Tropics, two parallels of latitude on the terrestrial globe lying equidistant from the equator from latitude 23°27' north to 23°27' south, the most northerly and southerly points on the earth's surface at which the sun is perpendicular at noon on at least one day of each year. Between these latitudes are all those points on the earth's surface over which the sun is almost directly overhead during the entire year. The tropic north of the equator is called the Tropic of Cancer, because the sun at the summer solstice (at which time it is vertically over the tropic) enters the constellation of Cancer; the southern one is, for a similar reason, called the Tropic of Capricorn. This belt of the earth's surface is known as the Torrid Zone. See Zone.