| MadSci Network: Astronomy |
As a matter of fact, black holes do not have infinite density, pressure, temperature, or gravity.
Black holes have exactly the same amount of gravity as any other object with the same amount of mass. If we could somehow magically replace the Sun with a black hole of the same mass, the Earth would continue quite happily in its orbit. (Though its inhabitants might notice it becoming colder! :)
I'm not sure what you mean by the pressure exerted by a black hole. As to the other two quantities, though, both are related to the mass of a black hole. The mass of a black hole is not infinite, thus neither the temperature nor the density are infinite.
Try the links in the MadSci Library for more information on Astronomy.