Editing Fundamental interaction (section)

== History ==
=== Classical theory ===
In his 1687 theory, [[Isaac Newton]] postulated space as an infinite and unalterable physical structure existing before, within, and around all objects while their states and relations unfold at a constant pace everywhere, thus [[absolute space and time]]. Inferring that all objects bearing mass approach at a constant rate, but collide by impact proportional to their masses, Newton inferred that matter exhibits an attractive force. His [[law of universal gravitation]] implied there to be instant interaction among all objects.<ref>{{cite web |title=Newton's Laws of Motion |url=https://www.grc.nasa.gov/www/k-12/airplane/newton.html |website=www.grc.nasa.gov |publisher=NASA}}</ref><ref>{{cite web |title=Newton's law of gravitation {{!}} Definition, Formula, & Facts |url=https://www.britannica.com/science/Newtons-law-of-gravitation |website=Encyclopedia Britannica |access-date=22 March 2021 |language=en}}</ref> As conventionally interpreted, Newton's theory of motion modelled a ''[[central force]]'' without a communicating medium.<ref>{{cite journal |last1=Nauenberg |first1=Michael |title=Newton's graphical method for central force orbits |journal=American Journal of Physics |date=October 2018 |volume=86 |issue=10 |pages=765–771 |doi=10.1119/1.5050620|bibcode=2018AmJPh..86..765N |s2cid=125197336 }}</ref><ref>Newton's absolute space was a medium, but not one transmitting gravitation.</ref> Thus Newton's theory violated the tradition, going back to [[Descartes]], that there should be no [[action at a distance]].<ref>{{cite journal |last1=Henry |first1=John |title=Gravity and De gravitatione: the development of Newton's ideas on action at a distance |journal=Studies in History and Philosophy of Science Part A |date=March 2011 |volume=42 |issue=1 |pages=11–27 |doi=10.1016/j.shpsa.2010.11.025|bibcode=2011SHPSA..42...11H |url=https://www.pure.ed.ac.uk/ws/files/9845098/HENRY_2011_Gravity_and_de_gravitatione.pdf |hdl=20.500.11820/b84d5f3c-47b3-453a-849f-eb9add123210 |hdl-access=free }}</ref> Conversely, during the 1820s, when explaining magnetism, [[Michael Faraday]] inferred a ''field'' filling space and transmitting that force. Faraday conjectured that ultimately, all forces unified into one.<ref>{{cite journal |last1=Faraday |first1=Michael |title=Experimental Researches in Electricity |date=2012 |doi=10.1017/cbo9781139383165.018}}</ref>

In 1873, [[James Clerk Maxwell]] unified electricity and magnetism as effects of an electromagnetic field whose third consequence was light, travelling at constant speed in vacuum. If his [[classical electrodynamics|electromagnetic field theory]] held true in all [[inertial frames of reference]], this would contradict Newton's theory of motion, which relied on [[Galilean relativity]].<ref>{{cite journal |last1=Goldin |first1=Gerald A. |last2=Shtelen |first2=Vladimir M. |title=On Galilean invariance and nonlinearity in electrodynamics and quantum mechanics |journal=Physics Letters A |date=February 2001 |volume=279 |issue=5–6 |pages=321–326 |doi=10.1016/S0375-9601(01)00017-2 |quote=no fully Galilean-covariant theory of a coupled Schrödinger-Maxwell system (where the density and current of the Schrödinger field act as source of the nonrelativistic Maxwell field) is possible|arxiv=quant-ph/0006067 |bibcode=2001PhLA..279..321G |s2cid=5398578 }}</ref> If, instead, his field theory only applied to reference frames at rest relative to a mechanical [[luminiferous aether]]—presumed to fill all space whether within matter or in vacuum and to manifest the electromagnetic field—then it could be reconciled with Galilean relativity and Newton's laws. (However, such a "Maxwell aether" was later disproven; Newton's laws did, in fact, have to be replaced.)<ref>{{cite journal |last1=Farhoudi |first1=Mehrdad |last2=Yousefian |first2=Maysam |title=Ether and Relativity |journal=International Journal of Theoretical Physics |date=May 2016 |volume=55 |issue=5 |pages=2436–2454 |doi=10.1007/s10773-015-2881-y|arxiv=1511.07795 |bibcode=2016IJTP...55.2436F |s2cid=119258859 }}</ref>

