Event Horizon

In general relativity, an event horizon is a boundary in spacetime beyond which events cannot affect an outside observer. In layman's terms it is defined as "the point of no return" i.e. the point at which the gravitational pull becomes so great as to make escape impossible. The most common case of an event horizon is that surrounding a black hole. Light emitted from beyond the horizon can never reach the observer. Likewise, any object approaching the horizon from the observer's side appears to slow down and never quite pass through the horizon, with its image becoming more and more redshifted as time elapses. The traveling object, however, experiences no strange effects and does, in fact, pass through the horizon in a finite amount of proper time.

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

Read more about Event Horizon:  Event Horizon of A Black Hole, Particle Horizon of The Observable Universe, Apparent Horizon of An Accelerated Particle, Interacting With An Event Horizon, Beyond General Relativity

Famous quotes containing the words event and/or horizon:

    The vanishing volatile froth of the present which any shadow will alter, any thought blow away, any event annihilate, is every moment converted into the Adamantine Record of the past.
    Ralph Waldo Emerson (1803–1882)

    The whole world of thought lay unexplored before me,—a world of which I had already caught large and tempting glimpses, and I did not like to feel the horizon shutting me in, even to so pleasant a corner as this.
    Lucy Larcom (1824–1893)