East is East?


Astronomical Orientation of Ancient Greek Temples

ResearchBlogging.orgI’m not plan­ning to blog a lot on the Astronomical Orientation of Ancient Greek Temples as is openly access­ible. Your com­ments are going to carry a lot more weight there than here. But I’ll try and keep track of what other people are say­ing else­where. I’m expect­ing this to be the first paper of a devel­op­ing argu­ment, so I’ll need to see what people identify as prob­lems and address them. There’s two com­ments in the Times today which I think neatly high­light one of the issues. One is from Efrosyni Boutsikas and the other from Mary Beard.

Boutsikas’ objec­tion is inter­est­ing. I wanted a com­par­ison data set to exam­ine for Greece and the only one I know of that’s pub­lished is Retallack’s in Antiquity. To be hon­est it’s not entirely fair to use Retallack’s data as he wasn’t that con­cerned with astro­nomy. Instead he was look­ing at geo­mor­pho­logy, and I think he has some really inter­est­ing res­ults. Now Boutsikas has her own sur­vey, which she did spe­cific­ally with archae­oastro­nomy in mind. That’s why I’m inter­ested when she says of 107 temples in Greece only 58% faced east. That might cause me some prob­lems and here’s why.

First we need three vari­ables. n is the num­ber of temples. That’s 107. p is the prob­ab­il­ity and event will hap­pen, and q the prob­ab­il­ity it won’t. p+q = 1 because some­thing has to either hap­pen or not hap­pen. So what value is p? It depends on what Boutsikas means by east. If she means the east­ern half of the hori­zon, then p is 0.5 and so is q. By pure chance we’d expect np temples to face east. That’s 53.5. In her sur­vey 62 temples faced east. That’s more than chance, so I’m right yes? Not so fast.

There’s never going to be exactly 53.5 temples facing east. Around 19 times out of twenty 20 there’ll be 53.5 plus or minus two stand­ard devi­ations. If you want the chance of a false pos­it­ive to be lower than 1 in a 100, then you need 53.5 plus or minus three stand­ard devi­ations. The stand­ard devi­ation (σ) for this kind of dis­tri­bu­tion is cal­cu­lated by the formula:

σ = √npq

If we want the one in twenty con­fid­ence that means

σ = √(107 × 0.5 × 0.5) = 5.2

So 19 times out of 20 you might expect to find between 43.1 and 63.9 temples facing east. The res­ult of 62 is inside this range, so there’s noth­ing sig­ni­fic­ant. How do I explain that? I’m not sure I can. I can’t say what time period her temples come from. If she’s looked at Bronze Age sites and Roman sites in Greece then we’re not com­par­ing like with like and it’s pos­sible that when we com­pare temples built in the archaic and clas­sical peri­ods as they were in Sicily then we’ll have more of a match. Another pos­sib­il­ity is that I’m simply wrong.

But this depends on Boutsikas mean­ing east­ern half of the hori­zon when she says east. I use dif­fer­ent defin­i­tions of east for dif­fer­ent tests and make clear which are which in the paper because it makes a dif­fer­ence. If Boutsikas has put her temples into four cat­egor­ies, north, east, south and west, then east means east­ern quarter of the sky and the equa­tions turn out differently.

np = 107 × 0.25 = 26.75 temples
σ = √(107 × 0.25 × 0.75) = 4.48

If east is the east­ern quarter then 19 times out of twenty at most we would expect at most 35.71 temples. By chance there’s be over 40.19 temples in the sample less than 1 time out of 100. 62 temples would be over seven stand­ard devi­ations away from the expec­ted res­ult. If that’s by chance it’s an amaz­ing freak res­ult. It means I can’t respond to Boutsikas’s claims until I can see the data to ana­lyse, so I know what east means. She might have proven my paper wrong, or else proven it very right. How can that be when only just over half of the temples face east?

Imagine you’re at a casino. Someone is spin­ning the roul­ette wheel. Half the time it lands on the num­bers 0–9 and the other half it lands on another num­ber. It doesn’t mat­ter than you can’t pre­dict exactly where the next ball will land. In the long term that casino will lose money because some­thing is affect­ing the wheel. This isn’t about hav­ing a hard and fast law for astro­nom­ical align­ments. It’s about whether or not a sig­ni­fic­ant num­ber of temples are aligned to the sun. If you’re going say that there is or isn’t a sig­ni­fic­ant num­ber, first you have to know what a sig­ni­fic­ant num­ber would look like. Typically in the social sci­ences that would np +/- 2σ. I prefer np +/- 3σ because I’m mak­ing claims which people might not be com­fort­able with, so it’s reas­on­able I should provide stronger evidence.

If I am right that doesn’t mean Boutsikas’ and Retallack’s sur­veys can be junked. In fact it means the oppos­ite. In Retallack’s case he’s show­ing there’s a clear cor­rel­a­tion between the ded­ic­a­tion of a temple and the soil type it’s built in. Now if there’s a gen­eral rule that Greek temples face east, the temples which don’t become more inter­est­ing because then you can ask “What’s spe­cial about those temples? Why were they built that way?” It’s the same for Boutsikas’ data. If there’s noth­ing spe­cial about the align­ments then temples which don’t face east are noth­ing spe­cial. If, using this method, her data shows a tend­ency for east­ern align­ments then she has a data set with plenty of inter­est­ing temples that could tell us some­thing about Greek reli­gion. For instance it could high­light where a local cult was doing some­thing spe­cial that you wouldn’t find else­where in Greece.

