Will an Accelerated Charge in an Isolated Universe Emit EM Waves?

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Discussion Overview

The discussion revolves around whether an accelerated charge in an isolated universe would emit electromagnetic (EM) waves, particularly focusing on the implications for energy conservation. Participants explore theoretical scenarios involving a single electron and various methods of acceleration, including the use of a spring system.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification
  • Mathematical reasoning

Main Points Raised

  • One participant questions if an electron in a universe with no other electric fields would still emit EM waves when accelerated, suggesting that energy could be continuously produced without external forces.
  • Another participant challenges the feasibility of accelerating a massless charge, asserting that a charge must have mass to be accelerated and that it would radiate energy, thus conserving energy overall.
  • Concerns are raised about the frame of reference for the electron's acceleration, with one participant emphasizing that without an external force, acceleration cannot occur.
  • A participant proposes using a spring to accelerate the charge and questions how the spring's electric fields might influence the situation.
  • Further clarification is provided regarding the spring system, indicating that it consists of particles with different properties, and questions whether the oscillating charge would produce EM waves and if this would violate energy conservation.
  • Another participant asserts that the oscillating charge would emit EM radiation and that energy conservation would not be violated, as the energy from the spring's oscillations would be utilized in the process.

Areas of Agreement / Disagreement

Participants express differing views on the conditions under which an accelerated charge can emit EM waves and the implications for energy conservation. There is no consensus on the resolution of these questions, and multiple competing perspectives remain.

Contextual Notes

Participants reference concepts such as Mach's principle and the nature of frames of reference, indicating that the discussion involves complex theoretical considerations that may not be fully resolved.

siddharth
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I learned that when we accelerate a charge we get EM radiation. If I have a universe with only 1 electron in it so that no other Electric Field exists, and I then procced to accelerate the charge, will I still get EM waves?

(Neglecting mass of charge)

Since there is no other force on this charge, because the Electric field cannot act on iteself, I need no external force to accelerate it. Therefore i can keep producing energy in form of em waves.

If yes, then is the energy conservation not violated?
 
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How do you propose accelerating the charge?
Garth
 
If the charge were massless it would move at the speed of light (special relativity) so then you couldn't accelerate it. Therefore it has mass. If you accelerate its mass it gets increasing kinetic energy, but it also radiates, losing energy. Energy is conserved, and the radiated energy is subtracted from the kinetic energy, slowing the acceleration down.
 
selfAdjoint said:
If the charge were massless it would move at the speed of light (special relativity) so then you couldn't accelerate it. Therefore it has mass. If you accelerate its mass it gets increasing kinetic energy, but it also radiates, losing energy. Energy is conserved, and the radiated energy is subtracted from the kinetic energy, slowing the acceleration down.
In what frame of reference is the lone electron accelerating or decelerating?

Garth
 
Lets say I use a spring to accelerate the charge in SHM. Now i have only the spring and the charge in the universe. Now what would happen. Would the E-fields due to spring affect the situation in anyway?
 
selfAdjoint said:
If the charge were massless it would move at the speed of light (special relativity) so then you couldn't accelerate it. Therefore it has mass. If you accelerate its mass it gets increasing kinetic energy, but it also radiates, losing energy. Energy is conserved, and the radiated energy is subtracted from the kinetic energy, slowing the acceleration down.


Also, Because of the fact that the charge is alone in the universe and there is no other field (In my first post). There is no external force which can act on the charge. Therefore how can it lose energy and slow down without an external force?

Modifying my last post let us assume that the spring is made of a particle which does not have charge but exhibits, say strong interactions.
 
You can't have it both ways! You can't say "accelerate a charge" and then say "there is no which can act on the charge". If there is no external force, then you can't accelerate it.

You said before "Lets say I use a spring to accelerate the charge in SHM." Okay, the spring is exerting an external force. In order to do that, the spring has to be attached to something or at least stationary in some frame of reference.
 
siddharth said:
Modifying my last post let us assume that the spring is made of a particle which does not have charge but exhibits, say strong interactions.
Then its not alone in the universe! My questions are centred on Mach's principle and the thought that if a particle were alone in the universe then it could not move or accelerate because there would be no way of measuring what it is moving with respect to.

If you had two particles, they could be two electrons, then they would repel each other and would accelerate away from each other. You could tie a non-inertial frame of reference to either particle, or an inertial frame of reference to an imaginary spot in the middle at the centre of mass.

Garth
 
I am sorry for not making my question clearer. I hope this clarifies it.

My spring system is made of two particles which exhibit the same type properties except for charge. The particle on the left end of the spring system does not possesses the property of charge. The spring itself is made of particles which does not posses the property of charge. The particle on the right end of the system has charge.

Now, when the spring undergoes SHM the center of mass of the system is at rest. Therefore I have a non-inertial frame. Furthermore I can accelerate the charge by forces other than coulumbic forces.

Therefore i ensure that the only electric field is due to the charge. Now my question is will the oscillating charge produce EM waves. If yes, then does it not violate the conservation of energy?
 
  • #10
siddharth said:
Therefore I have a non-inertial frame.

Read as: Therefore I have an inertial frame
 
  • #11
siddharth said:
I am sorry for not making my question clearer. I hope this clarifies it.

My spring system is made of two particles which exhibit the same type properties except for charge. The particle on the left end of the spring system does not possesses the property of charge. The spring itself is made of particles which does not posses the property of charge. The particle on the right end of the system has charge.

Now, when the spring undergoes SHM the center of mass of the system is at rest. Therefore I have a non-inertial frame. Furthermore I can accelerate the charge by forces other than coulumbic forces.

Therefore i ensure that the only electric field is due to the charge. Now my question is will the oscillating charge produce EM waves. If yes, then does it not violate the conservation of energy?
Yes and No. Yes the charge will emit EM radiation, and No energy conservation is not violated as the energy of the spring's oscillations will be used up.
Both two particles will also radiate gravitational waves, (very weakly) and the system will loose 'kinetic' mass as these two forms of radiation leak energy into empty space.

Garth
 

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