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Mitchell, William

(Encyclopedia)Mitchell, William (Billy Mitchell), 1879–1936, American army officer and pilot, b. Nice, France. He enlisted (1898) in the U.S. army in the Spanish-American War and received a commission in the regu...

hafnium

(Encyclopedia)hafnium hăfˈnēəm [key], metallic chemical element; symbol Hf; at. no. 72; at. wt. 178.49; m.p. about 2,227℃; b.p. 4,602℃; sp. gr. 13.31 at 20℃; valence +4. Hafnium is a lustrous, ductile, si...

Afghanistan War

(Encyclopedia)Afghanistan War, 1978–92, conflict between anti-Communist Muslim Afghan guerrillas (mujahidin) and Afghan government and Soviet forces. The conflict had its origins in the 1978 coup that overthrew A...

aviation medicine

(Encyclopedia)aviation medicine, scientific study of the biological effects of aviation, especially on human beings. Although aviation medicine is concerned with such problems as the spread of diseases by persons t...

engineering

(Encyclopedia)engineering, profession devoted to designing, constructing, and operating the structures, machines, and other devices of industry and everyday life. Until the Industrial Revolution there were only t...

equal-time rule

(Encyclopedia)equal-time rule, a Federal Communications Commission rule that requires equal air time for all major candidates competing for political office. It was preceded by the fairness doctrine, abolished in 1...

Iran-Iraq War

(Encyclopedia)Iran-Iraq War, 1980–88, protracted military conflict between Iran and Iraq. It officially began on Sept. 22, 1980, with an Iraqi land and air invasion of western Iran, although Iraqi spokespersons m...

Bossier City

(Encyclopedia)Bossier City bōˈzhər [key], city (2020 pop. 62,701), Bossier parish, NW La., on the Red River, ...

thunder

(Encyclopedia)thunder, sound produced along a path of a lightning flash, caused by the rapid heating and expansion of the adjacent air; lightning can heat air to temperatures as much as five times hotter than those...

Doolittle, James Harold

(Encyclopedia)Doolittle, James Harold, 1896–1993, American aviator, b. Alameda, Calif. After serving in World War I as a flier he returned to school and earned a Sc.D. from MIT. He then became noted for his speed...