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alternating current

(Encyclopedia)alternating current, abbr. AC, a flow of electric charge that undergoes periodic reverses in direction. In North America ordinary household current alternates at a frequency of 60 times per second. Se...

wave, in physics

(Encyclopedia)wave, in physics, the transfer of energy by the regular vibration, or oscillatory motion, either of some material medium or by the variation in magnitude of the field vectors of an electromagnetic fie...

Armageddon

(Encyclopedia)Armageddon ärˌməgedˈən [key], in the New Testament, great battlefield where, at the end of the world, the powers of evil will fight the powers of good. If the usual etymology is correct, the name...

Janssen, Pierre Jules César

(Encyclopedia)Janssen, Pierre Jules César pyĕr zhül sāzärˈ zhäNsĕnˈ [key], 1824–1907, French astronomer. In 1857–58, in Peru, he worked on the determination of the magnetic equator; in the Azores (1867...

Thales

(Encyclopedia)Thales thāˈlēz [key], c.636–c.546 b.c., pre-Socratic Greek philosopher of Miletus and reputed founder of the Milesian school of philosophy. He is the first recorded Western philosopher. Thales ta...

Pickering, William Henry

(Encyclopedia)Pickering, William Henry, 1858–1938, American astronomer, b. Boston, grad. Massachusetts Institute of Technology (B.S., 1879). He taught at the Massachusetts Institute of Technology (1880–87) and ...

hertz

(Encyclopedia)hertz hûrts [key] [for Heinrich R. Hertz], abbr. Hz, unit of frequency, equal to 1 cycle per second. The term is combined with metric prefixes to denote multiple units such as the kilohertz (1,000 Hz...

transit

(Encyclopedia)transit, in astronomy, passage of a body across a meridian or passage of a small body across the visible disk of a larger one. (The passage of a large body across a smaller one is called an eclipse or...

Hassel, Odd

(Encyclopedia)Hassel, Odd ôd häsˈəl [key], 1897–1981, Norwegian chemist, b. Christiania (now Oslo), grad. Oslo Univ. (1920), Ph.D. Univ. of Berlin (1924). After pursuing X-ray crystallographic studies in Germ...

Nambu, Yoichiro

(Encyclopedia)Nambu, Yoichiro yoiˈchērō nämˈbo͞o [key], 1921–2015, Japanese-American physicist, b. Tokyo, D.Sc. Univ. of Tokyo, 1952. He studied at the Institute for Advanced Study, Princeton, with Albert E...