Is it correct to assume that all known particles may be created as virtual particles in the vacuum? If so, is there a higher probability of a particular particle being produced than say some other particle type. For example, is an electron more likely to be created as a virtual particle than a photon or a quark? Or is the probability of all particles equal? If there is a bias as to the probability of one particle over another, is it tied to it's mass? In cases of complex particles such as a proton or neutron, not being a fundamental particle, (being made of quarks and gluons,) is its probability of appearing as a virtual particle tied to the individual probabilities of all its constituent particles simultaneously being created at the same place at the same time? And in the case of photons, as the wavelength of the photon gets shorter and shorter (or longer and longer), does its probability diminish? Or are all wavelengths of photons equally probable in the vacuum. Sorry there are so many questions here but they are all inter-related.