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Comets of DOOM

24 Jun


Full original text for Comets of DOOM video:

[I just saw Halley’s Comet she waved…]

Listen Brent, you didn’t see Halley’s Comet. Not in 2007. Be reasonable. It was Comet McNaught.

So I’m doing the Outer Solar System this month, but I’m working my way inward. Why am I starting with the Solar System? Cuz I been gone a while, and it’s easy.

And I’m working my way in because most people start at the Sun and then taper off by the time they hit Uranus and Neptune and the Kuiper Belt. Quite frankly, if anything needs to get the tired, sad, ‘I’m so over this topic’ treatment, it’s Mercury, not Neptune. So yeah.

What’s in the Outermost of the Outer Solar System?


Comets Are Unpredictable Because They Live Far Away and Visit Rarely

First of all, the Solar System is way bigger than most people imagine.

It’s bigger because we have this cloud of comets surrounding us, now called the ‘Oort Cloud’. That extends way out there.

The Oort Cloud almost definitely has more than a trillion comets in it, and it takes up an enormous amount of space. It starts at around 2000 Astronomical Units away and may stretch as far as 100,000 AU.

A lot of people still think of Pluto as being the end of the Solar System, but the Oort Cloud’s outer edge, that outer cometary edge, is about 2000 times farther away than Pluto is from us. Put that in perspective; if you lived in a tiny town, a town one mile wide by one mile wide in the middle of the continental US, and imagined that the Solar System we always hear about was in that town, everything up to and including Pluto, the Oort Cloud would be miles into the pacific ocean one way, the Atlantic Ocean the other way, in Canada, and Mexico.

My point is, it’s way out there. That’s the real end of the Solar System. The place where comets live.

Comets do come into the Inner Solar System from time to time, but it’s fairly rare. In fact, the setup of the Oort Cloud is what makes comets so… well… scary.

Comets, even today, aren’t super predictable. Even the ones that return, return with large margins of error, and often even look different from previous visitations – 1986 Comet Halley was no 1066 Comet Halley.

And it’s kind of hard to explain how upsetting it is to see something in the night sky that shouldn’t be there, because we’re all sort of used to it now. First of all, thanks to humans lighting up the night sky in perpetuity these days, very few Americans can even see the Milky Way from where they live. If you watch the night sky tonight, you’re likely to see far more planes than stars. We’re used to things moving up there.

But if you went back 100 years ago, even 50 years ago in most regions, you would see the same sky, every year, on the same day, forever.

And sure the sky moves, but it doesn’t really change – at least not on human timescales. Orion is always chasing Taurus and being followed by Canis Major. They move, but they never move in relation to each other. Orion will never show up in the night sky next to Scorpius. He can’t. He’s stuck chasing a bull and stepping on a bunny for a long time.

The Sky Is Remarkably Predictable – But Comets Aren’t

99% of what you see in the sky has a very regular pattern. Sure, planets move in relation to the background stars, but they move in predictable patterns. For example, Mars is really bright pretty much every two years. Every other year you’re going to get a bright red Mars in the night sky. And every other year, you’ll get a dim dumb Mars. Sure, it’s moving and changing way more than any given star, but it moves and changes in predictable ways.

Most of the night sky is like that. Now meteors and meteor showers can be shocking, but a meteor streaks across the sky for a second to a handful of seconds. And also, meteor shower intensity varies from year to year, for example, the Leonids peak about every 30 years so 2018 Leonids was no 2008 Leonids and 2008 Leonids was no 1833 Leonids, I’m just sayin. But they occur at roughly the same time every year (November) because meteor showers have to do with the position of the Earth in its orbit, and we orbit our star in a regular and predictable pattern.

Contrast this with comets. Comets will stay in the sky for days or weeks. They hang there like bright, ominous, tailed stars. They don’t really have a pattern. Mostly they just show up from time to time.

And that is shocking if you are used to seeing the night sky. Now I haven’t seen any bright comets. I’m up to PanSTARRS, Lovejoy, and Wirrtanen. None of them are stopping traffic.

But imagine you’re living a couple thousand years ago. You don’t what the Sun is, you don’t know what stars are, but you are aware of the heavens, how they look, and how they move. There’s no television, and you work outside a lot. And then a comet shows up. Even if comets are in the astronomical record of where you’re living, they are random, and surprising.

Cometary thought, at least, the cometary thought that’s been written down and preserved, often framed comets as omens.

And there is simply no way to talk about oldschool cometary theory without talking about superstition, astrology, religion, and doom.

So let’s talk about it.

