Changes

==Observation and Controversy==

==Methods of Observation==

Since black holes are literally invisible by traditional means of observation and so cannot be directly observed, it can never be conclusively demonstrated whether or not they exist.  However, scientists have attempted to find black holes through indirect means, such as the effect of their gravitational pull on nearby stars. Stars that are near black holes, e.g. by being part of a binary star system that contains one, show wobbles in their orbits similar to the tidal effects of the moon on Earth’s oceans. <ref>http://library.thinkquest.org/C007571/english/advance/english.htm</ref><ref>''Black Holes'' by Heather Cooper and Nigel Henbest (book)</ref>  Scientists have also observed stellar objects which have density consistent with black holes <ref>http://amazing-space.stsci.edu/resources/explorations/blackholes/lesson/whatisit/history.html</ref>.

Since black holes are literally invisible by traditional means of observation and so cannot be directly observed, their nature is determined from phenomena outside of the Schwarzschild radius.  Scientists have located and observed black holes through indirect means, such as the effect of their gravitational pull on nearby stars. Stars that are near black holes, e.g. by being part of a binary star system that contains one, show wobbles in their orbits similar to the tidal effects of the moon on Earth’s oceans. <ref>http://library.thinkquest.org/C007571/english/advance/english.htm</ref><ref>''Black Holes'' by Heather Cooper and Nigel Henbest (book)</ref>  Scientists have also observed stellar objects which have density consistent with black holes <ref>http://amazing-space.stsci.edu/resources/explorations/blackholes/lesson/whatisit/history.html</ref>.

While matter and energy, even light, may not escape a black hole, Stephen Hawking has shown that they should emit [[Hawking radiation]], which absent of an influx of mass-energy would lead to the evaporation of the black hole in a burst of gamma rays. Scientists are currently working to pick up one of these bursts, or the radiation itself, with any of several land- and space-based telescopes. However, the matter falling into black holes as well as the [[cosmic microwave background]] obscures the radiation and makes detection extremely difficult.

While matter and energy, even light, may not escape a black hole, Stephen Hawking has shown that when described by quantum mechanics, they should emit [[Hawking radiation]], which absent of an influx of mass-energy would lead to the evaporation of the black hole in a burst of gamma rays. Scientists are currently working to pick up one of these bursts, or the radiation itself, with any of several land- and space-based telescopes. However, the matter falling into black holes as well as the [[cosmic microwave background]] obscures the radiation and makes detection extremely difficult.

==Speculative Future Exploration==

==Speculative Future Exploration==