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.
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.
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.
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.
I’m writing up a paper, and because it’s one I haven’t actually finished yet I quite like it. It ties up some loose ends with project. It also adds something new to ancient politics without having to contradict a lot of people. It’s been going quite well so I’ve started writing up the Introduction and I must have been slightly on automatic because I’ve run smack into the question “What is Time?” A lot of people much more intelligent than me have been banging their heads against this problem for millennia, so I’ll be doing well to solve it in a couple of paragraphs. I think for my work I’ve managed to tighten the problem into two smaller questions. Is the modern experience of time as a largely objective passage of duration anachronistic when you look at the ancient world?
Plato in the Timaeus 38c says:
Wherefore, as a consequence of this reasoning and design on the part of God, with a view to the generation of Time, the sun and moon and five other stars, which bear the appellation of “planets,” came into existence for the determining and preserving of the numbers of Time. trans. Perseus ProjectCC licenced BY-SA
This means that Plato saw the planets as creating time. This is the inverse of how we think of time, because we think time would exist anyway and that time is something that planets move in. So do we need a radically different mental model for how ancient people though about time? I’m not sure. For a counter-argument here’s a bit of Clouds by Aristphanes. Strepsiades is bothered about his debts and how he cannot afford to pay them back. He goes to Socrates, to teach him how to think:
Do you, yourself, first find out and state what you wish.
You have heard a thousand times what I wish. About the interest; so that I may pay no one.
Come then, wrap yourself up, and having given your mind play with subtilty, revolve your affairs by little and little, rightly distinguishing and examining.
Ah me, unhappy man!
Keep quiet; and if you be puzzled in any one of your conceptions, leave it and go; and then set your mind in motion again, and lock it up.
(in great glee). O dearest little Socrates!
What, old man?
I have got a device for cheating them of the interest.
Now tell me this, pray; if I were to purchase a Thessalian witch, and draw down the moon by night, and then shut it up, as if it were a mirror, in a round crest-case, and then carefully keep it–
What good, pray, would this do you?
What? If the moon were to rise no longer anywhere, I should not pay the interest.
Why so, pray?
Because the money is lent out by the month.
In ancient Greece a month was a lunation, the period of time from one New Moon to the next. By removing the moon Strepsiades removes months. This seems to back up Plato’s ideas about planets generating time (the Sun and Moon were πλάνητες ἀστέρες, planetes asters or wandering stars, in the ancient world). But the joke only works if the solution is nonsense. Pulling down the moon is a daft idea, but is the idea that months would cease to have meaning too? The Romans lived perfectly well without lunar months.
Herodotus (II.4.1), writing around the same period, was clear that lunar months weren’t good ways to track time.
But as to human affairs, this was the account in which they all agreed: the Egyptians, they said, were the first men who reckoned by years and made the year consist of twelve divisions of the seasons. They discovered this from the stars (so they said). And their reckoning is, to my mind, a juster one than that of the Greeks; for the Greeks add an intercalary month every other year, so that the seasons agree; but the Egyptians, reckoning thirty days to each of the twelve months, add five days in every year over and above the total, and thus the completed circle of seasons is made to agree with the calendar. trans. Perseus ProjectCC licenced BY-SA
From this it looks like time is quantative. For example if today is Tuesday, then even if it feels like a Monday it can’t be Monday because Monday + 1 day = Tuesday. I think this cannot be purely the case for ancient Greece though.
For example McCluskey (2000:18) and Pritchett (2001) both note that the calendar can pause or skip days. The same is true for months. To keep the Greek calendar in line with the seasons they didn’t insert an extra day every so often, they inserted a whole month as Herodotus says above. You end up trying to match months against seasons and seasons have qualities. These days in the UK we say Spring starts on March 21. In reality Spring starts when the weather improves. Spring can come earlier or later. If you’re in a society that doesn’t recognise a fixed number of days in a solar year, like ancient Greece, then the quality of the days become important. The calendar is used to regulate religious acts and if a certain festival is supposed to be at the start of Spring and the flowers or animals associated with the festival are not yet out then it’s not the right day and the calendar needs to be corrected.
