In order to get my head around virtual particles I've created the following question. Maybe some bright person can answer this. If I can answer this question I feel I would have the required understanding to explain virtual particles to other people. In the diagram below, A is a radioactive source emitting positrons and B is a radioactive source emitting protons. Both sources emit particles within a small energy range. The covers of A and B are lifted simultaneously at an agreed time for 1 minute and then recovered. During this minute some virtual photons travel from the positrons to the protons faster than the speed of light. The particles are detected at A' and B'. Question: Given that even though the Feynman propagator is non-zero for space separations (virtual photons travel faster than the speed of light): (a) If the distance d is greater than 1 light minute the distributions of particles detected at A' and B' are unaffected by each other. In other words no signal passes from the protons to the positrons faster than the speed of light. (b) If the distance d is less than 1 light minute the protons and positrons feel a repulsive electromagnetic force and the distributions are pushed away from the centre. (c) At a later time if the distributions of particles detected at A' and B' are compared, even if d is greater than 1 light minute will there be any mathematical correlation between the distributions? Try to answer this question using the Feynman propagator ΔF(x-y). And try to express the distributions of the particles detected at A' and B' as functions of the separation distance d.