Polar circle

Due to their inherent climate environment, the bulk of the Arctic Circle, much of which is sea, is sparsely settled whereas this applies to all of Antarctica which is mainly land and sheltered ice shelves.

Instead, atmospheric refraction and the Sun's light reaching the planet as an extended object rather than a point source means that just within each circle the Earth's surface does not experience any proper polar night, 24 hours where the sun does not rise.

The latitude of the polar circles is + or −90 degrees (which refers to the North and South Pole, respectively) minus the axial tilt (that is, of the Earth's axis of daily rotation relative to the ecliptic, the plane of the Earth's orbit).

[citation needed] A further global factor for this numerical range is Earth's nutation, which is a very small change in tilt.

Observers higher above sea level can see a tiny amount of the Sun's disc (see horizon) where at lower places it would not rise.

The north polar circle on a polar projection .
The polar circle as lines on a modified cylindrical projection .
The Arctic Circle in Finland , 1975.
The Arctic Circle in Norway at Saltfjellet mountain plateau in July 2003.
Relationship between Earth's axial tilt (ε) to the tropical and polar circles