# A Couple Questions.

#### Inquiring_Mike

A Couple Questions.........

I was recently watching a t.v. show and the following terms came up: event horizon, singularity and schwarzchild radius.... Can anyone tell me what these things are?

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#### mathman

All these terms relate to black holes. The Schwarzchild radius (depends on mass of object) is the radius that an object has to have to become a black hole. That is if the object is bigger, it is not, if smaller, it is.

The event horizon is determined by the Schwarzchild radius and it refers to the point of no return for any object falling into a black hole.

A singularity (in this context) refers to the idea that all the mass of a black hole is concentrated at one point of infinite density - a prediction of general relativity. Since quantum theory breaks down under these circumstances, no one really knows what happens inside a black hole.

#### jcsd

Gold Member
The event horizon of a black hole is the point of no return, once an object is past this point it can only move towards the singularity.

The Schwarzchild radius is the radius of the sphere around the (Scwarzchild) black hole whose surface forms the event horizon and is given by the simple equation:

$$r_S = \frac{2GM}{c^2}$$

Ther singularity is the infintely dense point at the centre of a black hole which matter is pulled to.

#### Inquiring_Mike

Interesting........ Thanks....It all makes sense now.....

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