While the Greeks shared common religious beliefs, on the details they were fiercely independent. In this period taking part in a religious event was a political statement about belonging to a polis, a city-state. Non-citizens did not have the right to participate in the events in the same way as a citizen. So if religion was used to define us from them and the calendar was a religious tool, then a neutral objective count is not good enough. They wanted to be able to have their own distinctive calendrical cycle. I think that’ll be something I need to clarify. It’s not that the Greeks couldn’t make an accurate calendar. It’s that, for the job they wanted it to do, a less precise calendar was better.
Where does that leave Herodotus? Clearly the Greeks weren’t stupid and if Herodotus knew that a three-hundred and sixty-five day cycle made sense, you can be sure many in his audience did too. But Herodotus had his own axe to grind.
Herodotus was writing towards the end of the fifth century BC. Athens and Sparta had been rivals for decades contesting the power vacuum created by the defeat of Persia. Herodotus wrote about the Persian War, not his own time. His aim was to recall a Panhellenic glory shared by all Greeks. A three-hundred and sixty-five day cycle wouldn’t inherently dissolve all intra-Hellenic differences but it would social bonds between the Greeks. I don’t think it was a conscious political statement, but I think the comment on the Egyptian calendar reflected the Panhellenic ideals you find elsewhere in the History.
Every so often someone will tell me ‘there’s no such thing as ancient science’. Usually when I’m associated with the Centre for Interdisciplinary Science. They’re right. Science is a modern social construct that doesn’t fit neatly on to the ancient world. On the other hand it is a convenient label for attempts to produce generalised explanations and practices, without immediate recourse to supernatural beings, established with at least the attempt of a pretence at rational justification. And it’s good enough for the much cleverer people who write the various volumes in Routledge’s Sciences of Antiquity series. But I agree with the idea that if you’re not aware of the difference, it’s something that will come back to bite you. In the same way, I’m not sure that the way we think about Time can applied back to the past. The difficulty is that it’s such a slippery subject I don’t know if I always have a grasp about how I think about Time in the present.
Some posts take quite a while to write. This is a response to Candy Minx and Martin Rundkvist who were discussing the Antikythera Mechanism back in 2006 (Antikythera, Time, A Reply to the Minx). Candy Minx thought that the Antikythera Mechanism was an expression of what was already known and embedded in a society through things like myth and ritual. Martin thought that the mechanism was far more complex, indeed needlessly complex, for an ancient society and so was something quite different to the folk astronomy of the time. Originally I planned to write a fence-sitting compromise. I thought that Candy Minx was right to an extent, there was no need for a device like this because rituals and folk observation could allow people to time the year as well as they needed. At the same time I thought that Martin was right to point out that the mechanism gave results with far more accuracy than folk astronomy needed, or would even recognise. A different sort of astronomy is visible in the Antikythera Mechanism. I didn’t blog too much about the 2006 paper because I attended a few of Mike Edmunds’ talks on the topic and heard that more would be published, which happened in 2008. Anyhow in my own fluffy and fence-sitting way I’ll now offer my compromise.
Someone with an extraordinary imagination built the Antikythera Mechanism and, if he were alive today, we wouldn’t hesitate to call him a scientist. I don’t know if the designer was in the same league as Newton or Galileo, but he was certainly the equal of Kepler, Copernicus or Brahe. It’s hard to overstate how extraordinary the device described in the 2006 paper is, but I’m going to give it a go.
If you’re the one person who hasn’t heard of the Antikythera Mechanism then Nature have a handy video introduction.
All that remains now is a collection of corroded lumps found off the island of Antikythera. The 2006 paper described what the team discovered after x-raying the lumps to read the hidden inscriptions without prizing apart the device and damaging it. Prior to this paper it was thought that the device could keep track of the Sun and the Moon. This is no small feat.
