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| | A '''black hole''' is a theoretical formation in space which has nearly [[infinity|infinite]] density such that it draws all nearby matter into it with strong gravitational forces. The word "black" is in the name because these formations theoretically prevent even light ([[photon]]s) from escaping, thereby making them completely dark.<ref>They are assumed to come into existence from extremely large stars that collapse into a state of high density when they run out of fusion fuel. An object becomes a black hole when it lies entirely inside the Schwarzschild radius (see below) determined by its mass. For most objects, the Schwarzschild radius is very tiny compared with its size (for Earth it is about 1 centimeter), so the object could not lie inside that radius.</ref> | | A '''black hole''' is a theoretical formation in space which has nearly [[infinity|infinite]] density such that it draws all nearby matter into it with strong gravitational forces. The word "black" is in the name because these formations theoretically prevent even light ([[photon]]s) from escaping, thereby making them completely dark.<ref>They are assumed to come into existence from extremely large stars that collapse into a state of high density when they run out of fusion fuel. An object becomes a black hole when it lies entirely inside the Schwarzschild radius (see below) determined by its mass. For most objects, the Schwarzschild radius is very tiny compared with its size (for Earth it is about 1 centimeter), so the object could not lie inside that radius.</ref> |
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| − | Black holes are increasingly promoted by [[liberal]] publications, such as the science page of the ''[[New York Times]]'', glossy magazines, and the movies the ''Event Horizon'' (1997), ''The Black Hole'' (TV, 2006), and ''Interstellar'' (2014). As with the related theoretical concept of a "[[wormhole]]",<ref name="nytimes.com">The prediction of the existence of wormholes, and its naming in 1957, predates the prediction and naming (1967) of a black hole.[http://www.nytimes.com/2008/04/14/science/14wheeler.html?pagewanted=print]</ref> it is impossible to prove that no black hole exists anywhere, and thus they fail the [[falsifiability]] requirement of science. | + | Black holes are increasingly promoted by [[liberal]] publications, such as the science page of the ''[[New York Times]]'', glossy magazines, and the movies the ''Event Horizon'' (1997), ''The Black Hole'' (TV, 2006), and ''Interstellar'' (2014). Black holes fail the [[falsifiability]] requirement of science, because it is impossible to prove that do not exist anywhere in the universe. |
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| | Because of [[quantum mechanics|quantum-mechanical]] phenomena involving Hawking Radiation, discussed later in the article, black holes must emit radiation and thus are a logical contradiction at the microscopic level. | | Because of [[quantum mechanics|quantum-mechanical]] phenomena involving Hawking Radiation, discussed later in the article, black holes must emit radiation and thus are a logical contradiction at the microscopic level. |
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| | Black holes have never been directly observed, and there is no direct evidence for their existence. Even believers in black holes should admit that there are far fewer than predicted by theory, and they lose credibility when they fail to address that undisputed truth. They will cite evidence of observations of radiation from accretion disks, motion of stars near the center of the galaxy, and "gravitational lensing," around places where there are no visible objects. But at most the evidence for the existence of black holes is circumstantial, with heavy reliance on speculation. | | Black holes have never been directly observed, and there is no direct evidence for their existence. Even believers in black holes should admit that there are far fewer than predicted by theory, and they lose credibility when they fail to address that undisputed truth. They will cite evidence of observations of radiation from accretion disks, motion of stars near the center of the galaxy, and "gravitational lensing," around places where there are no visible objects. But at most the evidence for the existence of black holes is circumstantial, with heavy reliance on speculation. |
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| − | Black holes are conceptually associated with "[[wormhole]]s",<ref name="nytimes.com"/> which never caught on with the public, perhaps due to its unattractive terminology. | + | Black holes are conceptually associated with "[[wormhole]]s",<ref name="nytimes.com">The prediction of the existence of wormholes, and its naming in 1957, predates the prediction and naming (1967) of a black hole.[http://www.nytimes.com/2008/04/14/science/14wheeler.html?pagewanted=print]</ref> which never caught on with the public, perhaps due to its unattractive terminology. |
| | ==Mathematical description== | | ==Mathematical description== |
| | A '''black hole''' is any object that lies entirely inside its own Schwarzschild radius, given by | | A '''black hole''' is any object that lies entirely inside its own Schwarzschild radius, given by |
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| | ==Pre-history== | | ==Pre-history== |
| − | The notion of something that has gravity so strong that light can't escape actually dates back to the 18th century, when scientists became aware of the finite speed of light and the concept of escape velocity. The [[corpuscular theory of light]] held that light was made up of invisibly small particles, and that these particles moved along ballistic trajectories, like tiny bullets. In this framework, it was believed possible that a distant star could be so massive that light emitted from its surface would be dragged back down again. This theory was first advanced by John Michell, who wrote in 1783, "If the semi-diameter of a sphere of the same density as the Sun in the proportion of five hundred to one, and by supposing light to be attracted by the same force in proportion to its [[Mass (science)|mass]] with other bodies, all light emitted from such a body would be made to return towards it, by its own proper gravity."<ref name="r1">http://www.aps.org/publications/apsnews/200911/physicshistory.cfm</ref> | + | The notion of something that has gravity so strong that light can't escape actually dates back to the 18th century, when scientists became aware of the finite speed of light and the concept of escape velocity. The corpuscular theory of light held that light was made up of invisibly small particles, and that these particles moved along ballistic trajectories, like tiny bullets. In this framework, it was believed possible that a distant star could be so massive that light emitted from its surface would be dragged back down again. This theory was first advanced by John Michell, who wrote in 1783, "If the semi-diameter of a sphere of the same density as the Sun in the proportion of five hundred to one, and by supposing light to be attracted by the same force in proportion to its [[Mass (science)|mass]] with other bodies, all light emitted from such a body would be made to return towards it, by its own proper gravity."<ref name="r1">http://www.aps.org/publications/apsnews/200911/physicshistory.cfm</ref> |
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| | Suggesting the same possibility independently, Pierre-Simon Laplace wrote in 1796, "It is therefore possible that the greatest luminous bodies in the universe are on this account invisible."<ref name="r1" /> | | Suggesting the same possibility independently, Pierre-Simon Laplace wrote in 1796, "It is therefore possible that the greatest luminous bodies in the universe are on this account invisible."<ref name="r1" /> |