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lead, chemical element

(Encyclopedia)lead, metallic chemical element; symbol Pb [Lat. plumbum]; at. no. 82; at. wt. 207.2; m.p. 327.502℃; b.p. about 1,740℃; sp. gr. 11.35 at 20℃; valence +2 or +4. One of the oldest metals used by h...

environmentalism

(Encyclopedia)environmentalism, movement to protect the quality and continuity of life through conservation of natural resources, prevention of pollution, and control of land use. The philosophical foundations for ...

utility, public

(Encyclopedia)utility, public, industry required by law to render adequate service in its field at reasonable prices to all who apply for it. Public utilities frequently operate as monopolies in their market. In th...

Putin, Vladimir Vladimirovich

(Encyclopedia)Putin, Vladimir Vladimirovich vlŭdēmˈyĭr vlŭdēmˌyĭrˈəvyĭch po͞oˈtyĭn [key], 1952–, Russian government official and political leader, b. Leningrad (now St. Petersburg). After graduating...

marriage

(Encyclopedia)marriage, socially sanctioned union that reproduces the family. In all societies the choice of partners is generally guided by rules of exogamy (the obligation to marry outside a group); some societie...

relativity

(Encyclopedia)relativity, physical theory, introduced by Albert Einstein, that discards the concept of absolute motion and instead treats only relative motion between two systems or frames of reference. One consequ...

chemical warfare

(Encyclopedia)chemical warfare, employment in war of incendiaries, poison gases, and other chemical substances. Ancient armies attacking or defending fortified cities threw burning oil and fireballs. A primitive ty...

space medicine

(Encyclopedia)space medicine, study of the medical and biological effects of space travel on living organisms. The principal aim is to discover how well and for how long humans can withstand the extreme conditions ...

Truman, Harry S.

(Encyclopedia)Truman, Harry S., 1884–1972, 33d President of the United States, b. Lamar, Mo. Truman remained active in politics for many years after his retirement, campaigning around the country for Democrat...

Japan

(Encyclopedia)CE5 Japan jəpănˈ [key], Jap. Nihon or Nippon, country (2015 est. pop. 127,975,000), 145,833 sq mi (377,835 sq km), occupying an archipelago off the coast of E Asia. The capital is Tokyo, which, ...