Quantum vacuum, virtual particles and ''friction''

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Discussion Overview

The discussion centers around the concept of virtual particles in quantum vacuum and their potential effects on objects moving through space, specifically questioning why these virtual particles do not produce a frictional force on such objects. The scope includes theoretical considerations and conceptual clarifications related to quantum field theory (QFT).

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant questions the absence of a frictional effect from virtual particles that are said to pop in and out of existence in the vacuum.
  • Another participant argues that momentum conservation prevents any frictional force from arising, as any momentum imparted to virtual particle pairs would need to be accounted for after their annihilation.
  • A different viewpoint challenges the notion of virtual particles popping in and out of existence, suggesting that this idea may stem from misconceptions.
  • It is noted that the Abraham-Lorentz force relates to the dissipation caused by electromagnetic fields on charged particles, emphasizing that such dissipation occurs only during acceleration, not at constant velocity.
  • There is a mention of the distinction between position and momentum coupling to fields, indicating that different types of coupling could lead to different dissipation effects.

Areas of Agreement / Disagreement

Participants express differing views on the nature of virtual particles and their effects, with no consensus reached on the fundamental questions raised about friction and momentum conservation.

Contextual Notes

Some claims rely on specific interpretations of quantum field theory and the behavior of virtual particles, which may not be universally accepted or understood. The discussion reflects varying levels of familiarity with the technical aspects of the topic.

asimov42
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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.
 
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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.
 
asimov42 said:
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.
 
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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