Midnight sun
From Free net encyclopedia
- "Midnight Sun" is also the name of a fictional newspaper in the video game Deus Ex, and of a novel by Ramsey Campbell.
The midnight sun is a phenomenon occurring in latitudes north of the Arctic Circle and south of the Antarctic Circle where the sun is continuously visible for at least 24 hours once per year. Since there are no permanent human settlements south of the Antarctic Circle, the countries and territories whose population experiences it are limited to Alaska, northern Canada, Greenland, Iceland, northern Norway, Sweden and Finland, and extremities of Russia such as Novaya Zemlya and the cities of Murmansk, Norilsk and Vorkuta. A quarter of Finland's territory lies above the Arctic Circle, and as a consequence the midnight sun can be experienced — for more and more days, the further north one goes. At Finland's northernmost point, the sun does not set for 73 days during summer.
The opposite phenomenon, polar night, is observed in winter when the sun is sufficiently below the horizon, so that there is insufficient sunlight or no light at all. (A lingering dusk may occur, if the sun is only 12 degrees or less below the horizon.)
Since the Earth's axis is tilted with respect to the ecliptic by approximately 23 degrees 26 minutes (commonly rounded to 23 degrees and a half), the sun does not set at high latitudes in (local) summer. The duration of the midnight sun increases from one day during the summer solstice at the polar circle to approximately six months at the poles. At extreme latitudes, it is usually referred to as polar day. The length of the time when the sun is above the horizon varies from 20 hours at the Arctic Circle and Antarctic Circle to 186 days at the poles.
Due to refraction, the midnight sun may be experienced at latitudes slightly below the polar circle, though not exceeding one degree (depending on local conditions). For example, it is possible to experience the midnight sun in Iceland, even though most of it (Grímsey being a notable exception) is slightly south of the Arctic Circle.
White night
Locations at latitudes up to 60 degrees experience midnight twilight instead. The sun is just below the horizon, so that daytime activities, such as reading, are still possible without resorting to artificial light.
White nights have become a common symbol of Saint Petersburg, Russia, where they occur from about 11 June to 11 July, and the last 10 days of June are celebrated with cultural events. Scandinavia and Alaska, where this effect can also be observed, are both known as The Land of the Midnight Sun.
Popular culture
The movie Insomnia tells the story of a fictional police detective in Norway who suffers from insomnia due to, among other things, the midnight sun. A 2002 remake of the film is set in Alaska.