event horizon

== English == === Pronunciation === (General American) IPA(key): /əˈvɛnt həˈɹaɪ.zən/, /-zɪn/, [əˈvɛɾ̃ həˈɹaɪ.zən], [əˈvɛn -], [-zɪn] === Noun === event horizon (plural event horizons) (astrophysics) The gravitational sphere of a black hole within which the escape velocity is greater than the speed of light. (astrophysics) The furthest distance in the past of the universe from which light signals from an event can reach an observer at later times. (figuratively, by extension) A point of no return. ==== Coordinate terms ==== (astrophysics): ==== Derived terms ==== ==== Related terms ==== ==== Translations ==== ==== See also ==== general relativity special relativity === Further reading === event horizon on Wikipedia.Wikipedia