I Don’t Give a Damn About My Bad Reputation

Pretty much the earliest undeniable records of comets come from China, because of course they do. Specifically, they come from the Silk Book from China, dated to around 170 BC.

This is not the oldest record of comets, but it is the oldest illustration with written descriptions that we have of comets. And those descriptions by the way, are all predictive. That is, they tell us what the result of the comet will be. Some of them are really unspecific, like 1 means war is coming, and generals will die. But number 2 signals a 5-day rebellion, and number 22 signals 3 small battles, and 7 large battles. That’s… really specific. Now, not all the comets are bad, but most of them are bad. You got war, death, disease, grief, war, famine, more war, good crops but internal war, battles in specific places, and oh yeah, more war. I’m sensing a pattern…

And the length of the comet tail was supposed to indicate the severity of the doom.

Now, these doomy predictions aside, the most complete and specific ancient records we have of comets all come from Chinese historical documents. Because they didn’t just say, ‘oh a comet appeared last year’, they wrote, here was this comet in this exact spot and this is how big it was and this how long it lasted and these are constellations it moved through and this was the direction it was traveling. That’s why historians can now say, ‘oh look at that, Halley’s comet was first seen in China and we’re pretty darn sure it was Halley’s Comet.

Also, for any book (and I’ve seen a few) that says Peter Apian was the first to point out that comet tails always point away from the Sun… no.

Around AD 635 the History of the Chin Dynasty was written and Li Chung-feng recorded that comet tails always point away from the Sun. This is the first known account of the antisolar nature of comet tails. Which is getting WAY too close to science.

So back to DOOOOOM.

Looking at that Silk Book from China, this was during a time when the Greeks and the Chinese didn’t have a working relationship, that we know of, so the idea that comets were bad, was arrived at most likely, independently.

Every society on the planet has done astronomy, and it turns out that comets were typically thought of as bad pretty much all over the world.

Many diverse bands of native Australians viewed comets as bad. For example, the Tanganekald of South Australia perceived comets as omens of sickness and death. The Kaurna of Adelaide appear to have associated comets with a pair of evil sisters, the Gundidjmara of Victoria saw comets as omens of death, and the Euahlayi of New South Wales saw comets possibly as terrestrial phenomenon that could take the rain out of clouds and cause drought, a not-terribly uncommon theory the world over. Comets causing drought was a weirdly common belief.

Comets as omens was pretty popular, but comets weren’t seen as bad always and everywhere. For example, in India, some groups of people such as the Banjara and Kolam thought of comets as predictive, sure, but not always a bad omen. Could be a good or bad omen. Could go either way. But other groups in India, notably the Gond people, saw comets as an actively good sign that the bad things humans had done was going to be swept away. So comets in this case, didn’t predict good things to come, but acted more like a redemptive or neutralizing force.

So comets aren’t bad always and everywhere to everyone, but more often than not in cultures very far away from each other, they were seen as omens, typically of bad things.

And for the Greeks, that was definitely the case.

Even in really old sources, comets are bad. For example, Homer, in the Illiad, wrote on the helmet of Achilles: “Like the red star, that from his flaming hair [comet = hairy star in Greek] shakes down diseases, pestilence and war…”

Aristotle had issues with comets too, but it’s really later sources that solidified the astrological consequences of comets. Let’s talk about Pliny the Elder. This guy decided to “give a description of everything that is known to exist on Earth.” Oh is that all? His work, Natural History, takes up 37 volumes and covers tens of thousands of topics. Basically, this guy wanted to be Encyclopedia Britannica. He wrote that comets had 10 types. We have… Pogonias, a comet with a beard hanging from its lower part, Xiphias; pointy like a dagger, Lampadias, appearing as a burning torch, you get it. Like the Silk Book, the varieties of comets are all based on how they appear in the sky.

And Pliny did dedicate too much space to the disasters that these comets foretold. And his Natural History was influential. Unfortunately, Pliny couldn’t read the signs of his own very avoidable death.

Pliny was killed by Mount Vesuvius, not because he lived in Pompeii but because he sailed over to see what all the hubbub was about. Either that or he had a heart attack on the way. It’s unclear, but it does seem that he was an unnecessary casualty of Vesuvius. Kids these days, and their Fear Of Missing Out.

