Earth Ancients

What is the Solar Zenith Passage?Zenith is the highest point in the sky, directly overhead no matter where one stands.Solar zenith passage is the moment when the Sun passes through that very highest pointin the sky. Shadows cast directly down at that moment and a perfectly straight stickplanted in the ground, referred to as a gnomon, will cast no shadow at all. Conceptuallyzenith passage happens at noon, when the Sun crosses from the eastern to the westernhalf of the sky, but the actual moment varies slightly by how far off a time zone line onestands and by daylight savings hour changes. Take away the western notion of a clock,and zenith passage occurs during the noon-day sun. Zenith passage does not occur everywhere on Earth. In fact, it can only happen in thetropics. The tropics are defined by the longitudinal lines of the Tropics of Cancer andCapricorn, 23.5° N and 23.5° S respectively (Map 1). Above or below the tropics, thesun’s east to west daily passage occurs at such a steep angle that it can never cr