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event horizon

event horizon Boundary of a black hole, from which nothing can escape. Observers outside the event horizon can therefore obtain no information about the black hole's interior. The radius of the event horizon is called the Schwarzschild radius. At the event horizon, the escape velocity equals the velocity of light with the consequence that all electromagnetic radiation is trapped. Its presence can only be detected by its powerful gravitational force.

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event horizon

e·vent ho·ri·zon • n. Astron. a theoretical boundary around a black hole beyond which no light or other radiation can escape. ∎  fig. any point of no return: we're nearing the event horizon of the presidential election.

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"event horizon." The Oxford Pocket Dictionary of Current English. . Encyclopedia.com. 18 Aug. 2018 <http://www.encyclopedia.com>.

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Event Horizon

Event Horizon ★★½ 1997 (R)

Cross between “Alien” and “The Shining” has Fishburne heading an ensemble cast out to rescue a prototype spaceship that's been missing for seven years. Their own ship is sabatoged by their own demons and certain extraterrestial ones, too, that cause much mayhem on their once peaceful mission. 97m/C VHS, DVD . Laurence Fishburne, Sam Neill, Kathleen Quinlan, Joely Richardson, Richard T. Jones, Jack Noseworthy, Sean Pertwee, Jason Isaacs; D: Paul W.S. Anderson; W: Philip Eisner; C: Adrian Biddle; M: Michael Kamen.

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Event Horizon

Event Horizon

An event horizon, as defined within general relativity, is a boundary in spacetime (the four-dimensional structure of the universe, with three-dimensional space and one-dimensional time) in which events are not realized by an observer so cannot affect the observer. In general usage, an event horizon is a limiting boundary beyond which nothing can be observed or measured with regard to a particular phenomena (e.g., the cosmic event horizon beyond which nothing can be observed from Earth). Specifically, an event horizon is the regions around a gravity field of a black hole. Such a gravitation field bends light so much that it cannot escape from it and go out into the universe.

In early 2001, for instance, data gathered by NASAs Hubble Space Telescope and the Chandra X-ray Observatory independently provided strong evidence of an event horizon, the observable boundary region surrounding an unobservable black hole.

According to general relativity, the path taken by a beam of light is the shortest distance between two points; such a path is called a geodesic. Furthermore, gravity warps space, bending geodesics; the stronger a gravitational field is in a certain region, the more bent the geodesics are in that region. Within a certain radius of a black hole, all geodesics are so warped that a photon of light cannot escape to another part of the universe. Essentially, there are no straight lines connecting any point that is within a certain radius of a black hole (which, in theory, means there is no dimension) to any point that is farther away. The spherical surface defined by this radius is termed the event horizon of the black hole because events inside the event horizon can have no effect on events outside it. Whatever is inside the event horizon is sealed off forever from the space-time of outside observers.

The size of the event horizon surrounding a black hole is termed the Schwarzschild radius, named after German astronomer Karl Schwarzschild (18731916), who studied the properties of geometric space around a singularity when warped according to general relativity theory. Gravitational fields bend light, and within a black hole the gravity is so strong that light is actually bent back upon itself. Another explanation in accord with the wave-particle duality of light is that inside the event horizon the gravitational attraction of the singularity is so strong that the required escape velocity for light is greater than the speed of light. As a consequence, because no object can exceed the speed of light, not even light itself can escape from the region of space within the event horizon.

More evidence gathered in 2002 convinced many scientists that in addition to matter spinning violently into the vortex of a black hole, the black hole itself rotates just like a star.

The event horizon is an observational boundary on the cosmic scale because no information generated within the black hole can escape. Processes occurring at or near the event horizon, however, are observable and offer important insights into the physics associated with black holes.

An accretion disk surrounding a black hole forms as matter accelerates toward the event horizon. The accelerating matter heats and emits strong highly energetic electromagnetic radiation, including x rays and gamma rays, that may be associated with some of the properties exhibited by quasars.

