Changes

Black holes remain a controversial subject today.

Black holes remain a controversial subject today.

==Black Holes Through The Centuries==

==Historical Models==

The theoretical model of what we now call a black hole has evolved considerably over the centuries. The [[corpuscular theory of light]] held that light was made up of invisibly small particles, and that these particles moved along ballistic trajectories, like tiny bullets. In this framework, it was believed possible that a distant star could be so massive that light emitted from its surface would be dragged back down again. This theory was first advanced by John Michell, who wrote in 1783, "If the semi-diameter of a sphere of the same density as the Sun in the proportion of five hundred to one, and by supposing light to be attracted by the same force in proportion to its [mass] with other bodies, all light emitted from such a body would be made to return towards it, by its own proper gravity."<ref name="r1" />

The theoretical model of what we now call a black hole has evolved considerably over the centuries. The [[corpuscular theory of light]] held that light was made up of invisibly small particles, and that these particles moved along ballistic trajectories, like tiny bullets. In this framework, it was believed possible that a distant star could be so massive that light emitted from its surface would be dragged back down again. This theory was first advanced by John Michell, who wrote in 1783, "If the semi-diameter of a sphere of the same density as the Sun in the proportion of five hundred to one, and by supposing light to be attracted by the same force in proportion to its [mass] with other bodies, all light emitted from such a body would be made to return towards it, by its own proper gravity."<ref name="r1" />

==Controversy==

==Controversy==

The physical nature of these hypothetical objects makes their existence controversial. Since black holes by definition cannot be directly observed, some argue that it can never be conclusively demonstrated whether or not they exist.

Since black holes by definition cannot be directly observed, it can never be conclusively demonstrated whether or not they exist.  Numerous early scientists, including [[Albert Einstein]] and [[Arthur Eddington]], believed that they did not exist.  However, the current theory of [[general relativity]], which has been tested by numerous experiments including gravity [[space probe|probes]] and stellar observations during a [[solar eclipse]] and not disproven, says that black holes are possible.  Additionally, scientists have 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 science has not and cannot conclusively prove that black holes exist, prevailing scientific theory says that their existence is possible.

==External links==

==External links==