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/