Gluon << GLOO on >> is a subatomic particle that carries a powerful force which holds together the components of protons and neutrons. This force is called the strong interaction. Gluons are elementary particles—that is, they are not made up of smaller objects. Gluons have no mass. They travel at the speed of light.
Gluons are created and absorbed only by other gluons and by elementary particles known as quarks and antiquarks. Gluons act as messengers, carrying bundles of energy between elementary particles. This exchange of energy binds the particles to one another in a group called a hadron. Some hadrons contain a quark and an antiquark, but they are extremely unstable and disintegrate in a fraction of a second. The only hadrons found in ordinary matter are protons and neutrons, which have only quarks. Each proton and neutron also contains a swarm of gluons, which travel between the quarks, holding them together.
Gluons rapidly multiply themselves and are just as rapidly absorbed by other particles. The multiplication of gluons intensifies the strong interaction holding the particles together. This force is so strong that no gluon—or quark or antiquark—can be separated from a hadron long enough to be directly observed.
The modern theory of gluons was proposed by the American physicists David J. Gross and Frank A. Wilczek in 1973, and independently by the American physicist H. David Politzer in 1974. The theory is called quantum chromodynamics, or QCD. Researchers obtained the first direct evidence for the existence of gluons in 1979 at the German Electron Synchrotron Laboratory (DESY) in Hamburg.
