Article
Article
Antimatter
Article By:
Zeller, Michael E. Department of Physics, Yale University, New Haven, Connecticut.
Last reviewed:October 2019
DOI:https://doi.org/10.1036/1097-8542.041000
Matter that is composed of antiparticles, which have the same masses, spins, and decay lifetimes (if unstable) as particles of ordinary matter, but opposite electric charges, magnetic moments, lepton numbers, baryon numbers, strangeness, and charm. At the most fundamental level every type of elementary particle has its anti-counterpart, its antiparticle. The existence of antiparticles was implied by the relativistic wave equation derived in 1928 by P. A. M. Dirac in his successful attempt to reconcile quantum mechanics and special relativity. The antiparticle of the electron (the positron) was first observed in cosmic rays by C. D. Anderson in 1932, while that of the proton (the antiproton) was produced in the laboratory and observed by E. Segré, O. Chamberlain, and their colleagues in 1955. See also: Electron; Elementary particle; Positron; Proton; Quantum mechanics; Relativity
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