Science Interviews

Interview

Sun, 2nd Oct 2005

Rediscovering Archimedes With X-rays

Dr Uwe Bergmann, Stanford Linear Accelerator Center, USA.

Part of the show Science of Lasers, Light, Kung Fu and Archimedes

Chris - One thousand years old, and you're reading it for the first time. Tell us the story of the Archimedes Palimpsest.

Uwe - The palimpsest was first rediscovered in 1906 in Constantinople, and then disappeared again. It is text of Archimedes work copied in Ancient Greek. It contains some of the works that have been unknown to the scientists following him, in particular, a work called The Methods. The works were over-written by a monk. The problem with the palimpsest is that about 25% of it has still not been read.

Chris - And this is because somebody has defaced it by turning the original work of Archimedes into a prayer book.

Uwe - That is one of the reasons. There are other reasons, such as some of the pages have been over-painted by forgers in the 20th century, and a lot of the pages have suffered from mould and general decaying of the parchment.

Chris - So it's presently unreadable, but how are you solving the problem?

Uwe - We are using x-rays to go through the layers that obstruct the reading by regular light.

Chris - So how do x-rays make what's hidden, visible?

Uwe - If you take a regular chest or dental x-ray, you can do that by just shining x-rays through, and the different materials such as your bones absorb more, and you get a contrast like that. It doesn't work like that in the Archimedes Palimpsest because the quantity of ink remaining is so tiny that you wouldn't see a contrast. So we are using a slightly different method. As an analogy, you can say that you wouldn't look for stars in the sky during the day because there's so much background from the sunlight that you won't be able to see them. With this method we are using, we can basically remove all the unwanted scattering signal and we can only focus on the one quality in the ink that gives us a signal in our detector.

Chris - So what does it look like when you shine this highly focussed beam of x-rays at the parchment?

Uwe - You shine the very small beam, which is about the size of a human hair, and you scan it through like you do with a printer. Each time the x-rays strike even a minuscule particle of iron, it will give you a signal in your detector. You then use a computer to reconstruct the image, and what you see is an iron map of the palimpsest and has very little to do with you see with your eye. We then see the ancient writing.

Chris - So the ink actually contained a lot of iron in the old days?

Uwe - Exactly. The ink does contain a lot of iron, but it does contain other elements as well. We have started by looking at iron, but we are going to look at different elements as well.

Chris - How many pages have you got through so far?

Uwe - Basically we have just started with this x-ray method. So far we have read half a page of one of the forgery pages, and we have a lot more to go. We will be reading more over the next three years.

Chris - It must be very exciting to be reading something for the first time in a thousand years.

Uwe - Yeah, it's incredibly exciting. Of course, the difficulty is that you can't just get the text and read it. It takes a lot of effort to decipher. Often we have to do it character by character. It's the scholars who actually make sense of what is written.

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