Definitions

particle

wave-particle duality

Principle that subatomic particles possess some wavelike characteristics, and that electromagnetic waves, such as light, possess some particlelike characteristics. In 1905, by demonstrating the photoelectric effect, Albert Einstein showed that light, which until then had been thought of as a form of electromagnetic wave (see electromagnetic radiation), must also be thought of as localized in packets of discrete energy (see photon). In 1924 Louis-Victor Broglie proposed that electrons have wave properties such as wavelength and frequency; their wavelike nature was experimentally established in 1927 by the demonstration of their diffraction. The theory of quantum electrodynamics combines the wave theory and the particle theory of electromagnetic radiation.

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or elementary particle

Any of various self-contained units of matter or energy. Discovery of the electron in 1897 and of the atomic nucleus in 1911 established that the atom is actually a composite of a cloud of electrons surrounding a tiny but heavy core. By the early 1930s it was found that the nucleus is composed of even smaller particles, called protons and neutrons. In the early 1970s it was discovered that these particles are made up of several types of even more basic units, named quarks, which, together with several types of leptons, constitute the fundamental building blocks of all matter. A third major group of subatomic particles consists of bosons, which transmit the forces of the universe. More than 200 subatomic particles have been detected so far, and most appear to have a corresponding antiparticle (see antimatter).

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Device that accelerates a beam of fast-moving, electrically charged atoms (ions) or subatomic particles. Accelerators are used to study the structure of atomic nuclei (see atom) and the nature of subatomic particles and their fundamental interactions. At speeds close to that of light, particles collide with and disrupt atomic nuclei and subatomic particles, allowing physicists to study nuclear components and to make new kinds of subatomic particles. The cyclotron accelerates positively charged particles, while the betatron accelerates negatively charged electrons. Synchrotrons and linear accelerators are used either with positively charged particles or electrons. Accelerators are also used for radioisotope production, cancer therapy, biological sterilization, and one form of radiocarbon dating.

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or Higgs boson

Carrier of an all-pervading fundamental field (Higgs field) that is hypothesized as a means of endowing mass on some elementary particles through its interactions with them. It was named for Peter W. Higgs (born 1929) of the University of Edinburgh, one of those who first postulated the idea. The Higgs mechanism explains why the carriers of the weak force are heavy, while the carrier of the electromagnetic force has a mass of zero. There is no direct experimental evidence for the existence of either the Higgs particle or the Higgs field.

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