Editing Black body (section)

=== Black holes ===
{{See also|Hawking radiation}}
A [[black hole]] is a region of [[spacetime]] from which nothing escapes. Around a black hole there is a mathematically defined surface called an [[event horizon]] that marks the [[point of no return]]. It is called "black" because it absorbs all the light that hits the horizon, reflecting nothing, making it almost an ideal black body<ref name=Schutz/> (radiation with a wavelength equal to or larger than the diameter of the hole may not be absorbed, so black holes are not perfect black bodies).<ref name=Davies/> Physicists believe that to an outside observer, black holes have a non-zero temperature and emit [[black-body radiation]], radiation with a nearly perfect black-body spectrum, ultimately [[Black hole#Evaporation|evaporating]].<ref name=Wald/> The mechanism for this emission is related to [[vacuum fluctuations]] in which a [[virtual particles|virtual pair]] of particles is separated by the gravity of the hole, one member being sucked into the hole, and the other being emitted.<ref name=Carr/> The energy distribution of emission is described by [[Planck's law]] with a temperature ''T'':
:<math>T=\frac {\hbar c^3}{8\pi Gk_\text{B}M} \ ,</math>
where ''c'' is the [[speed of light]], ℏ is the [[reduced Planck constant]], ''k''<sub>B</sub> is the [[Boltzmann constant]], ''G'' is the [[gravitational constant]] and ''M'' is the mass of the black hole.<ref name=Frolov/> These predictions have not yet been tested either observationally or experimentally.<ref name=Wald2/>