midnight sun

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Path of the Midnight Sun over the course of 3 hours, South Cape, Spitsbergen.

The midnight sun at Nordkapp, Norway.

The Arctic Cathedral with surroundings in Tromsø illuminated by the midnight sun.

Midnight sun in Kiruna, Sweden.

The midnight sun (also known as the black sun^{[citation needed]}) is a natural phenomenon occurring in summer months at latitudes north and nearby to the south of the Arctic Circle, and south and nearby to the north of the Antarctic Circle where the sun remains visible at the local midnight. Given fair weather, the sun is visible for a continuous 24 hours, mostly north of the Arctic Circle and south of the Antarctic Circle. The number of days per year with potential midnight sun increases the farther poleward one goes.

There are no permanent human settlements south of the Antarctic Circle, so the countries and territories whose populations experience it are limited to the ones crossed by the Arctic Circle, i.e. Canada, United States of America (Alaska), Denmark (Greenland), Norway, Sweden, Finland, Russia, and extremities of Iceland. A quarter of Finland's territory lies north of the Arctic Circle and at the country's northernmost point the sun does not set for 73 days during summer. In Svalbard, Norway, the northernmost inhabited region of Europe, there is no sunset from approximately 19 April to 23 August. The extreme sites are the poles where the sun can be continuously visible for a half year.

The opposite phenomenon, polar night, occurs in winter when the sun stays below the horizon throughout the day.

Since the Earth's axis is tilted with respect to the ecliptic by approximately 23 degrees 27 minutes, 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 the sun is above the horizon varies from 20 hours at the Arctic Circle and Antarctic Circle to 186 days at the poles.

At the poles themselves, the sun only rises once and sets once, each year. During the six months when the sun is above the horizon at the poles, the sun spends the days constantly moving around the horizon, reaching its highest circuit of the sky at the summer solstice.

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. Even the northern extremities of Scotland (and those places on similar latitudes) experience a permanent "dusk" or glare in the northern skies at these times.

Time zones and daylight saving time

For purposes of this article, the term "midnight sun" refers to the phenomena of 24 consecutive hours of sunlight north of the Arctic Circle or south of the Antarctic Circle. There are, however, some instances which are sometimes referred to as "midnight sun", even though they are in reality due to meandering time zones and the observation of daylight saving time. For instance, in Fairbanks, Alaska, which is located south of the Arctic Circle, the sun sets at 12:47 a.m. on the Summer Solstice. This is because Fairbanks is one hour ahead of its idealized time zone (due to meandering for the purpose of keeping most of the state on one time zone) and because the state of Alaska observes daylight saving time. This means that solar culmination occurs at roughly 2 p.m. instead of at 12 noon, as in most places. Conversely, astronomical midnight occurs at 2 a.m. In Bethel, which is further south than Anchorage, the sun sets on the Summer Solstice at 12:24 a.m. for the same reasons. These examples are not true midnight sun phenomena, however, since the sun is below the horizon on every day of the year at the local astronomical midnight.

White Nights

Locations above 60 degrees latitude that are south of the Arctic Circle or north of the Antarctic Circle experience midnight twilight instead. The sun is at the horizon to 6 degrees below the horizon, so that daytime activities, such as reading, are still possible without artificial light, on the condition it is not cloudy.

White Nights have become a common symbol of Saint Petersburg, Russia, where they occur from about 11 June to 2 July, and the last 10 days of June are celebrated with cultural events.

When to see the midnight sun

Map showing the dates of midnight sun at various latitudes (left) and the total number of nights.

According to Visit Norway the midnight sun is visible at the Arctic Circle from June 12 until July 1. The further north you get the longer this period extends.

At North Cape, Norway, known as the northernmost point of Continental Europe this period extends approximately from May 14 to July 29. On the Svalbard archipelago further north this period extends from April 20 to August 22

Effect on people

Many find it difficult to fall asleep during the night when the sun is shining. In general, visitors and newcomers are most affected. Some natives are also affected, but in general to a lesser degree. The effect of the midnight sun, that is, not experiencing night for long durations of time is said to cause hypomania, which is characterized by persistent and pervasive elevated or irritable mood.

The midnight sun also poses special challenges to religious people such as Jewish people who have religious rites based around the 24 hour day/night cycle. In the Jewish community this has given rise to a body of Jewish law in the polar regions, which attempts to deal with the special challenges of adhering to the Mitzvah in such conditions. Similarly, the midnight sun poses a challenge during Ramadan.

In fiction

• In the film Insomnia and its American remake, the protagonist suffers from insomnia partially brought on by midnight sun while investigating a murder north of the Arctic Circle (Norway in the original, and Alaska in the remake).
• In The Midnight Sun, an episode of The Twilight Zone, the Earth is on a collision course with the sun, causing a midnight sun effect.

See also

Wikimedia Commons has media related to: Midnight sun

• Eagle Summit, which experiences midnight sun despite being south of the Arctic Circle.
• Land of the Midnight Sun
• Polar night - The opposite phenomenon experienced in winter: A day without sunrise.

External links

• Visit Norway - Midnight Sun Page
• Midnight sun seen from Fjellheisen Tromsø - 360 panorama