Folks, I have a question about virtual particles. I recently read in a Scientific American article which says that "virtual particles are indeed real particles. Quantum theory predicts that every particle spends some time as a combination of other particles in all possible ways. These predictions are very well understood and tested." I assume, from the above, that by "spending time as a combination of other particles", the author means that every particle is in a superposition, with some chance of appearing as a combination of other (virtual) particles, which can't be observed because they're virtual? E.g. a photon sometimes splits into a virtual electron/positron pair, and then reforms the original photon... So, assuming the above, my question is: what govern the amount of time / probability distribution for a particle appearing as other types of particles? Is it something intrinsic to the type of particle itself? Or does it have to do with the energy of the particle? For example, if I were to say, accelerate an electron by a significant amount, would that affect the amount of 'time' (for lack of a better word) that it spends as other, heavier particles? Not sure if the above is very clear, but any suggestions would be helpful. Thanks.