Carl David Anderson

Carl David Anderson
(1905-1991)

US physicist who discovered the positive electron (positron) in 1932; he shared the Nobel Prize for Physics 1936.
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 shared the 1936 Nobel prize with Victor Hess, the discoverer of cosmic rays.
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).