Finding Order Among the Particles
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 wayof 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 in machines called particle accelerators. Accelerators are used to create high-speed collisions among particles. Such collisions often result in the production of new types of particles.
Physicists began to look for a way to organize the many kinds of subatomic particles that would show how the different types were related. In other words, they were searching for a physics version of the periodic table of the chemical elements.
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