Thanks to all those who came along to my talk at the Royal Institution last night, it was great to see such a big turnout. As part of the presentation I was lucky enough to be able to show a gorgeous video of the Antikythera mechanism's workings, which judging from the spontaneous applause it received was a highlight for much of the audience. This animation has just been completed by Mogi Vicentini, an Italian astronomer and computer scientist who specialises in making both physical and virtual models of astronomy instruments. Lots of people came up to me afterwards to ask for more information, so here's a link to Mogi's website, with this page dedicated to the Antikythera mechanism. You can download the animation itself from here, this is the recommended hi res version, but if you have trouble running it you could try a lower res version, here.

However much you already know about this 2000-year-old machine, the video really is breathtaking. Based on the physical reconstruction made by curator Michael Wright, it builds up the gear wheels one by one before adding the front and back dials and finally the wooden case, and it gets across the sheer sophistication of the gearing in a way that I have never seen before. So thank you to Mogi!

UPDATE 6 August 2009:

By the way, a few people have said they're having trouble getting the file on Mogi's site to run - I got it to work by downloading a free VLC media player, or you can look at the version hosted by the Guardian in their blog post on my talk - lower res but still beautiful. 

Just a quick note today to say that I'll be giving a talk on the Antikythera mechanism at the Royal Institution in London on Tuesday 28 July. It's a wonderful venue, and if you're in the area it would be lovely to see you there - more details here.

 The date works perfectly to celebrate the launch of the paperback edition of Decoding the Heavens in the UK - it is officially out on 6 August, but advance copies will be available at the event.

We've all heard about shrunken heads - a ritual practice in which people from Melanesia and the Amazon basin preserved the heads of their enemies by removing the skull, then boiling down the skin and flesh (I love the collection at London's Horniman Museum). It's thought these objects had religious significance - that shrinking the head of anyone you killed in battle stopped their soul from coming back to seek revenge.

The trophy heads of Peru's Nasca people, however, are rather more mysterious. The Nascas lived in an area called the Nazca Drainage in southern Peru, one of the driest places on Earth, in the first to eighth centuries AD. They had sophisticated ceramics, textiles and a complex system of underground aqueducts, but they're best known for carving out the Nazca lines - giant geometrical shapes and animal figures - on the desert floor. It's still not clear what these were for - perhaps for the Gods to look at, perhaps to mark out astronomical alignments relevant to the agricultural calendar, perhaps to mark the routes of cermonial processions. We can probably rule out Erich von Daniken's theory that they were landing strips for alien spaceships...

The Nascas also did an impressive line in preserved heads. This time the skull was the main feature, with a hole drilled in the front so that it could be hung or carried on a cord. Scholars have been arguing for a while over what they were for. These may have had something to do with religious beliefs surrounding agriculture and fertility (which must have been of prime concern in such a dry location) because on some pottery vessels the heads are shown with plants growing out of the top. Other experts have emphasised their role in violence and warfare. One key question was whether the skulls came from enemy warriors from other populations, or from the Nascas' own dead.

Now a team of archaeologists including Kelly Knudson of Arizona State University has measured the levels of different strontium, oxygen and carbon isotopes in the tooth enamel of Nasca trophy heads from throughout the area, and compared them to those from ordinary burials. These isotopes provide information about the diet and geographical origins of the person concerned. I wrote about a similar technique last year, used to show that most of the crew of the doomed Mary Rose came not from England but from southern Europe, suggesting that language problems might have contributed to the ship's demise.

In the trophy heads study, Knudson and her colleagues showed that isotope levels in the trophies are very similar to those from the local population, indicating that the heads came from venerated ancestors, not scorned enemies. (This got mentioned by a few blogs in January, but the paper is in the current issue of Journal of Anthropological Archaeology, so I figured that was another excuse to write about it now.)

This result doesn't mean the heads were taken peacefully, however. Some scholars believe that the Nascas engaged in ritual warfare, undertaken purely to take heads to make into trophies. The very idea sends a chill down my spine, though in such a different culture perhaps being immortalised in this way would have been seen as an honour.

It does always amaze me how differently (and how easily) past societies seem to have viewed death. When the Greek philosopher Posidonius visited the Celtic lands of Gaul in the first century BC, he came back with tales of a violent people who would hang the severed heads of their enemies in doorways. Rowdy feasts would regularly end up in fights to the death, and sometimes, after a few glasses of wine, a man would lie face up on his shield to have his throat cut for the general amusement of the party.

Greek stone inscriptions might look pretty dry and impersonal to us, but actually the lettering hides personal clues as to the identity of the scribe, just as our own scribbled notes do today. Being able to match up which inscriptions were made by the same writer helps scholars to pin down the dates of particular texts more precisely, as well as revealing links and associations between different inscriptions. This has previously taken years of training, and a fair amount of subjective judgment, but now it looks as though computers could start doing the job instead.

Epigrapher Stephen Tracy of the Institute for Advanced Study in Princeton challenged computer scientists who knew nothing about Greek inscriptions to attribute 24 ancient writing samples to their rightful makers - the texts were written by six different people between 334 BC and 134 BC. To his surprise, the team, led by Michail Panagopoulos at the National Technical University in Athens, got every single one right. Tracy reckons their technique is a "real breakthrough" that could now allow Greek inscriptions to be analysed much more quickly and objectively.

Just as in modern handwriting, ancient writers had individual quirks in the way they formed particular letters. So Panagopoulos and his team overlaid digital scans of different examples of the same letter - the As for example - then used a computer algorithm to calculate the probability that they were carved by the same person. They did this with six different letters across all 24 inscriptions, and have written up their report in IEEE Transactions on Pattern Analysis and Machine Intelligence.

Archaeologists have tens of thousands of examples of ancient Greek inscriptions, and the idea now is to build a computer database of as many of them as possible, including scans, attributions and dates. Then any new finds could be slotted into that record. Presumably the technique would also work for other ancient texts, such as cuneiform tablets from Mesopotamia. Though I wonder whether some epigraphers might get a bit defensive about this part of their work being taken over by computers.