Hi all, I've read a number of posts on virtual particles (including one of my own), but I'm still confused about one aspect - the interaction between real and virtual particles. Say we have an electron moving from position A to position B. As the electron moves, there should be virtual electron-positron pairs popping into existence along the trajectory due to vacuum fluctuations (i.e., the vacuum energy). When computing the actual path of the electron, I should sum over all possible ways to get from A to B ... this would include interactions with the virtual particles (in which, e.g., the real electron annihilates with one of the virtual positrons), etc., etc., AND the case of no interactions at all - is this correct? Also as asked by a poster in another thread (and for my own curiosity): "And what's to prevent real particles from hitting a virtual particle (as it is in the process of popping into and out of existence) and then flying off in a different direction?" Thanks!