The earliest astronomers?

Reaching for the stars in Lascaux Cave

This post was chosen as an Editor's Selection for ResearchBlogging.orgThe short ver­sion of this post is that Astronomy in the Upper Palaeolithic? by Hayden & Villeneuve is a great paper. If you’re inter­ested in astro­nomy in hunter-gatherer soci­et­ies you should read it. I’m going to dis­agree with some parts of the paper below, but if Hayden & Villeneuve are wrong about some things, then it’s for inter­est­ing reas­ons. And it’s by no means cer­tain that I’m right to dis­agree about the things that I do.

Reaching for the stars in Lascaux Cave

Reaching for the stars in Lascaux Cave. Photo (cc) tourisme_vezere.

The archae­ology of astro­nomy is con­ten­tious at the best of times, but the Palaeolithic is a par­tic­u­larly dif­fi­cult period to study, because the remains are so frag­ment­ary and few in num­ber. So to put this in con­text we need to know when the Upper Palaeolithic is.

You’re prob­ably famil­iar with the Three Age System, Stone, Bronze and Iron Ages. In this sys­tem in Europe the Stone Age ends roughly between 4000 and 2500 BCE depend­ing on where you are and exactly where you want to draw the line. Everything before this is a long time period so you can split it up fur­ther. The Neolithic is a period when people settle down and become farm­ers, it starts between 8000 and 4000 BCE in Europe depend­ing on where you are. The south-east of Europe adopts farm­ing much sooner than the people in the north-west. The Palaeolithic, if you ignore all sorts of sub­tleties is the period before that. To nar­row down things fur­ther the Palaeolithic is sub-divided into three sec­tions, Lower, Middle and Upper. Again, roughly speak­ing, the Lower Palaeolithic is the time of early humans, the Middle is the time of Neanderthals roughly 300,000 BCE to 35,000 BCE, and the Upper Palaeolithic is the period after that with Homo Sapiens.

This gives the astro­nom­ical read­ers a rough idea of when we’re talk­ing about. Archaeological read­ers could very eas­ily pick holes in more or less everything I’ve said about the dates. One import­ant reason we’ll get to later is that when we use terms like Bronze Age or Palaeolithic, we’re not dir­ectly talk­ing about a spe­cific time, we’re talk­ing about the tech­no­logy we find that’s asso­ci­ated with a spe­cific time. So some ‘peri­ods’ make no sense out­side of Europe. If you live some­where where Obsidian was much easier to get than Bronze, then it’s pos­sible local people never bothered with a Bronze Age.

Hayden & Villeneuve real­ise that evid­ence from the Upper Palaeolithic is scant, but they also recog­nise that the Upper Palaeolithic is not just a time, but it’s tied to a place. What they’re inter­ested in is whether or not eth­no­graph­ies of mod­ern hunter-gatherer soci­et­ies can give us inform­a­tion about pos­sible uses for astro­nomy. You can’t simply say that mod­ern hunter-gatherers from now were exactly like hunter-gatherers twenty thou­sand years ago, but you can see if tack­ling astro­nom­ical prob­lems pro­duces debris sim­ilar to what archae­olo­gists find. You can also see if there are com­mon fea­tures in astro­nomy around the world from hunter-gatherers. If you can see hunter-gatherer astro­nomy in action then you have clues why hunter-gatherers used astro­nomy in the past and that can pro­duce work a lot more inter­est­ing than “there’s marks on this bone, people could be count­ing moon phases.“
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Blinded by the Viking Sunstones

A Viking Ship. Not the one you might expect, but wait and see.

So, there’s these sun­stones that some people think Vikings could have used to nav­ig­ate to America. It’s pos­sible though the evid­ence is weak.

A Viking Ship. Not the one you might expect, but wait and see. Photo by Eoghan O’Lionnain

A few months back there was a paper where the phys­ics was sound but the his­tor­ical con­text was lack­ing. Today the news is a new paper, A depol­ar­izer as a pos­sible pre­cise sun­stone for Viking nav­ig­a­tion by polar­ized sky­light. My prob­lem with the earlier paper was that while the phys­ics made sense, there was no real attempt at his­tor­ical con­text. This paper is different.

The test crys­tal from Ropars et al. 2011.

The Alderney Stone, from Ropars et al. 2011.

A depol­ar­izer as a pos­sible pre­cise sun­stone for Viking nav­ig­a­tion by polar­ized sky­light is not a paper about Viking nav­ig­a­tion at all. It’s about tests on a sun­stone found on an Elizabethan ship by Alderney. Update 15 Nov 2001. It’s about tests on a piece of Icelandic spar that the authors have used as a sub­sti­tute for the Alderney stone. The paper doesn’t describe the meth­ods used to ensure the sub­sti­tute was a good proxy for the ori­ginal. I’ve included the images of the ori­ginal and the test stone. I can see some super­fi­cial dif­fer­ences and more dis­cus­sion of how the test stone was pre­pared could have been help­ful. The phys­ics is lovely and makes sense, but this paper on Tudor nav­ig­a­tion doesn’t cite any research on Tudor navigation.

The argu­ment is this:

  1. If you place some­thing with a small hole in front of the Alderney sun­stone two areas of light appear.
  2. By get­ting the areas to the same bright­ness you can work out where the sun is.
  3. That might have been use­ful in Elizabethan times because can­nons can deflect mag­netic compasses.
  4. But we’ve not checked any his­tor­ical records to see how Tudor sail­ors coped with that, nor if our made-up hole thing has any his­tor­ical evid­ence for it
  5. Because sun­stones means Vikings! VIKINGS I TELL YOU!

Now, if you’re inter­ested in the optics of cal­cite, this is a good paper — but why would you be inter­ested in the optics of cal­cite? The only obvi­ous reason I can think of is his­tor­ical. And a paper that tackles a his­tor­ical prob­lem by pretty much ignor­ing the his­tor­ical period your arte­fact comes from seems to me to be eccentric.

Anyway, if you were sail­ing in north­ern lat­it­udes and you couldn’t see the sun due to mist, but the light was bright enough for polar­isa­tion to be detect­able, then you could use this device to loc­ate the dir­ec­tion of the sun. The sun­stones would have to be bet­ter polar­isers than the fil­ters I use for my cam­era, because I can’t detect any notice­able polar­isa­tion in the over­cast sky today. Once you have a dir­ec­tion, with no time or alti­tude for the obser­va­tion, what are you going to do with that?

The cov­er­age I’ve seen at the Guardian and at the BBC, is cred­ited to two good sci­ence journ­al­ists, yet neither has con­tac­ted a Tudor or Viking his­tor­ian for their opin­ion. This baffles me.

Update 3rd Nov 2011: Wired / ScienceNow do report that no sun­stone has been found with a Viking ship­wreck or set­tle­ment. They also have an inde­pend­ent expert com­ment­ing on the pos­sib­il­it­ies of Tudor nav­ig­a­tion. Unfortunately it’s a bio­lo­gist on the dif­fi­culty of sight­ing from a Viking ship.

Is there some­thing clever about the paper I’ve overlooked?

Photo: Viking Line by Eoghan O’Lionnain. Licenced under a Creative Commons BY-SA licence.