Anderson, Carl David (1905–1991)

US physicist. He shared the Nobel Prize for Physics in 1936 for his discovery in 1932 of the positive electron (positron). His discovery of another particle, the muon, in 1937 launched elementary-particle physics.

Anderson was born in New York and educated at the California Institute of Technology, where he spent his entire career.

Using a modified cloud chamber of his own devising, Anderson found that positive electrons, or positrons, were present in cosmic rays, energetic particles reaching Earth from outer space. For this discovery, Anderson was awarded Nobel prize. In 1937, Anderson found a new particle in cosmic rays, one with a mass between that of an electron and a proton. The new particle was first called a mesotron and then a meson muon. The muon was the first elementary particle to be discovered beyond the constituents of ordinary matter (proton, neutron, and electron).