Polar Night

Definition

Polar night is a natural phenomenon that occurs in polar regions, where the sun remains below the horizon for an extended period, resulting in complete darkness throughout the day. This phenomenon is closely tied to the Earth's tilt and its revolution around the sun, which determines the seasons in different parts of the world.

5 Must Know Facts For Your Next Test

1. Polar night occurs in the regions located within the Arctic Circle (north of 66°34' N) and the Antarctic Circle (south of 66°34' S).
2. The duration of the polar night varies depending on the latitude, with the longest periods occurring at the geographic poles, where the sun remains below the horizon for up to six months.
3. During the polar night, the only source of natural light comes from the moon, stars, and occasional auroras, which can create a stunning display of natural light in the night sky.
4. The lack of sunlight during the polar night has significant impacts on the local ecosystem, including changes in animal behavior, plant growth, and the overall energy balance of the region.
5. Polar night is an important consideration for human activities in the high latitudes, such as transportation, infrastructure, and outdoor recreation, as it requires adaptations to the unique lighting conditions.

Review Questions

• Explain how the Earth's tilt and revolution around the sun contribute to the occurrence of polar night.
  • The Earth's tilt of approximately 23.5 degrees relative to the plane of its orbit around the sun, combined with its revolution around the sun, results in the varying amounts of sunlight received by different regions of the planet throughout the year. During the winter months in the polar regions, the Earth's tilt causes these areas to be tilted away from the sun, leading to the sun remaining below the horizon for an extended period and the phenomenon of polar night.
• Describe the impacts of polar night on the local ecosystem and human activities in the high latitudes.
  • The lack of sunlight during the polar night has significant impacts on the local ecosystem. This includes changes in animal behavior, such as hibernation or migration, as well as impacts on plant growth and the overall energy balance of the region. For human activities in the high latitudes, the polar night requires adaptations, such as reliance on artificial lighting, changes in transportation and infrastructure, and adjustments to outdoor recreation. The unique lighting conditions during the polar night present both challenges and opportunities for those living and working in these regions.
• Analyze the relationship between the duration of the polar night and the latitude of the location.
  • $$ The duration of the polar night is directly related to the latitude of the location. The closer a region is to the geographic poles, the longer the period of polar night. At the poles themselves, the sun remains below the horizon for up to six months, resulting in complete darkness for half the year. This is due to the Earth's tilt and the fact that the poles receive the most extreme angles of sunlight throughout the year. As one moves away from the poles, towards the Arctic or Antarctic Circles, the duration of the polar night decreases, with the minimum occurring at the Circles themselves, where the sun just grazes the horizon for a brief period.

Related terms

Solstice: The point in the year when the sun is at its greatest distance from the celestial equator, marking the beginning of winter (winter solstice) or summer (summer solstice) in the respective hemisphere.

Equinox: The two points in the year when the sun is directly above the Earth's equator, resulting in equal lengths of day and night (12 hours each) for all locations on the planet.

Circumpolar Stars: Stars that appear to rotate around the celestial poles and never set below the horizon, as observed from locations near the Earth's poles.