Quark Facts



  • Quarks are one of the three tiniest basic, or elementary, particles from which every substance is made.
  • Quarks are too small for their size to be measured, but their mass can. The biggest quark, called a top quark, is as heavy as an atom of gold. The smallest, called an up quark, is 35,000 times lighter.
  • There are six kinds, or flavors, of quark: up (u), down (d), bottom (b), top (t), strange (s) and charm (c).
  • Down, bottom and strange quarks carry one-third of the negative charge of electrons; up, top and charm ones carry two-thirds of the positive charge of protons.
  • Quarks never exist separately but in combination with one or two other quarks. Combinations of two or three quarks are called hadrons.
  • Three-quark hadrons are called baryons and include protons and neutrons. Rare two-quark hadrons are mesons.
  • A proton is made from two up quarks (two lots of +2/3 of a charge) and one down quark (-1/3) and has a positive charge of 1.
  • A neutron is made from two down quarks (two lots of –1/3 of a charge) and an up quark (+2/3). The charges cancel each other out, giving a neutron no charge.
  • The theory of quarks was first proposed by Murray Gell-Mann and Georg Zweig in 1964.
  • Quarks are named after a famous passage in James Joyce’s hook Ulysses: ‘Three quarks for Muster Mark!’