Clearly Boutsikas’ objec­tion is ser­i­ous and I’ll need to con­sider it care­fully, but in this case it could be a case of cross-wired. I don’t think she’d seen my art­icle when she talked to the Times because I hadn’t emailed it to her till last night. We’ve both been work­ing on sim­ilar top­ics and so could have come to the same con­clu­sions. If we been talk­ing with each other then there could have been a bit of fric­tion if we saw our ideas in each other’s theses. She’s been put on the spot react­ing to a paper which she prob­ably hasn’t read, but she’s clearly an expert in the sub­ject because of her own research. She’ll go where her research takes her and I’ll go with mine. The reporter has picked up on that con­fu­sion. Does that leave him in the dog house? Definitely not.

I’m really pleased with the way Mark Henderson has writ­ten this up. It’s not his job to preach my won­der­ful­ness, it’s to report on how this research fits in with other research. Getting the quotes from Efrosyni Boutsikas was bril­liant because it shows there’s cur­rently two mod­els which come to oppos­ite con­clu­sions. As we both pub­lish more those mod­els will get fleshed out and adapt. Which one will be accep­ted? Hers? Mine? Some kind of hybrid, or even neither? It’s not just about get­ting the right answer. At the moment we might not even agree on what the right answer will look like. Which brings me to Mary Beard’s piece.

I think it’s great com­ment­ary. I think she’s spot on when she rejects the idea of a mod­ern astro­nomy in the ancient world. I would quibble with her reject­ing astro­nomy for the rhythms of day and night. That sounds astro­nom­ical to me and there’s also evid­ence the sea­sons were import­ant. I think she might be try­ing to emphas­ise the import­ance of cos­mo­lo­gical fea­tures, in the sense of nat­ural order, rather than strict obser­va­tion. The only real puzzle is that she’s say­ing that there’s it’s obvi­ous that Greek temples align east-west when in the column next to her Efrosyni Boutsikas is say­ing they obvi­ously don’t. This is a bit of an inter­dis­cip­lin­ary gap.

From the out­side you might expect archae­olo­gists and clas­si­cists to talk to each other. They’re deal­ing with the same people in the same time period. In real­ity this doesn’t always hap­pen. A few years back the Roman Archaeology Conference, the big con­fer­ence for Roman archae­olo­gists held once every couple of years was sched­uled oppos­ite the Classical Association con­fer­ence. The two sides don’t always talk to each other. In the past few years Boutsikas has been pub­lish­ing on her work. Ioannis Liritzis and Helena Vassiliou have been arguing that Greek temples were aligned towards or away from aurorae or stars. This is hav­ing no impact amongst clas­si­cists. Equally I can’t just turn around and say “Greek temples ten­ded to face east” because all the research­ers who dis­agree could ask “How do you know?” It’s obvi­ous doesn’t work as an aca­demic response, even though I agree with Mary Beard. I don’t ima­gine that would be her response in an aca­demic forum. But what she’s done is she’s very help­fully shown that if I want to talk to clas­si­cists then show why I think I have some­thing to talk about.

That’s why I’ve had to write this paper. I want to write more, but the first ques­tion any­one can ask is “How do you know that’s not just a chance res­ult?” That’s why I developed this method. I wanted some­thing simple and effect­ive. The reason I put it in PLoS One is that it also has to be access­ible. I’m plan­ning to write more art­icles for spe­cial­ist journ­als, but people read­ing those will need access to my data and my meth­od­o­logy. That needs to be avail­able to clas­si­cists, archae­olo­gists, astro­nomers and any­one else with an interest.

You can read the ori­ginal research for free and down­load it at PLoS One. If you leave com­ments there then they’ll be seen by every­one else who exam­ines the paper. If you’d like to blog about the paper there’s a col­lec­tion of pho­tos from Sicily at Flickr with a Creative Commons licence.

Salt, A. (2009). The Astronomical Orientation of Ancient Greek Temples PLoS ONE, 4 (11) DOI: 10.1371/journal.pone.0007903

2 thoughts on “East is East?

  1. Aaa

    Dear Dr. Salt,

    I’m not an (archeo)astronomy expert, but I am a Greek astro­phys­i­cist, with a good under­stand­ing of stat­ist­ics to be con­vinced by your argu­ment and puzzled by the greco-italian divide. So I’m bug­ging you because I have a crazy hypo­thesis: can it be that in Italy they point to Greece? If so oth­ers (in Africa, Middle East) should point Northwards, Westwards, etc.

    Athanasios Batagiannis

  2. That’s cer­tainly a plaus­ible idea, espe­cially as the ancient Greeks con­sidered Delphi the centre of the world. Off the top of my head temples in Turkey also tend to point east — but I don’t know if any­one has looked at them sys­tem­at­ic­ally. I think there are good phys­ical reas­ons for a temple to point east, like facing the sun so that it drives out the damp more quickly. Even so that wouldn’t rule out more temples facing west than would be expected.

    It’s an inter­est­ing idea and could help if there are two gen­eral motives in play, astro­nomy AND topography.

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