Midnight Sun, a name given the sun when it can be seen at midnight during the Arctic or Antarctic summer. From March 21 to September 23, the sun is visible 24 hours a day at the North Pole. As a person here moves southward toward the midnight sun's limit (just south of the Arctic Circle), the number of days of continuous sunshine decreases. Northern Scandinavia, which extends 300 miles (480 km) into the Arctic zone, is sometimes called Land of the Midnight Sun. Northern Russia, Alaska, Canada, and Greenland also experience the midnight sun. At the South Pole, the midnight sun is seen from September 23 to March 21.
The midnight sun occurs because the earth's axis tilts toward the sun in summer and away from the sun in winter. Thus the poles are exposed to the sun's rays for six months each. This tilting of the earth's axis, together with the revolution of the earth about the sun, also causes the seasons.