Polar circle

Polar circle
The polar circle in Finland, 1975.
The polar circle in Norway at Saltfjellet mountain plateau. The year 1940 was added to the inscription by German soldiers during World War II (along with a swastika in the centre of the number, later removed).

A polar circle is either the Arctic Circle or the Antarctic Circle. On Earth, the Arctic Circle is located at a latitude of 66° 33′ 44″ N, and the Antarctic Circle is located at a latitude of 66° 33′ 44″ S.[1]

Areas between each polar circle and its associated pole (North Pole or South Pole), known geographically as the frigid zones, would theoretically experience at least one 24 hour period when the sun is continuously above the horizon and at least one 24 hour period when the sun is continuously below the horizon annually. However, atmospheric refraction extends the continuous daylight area while shrinking the continuous darkness area somewhat.

The exact location of the polar circles differs annually as the rotation axis of the earth shifts due to nutation and precession. Therefore the latitudes noted above are an average of those yearly changes.[clarification needed]

World map with polar circles.svg
The polar circles.

See also

Notes

  1. ^ Trópico en movimiento (in Spanish)

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Look at other dictionaries:

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  • polar circle — either the Arctic or the Antarctic Circle. [1545 55] * * * …   Universalium

  • polar circle — po′lar cir′cle n. geo either the Arctic or the Antarctic Circle • Etymology: 1545–55 …   From formal English to slang

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  • polar — 1 adj. a of or near a pole of the earth or a celestial body, or of the celestial sphere. b (of a species or variety) living in the north polar region. 2 having magnetic polarity. 3 a (of a molecule) having a positive charge at one end and a… …   Useful english dictionary

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