=== Standard Model ===
{{Main|Standard Model}} {{See also|Standard Model (mathematical formulation)}}
[[Image:Standard Model of Elementary Particles.svg|thumb|350px|The [[Standard Model]] of elementary particles, with the [[fermion]]s in the first three columns, the [[gauge boson]]s in the fourth column, and the [[Higgs boson]] in the fifth column]]
The Standard Model of particle physics was developed throughout the latter half of the 20th century. In the Standard Model, the electromagnetic, strong, and weak interactions associate with [[elementary particles]], whose behaviours are modelled in [[quantum mechanics]] (QM). For predictive success with QM's [[Probability|probabilistic]] outcomes, [[particle physics]] conventionally models QM [[event (particle physics)|events]] across a field set to [[special theory of relativity|special relativity]], altogether relativistic quantum field theory (QFT).<ref>Meinard Kuhlmann, [http://www.scientificamerican.com/article.cfm?id=physicists-debate-whether-world-made-of-particles-fields-or-something-else "Physicists debate whether the world is made of particles or fields—or something else entirely"], ''Scientific American'', 24 Jul 2013.</ref> Force particles, called [[gauge boson]]s—''force carriers'' or ''[[messenger particles]]'' of underlying fields—interact with matter particles, called [[fermion]]s. 

[[Baryonic matter|Everyday matter]] is atoms, composed of three fermion types: [[quark|up-quarks and down-quarks]] constituting, as well as electrons orbiting, the atom's nucleus. Atoms interact, form [[molecule]]s, and manifest further properties through electromagnetic interactions among their electrons absorbing and emitting photons, the electromagnetic field's force carrier, which if unimpeded traverse potentially infinite distance. Electromagnetism's QFT is [[quantum electrodynamics]] (QED).

The force carriers of the weak interaction are the massive [[W and Z bosons]]. Electroweak theory (EWT) covers both electromagnetism and the weak interaction. At the high temperatures shortly after the [[Big Bang]], the weak interaction, the electromagnetic interaction, and the [[Higgs boson]] were originally mixed components of a different set of ancient pre-symmetry-breaking fields. As the early universe cooled, these fields [[symmetry breaking|split]] into the long-range electromagnetic interaction, the short-range weak interaction, and the Higgs boson. In the [[Higgs mechanism]], the Higgs field manifests Higgs bosons that interact with some quantum particles in a way that endows those particles with mass. The strong interaction, whose force carrier is the [[gluon]], traversing minuscule distance among quarks, is modeled in [[quantum chromodynamics]] (QCD). EWT, QCD, and the Higgs mechanism comprise [[particle physics]]' [[Standard Model]] (SM). Predictions are usually made using calculational approximation methods, although such [[perturbation theory (quantum mechanics)|perturbation theory]] is inadequate to model some experimental observations (for instance [[bound state]]s and [[soliton]]s). Still, physicists widely accept the Standard Model as science's most experimentally confirmed theory.

[[Beyond the Standard Model]], some theorists work to unite the electroweak and [[strong interaction|strong]] interactions within a [[Grand Unified Theory]]<ref>{{Cite journal|last=Krauss|first=Lawrence M.|title=A Brief History of the Grand Unified Theory of Physics|url=http://nautil.us/issue/46/balance/a-brief-history-of-the-grand-unified-theory-of-physics|journal=Nautilus|date=2017-03-16}}</ref> (GUT). Some attempts at GUTs hypothesize "shadow" particles, such that every known [[fermion|matter particle]] associates with an undiscovered [[Gauge boson|force particle]], and vice versa, altogether [[supersymmetry]] (SUSY). Other theorists seek to quantize the gravitational field by the modelling behaviour of its hypothetical force carrier, the [[graviton]] and achieve quantum gravity (QG). One approach to QG is [[loop quantum gravity]] (LQG). Still other theorists seek both QG and GUT within one framework, reducing all four fundamental interactions to a [[Theory of Everything]] (ToE). The most prevalent aim at a ToE is [[string theory]], although to model [[fermion|matter particles]], it added [[supersymmetry|SUSY]] to [[Gauge boson|force particles]]—and so, strictly speaking, became [[superstring theory]]. Multiple, seemingly disparate superstring theories were unified on a backbone, [[M-theory]]. Theories beyond the Standard Model remain highly speculative, lacking great experimental support.