The Sun's entering rays are perpendicular to the Tropic of Capricorn at 23.5 degrees south latitude during the northern hemisphere winter solstice. The sun's journey above the horizon is lowest north of the equator, and these areas get the shortest day of the year. South of the equator, the sun rises higher, and those regions experience longer days. The northern hemisphere summer solstice occurs when the Earth is at its farthest distance from the Sun in its orbit, which is also called "perihelion." At this time, the sun is highest in the sky at around 66 degrees north latitude. The southern hemisphere winter solstice happens when the Earth is closest to the Sun, which is called "aphelion." At this time, the sun is furthest from the horizon at around 44 degrees south latitude. The length of the day varies throughout the year because the Moon causes various tides to rise and fall. The average day is 12 hours long, but it can be as short as 10 hours or as long as 14 hours. During a lunar eclipse, the Earth's shadow falls on the moon. Because the shadow is dark, we see the moon tonight as if it were completely covered by earthshine—the light from the planet reflected back toward earth by the surface of the moon. Only certain parts of the moon are illuminated during a total lunar eclipse; the rest remains in darkness.