Editing Electron (section)

== Formation ==
[[File:Pair production.png|right|thumb|alt=A photon approaches the nucleus from the left, with the resulting electron and positron moving off to the right|[[Pair production]] of an electron and positron, caused by the close approach of a photon with an atomic nucleus. The lightning symbol represents an exchange of a virtual photon, thus an electric force acts. The angle between the particles is very small.<ref>
{{cite book
 |title=Selected Exercises in Particle and Nuclear Physics
 |first1=Lorenzo
 |last1=Bianchini
 |publisher=Springer
 |year=2017
 |isbn=978-3-319-70494-4
 |page=79
 |url=https://books.google.com/books?id=lktADwAAQBAJ&pg=PA79
 |access-date=2018-04-20
 |archive-date=2020-01-02
 |archive-url=https://web.archive.org/web/20200102022221/https://books.google.com/books?id=lktADwAAQBAJ&pg=PA79
 |url-status=live
}}</ref>]]

<!-- Big bang theory with focus on the electron -->
The [[Big Bang]] theory is the most widely accepted scientific theory to explain the early stages in the evolution of the Universe.<ref>
{{cite book
 | last = Lurquin | first = P.F.
 | title = The Origins of Life and the Universe
 | url=https://archive.org/details/originsoflifet00paul/page/2 |url-access=registration |page=2
 | publisher = Columbia University Press | year = 2003
 | isbn = 978-0-231-12655-7
}}</ref> For the first millisecond of the Big Bang, the temperatures were over 10&nbsp;billion&nbsp;[[kelvin]]s and photons had mean energies over a million [[electronvolt]]s. These photons were sufficiently energetic that they could react with each other to form pairs of electrons and positrons. Likewise, positron–electron pairs annihilated each other and emitted energetic photons:
: {{SubatomicParticle|photon|link=yes}} + {{SubatomicParticle|photon}} ↔ {{SubatomicParticle|positron|link=yes}} + {{SubatomicParticle|electron}}
An equilibrium between electrons, positrons and photons was maintained during this phase of the evolution of the Universe. After 15 seconds had passed, however, the temperature of the universe dropped below the threshold where electron-positron formation could occur. Most of the surviving electrons and positrons annihilated each other, releasing gamma radiation that briefly reheated the universe.<ref>
{{cite book
 | last = Silk | first = J.
 | title = The Big Bang: The Creation and Evolution of the Universe
 | pages = 110–112, 134–137
 | publisher = Macmillan | edition = 3rd | year = 2000
 | isbn = 978-0-8050-7256-3
}}</ref>

