The shadow cast by a vertical rod at noon was the basis for defining zonation. The intersection of the northernmost or southernmost points of the ecliptic defined the axial circles passing through those points as the two tropics ("tropikoi kukloi", "circles at the turning points") later named for the zodiacal constellations found there, Cancer and Capricorn. During noon of the summer solstice (therinē tropē) rods there cast no shadow. The latitudes between the tropics were called the torrid zone ("diakekaumenē", "burned up").