Polaripäivä

Polaripäivä, also known as the polar day or midnight sun, is an astronomical phenomenon that occurs in regions north of the Arctic Circle and south of the Antarctic Circle. During polaripäivä, the sun remains above the horizon for at least 24 consecutive hours. This means that during the polar day, the sun never sets, even at midnight.

The duration of polaripäivä varies depending on the latitude. The closer a location is to the poles, the longer the period of polaripäivä. At the Arctic Circle and Antarctic Circle themselves, polaripäivä lasts for one day each year, typically around the summer solstice. Further north or south, the phenomenon extends for weeks or even months. For example, at the North Pole, the sun remains above the horizon for approximately six months.

The opposite phenomenon is polar night, or yöhämärä, during which the sun remains below the horizon for at least 24 consecutive hours. Polaripäivä and polar night are a direct consequence of the Earth's axial tilt of approximately 23.5 degrees relative to its orbital plane around the sun. As the Earth orbits the sun, different parts of the planet are tilted towards or away from the sun, leading to these extreme variations in daylight hours at the polar regions.

The presence of polaripäivä has significant impacts on the local flora, fauna, and human activities. Many animals adapt their behavior to the continuous daylight, while vegetation experiences periods of intense growth. Human societies in these regions have also developed unique cultural practices and economic activities that take advantage of or adapt to the extended daylight hours.