Antarctic Circle
The Antarctic Circle is one of the five major circles or parallels of latitude that mark maps of the Earth. It is at latitude 66° 33′ 39″ south of the equator (in 2000; like its northern counterpart, the Arctic Circle, the value is currently slowly decreasing over time, pushing the Antarctic Circle southwards with about 15 m per year). For everywhere within the Antarctic Circle, there is at least twenty-four hours of continuous daylight on the Summer Solstice in December, and at least twenty-four hours of continuous nighttime on the Winter Solstice in June. That is to say, one whole day during which the sun does not set, and one whole day during which the sun does not rise. This is because the earth is tilted at a 23.5 degree angle, and during the winter solstice, the southern hemisphere is tilted away from the Sun, meaning that the antarctic circle is completely tilted away from the Sun, hence it experiences 24 hour nighttime, and vice versa. In practice these numbers are somewhat relaxed for various factors, the most important being: the atmospheric refraction, the real altitude of the observer above sea level, and mirages. Mirages on the antarctic continent tend to be even more spectacular than in arctic regions, creating, for example, a series of sunsets and sunrises while in reality during that period the sun was under the horizon all the time.
The area south of this circle is known as the Antarctic, and the zone to the north is the Southern Temperate Zone.
The continent of Antarctica forms a land mass covering much of the area within the Antarctic Circle.
There is no permanent human population on Earth south of the Antarctic Circle. There are several research centers from various nations on Antarctica that are inhabited by teams of scientists that rotate in and out of the stations on a seasonal basis. In previous centuries, some semipermanent whaling stations were established on the continent and some of the whalers would live there for a year or more. At least three children have been born in Antarctica, who would technically be citizens if there were a nation on the continent. (See Demographics of Antarctica).
See also
Categories
Lines of latitude | Antarctica