Pliny didn’t help the cause of comets, but the cometary fear that later infested Europe can be traced back, not to Pliny, but to Claudius Ptolemy – kind of. Ptolemy lived from about 100-170 A.D. and was extremely influential on astronomy well into the 1500s. He’s best known for The Almagest, which was way more popular than anything Carl Sagan, Stephen Hawking, or Neil DeGrasse Tyson ever wrote. Basically, the dude was influential. Ptolemy also wrote The Tetrabiblos, in which he talked about comets and defended astrology’s relationship to them. Here’s where things get fuzzy. He was credited with writing The Centiloquium which were 100 specific rules predicting disasters associated with comets. Rules such as: “If the comet’s direction moves west to east, a foreign foe will invade the country” and “If the comet remains stationary, then the foe is domestic.” Here’s the rub; Ptolemy probably didn’t write The Centiloquium. Modern historians do not believe The Centiloquium was actually Ptolemy’s. In short it’s a fake. While The Centiloquium often appeared with The Tetrabiblos, the first time it appears is about 700 years after Ptolemy had died. Could it have been a hidden work for all those years? Yeah sure, but come on, if you were trying to sell an original Ptolemy to some king, with new and original texts on comets, maybe you’d make up a list of 100 astrological rules for comets and tack it onto the very famous Tetrabiblos too. A person’s gotta make money. In any case, “Ptolemy’s” astrological rules for comets became extremely influential in the Middle Ages. And guess what? Comets? They’re bad.

The Middle Ages

So now we get to the real crazy stuff.

There was this general period after the Romans but before 1608 that people generally look at as… kinda bad. There’s a lot of reasons the Middle Ages weren’t a time travelers dream destination, but one of them was that Europeans got really religious and real serious about tying pretty much everything back to God.

For example, the idea that the Star of Bethlehem was in fact, a comet, is not a new idea. Origen of Alexandria [185-254] suggested the Star of Bethlehem was a comet, but that it portended the ‘commencement of new dynasties’. The new star was not a sign of peace, but the establishment of Christian dynasty. In fact, you can find an unnerving number of after-the-fact illustrations of a comet hovering over the Siege of Jerusalem, which occurred in 70 AD. Often, the comet looks exactly like a sword. In this case, the comet wasn’t seen as good or peaceful, it was still an omen of doom – just someone else’s doom.

Religious philosophers (so like, everyone with an opinion at the time) went back and forth on whether comets were brought in by God or the devil or they were causes of sin or the consequence of sin, but one thing they seemed to agree on was that they weren’t good.

Bede the Venerable of Yarrow (673-735) “stated that comets portend changes of rule, pestilence, wars, winds, or heat.”

Thomas Aquinas (1225-1274) did nothing to assuage the considerable fear of comets but wrote that they were among the 15 signs preceding the Lord’s coming to judgment. Also Aquinas was extremely responsible for almost deifying Aristotle, and making his views the views of the church. So if you love Aristotle as much as first-year philosophy student, you can thank Thomas Aquinas for your misplaced adoration.

But you know, it was the 1200s. What do you expect? Well, let’s jump forward a bit.

Ah, here we go. 1493. The Nuremberg Chronicle:

“A great comet appeared in the month of January 1472. It was flame-colored and had a black tail. It proceeded westward but veered to the north. It was seen for eighty days, and before it vanished, another comet with a fiery tail appeared, proceeding eastward. Then followed an unprecedented drought; and later the plague broke out in a number of places, and there arose many dissensions, revolts and cruel wars.”

So comets bad.

Martin Luther (1483-1546) went even further and said that comets are harlot stars. He is quoted as saying: “The heathen write that the comet may arise from natural causes, but God creates not one that does not foretoken a sure calamity.” So we’re now up to, God is throwing comets at us. Great.

The “Enlightenment”

Even the “scientists” thought comets were doom-riddled:

Roger Bacon (1214-1294) observed a comet in 1264 appear in Cancer and move toward Mars, which he went on to proclaim “presaged discord and wars” (Yeoman).

Michael Mastlin believed the origin of comets was a mystery known only to God, but once created they were indeed celestial phenomena. However, he believed that the comet of 1577, though celestial, was still a portent of doom and proclaimed that it would bring peace, but a peace purchased only by a bloody victory (Yeoman).

Though Tycho Brahe studied the 1577 comet and made accurate (for the time) predictions about its distance to Earth, he also spent half of his treatise on the astrology of the comet. Basing his predictions on the position and color of the comet, Tycho concluded that it would bring death. A lot of death (Yeoman).

