# Calculating the event horizon of black holes.

1. May 3, 2015

### William Henley

Hello, I remember hearing somewhere that it is possible to calculate the event horizon, I was just wondering if this is possible and what equations are used to calculate it.

2. May 3, 2015

### phinds

"hearing somewhere" is not a very solid reference, although it happens to be correct in this case. It is rather trivial for a non-rotating black hole. Have you done any research at all?

3. May 3, 2015

### virgil1612

I would give you a suggestion, as it very simple to do and quite satisfying... Think of a satellite around the Earth and find its escape velocity, you should get something very simple, function of the mass of the Earth and the distance to the satellite. Then equalize that velocity with the velocity of light, solve for the distance and voila, you get the radius of the horizon (or the Schwarzschild radius, as it is called)
Virgil.

4. May 3, 2015

### William Henley

Yeah I have, and I found that the Schwarzschild equation can be used to calculate the radius of the black hole. But I was wondering if someone could explain how to use the equation.

5. May 3, 2015

### virgil1612

Just an observation, it is not the radius of the black hole, but the radius of the horizon of the black hole.

6. May 3, 2015

### phinds

Which is usually called "the radius of the black hole" since a black hole does not have any other radius.