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Copernican system

(Encyclopedia)Copernican system, first modern European theory of planetary motion that was heliocentric, i.e., that placed the sun motionless at the center of the solar system with all the planets, including the ea...

momentum

(Encyclopedia)momentum mōmĕnˈtəm [key], in mechanics, the quantity of motion of a body, specifically the product of the mass of the body and its velocity. Momentum is a vector quantity; i.e., it has both a magn...

Steinbeck, John

(Encyclopedia)Steinbeck, John, 1902–68, American writer, b. Salinas, Calif., studied at Stanford. He is probably best remembered for his strong sociological novel The Grapes of Wrath, considered one of the great ...

speed

(Encyclopedia)speed, change in distance with respect to time. Speed is a scalar rather than a vector quantity; i.e., the speed of a body tells one how fast the body is moving but not the direction of the motion. If...

stroboscope

(Encyclopedia)stroboscope strŏbˈəskōp [key], optical instrument for making a moving object appear to be slowed down or stationary. This effect is created by interrupting the observer's view so that the object i...

Chatsworth

(Encyclopedia)Chatsworth, estate, Derbyshire, central England, near Chesterfield. It is the seat of the dukes of Devonshire. Begun in 1552, the present Classical-style Chatsworth House was rebuilt in 1686. It has n...

sound

(Encyclopedia)CE5 Sound waves: An air pressure wave radiating outward from a loudspeaker is perceived as sound. sound, any disturbance that travels through an elastic medium such as air, ground, or water to be ...

aberration of starlight

(Encyclopedia)aberration of starlight, displacement of the apparent path of light from a star, resulting in a displacement of the apparent position of the star from its true position; discovered by the English astr...

Allen, Woody

(Encyclopedia)Allen, Woody, 1935–, American actor, writer, and director, one of contemporary America's leading filmmakers, b. Brooklyn, N.Y., as Allen Stewart Konigsberg. Allen began his career writing for televi...

nutation

(Encyclopedia)nutation, in astronomy, a slight wobbling motion of the earth's axis. The causes of nutation are similar to those of the precession of the equinoxes, involving the varying attraction of the moon on th...