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In April of 1066, a streak of cool fire appeared in the heavens. The comet, called a “bearded star” back then, had appeared before. There are mentions of it around the world dating as far back as the fifth century B.C. It’s now called Halley’s Comet, for the 18th-century scientist who first calculated its return. But in the spring of 1066, the people of England saw this particular comet as a bad omen.
Across the English Channel, Duke William of Normandy viewed the bearded star as a good sign. A few months later, William’s army invaded England and, on Oct. 14, 1066, defeated Harold’s forces at the Battle of Hastings. The Anglo-Saxon king Harold was killed, and on Dec. 25, William was crowned King of England. The course of history changed forever.
In late September 2024, a similar spectral object smeared across the night sky. For much of October, Americans went out at night to photograph that comet, called C/2023 A3 Tsuchinshan–ATLAS. It was discovered both by China’s Purple Mountain Observatory and by the Asteroid Terrestrial-impact Last Alert System in early 2023, but it became visible with unaided eyes only this fall. It gradually faded from view as the calendar turned toward November. Was the Atlas comet also an omen, signifying a change in political leadership?
The answer is no: Comet A3 Tsuchinshan-ATLAS was not a portent of the American presidential election’s outcome, despite some social media posts suggesting as much. (By the way, the box office success of Top Gun: Maverick, also claimed as an omen of the return of Donald Trump to the White House, was not connected either.) What’s interesting to me is why people try to make these connections at all.
Astronomy is the study of what actually happens in the universe, which for most of us is represented by the night sky we can see. Astrology aims to ascribe meaning to those objects and their doings and, while I can appreciate that astrology connects us to the cosmos, it is not a form of science. And yet—comets make us stop for a moment.
More than the phases of the Moon, more than Mercury in retrograde orbit, more than meteor showers or the zodiac signs, comets can bridge the divide between astronomy and astrology. They are unique enough, and unsettling enough, to fit within both approaches to skywatching.
The earliest written mythology, the Epic of Gilgamesh, tells a story of a shooting star and questions what it could mean. References to Halley’s Comet are found in Babylonian clay tablets more than 2,000 years old. In China, the Mawangdui Silk Texts, an almanac dated to 168 B.C., contains the oldest known illustrated comet catalog. Later, Christian monks in the Middle Ages believed comets were visiting stars that brought messages or heavenly omens. The Venerable Bede, an Anglo-Saxon monk who lived in the eighth century, is the one who described them as having hair or beards.
In the past, a comet’s arrival almost always heralded change of some kind. Often, they were things to fear, but some cultures saw them as motivational. William of Normandy was neither the first nor last king to plan an assault under a comet’s auspices. Even after scientists began to understand them in the 17th century, people remain awed and inspired by their recurrence.
In a purely scientific sense, comets do represent us. Comets are leftovers from the primordial solar system, and might provide clues to the chemistry and physical conditions that existed when the sun was a young star and Earth and the other rocky terrestrial planets were young worlds. Gravity flings comets from the depths of the Oort Cloud, where the sun’s light barely outshines any other star, toward the center of our solar system and then back out, their comings and goings enabling us to understand how other things—like asteroids—might come flying in our direction one day.
Some astronomers and planetary scientists think comets helped make us who we are. They contain copious amounts of ice, which vaporizes as the comets approach the sun. It’s possible that these snowy dustballs could have brought water to Earth’s oceans. Edmund Halley himself, the astronomer who predicted the return of the great comet of 1066, theorized that comets could have delivered enough water to create a great deluge, perhaps the one responsible for the Great Flood in so many creation myths. An 18th-century Presbyterian minister and scientist popularized this theory, though most astronomers now think it holds little water. Although many astronomers think asteroids have historically done more damage, a few theorize that a comet flattened a massive area of Russian forest in 1908, a catastrophe known as the Tunguska Event. And a popular theory, though dismissed by many scientists, holds that a comet could have contributed to the Younger Dryas, a cool period after the end of the last ice age, and may have helped wipe out megafauna like the woolly mammoth.
We are still making meaning out of comets’ arrival, in other words. The fact that we can predict them, and even land on them, does not diminish their mystery.
Halley’s Comet will be back in 2061, and those who are still here will be treated to a show much older than our species. Comet Atlas has been here before, too. Its last visitation was 80,000 years ago. That is before civilization as we know it, before the Younger Dryas, before even the oldest human cave art. Our species was here then, as hunters and gatherers who would have chased bison and mammoth while running from saber-tooth tigers. Our distant ancestors would have looked up and noticed the comet. Viewing it near the Moon or bright stars at sunset, they would have wondered at its sudden appearance, and why it later vanished. They might have imagined it as fire, maybe viewed it as a gift, or a warning of something terrible to come.
We don’t know what people thought before written history, but we know they thought something. We know they would have derived meaning from it. Today, the meaning we make from comets is scientific, but no less human.
Wondersky columnist Rebecca Boyle is the author of Our Moon: How Earth’s Celestial Companion Transformed the Planet, Guided Evolution, and Made Us Who We Are (January 2024, Random House).