Glossary term: Polar circle

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Description: The polar circles are lines of latitude on the Earth. The polar circle at 66°33′48.8″ N is called the Arctic Circle and the polar circle at 66°33′48.8″ S is called the Antarctic Circle. Due the Earth's tilted rotation axis, regions north of the Arctic Circle and south of the Antarctic Circle experience "polar nights" during their winter and "polar days" during their summer. During a polar night the Sun is below the horizon for more than 24 hours and this period of darkness can last for months. During a polar day the Sun is above the horizon for more than 24 hours and daytime can last for months. Polar days and nights are longest closer to the poles. Polar nights happen before and after each polar region's winter solstice with polar days happening before and after the summer solstice.

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