The Arctic Circle is a circle of latitude that encompasses the northernmost pole of the Earth and is located at approximately 66°33′45.6″ north of the Equator. It is one of the five major circles of latitude shown on maps of Earth. The Arctic Circle marks the southernmost latitude at which, on the winter solstice (which is the shortest day of the year in the northern hemisphere), the Sun will not rise all day, and on the summer solstice (which is the longest day of the year in the northern hemisphere), the Sun will not set. The position of the Arctic Circle is not fixed and currently runs 66°33′49.7″ north of the Equator. Its latitude depends on the Earths axial tilt, which fluctuates within a margin of more than 2° over a 41,000-year period, owing to tidal forces resulting from the orbit of the Moon. Consequently, the Arctic Circle is currently drifting northwards at a speed of about 14.5 m (48 ft) per year.