Knowra Polar night Polar night Polar night is a period in polar regions when the Sun remains below the horizon for at least 24 hours. Earth’s axial tilt causes it, and its duration increases toward the poles.
Axial tilt : The angle between a rotating body's spin axis and the perpendicular to its orbital plane. Earth’s tilted axis directs each polar region away from the Sun during part of the year.
Longyearbyen : The largest settlement in Svalbard, Norway, at about 78° north latitude. Its high latitude brings several months each year without sunrise.
Twilight : The period when sunlight illuminates the sky while the Sun is below the horizon. Twilight can brighten the sky during polar night even when the Sun never rises.
Seasonal affective disorder : A recurrent mood disorder associated with seasonal changes, often involving depression during darker months. Reduced daylight during polar night can complicate seasonal mood and circadian rhythms.
Earth's orbit : The path Earth follows around the Sun, completing one revolution in about a year. As Earth travels around the Sun, the polar region experiencing continuous darkness shifts between hemispheres.
Tromsø : A city in northern Norway, located north of the Arctic Circle. Its winter polar night lasts for weeks, though twilight still brightens the midday sky.
Polar twilight : Twilight that occurs in polar regions while the Sun remains below the horizon. Its changing intensity divides the polar night into distinct stages of sky brightness.
Circadian rhythm : An internal biological cycle lasting about 24 hours that regulates processes such as sleep and hormone release. The absence of sunrise removes a major environmental cue for daily timing.
Arctic Circle : The parallel at about 66.5° north latitude, marking the southern limit of the Arctic polar day and night. North of this latitude, at least one day each year has no sunrise.
Utqiaġvik : A city on Alaska’s Arctic coast, formerly known as Barrow. Its location north of the Arctic Circle produces an extended winter period without sunrise.
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