Posted: Sep 25, 2011 4:52 pm
zaybu wrote:
But the "something happens" is not as nebulous as your diagram implies, it's more like: SEE ATTACHMENT
By considering all possible interactions that we can get very precise agreement between theory and experimental observation in QED.
No, those diagrams are only pictorial representations of a bunch of integrals you need to compute the scattering amplitude of the incoming and outgoing electrons. They're only a way of organising the mathematics. You only have to do it this way because you're using perturbation theory. We're only doing perturbation theory because we don't know how to set up and solve the equations of QED exactly.
The scattering amplitude is given by the sum of the contributions of all the diagrams to a given order. Each diagram (in configuration space) requires you to integrate over all the spacetime locations of each vertex. Only the sum has meaning. The electron never really emits a virtual photon.
Let me ask a question:
The diagram (a) in the picture represents a contribution of order α2, (where α is the fine structure constant), diagram (b) of order α4 etc...
To what order must we go in order to represent reality ? (just sticking to QED here - assuming no new physics, quantum gravity etc)