The Arctic Circle is one of the five major circles of latitude that mark maps of the Earth. This is the parallel of latitude that runs 66° 33' 38" north of the Equator. Everything north of this circle is known as the Arctic, and the zone just to the south of this circle is the Northern Temperate Zone.
The Arctic Circle marks the southern extremity of the solar day of the summer solstice and the solar night of the winter solstice. Within the Arctic Circle, the arctic Sun is above the horizon for at least 24 continuous hours per year, in conjunction with the Arctic's Summer Solstice. Likewise, in conjunction with the Arctic's Winter Solstice, the Arctic sun will be below the horizon for at least 24 continuous hours.
A border where the sun does not sink in the summer nor rise in the winter on its northern side - for at least one day a year. While quietly proceeding, the Arctic Circle fluctuates during its journey of 250 kilometres one or two meters every day - swinging back and forth, but nevertheless reaching each end along the way at interims of 40 000 years.