Overview

In 1961 the physicist Murray Gell-Mann (1929- ) developed a method of organizing the dozens of subatomic particles that had been discovered to date. This classification system led him to realize that many of these particles were made up of even smaller particles. Gell-Mann named these smaller particles quarks. Eventually, physicists used Gell-Mann's work to formulate the standard model, a way of describing the known types of matter in the universe.

Background

Atoms are composed of particles called protons, neutrons, and electrons. These are called subatomic particles because they are smaller than atoms. During the 1950s and 1960s, physicists discovered many new types of subatomic particles, which were given names such as positrons, pions, and muons. These particles do not generally exist as parts of atoms, but are observed in cosmic rays—high-energy radiation that reaches Earth from space—or created...