In general relativity, an absolute horizon is a boundary in spacetime, defined with respect to the external universe, inside of which events cannot affect an external observer. Light emitted inside the horizon can never reach the observer, and anything that passes through the horizon from the observer's side is never seen again. An absolute horizon is the boundary of a black hole by definition.
In the context of black holes, the absolute horizon is almost exclusively referred to as an event horizon, though this is often used as a more general term for all types of horizons. The absolute horizon is just one type of horizon. For example, important distinctions must be made between absolute horizons and apparent horizons. See also the articles on ergosphere, Cauchy horizon, the Reissner-Nordström solution, photon sphere, Killing horizon and naked singularity; the notion of a horizon in general relativity is subtle, and depends on fine distinctions.
Read more about Absolute Horizon: Definition, Nature of The Absolute Horizon
Famous quotes containing the words absolute and/or horizon:
“The research on gender and morality shows that women and men looked at the world through very different moral frameworks. Men tend to think in terms of “justice” or absolute “right and wrong,” while women define morality through the filter of how relationships will be affected. Given these basic differences, why would men and women suddenly agree about disciplining children?”
—Ron Taffel (20th century)
“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)