A positron is the antimatter equivalent of the negatively charged electron. A positron is equal to the electron in mass, but has a positive charge. In 1828, English physicist Paul Dirac advanced an equation that incorporated both quantum physics and the requirements of the theory of special relativity to provide a complete description of the electron. The equation resulted in a particle, however, that could be positively or negatively charged. On this basis, Dirac predicted the existence of the positron.

In 1932, American physicist Carl Anderson observed a new kind of particle in his cloud chamber. A particle too faint to be a proton or alpha particle entered the chamber, and then curved toward the negative area of the magnetic field that was around the chamber. It's velocity and mass indicated was the same as the electron but it swerved toward the negative pole and therefore had to carry a...