Size. In QCD, quarks are considered to be point-like entities, with zero size. As of 2014, experimental evidence indicates they are no bigger than 10−4 times the size of a proton, i.e. less than 10−19 metres.

David Deutsch

The biggest supercluster known in the universe is the Hercules-Corona Borealis Great Wall. It was first reported in 2013 and has been studied several times. It’s so big that light takes about 10 billion years to move across the structure. For perspective, the universe is only 13.8 billion years old.

According to their results, the up quark weighs approximately 2 mega electron volts (MeV), which is a unit of energy, the down quark weighs approximately 4.8 MeV, and the strange quark weighs in at about 92 MeV.

The sizes of atoms, nuclei, and nucleons are measured by firing a beam of electrons at an appropriate target. Thus, protons and neutrons are no more indivisible than atoms are; indeed, they contain still smaller particles, which are called quarks. Quarks are as small as or smaller than physicists can measure.

The slowest quarks produce the spherical shape that physicists generally expected to see. Another shape — a flattened round form like a bagel — is sort of a cousin to the peanut shape with the high-momentum quarks.

Or rather, it’s spherical-ish: the shape fluctuates around the spherical average, and those non-spherical flickers arise from the quarks and other bits inside the proton. While the fluctuations take many forms, the dominant ones are either a “peanut” shape or a “bagel” shape, in the words of physicist Gerald Miller .

Quarks are said to come in three colours—red, blue, and green. (The opposites of these imaginary colours, minus-red, minus-blue, and minus-green, are ascribed to antiquarks.)

Quarks and gluons must clump together to form hadrons. The two main types of hadron are the mesons (one quark, one antiquark) and the baryons (three quarks). Quarks and gluons cannot be separated from their parent hadron without producing new hadrons.

In technical terms, gluons are vector gauge bosons that mediate strong interactions of quarks in quantum chromodynamics (QCD). Gluons themselves carry the color charge of the strong interaction. This is unlike the photon, which mediates the electromagnetic interaction but lacks an electric charge.

The strong force binds quarks together in clusters to make more-familiar subatomic particles, such as protons and neutrons. It also holds together the atomic nucleus and underlies interactions between all particles containing quarks. The strong force originates in a property known as colour.

[+] The gluon exchanges that keep these entities stable are quite complicated, but require eight, not nine, gluons. One of the most puzzling features of the Universe is the strong nuclear force. Inside every proton or neutron-like particle, there are three quarks, each of which has their own color.