I'm having trouble understanding why it is necessary for there to be a particle antiparticle pair formation in order for the black hole to evaporate. According to my understanding of the theory, a particle anti particle pair are formed, and rather than colliding within a given period of time (dictated by the heisenburg uncertainty principle), in order to prevent the violation of conservation of mass, one of the particles falls into the black hole. According to wikipedia- "In order to fill the energy 'hole' left by the pair's spontaneous creation, energy tunnels out of the black hole and across the event horizon. By this process the black hole loses mass, and to an outside observer it would appear that the black hole has just emitted a particle." My first question is, what was preventing the energy from tunneling out of the black hole in the first place? I mean, isn't quantum tunneling simply a matter of probability? Say you have two states, the inside of the event horizon, and the outside of the event horizon. Treat the system as an energy hill, like an activation energy in chemistry, except the hill is infinitely high, which is why nothing can escape a black hole in classical physics. However, according to the theory of quantum physics, it's merely a matter of probability that the subject exists in one state, and not the other, so there is a chance that the subject could "tunnel", or appear, on the other side of the event horizon. My second question is, does the energy disappear? Say an anti proton falls into the black hole, and a proton escapes the event horizon. The black hole then parcels out some ammount of energy equivalent to the combined mass of both the particle and the anti particle, and that energy disseapears from the black hole, such that, not only has the gain in energy from the anti proton falling in been negated, but also an ammount of energy has been lost equivalent to the proton being "emited". But where does that energy go? I suspect there's something crucial missing in my understanding of the instantaneous creation and anihalation of particle anti particle pairs. Any help?