Editing Electron (section)

=== Virtual particles ===
{{Main|Virtual particle}}
In a simplified picture, which often tends to give the wrong idea but may serve to illustrate some aspects, every photon spends some time as a combination of a virtual electron plus its antiparticle, the virtual positron, which rapidly [[Annihilation|annihilate]] each other shortly thereafter.<ref>
{{cite magazine
 | last = Kane | first = G.
 | date = October 9, 2006
 | url = https://www.sciam.com/article.cfm?id=are-virtual-particles-rea&topicID=13
 | title = Are virtual particles really constantly popping in and out of existence? Or are they merely a mathematical bookkeeping device for quantum mechanics?
 | magazine = [[Scientific American]]
 | access-date = 2008-09-19 |df=dmy-all
}}</ref> The combination of the energy variation needed to create these particles, and the time during which they exist, fall under the threshold of detectability expressed by the [[Uncertainty principle|Heisenberg uncertainty relation]], Δ''E''&nbsp;·&nbsp;Δ''t''&nbsp;≥&nbsp;''ħ''. In effect, the energy needed to create these virtual particles, Δ''E'', can be "borrowed" from the [[Vacuum state|vacuum]] for a period of time, Δ''t'', so that their product is no more than the [[reduced Planck constant]], {{nowrap|''ħ'' ≈ {{val|6.6|e=-16|u=eV·s}}}}. Thus, for a virtual electron, Δ''t'' is at most {{val|1.3|e=-21|u=s}}.<ref name="taylor">
{{cite book
 | last = Taylor
 | first = J.
 | year = 1989
 | chapter = Gauge Theories in Particle Physics
 | chapter-url = https://books.google.com/books?id=akb2FpZSGnMC&pg=PA464
 | editor = Davies, Paul
 | title = The New Physics
 | page = 464
 | publisher = [[Cambridge University Press]]
 | isbn = 978-0-521-43831-5
 | access-date = 2020-08-25
 | archive-date = 2014-09-21
 | archive-url = https://web.archive.org/web/20140921171834/http://books.google.com/books?id=akb2FpZSGnMC&pg=PA464
 | url-status = live
}}</ref>

[[File:Virtual pairs near electron.png|right|thumb|alt=A sphere with a minus sign at lower left symbolizes the electron, while pairs of spheres with plus and minus signs show the virtual particles|A schematic depiction of virtual electron–positron pairs appearing at random near an electron (at lower left)]]
While an electron–positron virtual pair is in existence, the [[Coulomb's law|Coulomb force]] from the ambient [[electric field]] surrounding an electron causes a created positron to be attracted to the original electron, while a created electron experiences a repulsion. This causes what is called [[vacuum polarization]]. In effect, the vacuum behaves like a medium having a [[Relative permittivity|dielectric permittivity]] more than [[1|unity]]. Thus the effective charge of an electron is actually smaller than its true value, and the charge decreases with increasing distance from the electron.<ref name="genz">
{{cite book
 | last = Genz | first = H.
 | year = 2001
 | title = Nothingness: The Science of Empty Space
 | pages = 241–243, 245–247
 | publisher = [[Da Capo Press]]
 | isbn = 978-0-7382-0610-3
}}</ref><ref>
{{cite news
 | last = Gribbin
 | first = J.
 | date = January 25, 1997
 | title = More to electrons than meets the eye
 | magazine = [[New Scientist]]
 | url = https://www.newscientist.com/article/mg15320662.300-science--more-to-electrons-than-meets-the-eye.html
 | access-date = 2008-09-17
 | df = dmy-all
 | archive-date = 2015-02-11
 | archive-url = https://web.archive.org/web/20150211085433/http://www.newscientist.com/article/mg15320662.300-science--more-to-electrons-than-meets-the-eye.html
 | url-status = live
}}</ref> This polarization was confirmed experimentally in 1997 using the Japanese [[KEKB (accelerator)|TRISTAN]] particle accelerator.<ref>
{{cite journal
 | last1 = Levine | first1 = I. |display-authors=etal
 | year = 1997
 | title = Measurement of the Electromagnetic Coupling at Large Momentum Transfer
 | journal = [[Physical Review Letters]]
 | volume = 78 | issue = 3 | pages = 424–427
 | doi = 10.1103/PhysRevLett.78.424
 | bibcode=1997PhRvL..78..424L
}}</ref> Virtual particles cause a comparable [[shielding effect]] for the mass of the electron.<ref>
{{cite conference
 | last = Murayama | first = H.
 | date =10–17 March 2006
 | title = Supersymmetry Breaking Made Easy, Viable and Generic
 | conference = Proceedings of the XLIInd Rencontres de Moriond on Electroweak Interactions and Unified Theories
 | place = La Thuile, Italy
 | arxiv = 0709.3041
 | bibcode = 2007arXiv0709.3041M
}} – lists a 9% mass difference for an electron that is the size of the [[Planck length|Planck distance]].</ref>