For reasons that remain uncertain, during the annihilation process there was an excess in the number of particles over antiparticles. Hence, about one electron for every billion electron–positron pairs survived. This excess matched the excess of protons over antiprotons, in a condition known as [[baryon asymmetry]], resulting in a net charge of zero for the universe.<ref>
{{cite journal
 | last1 = Kolb
 | first1 = E.W.
 | last2 = Wolfram
 | first2 = Stephen
 | year = 1980
 | title = The Development of Baryon Asymmetry in the Early Universe
 | journal = [[Physics Letters B]]
 | volume = 91
 | issue = 2
 | pages = 217–221
 | doi = 10.1016/0370-2693(80)90435-9
 | bibcode = 1980PhLB...91..217K
 | s2cid = 122680284
 | url = https://authors.library.caltech.edu/99675/2/Development%20of%20Baryon%20Asymmetry%20in%20the%20Early%20Universe.pdf
 | access-date = 2020-08-25
 | archive-date = 2020-10-30
 | archive-url = https://web.archive.org/web/20201030105942/https://authors.library.caltech.edu/99675/2/Development%20of%20Baryon%20Asymmetry%20in%20the%20Early%20Universe.pdf
 | url-status = live
}}</ref><ref>
{{cite web
 | last = Sather
 | first = E.
 | date = Spring–Summer 1996
 | title = The Mystery of Matter Asymmetry
 | url = https://www.slac.stanford.edu/pubs/beamline/26/1/26-1-sather.pdf
 | periodical = Beam Line
 | publisher = Stanford University
 | access-date = 2008-11-01
 | df = dmy-all
 | archive-date = 2008-10-12
 | archive-url = https://web.archive.org/web/20081012012543/http://www.slac.stanford.edu/pubs/beamline/26/1/26-1-sather.pdf
 | url-status = live
}}</ref> The surviving protons and neutrons began to participate in reactions with each other—in the process known as [[nucleosynthesis]], forming isotopes of hydrogen and [[helium]], with trace amounts of [[lithium]]. This process peaked after about five minutes.<ref>
{{cite arXiv
 | last1 = Burles | first1 = S.
 | last2 = Nollett | first2 = K.M.
 | last3 = Turner | first3 = M.S.
 | year = 1999
 | title = Big-Bang Nucleosynthesis: Linking Inner Space and Outer Space
 |eprint=astro-ph/9903300
}}</ref> Any leftover neutrons underwent negative [[beta decay]] with a half-life of about a thousand seconds, releasing a proton and electron in the process,
: {{SubatomicParticle|Neutron|link=yes}} → {{SubatomicParticle|Proton|link=yes}} + {{SubatomicParticle|Electron}} + {{SubatomicParticle|Electron antineutrino|link=yes}}
For about the next {{val|300000}}–{{val|400000|u=years}}, the excess electrons remained too energetic to bind with [[Atomic nucleus|atomic nuclei]].<ref>
{{cite journal
 | last1 = Boesgaard | first1 = A.M.
 | last2 = Steigman | first2 = G.
 | year = 1985
 | title = Big bang nucleosynthesis&nbsp;– Theories and observations
 | journal = [[Annual Review of Astronomy and Astrophysics]]
 | volume = 23 | issue = 2 | pages = 319–378
 | bibcode =1985ARA&A..23..319B
 | doi =10.1146/annurev.aa.23.090185.001535
}}</ref> What followed is a period known as [[Chronology of the universe#Recombination, photon decoupling, and the cosmic microwave background (CMB)|recombination]], when neutral atoms were formed and the expanding universe became transparent to radiation.<ref name="science5789">
{{cite journal
 | last = Barkana | first = R.
 | year = 2006
 | title = The First Stars in the Universe and Cosmic Reionization
 | journal = [[Science (journal)|Science]]
 | volume = 313 | issue = 5789 | pages = 931–934
 | doi =10.1126/science.1125644
 | pmid =16917052 |arxiv = astro-ph/0608450
 | bibcode = 2006Sci...313..931B | citeseerx = 10.1.1.256.7276
 | s2cid = 8702746
}}</ref>

<!-- Stellar -->
Roughly one million years after the big bang, the first generation of [[star]]s began to form.<ref name="science5789" /> Within a star, [[stellar nucleosynthesis]] results in the production of positrons from the fusion of atomic nuclei. These antimatter particles immediately annihilate with electrons, releasing gamma rays. The net result is a steady reduction in the number of electrons, and a matching increase in the number of neutrons. However, the process of [[stellar evolution]] can result in the synthesis of radioactive isotopes. Selected isotopes can subsequently undergo negative beta decay, emitting an electron and antineutrino from the nucleus.<ref>{{cite journal | last1 = Burbidge | first1 = E.M. | display-authors = etal | year = 1957 | title = Synthesis of Elements in Stars | journal = [[Reviews of Modern Physics]] | volume = 29 | issue = 4 | pages = 548–647 | doi = 10.1103/RevModPhys.29.547 | bibcode = 1957RvMP...29..547B | url = https://authors.library.caltech.edu/45747/1/BURrmp57.pdf | doi-access = free | access-date = 2019-06-21 | archive-date = 2018-07-23 | archive-url = https://web.archive.org/web/20180723054833/https://authors.library.caltech.edu/45747/1/BURrmp57.pdf | url-status = live }}</ref> An example is the [[cobalt-60]] (<sup>60</sup>Co) isotope, which decays to form [[Isotopes of nickel|nickel-60]] ({{SimpleNuclide|Nickel|60}}).<ref>
{{cite journal
 | last1 = Rodberg | first1 = L.S.
 | last2 = Weisskopf | first2 = V.
 | year = 1957
 | title = Fall of Parity: Recent Discoveries Related to Symmetry of Laws of Nature
 | journal = [[Science (journal)|Science]]
 | volume = 125 | issue = 3249 | pages = 627–633
 | doi =10.1126/science.125.3249.627 | pmid =17810563
 | bibcode = 1957Sci...125..627R
}}</ref>
[[File:AirShower.svg|left|thumb|alt=A branching tree representing the particle production|An extended air shower generated by an energetic cosmic ray striking the Earth's atmosphere]]
At the end of its lifetime, a star with more than about 20 [[solar mass]]es can undergo [[gravitational collapse]] to form a [[black hole]].<ref>
{{cite journal
 | last = Fryer | first = C.L.
 | year = 1999
 | title = Mass Limits For Black Hole Formation
 | journal = [[The Astrophysical Journal]]
 | volume = 522 | issue = 1 | pages = 413–418
 | bibcode = 1999ApJ...522..413F
 | doi =10.1086/307647
 | arxiv = astro-ph/9902315 | s2cid = 14227409
}}</ref> According to [[classical physics]], these massive stellar objects exert a [[Gravitation|gravitational attraction]] that is strong enough to prevent anything, even [[electromagnetic radiation]], from escaping past the [[Schwarzschild radius]]. However, quantum mechanical effects are believed to potentially allow the emission of [[Hawking radiation]] at this distance. Electrons (and positrons) are thought to be created at the [[event horizon]] of these [[Compact star|stellar remnants]].

