Spin: A Property of Particles

With the bubble chamber and other tools, hundreds of new particles were discovered (Luis Alvarez, The Nobel Prize in Physics 1968). Three fundamental forms of matter were plausible, but hundreds? This posed quite a puzzle, because nature is supposed to be simple and elegant, not complex and ugly.

Trying to find some simplicity in nature, physicists began to classify all of these particles according to various properties. One of these properties was spin.

Spin is a value of angular momentum assigned to all particles. When a top spins, it has a certain amount of angular momentum. The faster it spins, the greater the angular momentum. Physicists found that this idea of angular momentum also applied to particles, but it appeared to be an intrinsic, unchangeable property. For example, an electron has and will always have 1/2 of spin.

In quantum theories, angular momentum is measured in units of = h/2p = 1.05 x 10^-34 Js (Max Planck, The Nobel Prize in Physics 1918). (Js is joule-seconds, and is pronounced "h bar.")