Here's a non-physicist asking a question: How can black holes have different masses and radii? I understand that black holes are formed when a critical density is reached and poof, all that matter is condensed into a sigularity, with so-called infinite density. Then we talk about black holes being massive, so many times the mass of the sun, etc. But, if there is only one critical density, then how can black holes have different masses? Wouldn't all the other mass be at the event horizon, since you can never actually approach the singularity? How can the singularity have different masses if by definition it is infinitely dense? Is this just our approximation? (I can see the possibility of two collapsing stars of different mass becoming black holes and prehaps any mass "within" the event horizon at the time of collapse would become part of the singularity, so maybe the black holes would have different masses, but to me talking about the mass of a singularity sounds funny.) If black holes are really singularities, then how can the radii of their event horizons differ? This sounds like a paradox that will most likely be explained very handily by someone out there.