Yöttömyysjaksojen

Yöttömyysjaksojen, often translated as "polar night," refers to periods in polar regions where the sun remains below the horizon for 24 consecutive hours or more. This phenomenon occurs during the winter months in the Arctic and Antarctic Circles. The duration of the yöttömyysjakso increases with latitude. At the Arctic Circle, for example, the polar night can last for just over 24 hours, while at the North Pole, it can last for approximately six months.

During yöttömyysjakso, daylight is absent, and the sky remains dark. However, this does not necessarily mean complete darkness. Twilight conditions, known as civil, nautical, or astronomical twilight, can still occur depending on the sun's position below the horizon. Civil twilight, the brightest form, provides enough light for many outdoor activities. In areas closer to the poles, even civil twilight may be absent, leading to prolonged periods of deep darkness.

The presence of snow and ice can reflect ambient light, such as moonlight and starlight, which can offer a degree of illumination. The aurora borealis and aurora australis, natural light displays caused by charged particles from the sun interacting with Earth's atmosphere, are also commonly visible during these dark periods, providing spectacular celestial shows. The ecological impact of yöttömyysjakso is significant, influencing animal behavior, plant life, and human activities in these regions.