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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 are suggested by the controversial [[theory of relativity]]. They 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.

'''Black holes''' are theoretical entities which are suggested by the controversial [[theory of relativity]]. They are postulated to be collapsed objects, usually [[stars]], which have so much mass that at a certain radius referred to as the Schwarzschild radius, there is an event horizon, beyond which the dilation of space-time due to the mass of the black hole results in all possible paths leading closer to the black hole.

 

Black holes have become an increasingly popular topic for magazines, the science page of the [[New York Times]], and science fiction, but whether they really exist remains uncertain.  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.

==History of the idea==

==History of the idea==