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Rabi, Isidor Isaac

(Encyclopedia)Rabi, Isidor Isaac rŏbˈē [key], 1898–1988, American physicist, b. Austria, grad. Cornell, 1919, Ph.D. Columbia, 1927. A teacher at Columbia from 1929, he became professor of physics in 1937. He i...

octave

(Encyclopedia)octave ŏkˈtĭv [key] [Lat.,=eighth], in music, the perfect interval between the 1st and 8th tones of the diatonic scale. The upper note of a perfect octave has a frequency of vibration twice that of...

liturgy, Islamic

(Encyclopedia)liturgy, Islamic, mandatory ritual prayer in Islam (salat) is performed five times a day at dawn, noon, afternoon, sunset, and night. It requires ritual cleanliness, and is preceded by ablutions. The ...

Three Kingdoms

(Encyclopedia)Three Kingdoms, period of Chinese history from 220 to 265, after the collapse of the Han dynasty. The period takes its name from the three states into which China was divided. Wei occupied the north. ...

electromagnetic radiation

(Encyclopedia)CE5 Electromagnetic spectrum electromagnetic radiation, energy radiated in the form of a wave as a result of the motion of electric charges. A moving charge gives rise to a magnetic field, and if ...

clock

(Encyclopedia)CE5 A pendulum clock: Weight-driven clock mechanism clock, instrument for measuring and indicating time. Predecessors of the clock were the sundial, the hourglass, and the clepsydra. See also watc...

stock exchange

(Encyclopedia)stock exchange, organized market for the trading of stocks and bonds (see bond; stock). Such markets were originally open to all, but at present only members of the owning association may buy and sell...

Hopper, Dennis Lee

(Encyclopedia) Hopper, Dennis Lee, 1936-2010, American filmmaker and actor, b. Dodge City, Ks. Hopper’s family relocated several times during his childhood, settli...

Ditko, Steve

(Encyclopedia)Ditko, Steve (Stephen John Ditko), 1927–2018, American comic-book artist, b. Johnstown, Pa., studied early 1950s Cartoonist and Illustrator School (later School of Visual Arts), New York City. Much ...

Hertz, Heinrich Rudolf

(Encyclopedia)Hertz, Heinrich Rudolf hĕrts [key], 1857–94, German physicist. He confirmed J. C. Maxwell's electromagnetic theory and in the course of experiments (1886–89) produced and studied electromagnetic...