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photoelectric cell

(Encyclopedia)CE5 Photoelectric cell: Light causes a photosensitive surface to emit electrons, which flow as current to the positive terminal. A galvanometer measures the current and thus indicates light intensi...

titanium

(Encyclopedia)titanium tītāˈnēəm, tĭ– [key] [from Titan], metallic chemical element; symbol Ti; at. no. 22; at. wt. 47.867; m.p. 1,675℃; b.p. 3,260℃; sp. gr. 4.54 at 20℃; valence +2, +3, or +4. Titani...

flag, symbolic cloth

(Encyclopedia)flag, piece of cloth, usually bunting or similar light material, plain, colored, or bearing a device, varying in size and shape, but often oblong or square, used as an ensign, standard, or signal or f...

Doppler effect

(Encyclopedia)Doppler effect, change in the wavelength (or frequency) of energy in the form of waves, e.g., sound or light, as a result of motion of either the source or the receiver of the waves; the effect is nam...

amyotrophic lateral sclerosis

(Encyclopedia)amyotrophic lateral sclerosis (ALS) āˌmīətrōfˈik, sklĭrōˈsĭs [key] or motor neuron disease, sometimes called Lou Gehrig's disease, degenerative disease that affects motor neurons in the brai...

mole, in zoology

(Encyclopedia)mole, in zoology, common name for the small, burrowing, insectivorous mammals of the family Talpidae, found throughout the temperate Northern Hemisphere. Moles are trapped as pests, although they prob...

aster

(Encyclopedia)CE5 Cross section of a sunflower, a member of the aster family aster [Gr.,=star], common name for the Asteraceae (Compositae), the aster family, in North America, name for plants of the genus Aste...

Liberty, Statue of

(Encyclopedia)Liberty, Statue of, statue on Liberty Island in Upper New York Bay, commanding the entrance to New York City. Liberty Island, c.10 acres (4 hectares), formerly Bedloe's Island (renamed in 1956), was t...

Powell, Colin Luther

(Encyclopedia)Powell, Colin Luther, 1937–2021, U.S. army general and government official, b. New York City, grad., City College (B.S., 1958); George Washington Univ...

precession of the equinoxes

(Encyclopedia)CE5 Precession of the equinoxes (the points at which the earth's celestial equator intersects its ecliptic) is due to the slow rotation of the earth's axis around a perpendicular to the ecliptic. ...