New light on ancient scrolls. (Input Output).
"Imaging spectroscopy was an outgrowth of planetary and space exploration," said Gregory Bearman, a physicist at Jet Propulsion Laboratory in Pasadena, Calif. "But up until the early 1990s, this stuff was all designed for a moving platform," such as aircraft or satellites like Landsat.
With the end of the Cold War new uses for defense-related technologies became a hot topic. An archeology buff and a student of Biblical literature, Bearman thought of trying this technique on ancient documents, which are often difficult to read. As an experiment, he worked on a small fragment of a Dead Sea Scroll--"the one in the worst shape"--then gave a talk and published a paper on his work. (Nowadays, Bearman is working on using multispectral imaging to discriminate between different shades of fluorescent dye in order to pick out particular proteins or organelles inside living cells.)
The Institute for the Study and Preservation of Ancient Religious Texts at Brigham Young University in Provo, Utah, asked Bearman to consult and share his technique. Steven Booras, director of technical operations for the Institute, has been spending the last several months in Naples, using such methods on papyri recovered from the ruins of Herculaneum, one of the towns buried in Vesuvius' eruption, which also destroyed Pompeii. These scrolls were recovered from the remains of a luxurious house known as the Villa of the Papyri, which contained what had evidently been a scholar's library. They had been carbonized by the heat of the volcano's lava, estimated to have been about 300[degrees]C. Many of the scrolls also had been crushed by falling debris and the weight of solidified rock above them or congealed into almost solid masses by seeping water.
In 1756, not long after the scrolls were first discovered, one Father Antonio Piaggio devised a mechanism that succeeded in unrolling many of the documents, and a few of the rolls were partially read. They proved to include many lost works of Epicurean philosophy. But in general, black ink on burnt black papyrus presented a challenge that the techniques of the mid-1700s were not equipped to meet. So the scrolls have been left to rest in a library in Naples for the last two and a half centuries. Among those few who did not forget about them completely, the writings accumulated an aura of mystery and a reputation for intractability.
Booras, who had honed his techniques on the Dead Sea Scrolls and other decaying ancient documents, set to work trying to recover images of writing that was often totally invisible. With a digital camera, he used a filter wheel that can rotate several different filters. The band-pass filters he uses allow only a specific wavelength of light to pass through to the camera. These bands of wavelengths are generally 10 nanometers wide, with some up to 40 nm, and they are spaced every 10 or 50 nm from 400 nm (blue-green light) right on up through the infrared to 1,100 nm. An image is taken with each filter and analyzed to find a wavelength where the ink reflects light and the surface of the papyrus drops out. Different inks respond differently, but "by and large the papyrus responds in the infrared," said Booras.
Problems remain, of course. Sometimes the writing is difficult to see, even with the filters. The bits and pieces of scrolls that were cut in two hundreds of years ago, are often difficult to rearrange in their original order. And early researchers sometimes scraped off one layer of text to get at another, so the first layer is gone for good. In fact, there is now a moratorium on unrolling new scrolls, as even current techniques are felt to be too destructive.
Booras spent a year in Naples not long ago imaging most of the scrolls; he is now back working on the 30 percent or so that remain. According to Roger T. McFarland, a professor of classical studies at Brigham Young who is working with the project, "They gave Booras the stuff they already knew first. Now he's getting to the stuff nobody cared about"--papyri that have previously been too difficult to read, or that look completely blank. On the last day of Booras's previous stay, McFarland noted, a papyrus that appeared to have little or no ink revealed a lost text by the philosopher Metrodorus. It is from these scrolls, which have never been read before, that the really exciting discoveries might come.
According to Booras, the archeologists believe that the main library of the Villa of the Papyri has yet to be excavated. Unfortunately, the Italian government has called a halt to further excavations, at least for the time being, to concentrate on conservation of the remains. But even so, according to McFarland, the work "has given scholars who have been struggling with these texts the first real relief in generations."
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|Title Annotation:||multispectral imaging|
|Comment:||New light on ancient scrolls. (Input Output).(multispectral imaging)|
|Article Type:||Brief Article|
|Date:||Apr 1, 2002|
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