From the Quantum Gravity thread we had:

 

Ed's Quantum Gravity paper can be found here

virtual photons, there as a result of Heisenberg’s, uncertainty principle, are turned into real particles by an accelerating object[/b']. The pressure caused by the particles hitting the object (and the resonance) causes inertia.

 

I understand about virtual photons, but how can a virtual photon be turned into a real photon???

Its not how but why!

The virtual photon was added to the calculations because of problems in physics.Adding virtual photons made the math hypothetically correct.Experiments have proven using the virtual photon makes everything hunky- dory again,however that does not mean that there is any such thing as virtual photons.

Swansont wold be able to explain it better.

The virtual photon was added to the calculations because of problems in physics.Adding virtual photons made the math hypothetically correct.

 

I thought virtual photons were a consequence of integrating over all of the momentum in the propagator, on mass-shell and off?

Virtual photons cannot be made real.

 

They are virtual because they have a missmatched energy and momentum. That is, we do not have E² = m²c⁴ + p²c². In principle, one could make them real by adding enough momentum or energy to make the equation work, but in practice there is no way to do this.

 

The reason is that the photon can only couple to charged objects and conservation of charge means that any interaction vertex with a photon must contain at least two charged particles. Therefore (since the interaction vertices usually involve three particles) any incoming photon is always destroyed. The particle which absorbes the photon can re-emit another photon though (since it is charged) and the new photon could be real, but there is no continuous link with the old virtual one.

Good good.... in that case, ed84c, your paper has a mistake!

 

(and thanks Severian)