The Antarctic Circle is one of the five major circles of latitude on Earth, located at approximately 66.5 degrees south of the equator. It marks the northernmost point where, during the summer solstice, the sun remains above the horizon for a full 24 hours. This phenomenon is known as the "midnight sun." In contrast, during the winter solstice, the Antarctic Circle experiences polar night, where the sun does not rise above the horizon for 24 hours. This circle encompasses the continent of Antarctica and surrounding ocean areas, playing a crucial role in Earth's climate and ecosystems.