What are imaginary (virtual) Photons?

Answer 1

They are the quantum mechanical way of making force arrive in packets. They sort of fall out of the equations. If you try to calculate the electromagnetic interaction quantum mechanically, you end up with these tings which look like ordinary photons which violate the conservation of energy and if allowed to propagate live for a very short amount of time. If something is around to absorb one of them, then the photon participates in an event--it has been measured, and the energy has to come from somewhere. Therefore there is an exchange of momentum between emitter and absorber, and this is the percieved force.