Editing Hawking radiation (section)

== Background ==
{{more citations needed section|date = May 2023}}
Modern black holes were first predicted by [[Einstein]]'s 1915 theory of [[general relativity]]. Evidence of the astrophysical objects termed [[black holes]] began to mount half a century later,<ref name="auto">{{Cite news|url=https://www.amnh.org/learn-teach/curriculum-collections/cosmic-horizons-book/john-michell-black-holes|title=John Michell: Country Parson Described Black Holes in 1783 &#124; AMNH|newspaper=American Museum of Natural History }}</ref> and these objects are of current interest primarily because of their compact size and immense [[gravitational attraction]]. Early research into black holes was done by individuals such as [[Karl Schwarzschild]] and [[John Archibald Wheeler|John Wheeler]], who modeled black holes as having zero entropy.<ref name="auto"/><ref>{{cite web|url=https://www.nbi.dk/~obers/MSc_PhD_files/Nikolaos_Karozis_MSc.pdf|title=Black Hole Entropy and 2D Conformal Field Theory - Towards Quantum Gravity|last1=Karozis|first1=Nikolaos}}</ref>

A black hole can form when enough [[matter]] or [[energy]] is compressed into a volume small enough that the [[escape velocity]] is greater than the speed of light. Because nothing can travel that fast, nothing within a certain distance, proportional to the mass of the black hole, can escape beyond that distance. The region beyond which not even light can escape is the [[event horizon]]: an observer outside it cannot observe, become aware of, or be affected by events within the event horizon.<ref name="Levin 2021"/>{{rp|25–36}}

[[File:Andrew Hamilton schwarzchild waterfall.gif|thumb|Picture of space [[Gullstrand–Painlevé coordinates|falling into a Schwarzschild black hole at the Newtonian escape speed]]. Outside the horizon (red), the infalling speed is less than the speed of light; inside it is greater. At the event horizon, the infalling speed equals the speed of light.<ref name="hamilton" /> ''Credit'': Andrew Hamilton, JILA]]
Alternatively, using a set of [[Gullstrand–Painlevé coordinates|infalling coordinates]] in general relativity, one can conceptualize the event horizon as the region beyond which space is infalling faster than the speed of light. (Although nothing can travel ''through'' space faster than light, space itself can infall at any speed.)<ref name="hamilton">{{cite web |last1=Hamilton |first1=Andrew |title=A Black Hole is a Waterfall of Space |url=https://jila.colorado.edu/~ajsh/insidebh/waterfall.html |website=jila.colorado.edu |access-date=1 September 2021 |quote=Physically, the Gullstrand–Painlevé metric describes space falling into the Schwarzschild black hole at the Newtonian escape velocity.... At the horizon, the velocity equals the speed of light.}}</ref> Once matter is inside the event horizon, all of the matter inside falls inevitably into a [[gravitational singularity]], a place of infinite curvature and zero size, leaving behind a warped spacetime devoid of any matter;{{verify source|date = May 2023}} a classical black hole is pure empty [[spacetime]], and the simplest (nonrotating and uncharged) is characterized just by its mass and event horizon.<ref name="Levin 2021">{{cite book |last1=Levin |first1=Janna |title=Black hole survival guide |date=2020 |publisher=Alfred A. Knopf, Penguin Random House |location=New York |isbn=9780525658221}}</ref>{{rp|37–43}}