# What is the radius of a black hole? [duplicate]

I know the formula for the event horizon is $$R_s = 2GM/c^2.$$ At this distance the escape velocity equals the speed of light so nothing can escape from a black hole from this distance or less. But escape from is not the same as leave. Take the earth as an analogy. The escape velocity at the surface is 11.2 $$km/s$$. Any object with this speed or less remains captured by the earth, ie it is doomed to fall back to earth. But such objects can and do leave the surface of the earth for a period of time depending on their velocity. Is the same true for a black hole? But if it is, what might stop such an object, temporarily outside the event horizon from colliding with a second object and being given enough velocity to escape the black hole?

What's the depth of a bottomless well? The radial parameter in the Schwarzschild solution isn't what you think: it's the circumference of a sphere around the black hole divided by $$4\pi$$. It's not the "distance from the black hole".