Napulkulma

Napulkulma is a Finnish term that translates to "polar limit" or "polar circle." It refers to the northernmost and southernmost latitudes where the sun can remain continuously above or below the horizon for at least one 24-hour period. The Arctic Circle, located at approximately 66.5 degrees North latitude, is the most commonly known example of a napulkulma. Similarly, the Antarctic Circle exists at approximately 66.5 degrees South latitude.

The phenomenon of the midnight sun occurs north of the Arctic Circle during the summer solstice, when the sun does not set for a full day or longer. Conversely, the polar night occurs in the same region during the winter solstice, when the sun remains below the horizon for at least 24 hours. The exact latitude of the napulkulma shifts slightly over time due to the Earth's axial tilt variations. These regions are characterized by extreme variations in daylight hours throughout the year, significantly influencing their ecosystems and human activities.