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ammonia
(Encyclopedia)ammonia, chemical compound, NH3, colorless gas that is about one half as dense as air at ordinary temperatures and pressures. It has a characteristic pungent, penetrating odor. Ammonia forms a minute ...supernova
(Encyclopedia)supernova, a massive star in the latter stages of stellar evolution that suddenly contracts and then explodes, increasing its energy output as much as a billionfold. Supernovas are the principal distr...jet propulsion
(Encyclopedia)CE5 Types of jet engines: In the propeller-driven turbine a stream of high-velocity gases provides the power to drive the turbine and turn the propeller. In the jet-driven turbine the stream of gas...science fiction
(Encyclopedia)science fiction, literary genre in which a background of science or pseudoscience is an integral part of the story. Although science fiction is a form of fantastic literature, many of the events recou...uranium
(Encyclopedia)uranium yo͞orāˈnēəm [key], radioactive metallic chemical element; symbol U; at. no. 92; mass number of most stable isotope 238; m.p. 1,132℃; b.p. 3,818℃; sp. gr. 19.1 at 25℃; valence +3, +4...Frederick II, king of Prussia
(Encyclopedia)Frederick II or Frederick the Great, 1712–86, king of Prussia (1740–86), son and successor of Frederick William I. Frederick was tolerant in religious matters, personally professing atheism to h...metal
(Encyclopedia)metal, chemical element displaying certain properties by which it is normally distinguished from a nonmetal, notably its metallic luster, the capacity to lose electrons and form a positive ion, and th...hydrogen
(Encyclopedia)hydrogen hīˈdrəjən [key] [Gr.,=water forming], gaseous chemical element; symbol H; at. no. 1; interval in which at. wt. ranges 1.00784–1.00811; m.p. −259.14℃; b.p. −252.87℃; density 0.08...artificial intelligence
(Encyclopedia)artificial intelligence (AI), the use of computers to model the behavioral aspects of human reasoning and learning. Research in AI is concentrated in some half-dozen areas. In problem solving, one mus...banking
(Encyclopedia)banking, primarily the business of dealing in money and instruments of credit. Banks were traditionally differentiated from other financial institutions by their principal functions of accepting depos...Browse by Subject
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