Time as an anachronism

Surreal time photo
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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 Project CC 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:

Socrates
Do you, your­self, first find out and state what you wish.

Strepsiades
You have heard a thou­sand times what I wish. About the interest; so that I may pay no one.

Soc.
Come then, wrap your­self up, and hav­ing given your mind play with sub­tilty, revolve your affairs by little and little, rightly dis­tin­guish­ing and examining.

Strep.
Ah me, unhappy man!

Soc.
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.

Strep.
(in great glee). O dearest little Socrates!

Soc.
What, old man?

Strep.
I have got a device for cheat­ing them of the interest.

Soc.
Exhibit it.

Strep.
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–

Soc.
What good, pray, would this do you?

Strep.
What? If the moon were to rise no longer any­where, I should not pay the interest.

Soc.
Why so, pray?

Strep.
Because the money is lent out by the month.

trans. Perseus Project CC licenced BY-SA



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 Project CC 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.

Bibliography

McCluskey, S.C., 2000. The Inconstant Moon: Lunar Astronomies in Different Cultures. Archaeoastronomy, 15, p.14–31.

Pritchett, W.K., 2001. Athenian Calendars and Ekklesias, J C Gieben.

The Antikythera Mechanism: Art or Science?

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The Antikythera Mechanism. Photo (cc) Tilemahos Efthimiadis.

The Antikythera Mechanism. Photo (cc) Tilemahos Efthimiadis.

This post was chosen as an Editor's Selection for ResearchBlogging.orgSome 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 Dhenry @ Wikimedia Commons.
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

Interdisciplinarity and peer-review

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Caesar3
Texas State University research­ers fol­low­ing the soggy foot­steps of Caesar.

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?

Estimate of the dove population of ancient Greece reduced by one

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Greek Dove
Greek Dove. Photo (cc) Kristie’s NaturesPortraits.

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.

Observing the solstice in ancient Greece

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Astronomical piggy
Astronomical piggy. Original photo (cc) Del far.

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.’

IC IV.11

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.

Update 8 Sept 2010

If you’re inter­ested in this inscrip­tion, there’s a dis­cus­sion at the Itanos blog (in French) that’s worth read­ing. It includes another his­tor­ian talk­ing about Zeus Epopsios that I’d missed.

Ancient Astronomy comes to Liverpool in 2008

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The Three Graces
The Three Graces. Photo (cc) Maddie Digital.

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.

Call for Mild Interest: Classics, Astronomy and Interdisciplinarity

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There might be a ses­sion Classics, Astronomy and Interdisciplinarity at the Classical Association con­fer­ence next year. It’s being organ­ised by Alexandra Smith at Cardiff University and I’m her glam­or­ous assistant.

She’s obvi­ously not one of life’s lucky people.

The aim of the ses­sion is to look at how you can integ­rate research from Classics, which is often qual­it­at­ive, data and Astronomy, which is often quant­at­ive data, and com­bine the two mean­ing­fully. We’re expec­ted to provide three or four speak­ers, so if you have a vague commitment-free interest in talk­ing about Astronomy and Classics then drop me a note in the com­ment box below and I’ll get in touch. I don’t have dates other than April 2008, or a venue other than Liverpool, England yet. I plan to talk if we need to bring the num­bers up to three or not talk if it reduces the num­bers to four.

This isn’t a proper Call for Papers as the ses­sion is not con­firmed yet.

Alex her­self will prob­ably be talk­ing about the dat­ing of eclipses, which is some­thing she’s work­ing on a lot. What I’ve read is impress­ive, so I’ll make of point of vis­it­ing the AMPAH con­fer­ence when she’s speaking.