The Arctic Circle is one of the two polar circles and the most northerly of the five major circles of latitude as shown on maps of Earth. It marks the northernmost point at which the centre of the noon sun is just visible on the December solstice and the southernmost point at which the centre of the midnight sun is just visible on the June solstice.The region north of this circle is known as the Arctic, and the zone just to the south is called the Northern Temperate Zone.
A polar circle is either the Arctic Circle or the Antarctic Circle. On Earth, the Arctic Circle is located at a latitude of 66°33′47.5″ N, and the Antarctic Circle is located at a latitude of 66°33′47.5″ S.
A circle of latitude on Earth is an abstract east–west circle connecting all locations around Earth at a given latitude.
A map is a symbolic depiction emphasizing relationships between elements of some space, such as objects, regions, or themes.
As seen from the Arctic, the Sun is above the horizon for 24 continuous hours at least once per year (and therefore visible at midnight) and below the horizon for 24 continuous hours at least once per year (and therefore not visible at noon). This is also true in the Antarctic region, south of the equivalent Antarctic Circle.
The Sun is the star at the center of the Solar System. It is a nearly perfect sphere of hot plasma, with internal convective motion that generates a magnetic field via a dynamo process. It is by far the most important source of energy for life on Earth. Its diameter is about 1.39 million kilometers, or 109 times that of Earth, and its mass is about 330,000 times that of Earth. It accounts for about 99.86% of the total mass of the Solar System. Roughly three quarters of the Sun's mass consists of hydrogen (~73%); the rest is mostly helium (~25%), with much smaller quantities of heavier elements, including oxygen, carbon, neon, and iron.
The horizon or skyline is the apparent line that separates earth from sky, the line that divides all visible directions into two categories: those that intersect the Earth's surface, and those that do not. The true horizon is actually a theoretical line, which can only be observed when it lies on the sea surface. At many locations, this line is obscured by land, trees, buildings, mountains, etc., and the resulting intersection of earth and sky is called the visible horizon. When looking at a sea from a shore, the part of the sea closest to the horizon is called the offing.
An hour is a unit of time conventionally reckoned as 1⁄24 of a day and scientifically reckoned as 3,599–3,601 seconds, depending on conditions.
The position of the Arctic Circle is not fixed; as of 6 April 2019, it runs 66°33′47.6″ north of the Equator. Its latitude depends on the Earth's axial tilt, which fluctuates within a margin of more than 2° over a 41,000-year period, due to tidal forces resulting from the orbit of the Moon. Consequently, the Arctic Circle is currently drifting northwards at a speed of about 15 metres (49 feet) per year.
An equator of a rotating spheroid is its zeroth circle of latitude (parallel). It is the imaginary line on the spheroid's surface, equidistant from its poles, dividing it into northern and southern hemispheres. In other words, it is the intersection of the spheroid's surface with the plane perpendicular to its axis of rotation and midway between its geographical poles.
In astronomy, axial tilt, also known as obliquity, is the angle between an object's rotational axis and its orbital axis, or, equivalently, the angle between its equatorial plane and orbital plane. It differs from orbital inclination.
In astronomy, axial precession is a gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis. In particular, it can refer to the gradual shift in the orientation of Earth's axis of rotation in a cycle of approximately 25,772 years. This is similar to the precession of a spinning-top, with the axis tracing out a pair of cones joined at their apices. The term "precession" typically refers only to this largest part of the motion; other changes in the alignment of Earth's axis—nutation and polar motion—are much smaller in magnitude.
The word arctic comes from the Greek word ἀρκτικός (arktikos: "near the Bear, northern")and that from the word ἄρκτος (arktos: "bear").
Greek is an independent branch of the Indo-European family of languages, native to Greece, Cyprus and other parts of the Eastern Mediterranean and the Black Sea. It has the longest documented history of any living Indo-European language, spanning more than 3000 years of written records. Its writing system has been the Greek alphabet for the major part of its history; other systems, such as Linear B and the Cypriot syllabary, were used previously. The alphabet arose from the Phoenician script and was in turn the basis of the Latin, Cyrillic, Armenian, Coptic, Gothic, and many other writing systems.
Ursa Major is a constellation in the northern sky, whose associated mythology likely dates back into prehistory. Its Latin name means "greater she-bear", standing as a reference to and in direct contrast with nearby Ursa Minor, the lesser bear. In antiquity, it was one of the original 48 constellations listed by Ptolemy, and is now the third largest constellation of the 88 modern constellations.
Bears are carnivoran mammals of the family Ursidae. They are classified as caniforms, or doglike carnivorans. Although only eight species of bears are extant, they are widespread, appearing in a wide variety of habitats throughout the Northern Hemisphere and partially in the Southern Hemisphere. Bears are found on the continents of North America, South America, Europe, and Asia. Common characteristics of modern bears include large bodies with stocky legs, long snouts, small rounded ears, shaggy hair, plantigrade paws with five nonretractile claws, and short tails.