Kepler thought that when a comet was created a special spirit formed to guide it. The comet and spirit were created together and they dissipated together. He also took the ‘comet of doom’ farther than astrological significance which, of course, he had. He said that if Earth came into contact with the tail the atmosphere would become impure and a ton of people would die. In Kepler’s 1619 essay De Cometis Libelli Tres, he not only talked about the physical nature of comets, on which he said a bunch of wrong things, but also talked about their astrological significance which, of course, spelled doom, including: horror, long lasting rans, floods, universal epidemics, headaches, dissiness, catarrh (phlegm), and pestilence. So doom. Yeah. Doom. Kepler was on the Comet = DOOM train.

While comets may not explicitly appear in the Bible, in 1st Chronicles 21:16 we find: “And David lifted up his eyes, and saw the angel of the Lord stand between the earth and the heaven, having a drawn sword in his hand stretched out over Jerusalem.” (KJV). Later, the Jewish historian Flavius Josephus the destruction of Jerusalem in 70 AD and mentions “a star, resembling a sword stood over the city, and a comet which continued for a year.” (Schechner).

When God kicks Adam and Eve out of the Garden of Eden he places a “flaming sword” to guard their way back in. In the poem La Seconde Sepmaine, ou Enfance du Monde (1584) Du Bartas writes:

“Of our first Parents, our of Eden driven

(of repeal hopeless) by the hand of Heaven;

For the Almighty set before the door

Of the holy Park, a Seraphin that bore

A waving sword, whose body shined bright,

Like flaming Comet in the midst of night.”

In John Milton’s Paradis Lost (1667) he says:

The brandished Sword of God before them blazed,

Fierce as a Comet; which with torrid heat…”

Milton also likens comets to Satan in Paradise Lost when he says:

” Incensed with indignation, Satan stood
Unterrified, and like a comet burned,
That fires the length of Ophiuchus huge
In the arctic sky, and from his horrid hair
Shakes pestilence and war.”

You get the picture. Comets are bad.

Now, you might be thinking, ‘yeah sure but Maestlin and Brahe and Kepler… that was at the beginning of the scientific revolution. People needed time to let go of their astrological fear of comets. Surely, by the late 1600s cometary fears were mostly gone.’ And if that’s a thought you had, all I got is, ‘oh honey, people killed themselves in 1997 to get to Comet Hale-Bopp. Stop having faith in humanity.’

Maybe, maybe comets could have shaken their bad reputation with the advent of the scientific revolution. But then two great comets came in 1664 and 1665.

And so did the plague.

It’s at least possible the two comets of 1664 and 1665 and the subsequent chronology of the Black Plague and the Great London Fire had something to do with re-popularizing the comet of doom ideas. And they were popular.

In this case, that comets were bringers of doom, made sense. In 1664, for example, a comet appeared. In 1665, 1 in every 5 people in London died of the plague. Oh yeah, and then a year after that London basically burned down. Even Daniel Defoe of Lost in Space fame, I mean Swiss Family Robinson, I mean Robinson Crusoe, I mean The Martian, wrote about the comet moving across the sky, that it “portended a heavy judgment, slow but severe, terrible and frightful, as the plague.”

So comets couldn’t shake their bad reputation, and they couldn’t shake astrology. But… it’s important to note that the astrologers were still very wrong. For example, John Gadbury, astrologer, wrote a treatise called De cometis (they’re all called that) in 1665 in which he laid out the zodiac and said that if a comet arose in one sign, it would bring about certain events. For example, a comet arising in Aries denotes diseases of the head and eyes, a comet in Taurus portends sickness, A comet in Gemini portends grievous diseases for children, etc. Here’s the thing… There were comets in 1664 and 1665. And that year the plague hit London hard. From May to December 1665 almost 90,000 people died or about 1 in 5 Londoners. Of Gadbury’s 12 zodiac signs, only a few have no pestilence, death, or disease. But, comets arising in Virgo and Capricorn portended scandals and fornication respectively. Guess which zodiacal signs the two comets appeared in. Yeah. If Gadbury’s astrology had been correct, London should have been in the midst of the roaring 20s. Instead, everyone was losing their skin.

By the time we get to the next great comet, the comet of 1680, well, of the 62 known broadsides that were written on the comet of 1680, 15 years after the previous two comets of doom, almost all of them were bad. Only 2 of the 62 broadsides ring of anything other than astrological death and destruction. (Schechner)

Eventually the learned men of science let astrology go. Not as soon as they should have. But it went. But did they give up the doom?

Not a chance.

Even Edmond Halley, of Halley’s Comet fame, fell victim to the doom train. And this was the late 1600s, ok? The Dutch were figuring out early engines, a woman was co-running England, the Americans were burning witches… ok it wasn’t all progressive, and what did Edmond Halley think about comets? Well, on top of making some very nice observations, he also went in front of the Royal Society and… blamed them for causing the Biblical Noah’s Flood in 1694.


