There are all sorts of cyclical events that ancient peoples are thought to be interested in, solstices, lunar cycles and eclipses. What rarely seems to get attention are meteor showers. It might seem odd, they’re annual, happening at the same point in the Earth’s orbit. They can also be spectacular. So why don’t they get much attention from archaeoastronomers? There are probably a couple of reasons.
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Meteor and Pleiades. Photo: Luis Argerich / Flickr.
One is that there’s not a lot of clear historical evidence that meteor showers were predictable in the ancient world. The ancient certainly saw meteor showers, one of my favourites is Plutarch writing on pleasure:
…[P]leasures, like gales of soft wind, move simpering, one towards one extreme of the body and another towards another, and then go off in a vapor. Nor are they of any long durance, but, as so many glancing meteors, they are no sooner kindled in the body than they are quenched by it.
Plutarch — Non posse suaviter vivi secundum Epicurum
It’s clear that whoever wrote that must have been familiar with fleeting meteors showers. There’s also evidence of periodic observations for meteors, again from Plutarch, but these weren’t annual events. From his biography of Agis, a king of Sparta:
Every ninth year the ephors select a clear and moonless night, and in silent session watch the face of the heavens. If, then, a star shoots across the sky, they decide that their kings have transgressed in their dealings with the gods, and suspend them from their office, until an oracle from Delphi or Olympia comes to the succour of the kings thus found guilty.
Plutarch — Agis 11.3
Every ninth year in this case means every eighth, because of inclusive counting. It seems that while meteors were well-known in the ancient world they were unexpected. If you count your calendar against the moon, as most ancient cultures did, then events like solstices happen on different days of the year. So too would meteor showers. Along with the vagaries of weather and they tend to be variable in strength anyway, it might be less of a surprise that they weren’t predicted and planned around.
It’s not just historical evidence we could look for though.
We could look for archaeological evidence. For example, if a lot of things were aligned to sunrise around the time we could expect a big meteor shower, that might be circumstantial evidence of meteors being important. Unfortunately not only do meteor showers vary from one year to the next, they also vary on longer scales too, and tonight might be an example of that.
The cause of meteor showers is the Earth crossing the orbit of a comet. The comet leaves debris, and if we pass through the cloud after a recent pass of the comet, we should get a good show. The orbits are regular, so if we crossed a shower today, then we should have also crossed it ten years ago, and also in ten years time. As a broad rule this is right, but the Earth’s orbit wobbles.
More significantly, we share a solar system with Jupiter. Jupiter can fling meteors into or out of the inner solar system and Earth orbit. It makes predicting the position of comets into the past difficult, and so the same for meteor showers too. For this reason we don’t know the timing of any meteor showers till relatively late in history. The earliest known is, I think, the Perseids recorded around the AD 900s in East Asia. Whether or not they happened before then is unknown. Maybe they did — and weren’t recorded, or maybe they were a new shower, like the Cameleopardalids might be tonight.
It’s a handy reminder that you can’t always just dial in a time into a planetarium and expect to see what the ancients saw.
Image
Meteor and Pleiades. Photo Luis Argerich / Flickr. CC BY-NC.