Editing Strong interaction (section)

== History ==
Before 1971, physicists were uncertain as to how the atomic nucleus was bound together. It was known that the nucleus was composed of [[proton]]s and [[neutron]]s and that protons possessed positive [[electric charge]], while neutrons were electrically neutral. By the understanding of physics at that time, positive charges would repel one another and the positively charged protons should cause the nucleus to fly apart. However, this was never observed. New physics was needed to explain this phenomenon.

A stronger attractive force was postulated to explain how the atomic nucleus was bound despite the protons' mutual [[electromagnetic repulsion]]. This hypothesized force was called the ''strong force'', which was believed to be a fundamental force that acted on the [[nucleons|protons and neutrons]] that make up the nucleus.

In 1964, [[Murray Gell-Mann]], and separately [[George Zweig]], proposed that [[baryon]]s, which include protons and neutrons, and [[meson]]s were composed of elementary particles. Zweig called the elementary particles "aces" while Gell-Mann called them "quarks"; the theory came to be called the [[quark model]].<ref>{{Cite journal |last=Wilczek |first=Frank |date=1982 |title=Quantum chromodynamics: The modern theory of the strong interaction |journal=Annual Review of Nuclear and Particle Science |volume=32 |issue=1 |pages=177–209 |doi=10.1146/annurev.ns.32.120182.001141|bibcode=1982ARNPS..32..177W }}</ref> The strong attraction between nucleons was the side-effect of a more fundamental force that bound the quarks together into protons and neutrons. The theory of [[quantum chromodynamics]] explains that quarks carry what is called a [[color charge]], although it has no relation to visible color.<ref>
{{cite book
 |last=Feynman |first=R.P. |author-link=Richard Feynman
 |year=1985
 |title=QED: The Strange Theory of Light and Matter
 |publisher=Princeton University Press
 |isbn=978-0-691-08388-9
 |page=136
 |quote=The idiot physicists, unable to come up with any wonderful Greek words anymore, call this type of polarization by the unfortunate name of 'color', which has nothing to do with color in the normal sense.
 |title-link=QED: The Strange Theory of Light and Matter
}}</ref> Quarks with unlike color charge attract one another as a result of the strong interaction, and the particle that mediates this was called the [[gluon]].