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atomic clock

(Encyclopedia)atomic clock, electric or electronic timekeeping device that is controlled by atomic or molecular oscillations. A timekeeping device must contain or be connected to some apparatus that oscillates at a...

superconductivity

(Encyclopedia)superconductivity, abnormally high electrical conductivity of certain substances. The phenomenon was discovered in 1911 by Heike Kamerlingh Onnes, who found that the resistance of mercury dropped sudd...

space probe

(Encyclopedia)space probe, space vehicle carrying sophisticated instrumentation but no crew, designed to explore various aspects of the solar system (see space exploration). Unlike an artificial satellite, which is...

McClatchy, J. D.

(Encyclopedia)McClatchy, J. D. (Joseph Donald McClatchy, Jr.), 1945–2018, American poet, b. Bryn Mawr, Pa., B.A. Georgetown Univ., 1967, Ph.D. Yale, 1974. His first collection of poems, Scenes from Another Life (...

sulfide

(Encyclopedia)sulfide, chemical compound containing sulfur and one other element or sulfur and a radical. Sulfides may be salts or esters of hydrogen sulfide, H2S, or may be formed directly, e.g., by heating a meta...

Sansovino, Jacopo

(Encyclopedia)Sansovino, Jacopo sänsōvēˈnō [key], 1486–1570, Italian sculptor and architect of the Renaissance. His surname was taken in place of his own, Tatti, as homage to the Florentine sculptor Andrea ...

Rhett, Robert Barnwell

(Encyclopedia)Rhett, Robert Barnwell, 1800–1876, American politician, b. Beaufort, S.C. His family changed its name from Smith to Rhett (after a colonial ancestor) in 1837. A lawyer, he was a state legislator, st...

Lloyd, Norman

(Encyclopedia)Lloyd, Norman, 1914-2021, American film and TV actor and director, b. Jersey City, N.J, as Norman Perlmutter. Lloyd began his stage career at age 9 appe...

radium

(Encyclopedia)radium rāˈdēəm [key] [Lat. radius=ray], radioactive metallic chemical element; symbol Ra; at. no. 88; mass number of most stable isotope 226; m.p. 700℃; b.p. 1,140℃; sp. gr. about 6.0; valence...

Halley, Edmond

(Encyclopedia)Halley, Edmond hălˈē, hôˈlē [key], 1656–1742, English astronomer and mathematician. He is particularly noted as the first astronomer to predict the return of a comet and the first to point out...