Equinox Alignments

Around September 23rd and March 20th each year, visitors gather at ancient monuments to witness the equinox. On these two days, day and night are equal everywhere on the planet. The sun rises exactly in the east and sets exactly in the west. Ancient architects, astronomers, and priests collaborated to align many structures with the equinox sun to create spectacular light effects. In a 5,000-year-old underground Celtic temple, the rising sun penetrates a long shaft to light an engraved wall. At a 4,000-year-old Egyptian monument, sunlight travels an east–west hallway to illuminate chosen statues. A thousand-year-old Mayan pyramid casts a shadow in the form of a snake down its entire face, which joins a giant carved serpent head. There are equinox sun alignments at Stonehenge, Machu Picchu, Angkor Wat, and many other ancient places, across nearly every culture. They created these solar light shows to determine and celebrate the autumn equinox—the start of the harvest and shortening days—and the spring equinox—the start of the planting season and a ceremonial time of rebirth. Religious holidays, like Easter, were set according to the equinox and still are. You may not have to travel far to see your own equinox sun alignment. In big cities with exact east–west street grids, the equinox sun rises and sets precisely at the ends of a canyon of skyscrapers. In Chicago, they call it Chicagohenge.