In the Northern Hemisphere, the Arctic Circle passes, and in the Southern, respectively, the line of the Southern Arctic Belt. The first is considered the boundary of the temperate climate belt and the Arctic. The southern polar circle is considered the climatic border of Antarctica. On June 21-22 (in the summer solstice) the sun does not set, and in the winter solstice (December 21-22) it does not rise.
Due to changes in the inclination of the earth's axis, the Arctic circle line is shifted daily to three meters per day and up to one hundred meters per year. Specialists made calculations until 2015. It was established that, at first, the Arctic Circle will shift to the north. In the next nine years after 2015, four hundred meters to the south.
The boundary of the polar night is determined by the polar circle, if the Sun is a luminous point, while the Earth does not have an atmosphere. In fact, the day begins when the upper point of the solar disk appears. Moreover, the visible position of the star above the real due to refraction (curvature of the rays in the atmosphere). In this regard, the Arctic Circle lies fifty minutes south of the polar night border.
The concept of the Arctic circle was first introduced by Eudoxus of Cnidus (a student of Plato). He understood the connection between the tilt of the planet’s axis and the illumination in different regions of the Earth, connected the climate and the latitude of the terrain. Eudoxus introduced the definition of “climate”. The location of the Arctic Circle, in his opinion, was at 54 degrees. All the places behind him were considered unfit for human life.
Around 327 BC the first seafarer who was able to cross the Arctic Circle was the geographer Pythaeus. He observed the Arctic day in the Norwegian Sea.
The first navigator to cross the Southern Circle was Cook. This happened during his trip around the world.
The Arctic Circle in Europe runs through the territory of Norway, Finland, Russia, Sweden. The line crosses the Republic of Karelia, the Murmansk Region, the Kandalaksha Gulf and the Mezen Bay in the White Sea, the Nenets Autonomous Okrug, Komi and other areas in Russia. The part of the mainland, which is located north of the circle, is called the Arctic.
Beyond the Bering Strait, the line continues in America. In this area, the Arctic Circle passes through Alaska, three districts of Canada. Further, the line goes along Baffin Island, Fox Bay, Greenland and the Davis Strait.
The northern circle in the North Atlantic runs along the Danish Strait, the island of Grimsey, owned by Iceland, as well as the Norwegian and Greenland seas.
The southern circle crosses a number of territories of Antarctica and the Southern Ocean. The line passes through the Antarctic Peninsula, the Lazarev, Weddell, Cosmonauts Sea, Amudsen Bay and the Riser-Lansen Sea. From the coast of Amudsen Bay, the line of the Arctic Circle crosses the Commonwealth Sea, the land of Enderby and Princess Elizabeth, the shore of Truth, the Davis Sea, Vincennes Bay in the Mawson Sea, and the Knox Coast. Further, the line alternately runs across the ocean and along various shores on the land of Wilkes. Not far from Dumont-Durville (French station), it enters the Pacific Ocean sector from the Antarctic continent.
