Re: Why do black holes have external gravity?

Hi Jeremy,

At present gravity can only be described in classical terms. No quantum theory of gravity is known. The space-time geometry is described by its metric. The metric is determined by the mass and energy distribution in the universe. So if we start with a mass distribution which corresponds to a black hole (spherically symmetric, non-rotating, uncharged), the resulting metric will be the Schwarzschild metric. The metric then determines how bodies propagate and move within space-time. This movement changes the mass and energy distribution, which again changes the metric ....

Classically, black holes are described by only 3 parameters, namely: mass, charge and angular momentum. For a complete picture of black holes, we need to describe them on a quantum level also. But so far no consistent quantum theory of gravity is available. On the quantum level, new effects occur, such as the evaporation of black holes by Hawking radiation.

I hope this helps
Michael