Changes

A '''black hole''' is a collapsed object, usually a [[star]], which has become so [[dense]] that within a certain radius its [[escape velocity]] exceeds the [[speed of light]]. Thus, it absorbs all matter and energy within that radius.  Light and matter can enter, but nothing can ever escape.

A '''black hole''' is a collapsed object, usually a [[star]], which has become so [[dense]] that within a certain radius its [[escape velocity]] exceeds the [[speed of light]]. Thus, it absorbs all matter and energy within that radius.  Light and matter can enter, but nothing can ever escape.

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 they fail 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>  

* M is the mass of the gravitating object;  

* M is the mass of the gravitating object;  

* C is the speed of light in vacuum.  

* C is the speed of light in vacuum.  

 

===Time and Distance===

===Time and Distance===