Shake a magnet fast enough, would i create light?

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Discussion Overview

The discussion centers around the question of whether shaking a magnet rapidly can produce light, exploring the conditions under which electromagnetic waves are generated and the implications of energy loss during this process. Participants also delve into the concept of radiation reaction and its effects on the motion of magnets and masses in experimental scenarios.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • Some participants propose that shaking a magnet can create light by generating electromagnetic waves, with the direction of shaking affecting the radiation pattern.
  • Others argue that moving the magnet at constant velocity does not produce radiation, suggesting that acceleration is necessary for light generation.
  • There is a discussion about energy loss when creating light, with some participants suggesting that this is akin to a slight resistance known as radiation reaction.
  • One participant questions whether the radiation reaction implies that an accelerated magnet resists further acceleration, to which others confirm this but note it is not significant.
  • A conceptual experiment is proposed to investigate center of mass displacement due to radiation reaction, with participants discussing the implications of mass and radiation on the center of mass of a system.
  • Concerns are raised about the conservation of the center of mass in the context of radiation, with one participant suggesting that the analysis of the experiment may overlook the mass of the radiation itself.

Areas of Agreement / Disagreement

Participants express multiple competing views regarding the conditions under which light is produced by shaking a magnet, the implications of radiation reaction, and the analysis of the proposed experimental scenarios. The discussion remains unresolved on several points, particularly regarding the effects of radiation on center of mass and energy loss.

Contextual Notes

Limitations include assumptions about the behavior of electromagnetic waves, the definitions of radiation reaction, and the treatment of mass in the proposed experiments. The discussion does not resolve these complexities.

skywolf
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if i were to shake a magnet fast enough, would i create light?,
and if so which direction would i need to shake it?

away then towards, up and down or sideways?
 
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Move it as slowly as you like and you will create an electromagnetic disturbance - i.e. light. It will propagate in all directions approximately with a dipole distribution.
 
but every time you produce constant velocity state, the radiation pattern will turn off.

Best regards

DaTario
 
DaTario said:
but every time you produce constant velocity state, the radiation pattern will turn off.

Best regards

DaTario

Quite correct! I used the word "move" in the context of the OPs term "shake" which implies acceleration.
 
since I am making light, does that mean that by moving it I am losing energy?
if so, is it kinda like a (very) slight resistance?
 
skywolf said:
if i were to shake a magnet fast enough, would i create light?
You will create an electromagnetic wave when you oscillate the magnet. Light is an electromagnetic wave within a certain frequency spectrum so you'd have to oscillate it at a really high rate and vibrating it that fast would make it fall apart before the frequency reaches light frequency.
skywolf said:
.and if so which direction would i need to shake it?
Any direction. Different directions of shakikng will give you different radiation patterns.
skywolf said:
since I am making light, does that mean that by moving it I am losing energy?
Yes.
skywolf said:
if so, is it kinda like a (very) slight resistance?
Yes. Its called a "radiation reaction". Its a "self-force" exerted by the magnet on the magnet. Same thing happens with charges when you accelerate them.

Pete
 
pmb_phy said:
Yes. Its called a "radiation reaction". Its a "self-force" exerted by the magnet on the magnet. Same thing happens with charges when you accelerate them.

Pete

Self-Force? Would this imply that an accelerated magnet nominally resists further acceleration due to this phenomenon?
 
pallidin said:
Self-Force? Would this imply that an accelerated magnet nominally resists further acceleration due to this phenomenon?
Yes but not by a significant amount.

Pete
 
pmb_phy said:
Yes but not by a significant amount.

Pete

Thank you. I think I understand it(perhaps a form of self-inductance that resists continuation of the acceleration) yet am somehow fascinated by it. If you or anyone could point me towards specific literature on the subject I would be grateful.
 
  • #10
pallidin said:
Thank you. I think I understand it(perhaps a form of self-inductance that resists continuation of the acceleration) yet am somehow fascinated by it. If you or anyone could point me towards specific literature on the subject I would be grateful.

See Classical Electrodynamics - 3rd Ed., D.D. Jackson, page Chapter 10. Most of the first part of this chapter deals with accelerating a charged particle and the extra force required to do so due to the creation and emission of radiation and its energy. Same idea that you're intersted in except Jackson addresses an accelerating charge rather than an accelerating magnetic. The ideas are the same. This phenomena is called the Radiation Reaction or Radiation Dampening.

Pete
 
  • #11
pmb_phy said:
See Classical Electrodynamics - 3rd Ed., D.D. Jackson, page Chapter 10. Most of the first part of this chapter deals with accelerating a charged particle and the extra force required to do so due to the creation and emission of radiation and its energy. Same idea that you're intersted in except Jackson addresses an accelerating charge rather than an accelerating magnetic. The ideas are the same. This phenomena is called the Radiation Reaction or Radiation Dampening.

Pete

Much appreciated. I have a very serious question. Please consider the following scenario:

Experiment: "Center of Mass Displacement due to the Radiation Reaction Phenomenon"

I set up two experimental scenarios. In the first, I have two precisely equal non-magnetic masses which are close together then separated by an accelerating force. In this scenario, the center of mass does not shift. This is my "control"

In the second, and separate scenario, I have replaced one of the "precisely equal" non-magnetic masses with a comparable mass consisting entirely of, say, a Grade40 neodymium magnet. Then, I separate the NIB mass and the non-magnetic mass by some rapid, accelerating force.

Under the pretense of "Radiation Reaction", the NIB mass will resist movement slightly more so than the non-magnetic mass, resulting in an end result being a vector-shifting of the center of mass of that "system"

Pete, is my conceptual experiment correct?
 
  • #12
pallidin said:
Much appreciated. I have a very serious question. Please consider the following scenario:

Experiment: "Center of Mass Displacement due to the Radiation Reaction Phenomenon"

I set up two experimental scenarios. In the first, I have two precisely equal non-magnetic masses which are close together then separated by an accelerating force. In this scenario, the center of mass does not shift. This is my "control".
Sounds okay so far.
In the second, and separate scenario, I have replaced one of the "precisely equal" non-magnetic masses with a comparable mass consisting entirely of, say, a Grade40 neodymium magnet. Then, I separate the NIB mass and the non-magnetic mass by some rapid, accelerating force.

Under the pretense of "Radiation Reaction", the NIB mass will resist movement slightly more so than the non-magnetic mass, resulting in an end result being a vector-shifting of the center of mass of that "system"

Pete, is my conceptual experiment correct?
Any experiment is a correct experiement. Its the analysis that can be correct/incorrect. In your analysis you seem to think that the center of mass of the entire system has changed. It has not. You have neglected to take into account the mass of the radiation into account. When all mass of a closed system is taken into account then the center of mass of that system is conserved.

Pete
 
  • #13
Ah, thanks. I understand now.
 

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