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photon

(Encyclopedia)photon fōˈtŏn [key], the particle composing light and other forms of electromagnetic radiation, sometimes called light quantum. The photon has no charge and no mass. About the beginning of the 20th...

seeing

(Encyclopedia)seeing, in astronomy, the clarity with which stars and other celestial objects can be observed. It is primarily determined by the atmosphere of the earth. The most obvious phenomenon is twinkling, whe...

Dolomites

(Encyclopedia)Dolomites or Dolomite Alps, Alpine group, N Italy, between the Isarco and Piave rivers, named for the dolomitic limestone of which it is composed. Famous for their strikingly bold outline (a stairstep...

falsetto

(Encyclopedia)falsetto fôlsĕtˈtō [key] [Ital.,=diminutive of false], high-pitched, unnatural tones above the normal register of the male voice, produced, according to some theories, by the vibration of only the...

margin requirement

(Encyclopedia)margin requirement, that part of a security's price that a buyer must pay for in cash. The balance of the price is met by the broker, who, in effect, is supplying a client with a loan. The smaller the...

Korzybski, Alfred Habdank

(Encyclopedia)Korzybski, Alfred Habdank kôrzĭbˈskē [key], 1879–1950, Polish-American linguist, b. Warsaw. In his system, which he called General Semantics, Korzybski aimed at a distinction between the word an...

tunneling

(Encyclopedia)tunneling, quantum-mechanical effect by which a particle can penetrate a barrier into a region of space that would be forbidden by ordinary classical mechanics. Tunneling is a direct result of the wav...

Zeeman, Pieter

(Encyclopedia)Zeeman, Pieter pēˈtər zāˈmän [key], 1865–1943, Dutch physicist. He was professor of physics at the Univ. of Amsterdam from 1900 and director of the Physical Institute, Amsterdam, from 1908. In...

mandates

(Encyclopedia)mandates, system of trusteeships established by Article 22 of the Covenant of the League of Nations for the administration of former Turkish territories and of former German colonies. As finally adopt...

wall

(Encyclopedia)wall, in architecture, protective, enclosing, or dividing vertical structure. Its thickness is determined by the material, height, and stress. It may be of studding and lath, either boarded or plaster...