polar night
natural phenomenon when the night lasts for more than 24 hours, occuring only inside the polar circles
AI overview
A polar night is a natural phenomenon where the sun doesn't rise above the horizon for more than 24 hours, occurring only in regions inside the polar circles near the Arctic and Antarctic. This extended darkness matters because it significantly affects the environment, wildlife, and human life in these extreme regions, influencing everything from animal behavior to the daily routines of people living there.
AI-generated from the Wikipedia summary — may contain errors.
Article
Polar night is a phenomenon that occurs in the northernmost and southernmost regions of Earth when the Sun remains below the horizon for more than 24 hours. This only occurs inside the polar circles. The opposite phenomenon, polar day or midnight sun, occurs when the Sun remains above the horizon for more than 24 hours.
There are multiple ways to define twilight, the gradual transition to and from darkness when the Sun is below the horizon. "Civil" twilight occurs when the Sun is between 0 and 6 degrees below the horizon. Nearby planets like Venus and bright stars like Sirius are visible during this period. "Nautical" twilight continues until the Sun is 12 degrees below the horizon. During nautical twilight, the horizon is visible enough for navigation. "Astronomical" twilight continues until the Sun has sunk 18 degrees below the horizon. Beyond 18 degrees, refracted sunlight is no longer visible. True night is defined as the period when the sun is 18 or more degrees below either horizon.