Can Virtual Photons Be Detected and Measured?

[physic31415]

No-one on the general board seems to have an answer. I really would like help on this one.

I am told that two static electrical charges exert a force on each other by the exchange of photons.

Nowhere have I read the answers to the following: what are the frequencies/energies of the exchange photons, and if they have infinite range, why cannot they (the photons) be intercepted and measured? - if the charges are very far apart it cannot be that the photons are virtual and have a very short life...

If I opened my eyes would I see exchange particles?

Help needed!

 

[Drakkith]

To the best of my knowledge, no you could not measure the photons or interact with them in any way. Perhaps someone more versed in this could explain it further.

 

[physic31415]

So the photons I pick up on my radio receiver aerial are definitely not the same as the exchange particle photons? I wonder why, if they exist, exchange particle photons cannot be intercepted?

 

[jtbell]

So the photons I pick up on my radio receiver aerial are definitely not the same as the exchange particle photons?

The photons that you "see by" with visible light, or that your radio aerial picks up, are real photons. The photons that mediate electrostatic forces are virtual photons.

Virtual photons don't "really exist" in the same sense that real photons do. They are an artifact of the perturbation-series techniques that we use for calculations in quantum electrodynamics (QED). For a couple of previous discussions on PF about the "reality" of virtual photons and other virtual particles, see

How "Real" Are Virtual Particles?

Virtual Photons as Force Carriers

 

[physic31415]

Thank you for your reply.

"Virtual photons don't "really exist" in the same sense that real photons do. They are an artifact of the perturbation-series techniques that we use for calculations in quantum electrodynamics (QED)."

If a diagram were drawn showing an electron interacting with another electron one light-year away, with the exchange of one photon, what would be the energy/frequency of that photon? Distance is one light year (x), the speed of the photon is known (c), is the energy of the photon, and thus the frequency simply given by the Heisenberg uncertainty with the smallest possible value for delta t being x/c? i.e. would there be a range of possible photon energies with a maximum energy photon following the shortest route? Or have I totally misunderstood?

 

[Phrak]

Virtual photons, as defined, are not constrained by c, and have other novel properties. This business is covered in the theory of quantum electrodynamics. You might pick up some easy reading such as Feynman's "QED, The Strange Theory of Light and Matter" for a starter.

 

[physic31415]

Virtual photons, as defined, are not constrained by c, and have other novel properties. This business is covered in the theory of quantum electrodynamics. You might pick up some easy reading such as Feynman's "QED, The Strange Theory of Light and Matter" for a starter.

Thanks. It is many years since I read Feynman's QED so I need to do some reading.

If they are not constrained by c and have other properties, what is it that defines them as photons rather than 'virtual exchange particles associated with electromagnetic interactions"?