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  2. Event horizon - Wikipedia

    en.wikipedia.org/wiki/Event_horizon

    In 1958, David Finkelstein used general relativity to introduce a stricter definition of a local black hole event horizon as a boundary beyond which events of any kind cannot affect an outside observer, leading to information and firewall paradoxes, encouraging the re-examination of the concept of local event horizons and the notion of black ...

  3. Black hole - Wikipedia

    en.wikipedia.org/wiki/Black_hole

    The Event Horizon Telescope (EHT) is an active program that directly observes the immediate environment of black holes' event horizons, such as the black hole at the centre of the Milky Way. In April 2017, EHT began observing the black hole at the centre of Messier 87.

  4. Schwarzschild radius - Wikipedia

    en.wikipedia.org/wiki/Schwarzschild_radius

    (Supermassive black holes up to 21 billion (2.1 × 10 10) M ☉ have been detected, such as NGC 4889.) [16] Unlike stellar mass black holes, supermassive black holes have comparatively low average densities. (Note that a (non-rotating) black hole is a spherical region in space that surrounds the singularity at its center; it is not the ...

  5. Firewall (physics) - Wikipedia

    en.wikipedia.org/wiki/Firewall_(physics)

    A black hole firewall is a hypothetical phenomenon where an observer falling into a black hole encounters high-energy quanta at (or near) the event horizon.The "firewall" phenomenon was proposed in 2012 by physicists Ahmed Almheiri, Donald Marolf, Joseph Polchinski, and James Sully [1] as a possible solution to an apparent inconsistency in black hole complementarity.

  6. Black hole information paradox - Wikipedia

    en.wikipedia.org/wiki/Black_hole_information_paradox

    The first image (silhouette or shadow) of a black hole, taken of the supermassive black hole in M87 with the Event Horizon Telescope, released in April 2019. The black hole information paradox [1] is a paradox that appears when the predictions of quantum mechanics and general relativity are combined.

  7. Gravitational singularity - Wikipedia

    en.wikipedia.org/wiki/Gravitational_singularity

    An example is the Schwarzschild solution that describes a non-rotating, uncharged black hole. In coordinate systems convenient for working in regions far away from the black hole, a part of the metric becomes infinite at the event horizon. However, spacetime at the event horizon is regular.

  8. Outline of black holes - Wikipedia

    en.wikipedia.org/wiki/Outline_of_black_holes

    Jacob Bekenstein - for the foundation of black hole thermodynamics and the elucidation of the relation between entropy and the area of a black hole's event horizon. Karl Schwarzschild - found a solution to the equations of general relativity that characterizes a black hole.

  9. 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 ...