Epicycle et deferent. Image by
The Sun would be moving slowly against the background stars, so over the course of a year it would pass through all the signs of the zodiac. The Moon however is more complex. The Moon also moves in front of the background stars, but it only takes about 27 days to do this. It’s called the sidereal period. So you need a couple of gears to drive those two motions. But you wouldn’t really think of the sidereal period as a month. For most people the synodic period, the time between one New Moon and the next or the time between one Full Moon and the next, is a month. This is around 29½ days. Throw in extra gears for driving other displays showing eclipse cycles and it’s clearly a complex device. The original studies found evidence of epicycles, gears mounted on other gears. Add other features like displays for eclipse and lunar cycles on the back and it’s obvious you have a complicated device. The 2006 research showed that in fact it was all a bit more complicated than that.
The Moon’s movement isn’t constant. It speeds up and slows down. This is because its orbit isn’t exactly circular. Instead it’s slightly egg-shaped. The point furthest from the earth is the apogee and the point closest to the Earth is the perigee. When it’s near the apogee it travels slowly, but when it moves closer to the Earth it picks up speed until it passes perigee and then it slows down again. This is called the first lunar anomaly. The difference is noticeable by the naked eye, if you’re willing to make systematic observations. This is all simply explained by Kepler’s Laws of Planetary Motion. There’s small problem. Kepler used ellipses.
You can’t use elliptical gears. The point of gears is that they must have intermeshing teeth. An elliptical gear would lose contact with the driving gear as its axis changed. Instead it seems that the mechanism used two gears, one slightly off-axis from the other. The rotation was connected by a pin-and-slot arrangement, so that the one gear wouldn’t turn at quite the same rate as the other gear. The on-axis gear can then be turned reliably by the drive gears, while the motion of the moon can driven by the off-axis gear. So you have a device that can track the sidereal, synodic and anomalistic months, all while the Earth is spinning round the Sun. If that’s causing your head to spin you might want to skip the next paragraph.
There’s another problem. The lunar anomaly describes the Moon’s travel from one apogee to the next. This apogee is also rotating around the earth. If the apogee is in Aries then two and a bit years later it will be in Cancer, and another two and a bit years to move into Libra until it too has travelled through the zodiac over about nine years. So now we have a device which tracks the Moon around the Earth, and its phases and it’s variable speed and variations in that variability, while also keeping track of the Sun’s position, potential lunar and solar eclipses and intercalation cycles so you know when to stick an extra month in to keep the lunar months in step with the solar year round gears, some mounted slightly off axis to create a pseudo-sinusoidal variation using circular gears to replace ellipses. If you have funny feeling near the back of your head right now, that’s probably your brain trying to crawl out of your ears. The Antikythera Mechanism is insanely complex. Still just because it’s insanely complex, that doesn’t make it scientific.
In fact you can argue about whether or not Science existed in the ancient world. Certainly a lot of elements like testing ideas with experiments didn’t really become popular till after Galileo. On the other hand some natural philosophy of the time was based on observation. There was certainly technology which was the result of applied knowledge. With those kind of provisos a lot of ancient historians would be happy with the idea of ancient science, albeit a science different to post-Renaissance science. In this case, the sheer intense observation and calculation involved in making the Antikythera Mechanism marks it out as a work of ancient science. There’s also another factor which might make it more scientific than artistic.
To some extent the Antikythera Mechanism Research Project have been interested in hanging a name on the device. It was thought to have originated in Rhodes and sunk on its way to Rome, which would have connected it to the home city of Hipparchus, one of the great astronomers of antiquity. The 2008 paper has examined the parapegma on the mechanism and discovered it may be connected to Syracuse, home of Archimedes.
