Firstly, let me just say that the virtual particle interpretation of black hole radiation is really the pop science method of understanding what is happening. The QFT calculation that you can do is pretty enigmatic about where the particles actually come from. Secondly, Walter is nitpicking again with points that are of very minor relevance to the overall concept. If I were you I'd simply ignore him - you won't miss much in the way of particle physics. The Dirac sea is a (not very good) way of thinking about antimatter, not virtual particles, if it were true the vacuum would have a charge. Not only would there be a charge but it would be infinite in magnitude. The Dirac sea really arises from treating the Dirac equation as an equation for a quantum particle which is not really what it is - it's the equation for a quantum field. In quantum field theory you can think of virtual particles like this. Suppose you have a loop diagram, for example Please Register or Log in to view the hidden image! You can measure the energy of each of the external legs so that is constrained. However, you can't measure the energy around the loop (the middle electron and the photon). To calculate the diagram you integrate over all possible energies going around the loop so the diagram doesn't represent a single event but a class of events that have that loop structure (that maybe obvious to you, but it took me a little while to get it). By all possible energies I really mean all possible energies, so virtual particles don't have to obey the equation of motion - the lingo is that they are "off shell." To conclude, we don't really think about virtual particles as single particles - they come out of QFT in sets that have average properties.