In 1928, Paul Dirac produced equations which predicted an unthinkable thing at the time— a positive charged electron. He did not believe his own theory. In 1932 in experiments with cosmic rays, Carl Anderson discovered the anti-electron, which showed that Dirac was right. Physicists call it the positron.
For each variety of matter there should exist a corresponding
‘opposite’ or antimatter. It is now known that antimatter exists. However, because matter and antimatter annihilates whenever they come in contact, it does not stay around for very long. (By the way, it is a great mystery as to why the universe is filled with mostly regular matter and not an equal amount of antimatter.)
There is not only an anti-electron but in 1955, the anti-proton was found, and later the anti-neutron. This allows the existence for anti atoms, a true form of antimatter.
