Quantum vacuum, virtual particles and ''friction''

  • Thread starter asimov42
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  • #1
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Hi folks,

I have a question that I so far haven't been able to locate an answer to - it's mostly for curiosity.

If virtual particles are continually popping in and out of existence in the vacuum, why do they not produce a frictional force on objects moving at constant velocity through space? is there a reason (in not too technical terms, for a non-physicist) why the frictional effect is absent?

Thanks.

J.
 

Answers and Replies

  • #2
K^2
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Momentum conservation. If any momentum was imparted on the fluctuation particle pairs, where should the momentum go after the pair annihilated?

If you work out the actual diagrams for the particle-vacuum interactions, it's possible to show that only non-zero contributions where particle passes its momentum to the virtual pair is where it gets that momentum back later on. So the total energy required to get the particle going changes and the mass appears to be higher than it really is, but there is no "friction".

Edit: If you are familiar with QFT, you can think of it in terms of contractions. Otherwise, don't worry about it.
 
  • #3
A. Neumaier
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Hi folks,

I have a question that I so far haven't been able to locate an answer to - it's mostly for curiosity.

If virtual particles are continually popping in and out of existence in the vacuum, why do they not produce a frictional force on objects moving at constant velocity through space? is there a reason (in not too technical terms, for a non-physicist) why the frictional effect is absent?
Because they don't pop in and out of existence, except in the imagination of esoterically minded people.
 
  • #4
The dissipation caused by the electromagnetic field upon a charged particle is known as the Abraham-Lorentz force. It does not dissipate motion but acceleration. [Technically that is not exactly true, only perturbatively true.] There will be no dissipation induced upon a particle traveling at constant velocity.

If the particle had a position coupling to the field instead of a momentum coupling, then it would dissipate motion.
 

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