equator

equator, imaginary great circle around the earth, everywhere equidistant from the two geographical poles and forming the base line from which latitude is reckoned. The equator, which measures c.24,902 mi (40,076 km), is designated as lat. 0°. It intersects N South America, central Africa, and Indonesia. The celestial equator is the projection of the plane of the earth's equator on the celestial sphere (see equatorial coordinate system).

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Equator

Great circle around the Earth that is everywhere equidistant from the geographic poles and lies in a plane perpendicular to the Earth's axis. This geographic, or terrestrial, Equator divides the Earth into the Northern and Southern Hemispheres and forms the imaginary reference line on the Earth's surface from which latitude is reckoned (i.e., 0° latitude). In astronomy, the celestial equator is the great circle in which the plane of the terrestrial Equator intersects the celestial sphere; it is thus equidistant from the celestial poles. When the Sun lies in its plane, day and night are everywhere of equal length; this happens at the equinoxes.

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equator

1. the great circle of the earth with a latitude of 0?, lying equidistant from the poles; dividing the N and S hemispheres

2. a circle dividing a sphere or other surface into two equal symmetrical parts

3. See magnetic equator

4. Astronomy See celestial equator

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equator [ē′kwād·ər]

(geodesy)

The great circle around the earth, equally distant from the North and South poles, which divides the earth into the Northern and Southern hemispheres; the line from which latitudes are reckoned.