A parapegma is a calendar, usually with holes for sticking a peg into for marking the days. In the case of ancient Greece they’re interesting when they tell you what day of the month it is, because each Greek city had its own set of months. The months were usually named after religious festivals, and this was tied into local politics. That meant having your own calendar was a good way of showing your independence. The best match for the months mentioned on the mechanism is Tauromenion, modern Taormina, in Sicily. This is likely to have shared some months with Syracuse as it was re-settled from there in the fourth-century BC, so Syracuse is a strong possibility for the home of this device. Archimedes is said to have invented a planetarium according to Cicero and is thought to have written a lost book on astronomical devices. However he could not have made this device. Archimedes died in 212 BC. The Antikythera Mechanism is currently thought to date to the second half of the second century BC, but that might change. But it was very likely to have been made after Archimedes death and that’s what makes it scientific.
Art can be collaborative, or it can be personal. Science in contrast is built on cumulative knowledge. The person who invented the gearing did not have to be the person who made the astronomical observations. He didn’t even need to live in the same century as the astronomer. In fact the maker of this device might not have done either. He could have followed a kit and added his own personal touches on the casing. There’s a core to this device which, once expressed, is independent of personal vision. Archimedes didn’t have his own personal Moon which moved in a different way to everyone else’s, while an artist can have a personal interpretation of the Moon.
A reason people might think the Antikythera Mechanism is a work of art is that it’s clearly the result of a lot of imagination. Great art requires imagination, but so too does great science. It requires the kind of imagination that can look at a toolbox full of circles and see ellipses. The kind of imagination that can watch wheels turn within wheels as bodies waltz to the music of the celestial spheres. Another common factor between art and science is that great art can show a new way of looking at the world, and great science does this too. That’s why I disagree with Candy Minx when she says “Science is always playing catch up with the poets.” Science can reveal beauty too, as a visit to the Antikythera Mechanism Research Group’s homepage would show.
Freeth, T., Bitsakis, Y., Moussas, X., Seiradakis, J., Tselikas, A., Mangou, H., Zafeiropoulou, M., Hadland, R., Bate, D., Ramsey, A., Allen, M., Crawley, A., Hockley, P., Malzbender, T., Gelb, D., Ambrisco, W., & Edmunds, M. (2006). Decoding the ancient Greek astronomical calculator known as the Antikythera Mechanism Nature, 444 (7119), 587–591 DOI: 10.1038/nature05357
Freeth, T., Jones, A., Steele, J., & Bitsakis, Y. (2008). Calendars with Olympiad display and eclipse prediction on the Antikythera Mechanism Nature, 454 (7204), 614–617 DOI: 10.1038/nature07130
Tony Keen has been casting a critical eye over the recent ancient astronomy stories which have been making the headlines recently. I half disagree with him, but I think he asks serious questions and his conclusions certainly aren’t unfair.
First off he raises questions about the recent ‘dating the Odyssey by an eclipse’ story. I think he’s right about this, it’s really not a viable piece of work. The thing that bothers me is that while the authors say there are some major assumptions, the one they seem to have ignored is the existence of a singular Homer. If the Odyssey is a patchwork of tales then dating is futile anyway. The return of the Odysseus could be from an earlier tale. For instance it’s been noticed that the Iliad borrows some metaphors from Gilgamesh. We only know that because we have both texts, which means even if something only appears in “Homer’s” work, we can’t be sure the original author was Homer.
The other thing is that it loses some of the meaning of an eclipse. The Sun and Moon are not isolated astronomical bodies in this period. They’re divine but also entwined with activity on Earth. An eclipse of the Sun is a a sign that something is anomalous with the cosmos. This could explain how Odysseus gets to slaughter a lot of people and remain a hero. The normal rules of the universe were suspended.
It’s points to a wider problem, in that PNAS is not a minor publication, but I’d be surprised if it had passed peer-review from a classicist. If it has that’s, marvellous news for me. I’ve got plenty of ideas which really wouldn’t stand rigorous scrutiny which I’d like to shift into publication. If it hasn’t then in what sense is the journal meaningfully peer-reviewed? This is not just a problem specific to PNAS. You can flip this back to Classics/Archaeology journals too.
