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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.]]

A '''black hole''' is a collapsed star which has become so [[mass (science)|mass]]ive that within a certain radius its [[escape velocity]] exceeds the [[speed of light]]. This it absorbs all matter and energy within that radius.   

A '''black hole''' is a collapsed star which has become so [[mass (science)|mass]]ive that within a certain radius its [[escape velocity]] exceeds the [[speed of light]]. This it absorbs all matter and energy within that radius.  Light and matter can enter, but nothing can ever escape.

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.

The black hole is a theoretical prediction of the [[theory of relativity]], which posits a region of [[spacetime]] into which light and other matter can enter, but out of which nothing can ever emerge.  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 it fails the [[falsifiability]] requirement of science.   

Black holes were first predicted by the [[theory of relativity]].  They 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 it fails the [[falsifiability]] requirement of science.   

==Nature of a Black Hole==

==Nature of a Black Hole==