Unwrapping the Past 

If you happen to be a time-traveler, do avoid Italy's Bay of Naples on Aug. 24, 79 AD. That's when Mount Vesuvius, dormant for 800 years, blew its top, completely engulfing several nearby Roman cities in a thick layer of volcanic ash. The disaster turned out to be a boon for future archaeologists. The most famous of the buried cities, Pompeii, was only rediscovered in 1599, and today you can wander its streets, enter into mosaic-rich courtyards and read graffiti on its walls.

Nearby (and less-visited) Herculaneum is the home of the Villa of the Papyri, so called for the hundreds of papyrus scrolls found there shortly after the 1709 serendipitous discovery of the city by workers digging a well. Unlike the papyrus scrolls from sites in Egypt and the Near East, Herculaneum's papyri and books in the form of rolled up animal skins were burnt to a crisp during the eruption. Over the years, archaeologists tried, disastrously, to unwrap the carbonized lumps which crumble at the lightest touch. Now, using really cool techniques (the next best thing to time-travel), researchers are bringing the ancient writings back to life.

In order to read a carbonized papyrus without damaging it, the charred black lump that once was a 20-foot-long scroll is scanned non-invasively with x-rays, one super-thin slice at a time. The resulting 3D digital model is then "virtually unrolled" to reveal the original writing. The technique involves two modern breakthroughs: microtomography (3D x-rays, used routinely in hospital CAT scans) and sophisticated software to process the huge database of information.

Computer scientist Brent Seales created the software. He and his team at the University of Kentucky pioneered the virtual unrolling technique on a scroll found in 1970 at the ancient En-Gedi synagogue on the western shore of the Dead Sea. A fire in the sixth century AD destroyed the complex, but in the wreckage archaeologists found the synagogue's Holy Ark, containing a lump of burnt papyrus. Israeli authorities presciently stored the En-Gedi scroll against the day when scientific progress could allow decipherment without damage to the fragile material. Forty-five years later, Seales' team was able to do just that, scanning and virtually unwrapping the carbonized scroll without touching it. Two years ago, the team announced its findings after reading — on a computer screen — a 1,700-year-old Hebrew text from the biblical Book of Leviticus.

The En-Gedi fragment was an easier challenge than the Herculaneum library scrolls because the Jewish scribes used ink containing iron, which stood out from the backing. (Iron absorbs x-rays more than does burnt papyrus.) In contrast, ink used on the Villa of the Papyri scrolls is carbon-based, and burnt animal skin is essentially ... carbon, so differential absorption couldn't be used. Instead, scientists used a new technique known as x-ray phase contrast tomography to read the scrolls by measuring the difference in refraction between the ink and the underlying papyrus.

Researchers have just started to analyze the Herculaneum scrolls. So far they've discovered 2,000-year-old texts written by a follower of Epicurus, the Greek philosopher who promoted ataraxia, peace of mind cultivated by living self-sufficiently in the company of friends. Hundreds of scrolls remain to be digitally read, with possibly thousands more — a potential treasure trove from the past — awaiting rediscovery in the unexcavated parts of Herculaneum. I bet Epicurus would have enjoyed the idea of his words being re-read by future generations — perhaps finding ataraxia in his contemplation.

Barry Evans ([email protected]) is still haunted by a day spent in Pompeii many years ago.