Now if I write this up as an article should I give a couple of examples? I have one from archaeology which says individuals are fractals without explaining how you’d calculate the Minkowski-Bouligand dimension of an individual. I’ve another classics article which says that Chaos Theory says nothing about the existence or non-existence of God. This is 100% true. Neither does Delia Smith’s “How to Cook” for exactly the same reason. Neither are theological works.*
So what how do you evaluate interdisciplinary work? I think interdisciplinary peer-review is a start. I also think you have to seriously get to grips with David Whitley’s arguments for post-positivism. This is why I have a lot more time for Donald Olson’s work on re-dating Caesar’s landing in Britain.
First off it would help to have a bit of context. This work fits in with the kind of thing thing Donald Olson’s been doing for Sky and Telescope for a few years. He looks at the veracity of astronomical records of historical events and how well they fit with modern calculations. Now, I’d agree with Tony that the calendar is a mess in this period. I think there’s reason to give it some consideration though because of how Olson is connecting the loose dating with the astronomy and the tides.
In the case of the tides, the equinocital tides are unusually high, which is his starting point. It has to be before the equinox because it’s in the last days of summer, and the phases of the moon allow you to point more at some dates than others. If that was it I wouldn’t be impressed, but Olson always goes that extra step. For many people doing ‘interdisciplinary’ work it’s enough if they haven’t found something in the field outside their expertise that contradicts them. Olson in contrast actively reads round the work of historians to see if there’s independent corroboration for his work, rather than just pulling facts from the stars. That’s a big step up from “I haven’t found anything which contradicts my claims”.
I can also sympathise with Tony’s lack of astonishment at the minor shift in date. Ancient Historians are so used to not even knowing what month events occurred in that a shift of a few days is not going to uproot many long-held beliefs. In Olson’s defence I’d say that context is important here. The work is appearing in Sky and Telescope. It’s a good magazine, but it’s a hobbyist’s magazine, and that hobby is astronomy. That’s who Olson is pitching his work at. However there could be a use. Olson’s work would suggest that Collingwood’s reading of the Gallic Wars is better in this case than the reading of others. That means we have some more reason to favour Collingwood over other interpreters when looking at other Latin texts.
In the longer term I think Olson’s work can show how dicey some accepted ancient dates are. That is a problem for me, because life would be so much easier if I could pin down dates for the battles at Thermopylae and Salamis. More usefully it shows that multiple routes of interrogation are necessary if you’re serious about interdisciplinary work, rather than a simple hypothesis-test postivist approach.
*If we’re moving to citation indices in the Humanities then I can cite any non-theological piece of work. Should I cite the highest bidder? Do I hear a packet of chocolate buttons?
Scientifically speaking a negative result is as important as a positive result. Nonetheless while positive results which no-one expected are publishable, negative results — which people would have expected if they’d thought about it a bit — are difficult to get published.
As an example, I’m looking at connections between ancient Greek constellations and the Greek calendar. One nice correlation is that the dove migration season in Greece starts about the same time that the constellation Columba, the Dove, rises in the morning sky for the first time. It’s particularly neat because doves tend to fly at night, so as Columba took to the skies, so did the doves. It would have slotted nicely into my model. There’s a small problem.
Columba is Noah’s Dove and wasn’t invented till AD 1679. Not only that, but if you read Aratus’s Phaenomena, which is a description of the sky dating from the 3rd century BC, he goes on at great length how there’s no constellation in that region. Unlike modern constellations, the Greek constellations were figures not regions and not all stars were thought to be in constellations. Some were considered amorphoi or unformed. If I’d really been awake I wouldn’t have needed to look up the constellation, as there are already doves in the ancient Greek sky. The Pleiades are, among other things, doves. That’s what the name means.
It’s surprising how specific the ancient sources are about which stars are in constellations or not. It raises the question of whether constellations named in ancient texts existed in more archaic times, because stars don’t have to be in a constellation.
