What is Antimatter? - Page 2

Dirac's prediction applies not only to the electron but to all the fundamental constituents of matter (particles). Each type of particle must have a corresponding antiparticle type. The mass of any antiparticle is identical to that of the particle. All the rest of its properties are also closely related, but with the signs of all charges reversed. For example, a proton has a positive electric charge, but an antiproton has a negative electric charge. The existence of antimatter partners for all matter particles is now a well-verified phenomenon, with both partners for hundreds of such pairings observed.

New discoveries lead to new language. In coining the term "antimatter," physicists in fact redefined the meaning of the word "matter." Until that time, "matter" meant anything with substance; even today school textbooks give this definition: "matter takes up space and has mass." By adding the concept of antimatter as distinct from matter, physicists narrowed the definition of matter to apply to only certain kinds of particles, including, however, all those found in everyday experience.

Any pair of matching particle and antiparticle can be produced anytime there is sufficient energy available to provide the necessary mass-energy. Similarly, any time a particle meets its matching antiparticle, the two can annihilate one another--that is, they both disappear, leaving their energy transformed into some other form.

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