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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. 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 ...

  4. Penrose diagram - Wikipedia

    en.wikipedia.org/wiki/Penrose_diagram

    Penrose diagram of an infinite Minkowski universe, horizontal axis u, vertical axis v. In theoretical physics, a Penrose diagram (named after mathematical physicist Roger Penrose) is a two-dimensional diagram capturing the causal relations between different points in spacetime through a conformal treatment of infinity.

  5. 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.

  6. Gullstrand–Painlevé coordinates - Wikipedia

    en.wikipedia.org/wiki/Gullstrand–Painlevé...

    It can not escape from the event horizon. Instead, it gets stuck at the event horizon. Since light moves faster than all others, matter can only move inward at the event horizon. Everything inside the event horizon is hidden from the outside world. Inside the event horizon, <, the rain observer measures that the light moves toward the center ...

  7. Rindler coordinates - Wikipedia

    en.wikipedia.org/wiki/Rindler_coordinates

    Both of these facts would also be true if we were considering a set of observers hovering outside the event horizon of a black hole, each observer hovering at a constant radius in Schwarzschild coordinates. In fact, in the close neighborhood of a black hole, the geometry close to the event horizon can be described in Rindler coordinates.

  8. 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

  9. Trapped surface - Wikipedia

    en.wikipedia.org/wiki/Trapped_surface

    The trapped surface is a spacelike surface of co-dimension 2, in a Lorentzian spacetime. It follows [4] that any normal vector can be expressed as a linear combination of two future directed null vectors, normalised by: k + · k − = −2 The k + vector is directed “outwards” and k − “inwards”. The set of all such vectors engenders ...