Apart from the three basic, stable particles of atoms – electrons, protons and neutrons – scientists have found over 200 rare or short-lived particles. Some were found in cosmic rays from space; some appear when atoms are smashed to bits in devices called particle accelerators.
Every particle also has a mirror-image anti-particle. Although antimatter maybe much rarer, it is every bit as real.
Cosmic rays contain not only electrons, protons and neutrons, but short-lived particles such as muons and strange quarks. Muons flash into existence for 2.2 micro-seconds just before the cosmic rays reach the ground.
Smashing atoms in particle accelerators creates short-lived high-energy particles such as taus and pions and three kinds of quark called charm, bottom and top.
Particles are now grouped into a simple framework called the Standard Model. It divides them into elementary particles and composite particles.
Elementary particles are the basic particles which cannot be broken down into anything smaller. There are three groups: quarks, leptons and bosons. Leptons include electrons, muons, taus and neutrinos. Bosons are ‘messenger’ particles that link the others. They include photons and gluons which ‘glue’ quarks together.
Composite particles are hadrons made of quarks glued together by gluons. They include protons, neutrons and ‘hyperons’ and ‘resonances.
To smash atoms scientists use particle accelerators, which are giant machines set in tunnels. The accelerators use powerful magnets to accelerate particles through a tube at huge speeds, and then smash them together.
Huge detectors pick up collisions between particles.