The Arctic Circle is the southernmost latitude in the Northern Hemisphere at which the centre of the sun can remain continuously above or below the horizon for twenty-four hours; as a result, at least once each year at any location within the Arctic Circle the sun is visible at local midnight, and at least once the centre is not visible at local noon.
The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's North Pole.
The midnight sun is a natural phenomenon that occurs in the summer months in places north of the Arctic Circle or south of the Antarctic Circle, when the Sun remains visible at the local midnight.
The polar night occurs in the northernmost and southernmost regions of the Earth when the night lasts for more than 24 hours. This occurs only inside the polar circles. The opposite phenomenon, the polar day, or midnight sun, occurs when the Sun stays above the horizon for more than 24 hours. "Night" is understood as the center of the Sun being below a free horizon. Since the atmosphere bends the rays of the Sun, the polar day is longer than the polar night, and the area that is affected by polar night is somewhat smaller than the area of midnight sun. The polar circle is located at a latitude between these two areas, at the latitude of approximately 66.5 degrees. In the northernmost city of Sweden, Kiruna, at 67°51'N, the polar night lasts for around 28 twenty-four-hour periods, while the midnight sun lasts around 50 twenty-four-hour periods. While it is day in the Arctic Circle, it is night in the Antarctic Circle, and vice versa.
Directly on the Arctic Circle these events occur, in principle, exactly once per year: at the June and December solstices, respectively. However, because of atmospheric refraction and mirages, and also because the sun appears as a disk and not a point, part of the midnight sun may be seen on the night of the northern summer solstice up to about 50 minutes (′) (90 km (56 mi)) south of the Arctic Circle; similarly, on the day of the northern winter solstice, part of the sun may be seen up to about 50′ north of the Arctic Circle. That is true at sea level; those limits increase with elevation above sea level, although in mountainous regions there is often no direct view of the true horizon.
The June solstice, is the solstice on the Earth that occurs each June falling on the 20th to 22nd according to the Gregorian calendar. In the Northern Hemisphere, the June solstice is the summer solstice, whilst in the Southern Hemisphere it is the winter solstice. It is also known as the northern solstice.
The December solstice, is the solstice that occurs each December – typically on Dec 21, and can vary ± 1 day according to the Gregorian calendar. In the Northern Hemisphere, the December solstice is the winter solstice, whilst in the Southern Hemisphere it is the summer solstice. It is also known as the southern solstice.
A solstice is an event occurring when the Sun appears to reach its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. Two solstices occur annually, around June 21 and December 21. The seasons of the year are determined by reference to both the solstices and the equinoxes.
Only four million people live north of the Arctic Circle due to the severe climate; nonetheless, some areas have been settled for thousands of years by indigenous peoples, who today make up 10% of the region's population.Tens of thousands of years ago, waves of people migrated from eastern Siberia across the Bering Strait into North America to settle.
The largest communities north of the Arctic Circle are situated in Russia, Norway, and Sweden: Murmansk (population 295,374), Norilsk (178,018), Tromsø (75,638), Vorkuta (58,133), and Kiruna (16,936). Rovaniemi (62,667) in Finland is the largest settlement in the immediate vicinity of the Arctic Circle, lying 6 kilometres (4 miles) south of the line.
In contrast, the largest North American community north of the Arctic Circle, Sisimiut (Greenland), has approximately 5,000 inhabitants. Of the Canadian and American Arctic communities, Utqiagvik, Alaska is the largest settlement with about 4,000 inhabitants.
The Arctic Circle is roughly 16,000 kilometres (9,900 mi) long. The area north of the Circle is about 20,000,000 km2 (7,700,000 sq mi) and covers roughly 4% of Earth's surface.
The Arctic Circle passes through the Arctic Ocean, the Scandinavian Peninsula, North Asia, Northern America, and Greenland. The land within the Arctic Circle is divided among 8 countries: Norway, Sweden, Finland, Russia, the United States (Alaska), Canada (Yukon, Northwest Territories, and Nunavut), Denmark (Greenland), and Iceland (where it passes through the small offshore island of Grímsey).
The climate inside the Arctic Circle is generally cold, but the coastal areas of Norway have a generally mild climate as a result of the Gulf Stream, which makes the ports of northern Norway and northwest Russia ice-free all year long. In the interior, summers can be quite warm, while winters are extremely cold. For example, summer temperatures in Norilsk, Russia will sometimes reach as high as 30 °C (86 °F), while the winter temperatures frequently fall below −50 °C (−58 °F).