Two years after Halley’s proposed cometary deluge, William Whiston, in a book published in 1696 took Halley’s suggestion a step further and said that the comet caused a tidal break in Earth’s surface allowing subterranean waters to rise up and start the deluge, Noah’s Flood. He also predicted the end of the world via comet saying that a comet would come in and alter Earth’s orbit and fling it into the Sun. And when is this end of the world? 2255. Oh man, but that’s before humans get a chance to go back in time to save the whales. [Star Trek Voyage Home] We are so screwed.

And if you haven’t heard of Whiston, you have heard of his job. He replaced Isaac Newton as the Lucasian Professor of Mathematics at the University of Cambridge.


Ok, so it’s hard to get away from the comets of doom theories, but…

Are there any good comets?

One notable exception was Seneca [circa 4 BC – 65 AD], who said that Emperor Nero “redeemed comets of their bad reputation.” Before taking that at face value, bear in mind that Seneca had a super interesting life and may not have been serious. First, he was condemned to death by the Roman emperor Caligula but Caligula died, and Valeria Messalina, the empress of the next Roman emperor, Claudius, arranged for Seneca instead to simply be exiled to Corsica. Messalina was later murdered by Tiberius Narcissus a high ranking courtier with Claudius. So now Claudius needs a new wife. Narcissus suggested Claudius remarry his second wife, Aelia Paetina, but Claudius is like ‘I’m getting someone new’ and marries Agrippina the Younger (who was also his niece because this story was apparently written by George RR Martin). Agrippina gets in bed with her uncle/husband, makes a kid, emperor Nero perhaps you’ve heard of him and then she murders her husband, executes Narcissus, and installs her child as the next emperor. In hindsight, Narcissus shoulda probably not killed Messalina. Just sayin. Good ol hindsight.

What does this have to do with Seneca? Well, Agrippina brings Seneca back from banishment to teach her boy, the young Emperor Nero.

Guess who kills Seneca in the end? Yeah, it was Nero. Because the Romans were f-ing nuts.

Around AD 63 Seneca wrote Natural Questions in which he wrote about two comets that appeared during the reign of Nero Ceasar, which he wrote “saw the joyous reign of Nero” and “redeemed comets from their bad character”. To be fair, Seneca could have been trying to save his own life, or making a joke – sarcasm was invented before the Internet I promise – but less than two years later Nero ordered him to commit suicide anyway. And uh… he did.

So, one vote for comets being good from a man who was probably trying to avoid death by saying they were good. It’s not the best track record.

Comets of Doom meet Science of Doom

You might expect that the scariest comet of all time would occur in ancient Rome or the middle ages, but probably the best candidate for ‘scariest comet of doom’ was Halley’s Comet in 1910. Paradoxically, it was the advancement of the scientific method that lead to its ultimate position on the doom charts.

By 1910 scientists around the world generally understood that comets weren’t dangerous, but widespread public opinion hadn’t caught up. Also spectroscopy, a way to determine what elements or molecules a distant object possesses by essentially splitting light, was becoming the biggest tool in astronomy at the turn of the century, and scientists found out that good old Halley’s comet had toxic cyanogen gas in its tail. You know, like cyanide. So this combination of legitimate scientific eyebrow raising at the comet’s tail, and people’s long held suspicion of comets as bringers of doom meant that Halley 1910 was feared, almost worldwide.

Newspaper reports from China suggested that people were afraid they would be killed and that the comet might poison the water. In Croatia, France, and Austria-Hungary people sold their possessions in preparation for a short but happy rest of their lives. In Malta there was a successful press campaign to reassure the public that the comet wouldn’t harm them, but in Rome Pope Pius X had to denounce the hoarding of oxygen cylinders. And there were people that bought (and sold) anti-comet-tail pills. Similar stories come out of the United States, Russia, and England – which is understandable since King Edward VII did in fact die about a month before Halley reached naked eye visibility. (It couldn’t have been his almost constant smoking. It was the comet.)

Halley’s Comet 1910 was probably, hopefully, the last real vestige of belief in comets as harbingers of doom.

Join me next time for a tour of comet experts everywhere asking: But what even are comets, really?



Comets: A Chronological History of Observation, Science, Myth, and Folklore by Donald K. Yeomans (1991)

Comets, Popular Culture, and the Birth of Modern Cosmology by Sara Schechner (1999)

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Links and things:

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