Gravity and radiation from charge

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Discussion Overview

The discussion revolves around the topic of radiation emitted by charged particles in various gravitational and inertial frames. Participants explore the implications of gravity, acceleration, and reference frames on the radiation emitted by charges, touching on theoretical aspects and the equivalence principle.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant suggests that a charge resting on a table experiences balanced forces from gravity and the table, leading to no net force and thus no radiation.
  • Another participant questions whether a charge on Earth, which is rotating around the Sun, would emit synchrotron radiation, proposing that it might occur but in a negligible amount.
  • A participant raises a scenario of a charge in free fall near a neutral planet, noting that while radiation occurs due to acceleration, in a co-moving frame, no radiation would be detected, prompting a need for reconciliation of these perspectives.
  • One response emphasizes that the detection of radiation is frame dependent, suggesting that what is invariant is the detection of fluctuating voltage/current rather than the existence of radiation itself.
  • Another participant reflects on the idea that electromagnetic waves radiated at the speed of light are recognized across all inertial frames, but this does not apply to non-inertial frames.
  • A claim is made that the equivalence principle is only valid locally and does not hold in nonlocal situations, with radiation being categorized as a nonlocal phenomenon.

Areas of Agreement / Disagreement

Participants express differing views on the conditions under which radiation occurs and the implications of reference frames. There is no consensus on the reconciliation of these views, indicating ongoing debate and exploration of the topic.

Contextual Notes

Limitations include the dependence on definitions of local versus nonlocal phenomena and the unresolved nature of how different frames affect the perception of radiation.

sweet springs
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Reading a thread in relativity I would like to know more precisely about radiation from charge.

1
I put a charge on the table of my house. Gravity and table reaction force work on the charge.
They cancel so net force does not work on the charge, thus no-force no-velocity cause no radiation. Am I right ?
2
A charge is put on the Earth that rotates around the Sun. Does synchrotron radiation by rotation motion take place ? Does it takes place but in non measurable tiny amount ?
3
Say a charge is free falling attracted by gravity of an electrically neutral planet, radiation takes place from a charge due to acceleration motion. But in co-moving local frame of reference with the charge, nothing particular including radiation would take place. How do we conciliate these views?
 
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sweet springs said:
How do we conciliate these views?
You simply recognize that radiation is frame dependent. What is invariant is not whether or not there is radiation, but whether or not a given detector detects a fluctuating voltage/current.
 
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I have thought something running with speed c, radiated electromagnetic wave, is commonly recognized to all the frames. I will do practice with your teaching. Thanks.
 
sweet springs said:
I have thought something running with speed c, radiated electromagnetic wave, is commonly recognized to all the frames.
All inertial frames, yes. Not non inertial frames.
 
Thanks for your teaching. I will read PDF to get it.
 

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