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photovoltaic cell

(Encyclopedia)photovoltaic cell: see photoelectric cell; solar cell. ...

Thales

(Encyclopedia)Thales thāˈlēz [key], c.636–c.546 b.c., pre-Socratic Greek philosopher of Miletus and reputed founder of the Milesian school of philosophy. He is the first recorded Western philosopher. Thales ta...

civil time

(Encyclopedia)civil time, local time based on universal time. Civil time may be formally defined as mean solar time plus 12 hr; the civil day begins at midnight, while the mean solar day begins at noon. Civil time ...

exoplanet

(Encyclopedia)exoplanet or extrasolar planet, a planet located outside the solar system. See planet; planetary system. ...

sunspots

(Encyclopedia)sunspots, dark, usually irregularly shaped spots on the sun's surface that are actually solar magnetic storms. The spots are darker because the temperature of the spots is lower than that of the surro...

second

(Encyclopedia)second, abbr. sec or s, fundamental unit of time in all systems of measurement. In practical terms, the second is 1/60 of a minute, 1/3,600 of an hour, or 1/86,400 of a day. Since the length of the da...

time , sequential arrangement of all events

(Encyclopedia)time, sequential arrangement of all events, or the interval between two events in such a sequence. The concept of time may be discussed on several different levels: physical, psychological, philosophi...

astronomical unit

(Encyclopedia)astronomical unit (AU), mean distance between the earth and sun; one AU is c.92,960,000 mi (149,604,970 km). The astronomical unit is the principal unit of measurement within the solar system, e.g., M...

Caslon, William

(Encyclopedia)Caslon, William kăzˈlən [key], 1692–1766, English type designer, b. Worcestershire. He worked first in London as an engraver of gunlocks, then set up his own foundry in 1716. The merits of Caslon...

space probe

(Encyclopedia)space probe, space vehicle carrying sophisticated instrumentation but no crew, designed to explore various aspects of the solar system (see space exploration). Unlike an artificial satellite, which is...