What is "arctic circle"

1550s, in reference to a celestial circle, a line around the sky which, in any location, bounds the stars which \nare ever-visible from that latitude (in the Northern Hemisphere, this is focused on the celestial north pole); the concept goes back to the ancient Greeks, for whom this set of constellations included most prominently the two bears (arktoi), hence the name for the circle (see arctic). Of Earth, the circle 66 degrees 32 minutes north of the equator, marking the southern extremity of the polar day, it is recorded from 1620s.

n. (alternative spelling of Arctic Circle English)

Arctic Circle is one of the five major circles of latitude that mark maps of the Earth.

It may also refer to:

• Arctic Circle Restaurants, a chain of burger and shake restaurants based in Midvale, Utah, USA
• Arctic Circle Air, an American airline based in Fairbanks, Alaska, USA
• Arctic Circle Raceway, the biggest race track in Norway
• Arctic circle theorem in mathematics
• Arctic Circle (organization), an annual interdisciplinary conference related to Arctic issues based in Reykjavík, Iceland
• Arctic Circle Trail, a trekking tour in West Greenland

In the astronomy of the ancient Greeks, the "Arctic Circle" was an observer-dependent circle on the celestial sphere, centred on the northern celestial pole and tangential to the horizon, within which all the northern circumpolar stars lie.

The Arctic Circle is the most northerly of the five major circles of latitude that mark maps of the Earth. The region north of this circle is known as the Arctic, and the zone just to the south is called the Northern Temperate Zone. North of the Arctic Circle, the sun is above the horizon for twenty-four continuous hours at least once per year (and therefore visible at midnight) and below the horizon for twenty-four continuous hours at least once per year (and therefore not visible at noon); this is also true within the equivalent polar circle in the Southern Hemisphere, the Antarctic Circle.

The position of the Arctic Circle is not fixed; as of , it runs north of the Equator. Its latitude depends on the Earth's axial tilt, which fluctuates within a margin of 2° over a 40,000-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 per year.

The Arctic Circle is a nonprofit organization introduced by President Ólafur Ragnar Grímsson of Iceland on April 15, 2013, at the National Press Club in Washington. The organization's mission is to facilitate dialogue among political and business leaders, environmental experts, scientists, indigenous representatives, and other international stakeholders to address issues facing the Arctic as a result of climate change and melting sea ice. The organization is led by Ólafur, who serves as chairman of the honorary board, and by Alaska Dispatch publisher and Arctic Imperative Summit founder Alice Rogoff, who chairs the advisory board.