Back Arktiese Sirkel Afrikaans الدائرة القطبية الشمالية Arabic Círculu polar árticu AST Şimal Qütb dairəsi Azerbaijani Төньяҡ поляр түңәрәк Bashkir Lingkehan Arktik BAN Sirkulong Arktiko BCL Паўночны палярны круг Byelorussian Паўночны палярны круг BE-X-OLD Северен полярен кръг Bulgarian
The Arctic Circle is one of the two polar circles, and the northernmost of the five major circles of latitude as shown on maps of Earth at about 66° 34' N.[1] Its southern counterpart is the Antarctic Circle.
The Arctic Circle marks the southernmost latitude at which, on the winter solstice in the Northern Hemisphere, the Sun does not rise all day, and on the Northern Hemisphere's summer solstice, the Sun does not set. These phenomena are referred to as polar night and midnight sun respectively, and the further north one progresses, the more obvious this becomes. For example, in the Russian port city of Murmansk, three degrees north of the Arctic Circle, the Sun stays below the horizon for 20 days before and after the winter solstice, and above the horizon for 20 days before and after the summer solstice. [2][3][4]
The position of the Arctic Circle is not fixed and currently runs 66°33′50.3″ north of the Equator.[5] Its latitude depends on Earth's axial tilt, which fluctuates by a margin of some 2° over a 41,000-year period, due to tidal forces resulting from the orbit of the Moon.[6] Consequently, the Arctic Circle is currently drifting northwards at a speed of about 14.5 m (48 ft) per year.
- ^ "Arctic FAQ - Frequently Asked Questions about the Arctic".
- ^ "40 days without the sun. How? Polar Night begins in Murmansk". Auroravillage.info. 3 December 2018. Retrieved 24 March 2022.
- ^ Burn, Chris. The Polar Night (PDF). The Aurora Research Institute. Retrieved 28 September 2015.
- ^ N.B.: This refers to the true geometric center which actually appears higher in the sky because of refraction by the atmosphere.
- ^ "Obliquity of the Ecliptic (Eps Mean)". Neoprogrammics.com. Retrieved 13 May 2014.
- ^ Berger, A. L. (1976). "Obliquity and Precession for the Last 5000000 Years". Astronomy & Astrophysics. 51 (1): 127–135. Bibcode:1976A&A....51..127B.