Virtual photons and long range force carrier

In summary: For example, in the first sentence, it says "real photons are NOT virtual photons." But then in the next sentence it says "the Coulomb force is a quasistatic approximation for particles nearly at rest." So which is it? Are real photons virtual or not?
  • #1
ftr
624
47
It is often said that the photon is the long range force carrier like the static force between electrons. Let's say we have two electrons galaxy apart, wouldn't the virtual particles have to travel long distances and "virtually" become real.

And isn't the first sentence is wrong anyway since real photons are NOT virtual photons.
 
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  • #2
I don't know, why many people want to confuse themselves as thinking about the Coulomb field between electrons as "virtual photons". It's much simpler to think about them as what they are, namely fields. The Coulomb force is a quasistatic approximation for particles nearly at rest, meaning moving with speeds much slower than the speed of light.

Of course, you can derive this approximation from perturbative QED. You have to resum the socalled soft-photon ladder-diagrams for the two-body scattering-Feynman diagram. This is important to establish the approximation but doesn't help very much in the intuitive understanding of what's going on.

A very good treatment of this issue is found in

Weinberg, Quantum Theory of Fields I.
 
  • #3
vanhees71 said:
I don't know, why many people want to confuse themselves as thinking about the Coulomb field between electrons as "virtual photons". It's much simpler to think about them as what they are, namely fields. The Coulomb force is a quasistatic approximation for particles nearly at rest, meaning moving with speeds much slower than the speed of light.

Of course, you can derive this approximation from perturbative QED. You have to resum the socalled soft-photon ladder-diagrams for the two-body scattering-Feynman diagram. This is important to establish the approximation but doesn't help very much in the intuitive understanding of what's going on.

A very good treatment of this issue is found in

Weinberg, Quantum Theory of Fields I.

Thanks for the reply. of course I know about the math, I have tons of books on QFT. But sometimes the descriptive statements can become annoyingly confusing.
 

1. What are virtual photons?

Virtual photons are particles that are not directly observable, but are instead used to describe interactions between particles. They are considered "virtual" because they only exist for a very short amount of time before being absorbed or converted into other particles.

2. What is the role of virtual photons in long range forces?

Virtual photons are the carriers of electromagnetic force, which is a long range force. They are constantly exchanged between charged particles, allowing them to interact with each other even at a distance.

3. How do virtual photons mediate long range forces?

Virtual photons mediate long range forces by acting as the carriers of electromagnetic interactions. When two charged particles are interacting, they exchange virtual photons, which results in a force between them.

4. Can virtual photons be observed in experiments?

No, virtual photons cannot be observed directly in experiments. They are only theoretical particles that are used to explain the behavior of particles at the quantum level.

5. Are virtual photons responsible for all long range forces?

No, virtual photons are only responsible for mediating electromagnetic forces. Other long range forces, such as the strong and weak nuclear forces, have their own unique particles that act as carriers.

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