What is the Event Horizon of a Black Hole?

[AbsoluteZer0]

Hi,

I've heard a fair bit about the event horizon of a black hole. What exactly is the event horizon?

Thanks,

 

[Janus]

It is the point where the escape velocity equals the speed of light. It not a physical thing, but marks the boundary of "no return" . Anything that passes closer to the black hole than its event horizon, can never do anything but fall in closer to the black hole, this includes light.

 

[Naty1]

Nice introductory explanation here:

http://en.wikipedia.org/wiki/Event_horizon

 

[Radrook]

The mothers of all event horizons!Excerpt:

Astronomers Find the Most Supermassive Black Holes Yet
by Amy Shira Teitel on December 7, 2011Each of these black holes has an event horizon — the point of no return where nothing, not even light can escape their gravity — 200 times larger than the orbit of Earth (or five times the orbit of Pluto). That’s a mind-boggling 29,929,600,000 kilometres or 18,597,391,235 miles.

Beyond the event horizon, each has a gravitational influence that extends over 4,000 light years in every direction.
http://www.universetoday.com/91625/astronomers-find-the-most-supermassive-black-holes-yet/

 

[pmacias]

The event horizon is a theoretical boundary surrounding a black hole, beyond which no light or matter can escape. It is the point of no return for anything entering the black hole, as the gravitational pull becomes infinitely strong at this point. The event horizon is defined by the Schwarzschild radius, which is dependent on the mass of the black hole. Anything that passes through the event horizon is pulled into the singularity at the center of the black hole, where the laws of physics as we know them break down. The event horizon is an important concept in understanding the behavior of black holes and their effects on the surrounding space.