnets to deflect the electrons, which as a result emit X-rays. If you were racing around the ring along with the electrons being similarly deflected, you'd still get a faceful of X-rays. You'd be emitting X-rays too and it wouldn't be too comfortable in there, but those X-rays don't go away. 

[graham.d]

I have done a little reading on whether there is a paradox regarding: a co-moving observer with a charged particle in orbit (who sees no radiation because he in the same free falling frame as the charge) vs a distant stationary observer who sees radiation from the accelerating charged particle. The paradox is that the distant observer should see the orbit decay and the comoving observer should not; events on which they must agree.

It seems this is an unresolved issue. Feynman reasoned that the equation for radiation needs to involve the third derivative (changing acceleration) but this is disputed. A good description of the problem, though not exactly as I state above, though related is:

http://www.mathpages.com/home/kmath528/kmath528.htm

[Farsight]

Interesting article graham, thanks. There's some interesting comments re Einstein and gravity, about point particles, and even the near field aka evanescent wave:

Much of the literature on the question of radiation from accelerating charges focuses on the Lorentz-Dirac equation of motion for a classical charged point-like particle interacting both with an external field and with its own field. This equation is the source of equation (1), but it's important to remember that it is based on classical electrodynamics of point-like particles, rather than on quantum electrodynamics, so it's physical relevance is questionable. Moreover, the internal validity of the Lorentz-Dirac equation is cast into doubt by the existence of run-away solutions (see below)...

In addition, the usual neglect of the "near" static field when dealing with the "far" radiation field...

[Ron Hughes (OP)]

If the velocity and acceleration referred to in Einstein's Relativity is correct then the paradox is resolved. I will post what I consider to be an explanation of the double slit,both the photon and the electron, sometime this afternoon or tonight here    http://www.thenakedscientists.com/forum/index.php?topic=28667.msg299038#msg299038

[graham.d]

Should anyone think that there is an easy answer to this paradox, they should read this excellent paper:

http://www.google.co.uk/url?sa=t&source=web&ct=res&cd=1&ved=0CAcQFjAA&url=http%3A%2F%2Fwww.hep.princeton.edu%2F~mcdonald%2Fexamples%2FEM%2Feriksen_ap_297_243_02.pdf&rct=j&q=accelerated+charge+lose+energy&ei=i6t6S831B5z00gTv4YWrCQ&usg=AFQjCNHL3JQTS5gumdI8rWsor2NkHi0Uuw

Sorry about the long link - I hope it works.

[Ron Hughes (OP)]

Good link Graham. His paper agrees with my own view.

[graham.d]

The simple answer to my question, which now seems obvious, is that a charged particle in a circular orbit does not emit radiation. Even looking at this classically, you can consider a continuous line of charges in orbit. This would be the same as an electric current and would produce a constant magnetic field, but not em radiation. The only energy used is in establishing the field i.e. getting the electrons into orbit.

The first proposed question about being in free fall, but not in orbit. i.e. following a hyperbolic path or simply falling to the ground, is more complicated. By hyperbolic here I mean simply a hyperbolic path in Euclidean space and not Hyperbolic acceleration (Contant Proper Acceleration) as in the paper a cited. I don't think the paper fully answers this directly, though it needs much study to grasp all the concepts and to appreciate the comments on the large number of differing views on this that are presented. It seems that a charged particle in free fall will fall equally fast as a non-charged particle, but will radiate (according to Rohrlich). The energy he attributes being supplied by the "Schott Acceleration Energy". I have not come across this before and would like to get a better understanding when time allows. The maths and concepts are not trivial. The paper suggests that Schott energy is located locally around the particle but does not contribute to its rest mass (which would be really troubling).

I am unclear whether a comoving observer would see the radiation. I don't think so. But this would not necessarily be ruled out on the basis of equivalence because there has to be boundary conditions which may result in there having to be a converging gravity field. I'm not sure about this.

[Ron Hughes (OP)]

" The paper suggests that Schott energy is located locally around the particle but does not contribute to its rest mass (which would be really troubling). " Yes Graham, I would find it extremely troubling. Later I will dig into that a little more.

[yor_on]

An electron in orbit around a gravitating body is accelerating. In Classical terms, inwards toward the centre of the body at a rate of (v^2)/r. From my distant position I see that electron accelerating due to the force of gravity exerted by the body. If it is accelerating will it emit radiation? If so will it's orbit decay? If it's orbit decays then if you are orbiting with the electron I will see the electron orbit decay but you stay in your orbit. Now, the fact that we are different observers cannot account for two different events. From your co-orbit perspective why would the electron move away from you as you are both in free fall and following the same geodesic?

This "An electron in orbit around a gravitating body is accelerating. In Classical terms, inwards toward the centre of the body at a rate of (v^2)/r."

Would that be a uniformly accelerating velocity Graham?
Both this and mine free falling particle seems to fall outside that scenario if we by 'uniformly accelerating' means accelerating at a constant 'gravity' within its own frame of reference, as f.ex at one G.?

And if our cases won't meet that 'prerequisite' I think what we are discussing is a different scenario from Ron's?
Or am I wrong here??

Why I think so is because what Ron's scenario describes as well as Antiphons seems to be a universe from the 'Rindler observers' perspective 'locally'?
==

Okay I saw that you already answered that one. Sorry, missed it Graham..

[Ron Hughes (OP)]

The point is this. An observer that is stationary in space far from the gravitating body will see the electron emit radiation. An observer that is at the center of the gravitating body will not see the electron emit radiation. This scenario fits perfectly with GR.

[graham.d]

A charged body in orbit will not radiate, but a charged body that is in some non-periodic motion (falling or on a hyperbolic path) will, I think, according to Eriksen's paper. The Larmor formula seems a special case and not universally applicable.

Ron, I don't see how you reach that conclusion. Nobody has been speaking about an observer at the centre of the gravitating body. And it is not 100% clear, given the eminent physicists in disagreement, that the theory does all fit with GR. The maths, at present, results in an asymmetry with time and a non-causal pre-acceleration of a body in certain cases of abrupt directional changes. These results are cause for some concern at least.

[Ron Hughes (OP)]

I think but I could be wrong that for every scientist you find that does not believe GR I can find ten thousand that do.