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  2. Event horizon - Wikipedia

    en.wikipedia.org/wiki/Event_horizon

    In astrophysics, an event horizon is a boundary beyond which events cannot affect an outside observer. Wolfgang Rindler coined the term in the 1950s. [1]In 1784, John Michell proposed that gravity can be strong enough in the vicinity of massive compact objects that even light cannot escape. [2]

  3. Trapped surface - Wikipedia

    en.wikipedia.org/wiki/Trapped_surface

    Closed trapped surfaces are a concept used in black hole solutions of general relativity [1] which describe the inner region of an event horizon. Roger Penrose defined the notion of closed trapped surfaces in 1965. [2] A trapped surface is one where light is not moving away from the black hole.

  4. Horizon (general relativity) - Wikipedia

    en.wikipedia.org/wiki/Horizon_(general_relativity)

    A horizon is a boundary in spacetime satisfying prescribed conditions. There are several types of horizons that play a role in Albert Einstein 's theory of general relativity : Absolute horizon , a boundary in spacetime in general relativity inside of which events cannot affect an external observer

  5. Event (relativity) - Wikipedia

    en.wikipedia.org/wiki/Event_(relativity)

    For example, a glass breaking on the floor is an event; it occurs at a unique place and a unique time. [1] Strictly speaking, the notion of an event is an idealization , in the sense that it specifies a definite time and place, whereas any actual event is bound to have a finite extent, both in time and in space.

  6. Absolute horizon - Wikipedia

    en.wikipedia.org/wiki/Absolute_horizon

    In general relativity, an absolute horizon is a boundary in spacetime, defined with respect to the external universe, inside 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 by the observer.

  7. Kruskal–Szekeres coordinates - Wikipedia

    en.wikipedia.org/wiki/Kruskal–Szekeres_coordinates

    The black hole event horizon bordering exterior region I would coincide with a Schwarzschild t-coordinate of + while the white hole event horizon bordering this region would coincide with a Schwarzschild t-coordinate of , reflecting the fact that in Schwarzschild coordinates an infalling particle takes an infinite coordinate time to reach the ...

  8. Point of no return - Wikipedia

    en.wikipedia.org/wiki/Point_of_no_return

    Event horizon – Region in spacetime from which nothing can escape; Fail-safe – Design feature or practice; Hobson's choice – Free choice in which only one option is actually offered; Sunk cost – Cost that has already been incurred and cannot be recovered; Ultimatum – Final demand backed up by a threat; Window of opportunity – Period ...

  9. Ergosphere - Wikipedia

    en.wikipedia.org/wiki/Ergosphere

    It is the speed of light that arbitrarily defines the ergosphere surface. Such a surface would appear as an oblate that is coincident with the event horizon at the pole of rotation, but at a greater distance from the event horizon at the equator. Outside this surface, space is still dragged, but at a lesser rate. [citation needed]