Ancient structures were engineered to track a 26,000-year wobble in Earth's axis

Ancient architects designed structures with such precision that they could track the precession of the equinoxes, a 26,000-year wobble in Earth's axis. At the Mayan pyramid of El Castillo, the sun's alignment during the equinox creates a shadow that looks like a serpent descending the stairs. This occurs when the Earth's 23.5-degree tilt positions the sun directly above the equator, resulting in exactly 12 hours of light and darkness.