- Arctic Circle
an imaginary line drawn parallel to the equator, at 23°28prime; S of the North Pole: between the North Frigid Zone and the North Temperate Zone. See diag. under zone.
* * *Parallel of latitude approximately 66.5° north of the Equator that circumscribes the northern frigid zone. It marks the southern limit of the area within which, for one day or more each year, the sun does not set or rise. The length of continuous day or night increases northward from the Arctic Circle, mounting to six months at the North Pole.
* * *parallel, or line of latitude around the Earth, at approximately 66°30′ N. Because of the Earth's inclination of about 23 1/2° to the vertical, it marks the southern limit of the area within which, for one day or more each year, the Sun does not set (about June 21) or rise (about December 21). The length of continuous day or night increases northward from one day on the Arctic Circle to six months at the North Pole. The Antarctic Circle is the southern counterpart of the Arctic Circle, where on any given date conditions of daylight or darkness are exactly opposite.
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