Antiparticle (Encyclopedia of Science)
Antiparticles are subatomic particles that are the opposite of other subatomic particles in some way or another. In the case of the antielectron and the antiproton, this difference is a matter of charge. The electron is negatively charged, and the antielectron is positively charged; the proton is positively charged, and the antiproton is negatively charged. Since the neutron carries no electric charge, its antiparticle, the antineutron, is characterized has having a spin opposite to that of the neutron.
The discovery of antiparticles is a rather remarkable scientific detective story. In the late 1920s, British physicist Paul Dirac (1902984) was working to improve the model of the atom then used by scientists. As he performed his mathematical calculations, he found that electrons should be expected in two energy states, one positive and one negative. However, the concept of negative energy was unknown to scientists at that time.
Dirac suggested that some electrons might carry a positive electrical charge, the opposite of that normally found in an electron. Scientists were skeptical about the idea. Electrons were well known, and the only form in which they had ever been observed was with a negative charge.
The dilemma was soon resolved, however. Only five years after Dirac proposed the concept of a...
(The entire section is 418 words.)
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