Polar night is a natural phenomenon in Earth’s polar regions, characterized by a continuous period of darkness where the sun remains below the horizon for over 24 hours. This extended absence of sunlight defines the winter months in these extreme latitudes. The experience ranges from a prolonged twilight to complete darkness, depending on the specific location and its proximity to the poles.
Understanding the Polar Night Phenomenon
Polar night is a direct consequence of Earth’s axial tilt as it orbits the sun. Our planet is tilted on its axis by approximately 23.5 degrees relative to its orbital plane. During the winter months, this tilt causes one of the poles to be continuously angled away from the sun. As a result, the sun’s rays do not reach that polar region, keeping it below the horizon for an extended duration.
The further one travels from the equator towards either pole, the more pronounced this effect becomes. While areas closer to the polar circles may experience some hours of twilight, those at higher latitudes endure longer periods of minimal or no direct sunlight. The varying degrees of darkness, from civil twilight to true polar night, are determined by how far the sun dips below the horizon.
Geographic Reach and Annual Timing
Polar night occurs exclusively within the polar circles: north of the Arctic Circle and south of the Antarctic Circle, both located at approximately 66.5 degrees latitude. The duration of continuous darkness varies significantly by latitude, from just over 24 hours at the edge of the polar circles to several months at the geographic poles.
In the Northern Hemisphere, polar night typically begins around the winter solstice (December 21st). At the North Pole, the sun sets in late September and does not rise until mid-March, resulting in approximately six months of darkness.
Further south, in Longyearbyen, Svalbard (78 degrees North), civil polar night lasts from November 14th to January 29th, totaling about 113 days. In Utqiagvik (formerly Barrow), Alaska (71.17 degrees North), the sun sets around November 18th and reappears around January 22nd or 23rd, leading to about 64 to 66 days of darkness. In the Southern Hemisphere, polar night occurs during its winter months, around the June solstice. The South Pole experiences about six months of darkness, from March 20th to September.
Life During Polar Night
Living through polar night presents distinct challenges and requires adaptation for both human and animal populations. Humans in these regions often experience disruptions to their circadian rhythms, leading to fatigue, altered sleep patterns, and a higher prevalence of seasonal affective disorder (SAD). The lack of natural light significantly impacts mood and energy levels. Additionally, the absence of sunlight prevents the skin’s natural production of vitamin D, making supplementation crucial for residents.
Communities adapt by maximizing artificial lighting, including light therapy lamps that mimic natural sunlight, to regulate internal clocks and mitigate mood disturbances. Indoor activities, strong social bonds, and cultural festivities become central to daily life, providing warmth and connection during the dark months. The darkness also offers unique opportunities, such as frequent sightings of the aurora borealis.
Wildlife in polar regions demonstrates remarkable adaptations to survive the prolonged darkness and cold. Animals like muskoxen and reindeer possess thick insulating coats that protect them from extreme temperatures. Reindeer’s eyes change color during winter, increasing their sensitivity to limited light, including ultraviolet reflections from snow and ice. Some marine animals, like zooplankton, may alter their behavior and respond to moonlight. Emperor penguins in Antarctica endure polar night by relying on stored fat reserves and navigating the dark waters.