Gluons are the fundamental particles that mediate the strong nuclear force in quantum chromodynamics (QCD). They are responsible for binding quarks together to form protons, neutrons, and other hadrons.
Key characteristics of gluons:
- Unlike photons (which mediate electromagnetism), gluons themselves carry color charge. Each gluon has a combination of a color and an anticolor, such as red–antigreen.
- There are eight independent types of gluons due to the combinations of color and anticolor charges allowed by QCD.
- Because they carry color charge, gluons can interact with each other, making the strong force highly nonlinear and complex.
Gluons are massless and travel at the speed of light, but due to their self-interactions, the force they generate does not diminish with distance in the same way as electromagnetism. Instead, the force becomes stronger as quarks are pulled apart, leading to quark confinement—quarks cannot be isolated and are always found in groups.
Inside hadrons like protons and neutrons, gluons create a constant exchange of color charge between quarks, forming a dynamic and tightly bound system. This interaction is what gives rise to the vast majority of the mass of ordinary matter—even more than the mass from the quarks themselves.