Final answer:
The Arctic and Antarctic Circles mark the latitude where the sun does not set or rise for a full 24-hour period at least once a year. This results in the midnight Sun during summer and 24-hour night during winter, caused by Earth's axial tilt which affects sunlight exposure.
Step-by-step explanation:
The Arctic and Antarctic Circles mark the area where the sun is either above or below the horizon for at least 24 hours. These circles of latitude are significant because they represent the limits of the polar day and the polar night. The Arctic Circle is located at 66.5 degrees north latitude and the Antarctic Circle is at 66.5 degrees south latitude.
During the summer solstice, which occurs around June 21st, all places within the Arctic Circle experience at least one full day when the sun does not set, known as the midnight Sun. Conversely, during the winter solstice, around December 21st, these locations experience at least one full day when the sun does not rise above the horizon, resulting in a 24-hour period of darkness. The situation is reversed in the Antarctic Circle with the midnight Sun occurring during the Southern Hemisphere's summer and the 24-hour night during its winter.
The occurrence of these phenomena is primarily due to the tilt of the Earth's axis, which is approximately 23.5 degrees relative to the plane of the Earth's orbit around the sun. This tilt causes different parts of the Earth to receive varying amounts of sunlight throughout the year, leading to the changing seasons and the unique solar patterns at the poles.