Now, i just heard that the particle anti particle pairs that zip in and out of existence every planck second both have positive mass. if that is so, how does hawking radiation work? black holes lose mass when the particle with negative mass falls into the black hole and cancels out some of the positive mass in it? but, if both particles are positive, the black hole should gain mass instead of losing it. what exactly is going on here?
The quantum fluctuations you are referring to are 'virtual pairs'. One could object that their creation is a violation of the conservation of energy principle, but this is allowed in quantum mechanics due to the brevity of their existence. Their creation and annihilation leaves no net gain or loss to the total energy of the system normally, but when one particle is within the event horizon the orphaned counter-part cannot annihilate with it, and thus must exist. This particle, now real, accounts for some new energy to the system and we cannot draw that from the vacuum, it is thus taken from the black hole; accounting for a very small loss of energy. The creation of the surviving particle requires more energy than the consumption of its counterpart provides to the black-hole. I hope this helps, feel free to request further specificity if needed.