Although light and matter can not escape a black hole by crossing the event horizon, English physicist Stephen Hawking (1942) formed an important concept later named Hawking radiation that offers a possible explanation to possible matter and energy leakage from black holes. Relying on quantum theories regarding virtual particles (particle-antiparticle pairs that exist so briefly only their effects (not their masses) can be measured), Hawking radiation occurs when a virtual particle crosses the event horizon and its partner particle cannot be annihilated and, thus, becomes a real particle with mass and energy. With Hawking radiation, mass can thus leave the black hole in the form of new particles created just outside the event horizon.

As a 2006 meeting of the American Astronomical Society, scientists stated that vanishing gas is strong evidence for the existence of event horizons at black holes. Using NASAs Rossi X-ray Timing Explorer, scientists found X-ray bursts from neutron stars but none were identified from black holes. X-ray bursts are quick thermonuclear eruptions that occur on neutron stars, small, dense stars. The eruptions occur when gas is taken from the companion star of s neutron star.

See also Astronomy; Astrophysics; Atomic models; Black hole; Blackbody radiation; Electromagnetic spectrum; Quantum mechanics; Quasar; Radio astronomy; Radio waves; Radio; Relativity, general; Relativity, special; Stellar evolution.

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Event Horizon

Event horizon

In early 2001, data gathered by NASA's Hubble Space Telescope and the Chandra X-ray Observatory independently provided strong evidence of an event horizon , the observable boundary region surrounding an unobservable black hole .

The size of the event horizon surrounding a black hole is termed the Schwarzschild radius, named after the German astronomer Karl Schwarzschild (1873–1916), who studied the properties of geometric space around a singularity when warped according to general relativity theory. Gravitational fields bend light , and within a black hole the gravity is so strong that light is actually bent back upon itself. Another explanation in accord with the wave-particle duality of light is that inside the event horizon the gravitational attraction of the singularity is so strong that the required escape velocity for light is greater than the speed of light. As a consequence, because no object can exceed the speed of light, not even light itself can escape from the region of space within the event horizon.

More evidence gathered in 2002 convinced many scientists that in addition to matter spinning violently into the vortex of a black hole, the black hole itself rotates just like a star .

The event horizon is an observational boundary on the cosmic scale because no information generated within the black hole can escape. Processes occurring at or near the event horizon, however, are observable and offer important insights into the physics associated with black holes.

An accretion disk surrounding a black hole forms as matter accelerates toward the event horizon. The accelerating matter heats and emits strong highly energetic electromagnetic radiation , including x rays and gamma rays, that may be associated with some of the properties exhibited by quasars.

Although light and matter can not escape a black hole by crossing the event horizon, English physicist Stephen Hawking (1942–) formed an important concept later named Hawking radiation that offers a possible explanation to possible matter and energy leakage from black holes. Relying on quantum theories regarding virtual particles (particle-antiparticle pairs that exist so briefly only their effects (not their masses) can be measured), Hawking radiation occurs when a virtual particle crosses the event horizon and its partner particle cannot be annihilated and thus becomes a real particle with mass and energy. With Hawking radiation, mass can thus leave the black hole in the form of new particles created just outside the event horizon.

In general usage, an event horizon is a limiting boundary beyond which nothing can be observed or measured with regard to a particular phenomena (e.g., the cosmic event horizon beyond which nothing can be observed from Earth ).

See also Astronomy; Astrophysics; Atomic models; Black hole; Blackbody radiation; Electromagnetic spectrum; Quantum mechanics; Quasar; Radio astronomy; Radio waves; Radio; Relativity, general; Relativity, special; Stellar evolution.

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"Event Horizon." The Gale Encyclopedia of Science. . Encyclopedia.com. 18 Aug. 2018 <http://www.encyclopedia.com>.

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"Event Horizon." The Gale Encyclopedia of Science. . Retrieved August 18, 2018 from Encyclopedia.com: http://www.encyclopedia.com/science/encyclopedias-almanacs-transcripts-and-maps/event-horizon-0

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Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

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