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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 ...
The event horizons bounding the black hole and white hole interior regions are also a pair of straight lines at 45 degrees, reflecting the fact that a light ray emitted at the horizon in a radial direction (aimed outward in the case of the black hole, inward in the case of the white hole) would remain on the horizon forever. Thus the two black ...
Although charged black holes with r Q ≪ r s are similar to the Schwarzschild black hole, they have two horizons: the event horizon and an internal Cauchy horizon. [8] As with the Schwarzschild metric, the event horizons for the spacetime are located where the metric component diverges; that is, where + = =
Within an apparent horizon, light does not move outward; this is in contrast with the event horizon. In a dynamical spacetime, there can be outgoing light rays exterior to an apparent horizon (but still interior to the event horizon). An apparent horizon is a local notion of the boundary of a black hole, whereas an event horizon is a global notion.
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.
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.
An absolute horizon is thought of as the boundary of a black hole. In the context of black holes, the absolute horizon is generally 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.
Event horizon, a boundary in spacetime beyond which events cannot affect the observer, thus referring to a black hole's boundary and the boundary of an expanding universe; Apparent horizon, a surface defined in general relativity; Cauchy horizon, a surface found in the study of Cauchy problems; Cosmological horizon, a limit of observability