A fairly common theme in astronomical explanations of ancient sites is that they were set up with a connection to the solstices. The statistical evidence leads me to think that it’s right, but it poses a serious problem, which day is the solstice? That should be an easy question to answer, it’s the day when the sunrise or sunset reaches it’s farthest position north or south. The reality is harder. The point where the sun rises over the horizon in the morning changes over the course of a year in a similar way to the way a pendulum swings. When it’s passing through the middle the change is large, about one sun-width each morning. When it reaches the solstices though the sun slows down and appears to stop in the same place for a few days. There is change, but it’s tiny about 1/30th of the sun’s width each day. That’s where the name solstice comes from. It’s derived from the Latin sol from sun and sistere to stand still.
It’s because this effect is so difficult to view that many people argue for high-accuracy observation of astronomical events. In some ways this can make arguments a bit circular. How do we know a place is an observatory? It’s because it must have been important to get the exact day of the solstice. How do we know that the exact day of the solstice was important? Because the extremely high accuracy makes it so likely.
There’s some highly intelligent and simple methods people have proposed for observing the solstice. I like one example used at Brainport in Scotland where it’s been proposed that a marker slightly off-solstice was used. If you do that then you can more accurately count the days between sun’s passes of the marker. The next year you know that the solstice is half that number of days after the first pass. It’s possible and it also allows a flexible marking of the solstice to coincide with lunar months. If the alignment to the solstice is symbolic and for special effects in the ceremony then you can hold the solstice event on a few days. The problem is without historical evidence it gets hard to argue whether or not a very specific explanation is convincing.
In Ancient Greek Agriculture: An Introduction by Signe Isager and Jens Erik Skydsgaard they do find historical evidence of the solsticial observation over a standing stone. From on page 163 they talk about a stele from Crete with this inscription.
Patron set this up for Zeus Epopsios. Winter solstice. Should anyone wish to know: off ‘The little pig’ and the stele the sun turns.’
They go on to explain that ‘The little pig’ was a rock jutting out at some distance away in the water. They argue that it indicates that it was a foresight and the stele a labelled backsight for observing the winter solstice.
The reason Isager and Skydsgaard argue that the stele was set up for the winter solstice was that they think the rising of Orion was the marker for the summer solstice, which is easily observable and so a marker wasn’t necessary. I’ve argued elsewhere that Delphinus would make a suitable marker for the winter solstice, and it’s found mentioned surprisingly often for a small and faint constellation on parapegmata, stone calendars with holes for a peg which would mark the day.
Nonetheless it is useful and rare to find an astronomical site with the instruction manual for how it should be used. Thanks to Prof. Graham Shipley for passing along the reference.
Things to do: That kind of observation in Crete doesn’t automatically mean that similar observations were made in Greek Sicily. What would be helpful would be to look up the inscription and see when it dates from. If it’s early then that could be more persuasive, because it’s thought that settlers from Crete came to Sicily. If that’s the case then it’s more likely that the practice transferred with them.
One of the things I’m working on has moved a step closer to fruition. I say I’m working on, Alexandra Smith at Cardiff is doing most of the work at the moment. Anyway, there’ll be a session on Classics, Astronomy and Interdisciplinarity at the Classical Association 2008 Meeting in Liverpool. There’ll be four papers:
Astronomy and Ancient Greek Cult: New Perspectives to Greek Religious Architecture and Cult Practices. Dr. Efrosyni Boutsikas (Leicester)
Astronomy, Stoicism and Politics in Aratus’ Phaenomena. Stamatina Mastorakou (Imperial)
Impossible to Ignore? Some Uncomfortable Implications of the Antikythera Mechanism. Prof. Mike Edmunds (Cardiff University and The Antikythera Mechanism Research Project)
Eclipses as a Tool of Chronology. Alexandra Smith (Cardiff)
I’m not giving a talk as sessions are limited to four spaces. I already know what I would say and think I’d benefit more from listening to someone else speak. However I am listed as compère session chair. We don’t have a firm date yet, though I’m told it’s more likely to be on the weekend rather than the Friday.
I’ll put up more information when it goes live on the Liverpool site. I’ve no desire to annoy them as they’re doing a fantastic job. Some of the requests I put in were unusual. The dates for your diary are the 27th to the 30th of March.