Polar circle
Arctic Circle is called the 66 ° 33 ' 44 "( = 66.56 ° ) north ( Arctic Polar Circle ) and south ( Antarctic Polar Circle ) Width situated width circles on which the sun on the days of the solstice just no longer up or goes down. You have from the North or South Pole at the same distance as the tropics from the equator.
Location
The polar circles limit the polar regions. Your situation arises from the inclination of the Earth opposite the ecliptic from the current 23.44 °. The pole pitch of the Arctic Circle is 2602 km and the equatorial distance 7383 km.
Since the inclination of the Earth's axis slowly changes ( precession ), so does the polar circles move. At the moment they approach the poles by about one minute of arc in 128 years or 14.4 meters per year.
In 2011, the Arctic Circle were at about 66 ° 33 ' 44 " north or south latitude.
Importance
In the Arctic Circle, the sun never sets on the day of summer solstice. This phenomenon, which is called midnight sun, falls on the northern hemisphere usually on the 21th of June and in the southern hemisphere on 21 or 22 December. The St. John's on June 24, is also connected with festivities during the summer solstice.
- Images Arctic Circle
Arctic Circle in Norway 1975
Arctic Circle in Norway between Mo i Rana and Fauske
Arctic Circle on the Inland Railway in Sweden
Arctic Circle on the iron ore railway in Sweden
Arctic Circle in Jokkmokk, Sweden
Arctic Circle in Juoksenki, Finland, on the E 8
Arctic Circle in the Yukon Territory, Canada
Arctic Circle on the Dalton Highway, Alaska
Arctic Circle on the road Egwekinot - Iultin - Mys SmithA to Chukotka, Russia
On the day of the winter solstice, the sun never sets on the Arctic Circle. This is the day on which on the other hemisphere, the summer solstice.
Because of the refraction of light in the atmosphere ( see astronomical refraction), it is not only exactly on the Arctic Circle, but also something polferner (from about ± 65.96 ° latitude ) to the phenomenon that the sun never sets on one day a year.
The same applies to the winter solstice. Because of the astronomical refraction you have here, however, still be somewhat polnäher to see no dawning: from about ± 67.16 ° latitude is only half the solar disk above the horizon, from about ± 67.41 ° not even the upper the solar limb. At this time, however, it is bright - dim as shortly before sunrise or sunset, because the sun is just below the horizon. The closer you get to the pole, the deeper below the horizon it is located. From about 73.2 ° latitude it is always too dark to read the newspaper, because not even the civil twilight is achieved. From about 79.2 ° latitude, the brightest stars are constantly seen, from 85.2 ° also reaches no twilight of the sun more to the site.
Polar night and polar day
Areas within the Arctic Circle do not exceed every day day - night boundary. In areas lying within the Arctic Circle, it comes to the polar night and half a year later to the polar day: in winter it there for at least a day ( with increasing width more) the sun is not up, in the summer, however, seems to have the same number of days of the midnight sun, that is, the sun does not sink below the horizon.
In the polar night, it remains within the Arctic Circle but not necessarily dark because other factors must be considered:
- Because of refraction ( refraction in the Earth's atmosphere ) the sun near the horizon seems to be much higher than it actually is, so it can so completely absorbed in spite of " theoretical " polar night.
- The Sun's disk can rise partly, it rises just not completely over the horizon.
- When the sun is only slightly below the horizon, there is twilight. In continental Europe, the polar night is therefore nowhere so dark that the stars are continuously visible.