The Arctic Circle is one of the five major circles of latitude (imaginary lines around the Earth) that are often marked on maps of the Earth. This is the parallel of latitude that (in 2000) runs 66° 33' 39" north of the Equator. North of this line, the Sun never rises at the Winter Solstice and never sets at the Summer Solstice.
Countries which are partly within the Arctic Circle are:
- Denmark (Greenland)
- United States of America (Alaska)
- Iceland (less than 1 square kilometre)
The position of the Arctic Circle is not fixed. It directly depends on the Earth's axial tilt. The axial tilt fluctuates within a margin of 2° over a 40,000-year period, mostly due to tidal forces from the orbit of the Moon. The tilt is currently diminishing, so the Arctic Circle is drifting northwards at a speed of about 15 m (49 ft) per year.