# Quantum vacuum, virtual particles and ''friction''

• asimov42
In summary, the question is about the absence of frictional force from virtual particles in the vacuum. The answer is that according to momentum conservation, any momentum imparted on fluctuation particle pairs is later returned, leading to no net effect on objects moving at constant velocity. Additionally, the Abraham-Lorentz force only dissipates acceleration, not motion, and if the particle had a position coupling to the field, motion would be dissipated.

#### asimov42

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.

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.

## 1. What is the quantum vacuum?

The quantum vacuum is the lowest energy state of a quantum field, which is a field that permeates all of space and is responsible for particles and forces in the universe. It is not empty, but rather filled with virtual particles that constantly fluctuate in and out of existence.

## 2. What are virtual particles?

Virtual particles are particles that do not have a physical existence like normal particles, but instead pop in and out of existence in the quantum vacuum. They are a manifestation of the uncertainty principle and play a crucial role in quantum field theory.

## 3. How do virtual particles cause friction?

Virtual particles can cause friction through the process of quantum tunneling. This occurs when a virtual particle near the surface of an object suddenly becomes a real particle and escapes into the surrounding space. This creates a force on the object, which we perceive as friction.

## 4. Can virtual particles be observed?

No, virtual particles cannot be observed directly because they do not have a lasting physical existence. However, their effects can be observed and measured through various experiments and calculations in quantum mechanics.

## 5. How does the concept of the quantum vacuum and virtual particles relate to modern technology?

The understanding of the quantum vacuum and virtual particles has led to the development of technologies such as quantum computing and quantum cryptography. It also plays a crucial role in our understanding of fundamental particles and the behavior of matter on a microscopic scale.