Starting at the prime meridian and heading eastwards, the Arctic Circle passes through:
In astronomy, declination is one of the two angles that locate a point on the celestial sphere in the equatorial coordinate system, the other being hour angle. Declination's angle is measured north or south of the celestial equator, along the hour circle passing through the point in question.
The Tropic of Cancer, which is also referred to as the Northern Tropic, is the most northerly circle of latitude on Earth at which the Sun can be directly overhead. This occurs on the June solstice, when the Northern Hemisphere is tilted toward the Sun to its maximum extent. It is currently 23°26′12.4″ (or 23.43679°) north of the Equator.
A circumpolar star is a star, as viewed from a given latitude on Earth, that never sets below the horizon due to its apparent proximity to one of the celestial poles. Circumpolar stars are therefore visible from said location toward the nearest pole for the entire night on every night of the year.
In observational astronomy, culmination is the instant of time of the transit of a celestial object across the observer's local meridian. During each day, every celestial object appears to move along a circular path on the celestial sphere due to the Earth's rotation creating two moments when it crosses the meridian. Except at the geographic poles, any celestial object passing through the meridian has an upper culmination, when it reaches its highest point above the horizon, and nearly twelve hours later, is followed by a lower culmination, when it reaches its lowest point. The time of culmination is often used to mean upper culmination.
Sunset, also known as sundown, is the daily disappearance of the Sun below the horizon due to Earth's rotation. As viewed from the Equator, the equinox Sun sets exactly due west in both spring and fall. As viewed from the middle latitudes, the local summer Sun sets to the northwest for the Northern Hemisphere, but to the southwest for the Southern Hemisphere.
The polar regions, also called the frigid zones, of Earth are the regions of the planet that surround its geographical poles, lying within the polar circles. These high latitudes are dominated by Earth's polar ice caps: the northern resting on the Arctic Ocean and the southern on the continent of Antarctica.
Twilight on Earth is the illumination of the lower atmosphere when the Sun itself is not directly visible because it is below the horizon. Twilight is produced by sunlight scattering in the upper atmosphere, illuminating the lower atmosphere so that Earth's surface is neither completely lit nor completely dark. The word twilight is also used to denote the periods of time when this illumination occurs.
The five main latitude regions of the Earth's surface comprise geographical zones, divided by the major circles of latitude. The differences between them relate to climate. They are as follows:
On Earth, daytime is roughly the period of the day during which any given point in the world experiences natural illumination from especially direct sunlight. Daytime occurs when the Sun appears above the local horizon, that is, anywhere on the globe's hemisphere facing the Sun. During daytime, an observer sees indirect sunlight while in the shade, which includes cloud cover. 'Day' is sometimes used instead of 'daytime', in this case 'day' will mean 'the period of light between dawn and nightfall; the interval from sunrise to sunset', which is synonymous with daytime. However, in this context, in order to be clear "daytime" should be used distinguish it from "day" which typically refers to a 24-hour period.
Sun path, sometimes also called day arc, refers to the daily and seasonal arc-like path that the Sun appears to follow across the sky as the Earth rotates and orbits the Sun. The Sun's path affects the length of daytime experienced and amount of daylight received along a certain latitude during a given season.
The 73rd parallel north is a circle of latitude that is 73 degrees north of the Earth's equatorial plane, in the Arctic. It crosses the Atlantic Ocean, Europe, Asia, the Arctic Ocean and North America.
The North American Arctic comprises the northern portions of Alaska (USA), Northern Canada and Greenland. Major bodies of water include the Arctic Ocean, Hudson Bay, the Gulf of Alaska and North Atlantic Ocean. The western limit is the Seward Peninsula and the Bering Strait. The southern limit is the Arctic Circle latitude of 66° 33’N, which is the approximate limit of the midnight sun and the polar night.
The Arctic Circle is one of the five major circles of latitude that mark maps of the Earth.
The Antarctic Circle is the most southerly of the five major circles of latitude that mark maps of the Earth. The region south of this circle is known as the Antarctic, and the zone immediately to the north is called the Southern Temperate Zone. South of the Antarctic Circle, the sun is above the horizon for 24 continuous hours at least once per year and the centre of the sun is below the horizon for 24 continuous hours at least once per year ; this is also true within the equivalent polar circle in the Northern Hemisphere, the Arctic Circle.
Tromsø is a city in Tromsø Municipality in Troms county, Norway. The city is the administrative centre of the municipality as well as the administrative centre of Troms county. The Diocese of Nord-Hålogaland is and its Bishop are based at the Tromsø Cathedral in the city. The city is located on the island of Tromsøya which sits in the Tromsøysundet strait, just off the mainland of Northern Norway. The mainland suburb of Tromsdalen is connected to the city centre on Tromsøya by the Tromsø Bridge and the Tromsøysund Tunnel. The suburb of Kvaløysletta on the island of Kvaløya is connected to the city centre by the Sandnessund Bridge.
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