When a pair of virtual particles (such as an electron and positron) is created in the vicinity of the event horizon, random spatial positioning might result in one of them to appear on the exterior; this process is called [[quantum tunnelling]]. The [[gravitational potential]] of the black hole can then supply the energy that transforms this virtual particle into a real particle, allowing it to radiate away into space.<ref>
{{cite journal
 |last1   = Parikh |first1  = M.K.
 |last2   = Wilczek |first2  = F.
 |year    = 2000
 |title   = Hawking Radiation As Tunneling
 |journal = [[Physical Review Letters]]
 |volume  = 85 |issue   = 24 |pages   = 5042–5045
 |doi = 10.1103/PhysRevLett.85.5042 |pmid = 11102182 |hdl = 1874/17028
 |bibcode = 2000PhRvL..85.5042P |arxiv = hep-th/9907001
 |s2cid = 8013726
}}</ref> In exchange, the other member of the pair is given negative energy, which results in a net loss of mass–energy by the black hole. The rate of Hawking radiation increases with decreasing mass, eventually causing the black hole to evaporate away until, finally, it explodes.<ref>
{{cite journal
 | last = Hawking | first = S.W.
 | year = 1974
 | title = Black hole explosions?
 | journal = [[Nature (journal)|Nature]]
 | volume = 248 | issue=5443 | pages = 30–31
 | doi =10.1038/248030a0 |bibcode = 1974Natur.248...30H
 | s2cid = 4290107
}}</ref>

<!-- Other sources -->
[[Cosmic ray]]s are particles traveling through space with high energies. Energy events as high as {{val|3.0|e=20|u=eV}} have been recorded.<ref>
{{cite journal
 | last1 = Halzen | first1 = F. | author-link1 = Francis Halzen
 | last2 = Hooper | first2 = D.
 | year = 2002
 | title = High-energy neutrino astronomy: the cosmic ray connection
 | journal = [[Reports on Progress in Physics]]
 | volume = 66 | issue = 7 | pages = 1025–1078
 | bibcode = 2002RPPh...65.1025H |arxiv = astro-ph/0204527
 | doi =10.1088/0034-4885/65/7/201
 | s2cid = 53313620
}}</ref> When these particles collide with nucleons in the [[Atmosphere of Earth|Earth's atmosphere]], a shower of particles is generated, including [[pion]]s.<ref>
{{cite journal
 | last = Ziegler | first = J.F.
 | year = 1998
 | title = Terrestrial cosmic ray intensities
 | journal = [[IBM Journal of Research and Development]]
 | volume = 42 | issue = 1 | pages = 117–139
 | doi =10.1147/rd.421.0117 | bibcode = 1998IBMJ...42..117Z
}}</ref> More than half of the cosmic radiation observed from the Earth's surface consists of [[muon]]s. The particle called a muon is a lepton produced in the upper atmosphere by the decay of a pion.
: {{SubatomicParticle|Pion-|link=yes}} → {{SubatomicParticle|Muon|link=yes}} + {{SubatomicParticle|Muon antineutrino|link=yes}}
A muon, in turn, can decay to form an electron or positron.<ref>
{{cite news
 | last = Sutton
 | first = C.
 | date = August 4, 1990
 | title = Muons, pions and other strange particles
 | url = https://www.newscientist.com/article/mg12717284.700-muons-pions-and-other-strange-particles-.html
 | magazine = [[New Scientist]]
 | access-date = 2008-08-28
 | df = dmy-all
 | archive-date = 2015-02-11
 | archive-url = https://web.archive.org/web/20150211085842/http://www.newscientist.com/article/mg12717284.700-muons-pions-and-other-strange-particles-.html
 | url-status = live
}}</ref>
: {{SubatomicParticle|Muon}} → {{SubatomicParticle|Electron}} + {{SubatomicParticle|Electron antineutrino|link=yes}} + {{SubatomicParticle|Muon neutrino|link=yes}}