Figure 2.10
December solstice day length. Imagine you are standing at 66.5° south, on the Antarctic Circle. At that location, you will never cross the circle of illumination as Earth rotates, and the Sun will not set at your location. Now imagine standing at 41° south latitude. Here you will rotate into the night side of the planet, but you will be on the daylight side much longer than you are on the night side. Day length is 15 hours and night length is 9 hours. On the equator, day and night are equal. At 41° north latitude, day length becomes 9 hours and night length is 15 hours. At 66.5° north latitude, on the Arctic Circle, you will receive no direct sunlight because that location does not cross the circle of illumination into the lighted side of the globe as Earth rotates. Locations just north of the Arctic Circle experience twilight for several hours as the Sun approaches, but it does not rise above the horizon.