According to theory of black hole radiation, black holes are expected to emit a thermal spectrum of radiation, and thereby loss mass, owing to the E=mc2 equation. Well, everything was clear to me till I got to the last point. why should there be loss only in mass?? couldn't the mass be same and velocity change, in order to satisfy the above equation?? Let me know if am going anywhere wrong and what does the "c" represent to in this case? I mean...velocity of what??