Quantum Chromodynamics: The Theory of Quarks and Gluons

Quantum Chromodynamics (QCD) is the theory describing how quarks and gluons interact.
It explains the strong nuclear force, the most powerful force in nature.
Quarks carry a property called color charge—red, green, or blue in analogy, not actual color.
Gluons are the force carriers that “glue” quarks together inside protons and neutrons.
QCD predicts confinement: quarks can never exist alone, only in groups.
It also explains asymptotic freedom, where quarks behave almost freely at very high energies.
Most of a proton’s mass comes from the energy of gluon fields, not the quarks themselves.
QCD is one of the key pillars of the Standard Model of particle physics.
Testing QCD requires massive experiments like those at the Large Hadron Collider.
Understanding QCD helps scientists probe the early universe and the structure of matter.