Editing Big Bang (section)

=== Inflation and baryogenesis ===
{{Main|Inflation (cosmology)|Baryogenesis}}
The earliest phases of the Big Bang are subject to much speculation, given the lack of available data. In the most common models the universe was filled homogeneously and isotropically with a very high [[energy density]] and huge temperatures and [[pressure]]s, and was very rapidly expanding and cooling. The period up to 10<sup>−43</sup> seconds into the expansion, the [[Planck epoch]], was a phase in which the four [[fundamental force]]s—the [[electromagnetic force]], the [[strong nuclear force]], the [[Weak-Nuclear Force|weak nuclear force]], and the [[gravitational force]], were unified as one.<ref name=":0">{{cite book|editor1-last=Unruh |editor1-first=W.G. |editor2-last=Semenoff |editor2-first=G.W.|title=The early universe|date=1988|publisher=Reidel|isbn=90-277-2619-1|oclc=905464231}}</ref> In this stage, the [[Characteristic length|characteristic scale length]] of the universe was the [[Planck length]], {{val|1.6|e=-35|u=m}}, and consequently had a temperature of approximately 10<sup>32</sup> degrees Celsius. Even the very concept of a particle breaks down in these conditions. A proper understanding of this period awaits the development of a theory of [[quantum gravity]].<ref name=Hawley_Holcomb_2005>{{cite book | title=Foundations of Modern Cosmology | first1=John F. | last1=Hawley | first2=Katherine A. | last2=Holcomb | date=July 7, 2005 | publisher=OUP Oxford | isbn=9780198530961 | page=355 | url=https://books.google.com/books?id=s5MUDAAAQBAJ&pg=PA355 }}</ref><ref>{{cite web|url=http://www.astro.ucla.edu/~wright/BBhistory.html|title=Brief History of the Universe|website=www.astro.ucla.edu|access-date=2020-04-28}}</ref> The Planck epoch was succeeded by the [[grand unification epoch]] beginning at 10<sup>−43</sup> seconds, where gravitation separated from the other forces as the universe's temperature fell.<ref name=":0" />

At approximately 10<sup>−37</sup> seconds into the expansion, a [[phase transition]] caused a [[Inflation (cosmology)|cosmic inflation]], during which the universe grew [[Exponential growth|exponentially]], unconstrained by the [[speed of light|light speed invariance]], and temperatures dropped by a factor of 100,000. This concept is motivated by the [[flatness problem]], where the [[density of the universe|density of matter and energy]] is very close to the critical density needed to produce a [[flat universe]]. That is, the [[shape of the universe]] has no overall [[Spacetime curvature|geometric curvature]] due to gravitational influence. Microscopic [[quantum fluctuation]]s that occurred because of [[uncertainty principle|Heisenberg's uncertainty principle]] were "frozen in" by inflation, becoming amplified into the seeds that would later form the large-scale structure of the universe.<ref name="Guth1998">{{harvnb|Guth|1998}}</ref> At a time around 10<sup>−36</sup> seconds, the [[electroweak epoch]] begins when the strong nuclear force separates from the other forces, with only the electromagnetic force and weak nuclear force remaining unified.<ref name=":1">{{cite web|url=http://hyperphysics.phy-astr.gsu.edu/hbase/Astro/planck.html|title=Big Bang models back to Planck time|website=hyperphysics.phy-astr.gsu.edu|access-date=2020-04-28}}</ref>

Inflation stopped locally at around 10<sup>−33</sup> to 10<sup>−32</sup> seconds, with the observable universe's volume having increased by a factor of at least 10<sup>78</sup>. Reheating followed as the [[inflaton field]] decayed, until the universe obtained the temperatures required for the [[Pair production|production]] of a [[quark–gluon plasma]] as well as all other [[elementary particle]]s.<ref>{{cite magazine |last1=Schewe |first1=Phillip F. |last2=Stein |first2=Ben P. |date=20 April 2005 |title=An Ocean of Quarks |url=http://www.aip.org/pnu/2005/split/728-1.html |url-status=dead |magazine=Physics News Update |volume=728 |issue=1 |archive-url=https://web.archive.org/web/20050423224100/http://www.aip.org/pnu/2005/split/728-1.html |archive-date=23 April 2005 |access-date=30 November 2019}}</ref><ref>{{cite journal|last=Høg|first=Erik|date=2014|title=Astrosociology: Interviews about an infinite universe|journal=Asian Journal of Physics|arxiv=1408.4795|bibcode=2014arXiv1408.4795H}}</ref> Temperatures were so high that the random motions of particles were at [[Special relativity|relativistic]] [[Relativistic speed|speeds]], and [[Antimatter|particle–antiparticle pairs]] of all kinds were being continuously created and destroyed in collisions.<ref name="HTUW" /> At some point, an unknown reaction called [[baryogenesis]] violated the conservation of [[baryon number]], leading to a very small excess of [[quark]]s and [[lepton]]s over antiquarks and antileptons—of the order of one part in 30&nbsp;million. This resulted in the predominance of matter over antimatter in the present universe.<ref name="kolb_c6">{{harvnb|Kolb|Turner|1988|loc=chpt. 6}}</ref>