Changes

Black holes 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 does not lie inside that radius.

Black holes 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 does not lie inside that radius.

In some very advanced and esoteric theories of physics, black holes are sometimes associated with "[[wormhole]]s",<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>, another very catchy name and very catchy subject for science fiction stories.

Black holes are conceptually associated with "[[wormhole]]s",<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> which never caught on with the public, perhaps due to its poor terminology.

==History of the idea==

==History of the idea==