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color index

(Encyclopedia)color index, in astronomy, difference in an object's brightness as recorded between any two well-defined bands of the electromagnetic spectrum by using optical filters of different colors. If blue and...

Challenger

(Encyclopedia)Challenger, U.S. space shuttle. It exploded (Jan. 28, 1986) 73 seconds into its tenth flight, killing all seven crew members, including the first civilian in space, schoolteacher Christa McAuliffe. Th...

house plants

(Encyclopedia)house plants, varied group of plants grown indoors and requiring no special care. They are usually grown singly in pots, but can also be grouped and planted together in dish gardens and terrariums. So...

analog circuit

(Encyclopedia)analog circuit, electronic circuit that operates with currents and voltages that vary continuously with time and have no abrupt transitions between levels. Generally speaking, analog circuits are cont...

molar volume

(Encyclopedia)molar volume, the volume occupied by a mole of a substance at STP. According to Avogadro's law, at a given temperature and pressure a given volume of any gas contains the same number of molecules. At ...

neoteny

(Encyclopedia)neoteny nēŏtˈənē [key], in biology, sexual maturity reached in the larval stage of some animals. Certain environmental conditions can inhibit the completion of metamorphosis; low temperature or l...

kiln

(Encyclopedia)kiln kĭl, kĭln [key], furnace for firing pottery and enamels, for making brick, charcoal, lime, and cement, for roasting ores, and for drying various substances (e.g., lumber, chemicals). Kilns may ...

Boltzmann, Ludwig

(Encyclopedia)Boltzmann, Ludwig lo͝otˈvĭkh bôltsˈmän [key], 1844–1906, Austrian physicist, b. Vienna, educated at Univ. of Vienna. He began teaching (1869) at Graz Univ. In 1873 he became mathematics profes...

starvation

(Encyclopedia)starvation, condition in which deprivation of food has forced the body to feed on itself. Causes are famine, fasting, malnutrition, or abnormalities of the mucosal lining of the digestive system. Fami...

timberline

(Encyclopedia)timberline, elevation above which trees cannot grow. Its location is influenced by the various factors that determine temperature, including latitude, prevailing wind directions, and exposure to sunli...