In August, a total solar eclipse will traverse Ameica for the first time in nearly a century. So many tourists are expected to flood states along the eclipse’s path that authorities are concerned about illegal camping, wildfire risks and even devastating porta-potties shortages. There’s a reason for all this eclipse mania.
A total solar eclipse—when the moon passes between the sun and the Earth—is a stunning natural event. For a few breathtaking minutes, day turns to night; the skies darken; the air chills. Stars may even appear.
As awe-inspiring as an eclipse can be, it can also evoke a peculiar fear and unease. It doesn’t seem to matter that science has reassured us that eclipses present no real dangers (aside from looking straight into the sun, of course): When that familiar, fiery orb suddenly winks out, leaving you in an eerie mid-day darkness, apprehension begins to creep in.
So it’s perhaps not surprising that there’s a long history of cultures thinking of eclipses as omens that portend significant, usually bad happenings. The hair-raising sense that something is “off” during these natural events has inspired a wealth of myths and rituals intended to protect people from supposed evils.
At the same time, eclipse anxiety has also contributed to a deeper scientific understanding of the intricate workings of the universe—and even laid the foundation for modern astronomy.
The idea of eclipses as omens stems from a belief that the heavens and the Earth are intimately connected. An eclipse falls outside of the daily rhythms of the sky, which has long been seen as a sign that the universe is swinging out of balance. “When anything extraordinary happens in nature … it stimulates a discussion about instability in the universe,” says astronomer and anthropologist Anthony Aveni, author of In the Shadow of the Moon: The Science, Magic, and Mystery of Solar Eclipses. Even the biblical story of Jesus connects Christ’s birth and death with celestial events: the first by the appearance of a star, the second by a solar eclipse.
Because eclipses were considered by ancient civilizations to be of such grave significance, it was of utmost importance to learn how to predict them accurately. That meant avidly monitoring the movements of the sun, moon and stars, keeping track of unusual celestial events and using them to craft and refine calendars. From these records, many groups—the Babylonians, the Greek, the Chinese, the Maya and others—began to tease out patterns that could be used to foretell when these events occurred.
The Babylonians were among the first to reliably predict when an eclipse would take place. By the eighth century B.C., Babylonian astronomers had a firm grasp of the pattern later dubbed the Saros cycle: a period of 6,585.3 days (18 years, 11 days, 8 hours) in which sets of eclipses repeat.
While the cycle applies to both lunar and solar eclipses, notes John Dvorak, author of the book Mask of the Sun: The Science, History and Forgotten Lore of Eclipses, it’s likely they could only reliably predict lunar eclipses, which are visible to half of the planet each time they occur. Solar eclipses, by contrast, cast a narrow shadow, making it much rarer to see the event multiple times at any one place.
Babylonians believed that an eclipse foretold the death of their ruler, leading them to use these predictions to put kingly protections in place. During the period of time that lunar or solar eclipses might strike, the king would be replaced with a substitute. This faux ruler would be dressed and fed like royalty—but only for a brief time. According to ancient Babylonian astronomers’ inscriptions on cuneiform tablets, “the man who was given as the king’s substitute shall die and … the bad omens will not affect that [ki]ng.”
The Babylonian predictions, though accurate, were all based purely on observations, says Dvorak; as far as scholars know, they never understood or sought to understand the mechanism behind planetary motions. “It was all done on the basis of cycles,” he says. It wasn’t until 1687, when Isaac Newton published the theory of universal gravitation—which drew heavily on insights from Greek astronomers—that scientists began to truly grasp the idea of planetary motion.