Midnight sun

The midnight sun is the Sun remaining above the horizon at local midnight for at least one day. It occurs during summer within the Arctic and Antarctic circles because Earth’s axial tilt keeps the Sun above the horizon.

Axial tilt: The angle between a body's rotational axis and the perpendicular to its orbital plane. Earth's tilt toward the Sun in summer keeps high-latitude regions illuminated overnight.
Svalbard: A Norwegian archipelago in the Arctic Ocean, north of mainland Europe. Its high latitude brings months when the Sun does not set.
Polar night: A period when the Sun remains below the horizon for at least 24 hours. It is the winter counterpart of the midnight sun, caused by the same axial tilt.
Circadian rhythm: An approximately 24-hour internal cycle regulating sleep, hormones, and other biological processes. Persistent summer light can weaken environmental cues that normally synchronize this cycle.
Arctic Circle: The southern boundary of the region where the Sun can remain above the horizon for 24 hours. North of this latitude, at least one day each year has a midnight sun.
Tromsø: A city in northern Norway located within the Arctic Circle. Its summer midnight sun is a prominent feature of local life and tourism.
Twilight: The interval when sunlight illuminates the sky while the Sun is below the horizon. Unlike the midnight sun, twilight can brighten the sky without the Sun being visible.
Melatonin: A hormone that helps regulate sleep timing and responds to light exposure. Bright nights can suppress its evening rise and make sleep timing more difficult.
Antarctic Circle: The northern boundary of the region where the Sun can remain above the horizon for 24 hours. South of this latitude, the phenomenon occurs during austral summer.
North Cape: A headland on the island of Magerøya in northern Norway, near the Arctic coast. It is a well-known destination for viewing the Sun at midnight.

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