Editing Black hole (section)

==== Primordial black holes and the Big Bang ====
Gravitational collapse requires great density. In the current epoch of the universe these high densities are found only in stars, but in the early universe shortly after the Big Bang densities were much greater, possibly allowing for the creation of black holes. High density alone is not enough to allow black hole formation since a uniform mass distribution will not allow the mass to bunch up. In order for [[primordial black holes]] to have formed in such a dense medium, there must have been initial density perturbations that could then grow under their own gravity. Different models for the early universe vary widely in their predictions of the scale of these fluctuations. Various models predict the creation of primordial black holes ranging in size from a [[Planck mass]] (<math> m_P = \sqrt{\hbar c/G} </math> ≈ {{val|1.2|e=19|ul=GeV/c2}} ≈ {{val|2.2|e=-8|u=kg}}) to hundreds of thousands of solar masses.<ref name="carr primordial">{{cite book |last1=Carr |first1=B. J. |chapter=Primordial Black Holes: Do They Exist and Are They Useful? |editor1-first=H. |editor1-last=Suzuki |editor2-first=J. |editor2-last=Yokoyama |editor3-first=Y. |editor3-last=Suto |editor4-first=K. |editor4-last=Sato |title=Inflating Horizon of Particle Astrophysics and Cosmology |pages=astro–ph/0511743 |publisher=Universal Academy Press |date=2005 |isbn=978-4-946443-94-7 |arxiv=astro-ph/0511743 |bibcode=2005astro.ph.11743C}}</ref>

Despite the early universe being extremely [[density|dense]], it did not re-collapse into a black hole during the Big Bang, since the expansion rate was greater than the attraction. Following [[inflation theory]] there was a net repulsive gravitation in the beginning until the end of inflation. Since then the [[Hubble flow]] was slowed by the energy density of the universe.

Models for the gravitational collapse of objects of relatively constant size, such as [[star]]s, do not necessarily apply in the same way to rapidly expanding space such as the Big Bang.<ref>{{cite web |author1=Philip Gibbs |title=Is the Big Bang a black hole? |url=http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/universe.html |publisher=[[John Baez]] |access-date=16 March 2018 |archive-date=31 December 2018 |archive-url=https://web.archive.org/web/20181231021714/http://math.ucr.edu/home/baez/physics/Relativity/BlackHoles/universe.html |url-status=live }}</ref>