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| | [[Image:Iu8969hu.jpg|right|thumb|300px|Artist's conception of a binary system consisting of a black hole and a main sequence star. The black hole is drawing matter from the main sequence star via an [[accretion disk]] around it, and some of this matter forms a gas jet.]] | | [[Image:Iu8969hu.jpg|right|thumb|300px|Artist's conception of a binary system consisting of a black hole and a main sequence star. The black hole is drawing matter from the main sequence star via an [[accretion disk]] around it, and some of this matter forms a gas jet.]] |
| − | '''Black holes''' are theoretical entities which cannot be directly observed and may not exist. Suggested by the [[theory of relativity]] (see [[Counterexamples to Relativity]]), black holes are postulated to be collapsed objects, usually [[stars]], which have so much mass that within a certain radius the effect if it's mass results in an event horizon, past which both light and matter inevitably move towards the center over time . Thus, they absorb all matter and energy within that radius. Light and matter can enter, but nothing can escape, unless one accepts the theory of "Hawking" radiation, a result of applying quantum theory to black holes. | + | '''Black holes''' are theoretical entities which cannot be directly observed and may not exist. Suggested by the controversial [[theory of relativity]] (see [[Counterexamples to Relativity]]), black holes are postulated to be collapsed objects, usually [[stars]], which have become so [[dense]] that within a certain radius their [[escape velocity]] exceeds the [[speed of light]]. Thus, they absorb all matter and energy within that radius. Light and matter can enter, but nothing can ever escape. |
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| | + | Black holes are increasingly favored by [[liberal]] publications, such as the science page of the [[New York Times]] and glossy magazines, as well as science fiction writers. As with the related theoretical concept of a "[[wormhole]]",<ref>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. |
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| − | Black holes have generated much interest among [[liberal]] publications, such as the science page of the [[New York Times]] and glossy magazines, as well as science fiction writers. As with the related theoretical concept of a "[[wormhole]]",<ref>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 make direct observations of black holes, which means that observation is conducted by looking at phenomena associated with the black hole that occurs outside of the event horizon.
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| | ==History of the idea== | | ==History of the idea== |
| | The theoretical model of what we now call a black hole has evolved considerably over the centuries. 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] 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 theoretical model of what we now call a black hole has evolved considerably over the centuries. 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] 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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| | ===Inside the Event Horizon=== | | ===Inside the Event Horizon=== |
| − | What actually exists inside the event horizon of a black hole is a question that illuminates the divergence of quantum mechanics and classical mechanics. Some postulate that within the event horizon exists a point of zero (or nearly zero) volume but infinite energy density, a point sometimes referred to as a ''gravitational singularity,'' after the notion of a mathematical singularity (a term equaling infinity) in a field equation. Others suspect that infinite energy density is a physical impossibility, and that a black hole contains actual finitely-dense matter compressed into a [[degenerate matter|degenerate]] form, such as quark-degenerate matter. Classical theory suggests that since the black hole loses much of it's complexity in formation, information is lost, and as a result, maintains only mass, angular momentum, and charge. Quantum theory, however, predicts that complextiy, and therefore, information, cannot be lost. This suggests the unproven existence of "Hawking radiation", which would be very small magnitude and difficult to detect. | + | What actually exists inside the event horizon of a black hole is a question physics is unable to answer. Some postulate that within the event horizon exists a point of zero (or nearly zero) volume but infinite energy density, a point sometimes referred to as a ''gravitational singularity,'' after the notion of a mathematical singularity (a term equaling infinity) in a field equation. Others suspect that infinite energy density is a physical impossibility, and that a black hole contains actual finitely-dense matter compressed into a [[degenerate matter|degenerate]] form, such as quark-degenerate matter. Since all black holes are surrounded by an event horizon which prevents any information or messages from leaving, all these theories are non-[[falsifiable]]; we can never be sure what the interior structure of a black hole is like. |
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| | ===Properties of Black Holes=== | | ===Properties of Black Holes=== |