The quark model was independently proposed by physicists Murray Gell-Mann and George Zweig in 1964. For every quark flavor there is a corresponding type of antiparticle, known as an antiquark, that differs from the quark only in that some of its properties (such as the electric charge) have equal magnitude but opposite sign.

Because of this, up and down quarks are generally stable and the most common in the universe, whereas strange, charm, bottom, and top quarks can only be produced in high energy collisions (such as those involving cosmic rays and in particle accelerators). The heavier quarks rapidly change into up and down quarks through a process of particle decay: the transformation from a higher mass state to a lower mass state. Up and down quarks have the lowest masses of all quarks. There are six types, known as flavors, of quarks: up, down, charm, strange, top, and bottom. They are the only elementary particles in the Standard Model of particle physics to experience all four fundamental interactions, also known as fundamental forces ( electromagnetism, gravitation, strong interaction, and weak interaction), as well as the only known particles whose electric charges are not integer multiples of the elementary charge. Quarks have various intrinsic properties, including electric charge, mass, color charge, and spin. For this reason, much of what is known about quarks has been drawn from observations of hadrons. Owing to a phenomenon known as color confinement, quarks are never found in isolation they can be found only within hadrons, which include baryons (such as protons and neutrons) and mesons, or in quark–gluon plasmas. All commonly observable matter is composed of up quarks, down quarks and electrons.

Quarks combine to form composite particles called hadrons, the most stable of which are protons and neutrons, the components of atomic nuclei. 6 ( up, down, strange, charm, bottom, and top)Ī quark ( / k w ɔːr k, k w ɑːr k/) is a type of elementary particle and a fundamental constituent of matter.

Quarky and quasars game