Polar Night

Polar night is the phenomenon in which the sun stays below the horizon for more than 24 hours straight, the opposite of the midnight sun, and it occurs only inside the Arctic and Antarctic polar circles at roughly 66.5 degrees latitude. It results from the axial tilt of Earth: as the planet orbits the sun, one polar circle tips away from the sun while the other tips toward it, so polar night in the Arctic corresponds to continuous daylight in the Antarctic and vice versa. Its length grows with latitude, from about 24 hours right at the polar circles to roughly 179 days at the North Pole and 186 days at the South Pole.