Have you ever seen an equinox? On Monday, March 20, 2023, our planet—spinning on its tilted axis—will be side-on to the Sun. Instead of one hemisphere being bathed in more sunlight, the world will briefly be equal.
An equal night and equal day will occur for both hemispheres. It’s an equinox (equi is Latin for equal, nox for night).
It’s an occasion—along with September’s equinox and the solstices in June and December—that’s been marked by humans for thousands of years.
How did ancient people know when the equinoxes weres? Sunrise and sunset points change during the year. An annual pattern sees sunrise and sunset closer to the north while in winter those points are closer to the south. Only at an equinox does the Sun rises due east and set due west, which can have alarming effects. Before an equinox shadows move one way, but after it they can move another. The light changes across landscapes like a tide.
You can go watch alignments with sunrise on the equinox with your own eyes at some of the planet’s most famous and best-loved ancient monuments—and a few you’ve probably never heard of.
Here’s where to go to watch an alignment of Earth and the Sun at sunrise and/or sunset—and peer into ancient cultures that observed the night sky so much more carefully than we do today.
Angkor Wat, Cambodia
On the dates of the equinoxes in both March and September each year the Sun rises directly over the center-most of the five huge lotus towers that dominate the 12th-century temple complex in Cambodia. It projects a shadow that aligns exactly with the causeway/entrance bridge to the west. Visitors get the best effect if they stand on the causeway. Angkor Wat in its entirety is aligned west-east.
Chaco Canyon, New Mexico
In an isolated valley in northwestern New Mexico between Albuquerque and Farmington is Chaco Culture National Historical Park, which protects the architecture of an ancestral Puebloan culture dating back to about 850 A.D. Among a wealth of astronomical alignments, sunrise on the equinoxes causes sunlight to stream through niches at Casa Rinconada, the park’s most precious kiva (ceremonial chamber). The park also includes petroglyphs that some think represent a crescent Moon, a supernova and a solar eclipse.
The Sphinx and the Pyramids of Giza, Egypt
The most famous ancient Egyptian monuments, the pyramids, are aligned with the stars and the cardinal points. The famous Sphinx is perched to the east of the Great Pyramid of Khafre and watches the Sun rise each day. On the equinoxes, the rising Sun appears to sink into the shoulder of the half-man, half-lion and then into the pyramid’s side.
Chichén Itzá, Mexico
A popular destination for tourists in the Yucatan Peninsula, it’s possible to take equinox-themed tours at this Mayan archaeological site from around 1,000 AD. Its Pyramid of Kukulcán (also called El Castillo) is aligned with the cardinal points and at sunrise, on the equinoxes, seven triangular shadows that resemble a snake appear to move down the pyramid steps. This so-called “descent of the serpent” can be very popular.
Casa Grande, Arizona
A short drive southeast from Phoenix, Arizona is Casa Grande, the remains of an ancestral Sonoran Desert People’s farming community and what’s presumed to be the epicenter of a village. On the equinoxes, the rising Sun lines up with twin openings in the top floor of the Great House.
Palenque is a Maya city in southern Mexico that dates back to the 8th century. Sunlight fills its aptly-named Temple of the Sun on the date of the equinoxes, projecting a narrow shaft of light on the rear wall.
Wishing you clear skies and wide eyes.