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sonar

(Encyclopedia)sonar sōˈnär [key], device used underwater for locating submerged objects and for submarine communication by means of sound waves. The term sonar is an acronym for sound navigation ranging. The mai...

Cabot, Sebastian

(Encyclopedia)Cabot, Sebastian, b. 1483–86?, d. 1557, explorer in English and Spanish service; son of John Cabot. He may well have accompanied his father on the 1497 and 1498 voyages, and he was for many years gi...

Bryan, William Jennings

(Encyclopedia)Bryan, William Jennings brīˈən [key], 1860–1925, American political leader, b. Salem, Ill. Although the nation consistently rejected him for the presidency, it eventually adopted many of the refo...

navigation satellite

(Encyclopedia)navigation satellite, artificial satellite designed expressly to aid the navigation of sea and air traffic. Early navigation satellites, from the Transit series launched in 1960 to the U.S. navy's Nav...

Sung

(Encyclopedia)Sung so͝ong [key], dynasty of China that ruled 960–1279. It was divided into two periods: Northern Sung (907–1126) with its capital at Kaifeng and Southern Sung (1127–1279) with its capital at ...

advertising

(Encyclopedia)advertising, in general, any openly sponsored offering of goods, services, or ideas through any medium of public communication. At its inception advertising was merely an announcement; for example, en...

nuclear weapons

(Encyclopedia)nuclear weapons, weapons of mass destruction powered by atomic, rather than chemical, processes. Nuclear weapons produce large explosions and hazardous radioactive byproducts by means of either nuclea...

Monitor and Merrimack

(Encyclopedia)Monitor and Merrimack, two American warships that fought the first engagement between ironclad ships. When, at the beginning of the Civil War, the Union forces abandoned the Norfolk Navy Yard at Ports...

Saint Lawrence Seaway

(Encyclopedia)Saint Lawrence Seaway, international waterway, 2,342 mi (3,769 km) long, consisting of a system of canals, dams, and locks in the St. Lawrence River and connecting channels between the Great Lakes; op...

communications satellite

(Encyclopedia)communications satellite artificial satellite that functions as part of a global radio-communications network. Echo 1, the first communications satellite, launched in 1960, was an instrumented inflat...