The interaction with virtual particles also explains the small (about 0.1%) deviation of the intrinsic magnetic moment of the electron from the Bohr magneton (the [[Anomalous magnetic dipole moment|anomalous magnetic moment]]).<ref name=Hanneke>
{{cite journal
 | last1 = Odom | first1 = B. |display-authors=etal
 | year = 2006
 | title = New Measurement of the Electron Magnetic Moment Using a One-Electron Quantum Cyclotron
 | journal = [[Physical Review Letters]]
 | volume = 97 | issue=3 | pages = 030801
 | doi = 10.1103/PhysRevLett.97.030801
 | pmid=16907490 | bibcode=2006PhRvL..97c0801O
}}</ref><ref>
{{cite journal
 | last = Schwinger | first = J.
 | year = 1948
 | title = On Quantum-Electrodynamics and the Magnetic Moment of the Electron
 | journal = [[Physical Review]]
 | volume = 73 | issue = 4 | pages = 416–417
 | doi = 10.1103/PhysRev.73.416 | doi-access = free
 | bibcode = 1948PhRv...73..416S
}}</ref> The extraordinarily precise agreement of this predicted difference with the experimentally determined value is viewed as one of the great achievements of [[quantum electrodynamics]].<ref>
{{cite book
 | last = Huang
 | first = K.
 | year = 2007
 | title = Fundamental Forces of Nature: The Story of Gauge Fields
 | url = https://books.google.com/books?id=q-CIFHpHxfEC&pg=PA123
 | pages = 123–125
 | publisher = [[World Scientific]]
 | isbn = 978-981-270-645-4
 | access-date = 2020-08-25
 | archive-date = 2022-02-04
 | archive-url = https://web.archive.org/web/20220204071144/https://books.google.com/books?id=q-CIFHpHxfEC&pg=PA123
 | url-status = live
}}</ref>

The apparent paradox in [[classical physics]] of a point particle electron having intrinsic angular momentum and magnetic moment can be explained by the formation of [[Virtual particle|virtual photons]] in the electric field generated by the electron. These photons can heuristically be thought of as causing the electron to shift about in a jittery fashion (known as [[zitterbewegung]]), which results in a net circular motion with [[precession]].<ref>
{{cite journal
 | last1 = Foldy | first1 = L.L.
 | last2 = Wouthuysen | first2 = S.
 | year = 1950
 | title = On the Dirac Theory of Spin 1/2 Particles and Its Non-Relativistic Limit
 | journal = [[Physical Review]]
 | volume = 78 | issue = 1 | pages = 29–36
 | doi = 10.1103/PhysRev.78.29
 |bibcode = 1950PhRv...78...29F
}}</ref> This motion produces both the spin and the magnetic moment of the electron.<ref name="curtis74" /> In atoms, this creation of virtual photons explains the [[Lamb shift]] observed in [[spectral line]]s.<ref name="genz" /> The Compton Wavelength shows that near elementary particles such as the electron, the uncertainty of the energy allows for the creation of virtual particles near the electron. This wavelength explains the "static" of virtual particles around elementary particles at a close distance.