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Roche limit

(Encyclopedia)Roche limit, the closest distance that a celestial body held together only by its own gravity can come to a planet without being pulled apart by the planet's tidal (gravitational) force. This distance...

center of mass

(Encyclopedia)center of mass, the point at which all the mass of a body may be considered to be concentrated in analyzing its motion. The center of mass of a sphere of uniform density coincides with the center of t...

tangent

(Encyclopedia)tangent, in mathematics. 1 In geometry, the tangent to a circle or sphere is a straight line that intersects the circle or sphere in one and only one point. For other curves and surfaces the tangent l...

Autolycus, Greek astronomer and mathematician

(Encyclopedia)Autolycus ôtŏlˈĭkəs [key], fl. 4th cent. b.c., astronomer and mathematician of Pitane in Aeolis. Of his two extant works, that on the revolving sphere is said to be the oldest completely preserve...

evaporimeter

(Encyclopedia)evaporimeter ĭvăpˌərĭmˈətər [key], instrument that measures the rate of evaporation of water into the atmosphere, sometimes called an atmometer. Evaporimeters are of two types, those that meas...

Orion, in astronomy

(Encyclopedia)Orion, in astronomy, constellation located on the celestial equator. It is one of the most conspicuous and easily recognizable constellations in the entire sky. From ancient times it has been mentione...

Max, Peter

(Encyclopedia)Max, Peter, 1937–, American artist, b. Berlin. Max is noted for his undulating graphic designs in bright, vibrating colors. His style has influenced much commercial art. It is reminiscent of art nou...

azimuth

(Encyclopedia)azimuth ăzˈəməth [key], in astronomy, one coordinate in the altazimuth coordinate system. It is the angular distance of a body measured westward along the celestial horizon from the observer's sou...

Hathor

(Encyclopedia)Hathor hăthˈôr [key], in Egyptian religion, celestial goddess of love and festivity. The personification of the sky, she was represented as a star-studded cow or as a woman with the head of a cow. ...

Habash al-Hasib

(Encyclopedia)Habash al-Hasib häbäshˈ äl-häsēbˈ [key], d. c.870, Arab mathematician and astronomer. Habash al-Hasib was born in what is now Mary, Turkmenistan, and worked in Baghdad. He calculated tables of ...