what is event horizon?

Question

and please don't say "a movie"

Answer 1

To put it into plain english...

The event horizon when referring to light is the boundary in which we on Earth cannot observe beyond. For example, there are stars in existence that we do not know exist (other than the probability of their existence being so high) because the light that they have emitted has not had enough time to reach the Earth. Every nanosecond of every day our event horizon is growing, meaning that we can see more and more of the universe simply because we are receiving more and more light.

Now the event horizon of a black hole is much different. It is the point of no return for objects (including light) to escape a black hole. Once an object has passed this boundary, it will inevitably be absorbed by the black hole.

Answer 2

event horizon is a general term for a boundary in spacetime, defined with respect to an observer, beyond which events cannot affect the observer. Light emitted beyond the horizon can never reach the observer, and anything that passes through the horizon from the observer's side is never seen again. A black hole is surrounded by an event horizon, for example. This means that an outside observer cannot be affected by anything inside the black hole.

More specific types of horizons include the related but distinct absolute and apparent horizons found around a black hole. Still other distinct notions include the Cauchy and Killing horizon; particle and cosmological horizons relevant to cosmology; and isolated and dynamical horizons important in current black hole research.

Answer 3

The event horizon is the gravity field of a black hole where the space-time is so bent that light cannot escape it. The event horizon creates a region in space where nothing can escape, if nothing can go beyond the speed of light. Thus when something enters the event horizon, it will vanish without a trace. Should the object be emitting something, after it is enveloped by the event horizon, not even the emissions that traced its existence will escape the black hole.

Answer 4

An event horizon is any barrier that prevents information from comming back to you .
A well received example is a black hole this is a good illustration of what an event horizon is [A black hole is a theoretical entity that cannot and does not exist]

Answer 5

Some one has already replied ( Cut & paste ) from
http://en.wikipedia.org/wiki/Event_horizon

This is a good link

The 'event horizon' is the boundary defining the region of space around a black hole from which nothing (not even light) can escape

ref : http://cosmos.swin.edu.au/lookup.html?e=eventhorizon


Ramesh
The Human Search Engine