High tech helps solve mystery of ancient calculator

2,000-year-old Antikythera Mechanism: "It multiplies, divides and subtracts, but you can't program it."

Results of a high-tech research project to be released next week promise to finally unravel much of the remaining mystery of a 2,000-year-old astronomical calculator.

Results of a high-tech research project to be released next week promise to finally unravel much of the remaining mystery of a 2,000-year-old astronomical calculator (update).

Since its discovery in 1902, the Antikythera Mechanism -- with its intricate and baffling system of about 30 geared wheels -- has been an enigma. Our knowledge of its functions has increased as computer-based imaging, analysis and X-ray technologies have evolved. During the last 50 years, researchers have identified various astronomical and calendar functions, including gears that mimic the movement of the sun and moon.

But it has taken some of the most advanced technology of the 21st century to decipher during the past year the most advanced technology of the 1st century B.C.

No artifact this complex has been recovered from the ancient world, though there are numerous written references, by Greek and later by Arab writers, to different types of geared mechanisms. The level of mechanical sophistication found in the Antikythera Mechanism was not to be seen again until the rise of European clock-making during the Middle Ages, more than a millennium later.

Revealing the results

An international team of researchers will reveal the results of this most recent research, carried out over the past year with help from HP Laboratories and X-Tek Systems, a U.K.-based manufacturer of high resolution X-ray inspection equipment. The Antikythera Mechanism Research Project, a joint effort by researchers in Greece and the United Kingdom, hosts a two-day conference starting Nov. 30 in Athens.

The team includes astrophysicists, radio astronomers, mathematicians and philologists (philology is the study of ancient texts and original documents), reflecting the complexity of the Antikythera Mechanism (see related story detailing the research project group).

Team members wouldn't comment beforehand on the details. But they are confident they've unraveled many of the remaining puzzles.

See a slide show of the mechanism.

"We believe we've found the functions with regard to the sun and moon movements, and to its calendrical function," says Michael Edmunds, a professor in the School of Physics and Astronomy at Cardiff University in Wales, and a specialist in the chemical composition of galaxies. The Mechanism caught his interest when he was working in 2000 with a student who chose the device as a research project.

"We believe we [now] understand what the gear trains did," Edmunds says. Other advances include definitive tooth counts, and new details of gears and their assemblies.

In addition, the team more than doubled the number of letters previously found on the device, to more than 2,000, and has translated these, says John Seiradakis, a professor with the Department of Physics, Aristolean University of Thessaloniki, in Greece.

A sponge diver's chance discovery

The Mechanism is named after the Greek island of Antikythera [antih-KITH-ehra], where in 1900 a sponge diver taking shelter from a storm found an ancient shipwreck 200 feet below the Mediterranean's surface. Archeologists removed an array of artifacts, but it wasn't until mid-1902, that one of them noticed that embedded in what was thought to be a lump of broken calcified bronze statuary was a gear wheel.

The lump turned out to be an encrusted, partially destroyed set of bronze gear wheels, dials and plates. About 13 inches high, 7 inches wide and just under 4 inches deep, the mechanism was held in place by the remains of its original, well-made wooden case, which dried out and crumbled away after being excavated. Inscribed Greek letters and some inscriptions were visible on the metal plates.

Even then, the complexity of the Mechanism was obvious, so obvious in fact that some observers speculated that it actually was created during the Renaissance in the 1400s, had been lost overboard, and landed on the much more ancient wreck. Today, there is no question the Mechanism dates from around 65 B.C.

Study, speculation, theories

In 1974, a paper by science historian Derek de Solla Price and Greek nuclear physicist Charalampos Karakalos, based on gamma-ray and X-ray analysis, presented new details of the device. Price described the mechanism as a calendar computer and famously identified the presence of a differential gear -- a set of gears that can move two axles at different speeds.

In the late 90s, another research effort, including 700 X-ray plates digitized for computer-aided analysis, was carried out by Michael Wright, a specialist in the history of mechanicism and now with the Imperial Museum in London, and the late Allen Bromley of the University of Sydney.

In a paper presented a year ago, "Understanding the Antikythera Mechanism," Wright faulted some of Price's conclusions. Wright speculated that the Mechanism could be an elaborate planetarium, designed to show the movements of the five then-known planets in addition to the sun and moon, and to predict eclipses. He also suggested that the Mechanism was actually a marriage of at least two separate devices, one being added to the device already in the wooden case. He demonstrated that Price's differential gear was actually an epicyclical gear, in which a central wheel meshes with one or more peripheral gears, which rotate around the center.

Cardiff's Edmunds says the current research has not, in fact, found evidence of planetary displays, based on what's now known about the gear trains, but there is evidence of "planetary functions." He prefers the term calculator to computer: "It multiplies, divides and subtracts, but you can't program it," he says.

"Our interpretation will be somewhat different from both Price and Wright, though it will have some common elements," he says.

That interpretation has been made possible by advanced digital imaging and X-ray technologies.

Re-imaging the surface

Tom Malzbender, a senior research scientist with HP Laboratories, and colleagues Dan Gelb and Hans Wolters developed a digital technique, called reflectance imaging, for re-imaging how light is reflected from a surface. "By changing these reflectance functions, we could enhance the surface, and bring out details that weren't visible before," he says.

Essentially, it’s a computerized version of what most of us have done with the oil dip stick in our car: you hold it up to the light and twist and turn it, until the light shows up the oil film and the inscribed markings. The HP researchers do it by putting an object inside a dome that's fitted with a camera, scores of light bulbs, and a laptop computer to control it. A separate laptop runs a program to create a polynomial texture map (PTM) of the captured images, letting the researchers then change the lighting and surface characteristics.

"If you make the [object's] surface 'like' obsidian, which has virtually no diffuse reflectants but has very strong specular [shiny highlight] characteristics, this brings out a lot of surface detail," Malzbender says.

Malzbender's work was presented in a 2001 SIGGRAPH paper that came to the attention of one of Edmunds' colleagues on the Antikythera project, mathematician and filmmaker Tony Freeth. Last fall, Malzbender and Gelb and Bill Ambrisco of Foxhollow Technology, traveled to Athens for a week to take photos of the front and back of each of the Mechanism's 70 large fragments, working 12 hours a day and more in a dark, cramped basement room with poor ventilation.

"It was completely exciting," he says. "We'd capture some pictures, and five minutes later we have the PTMs on the laptop and all these guys huddled around it, trying to read it." The HP crew captured and stored 4,500 images.

Going beneath the surface

The complete PTM system was contained in one 150-pound box. The high resolution X-ray gear from X-Tek weighed nearly 8 tons. "The Mechanism is about 250 millimeters across, a fairly large object, so we needed high energy beams to penetrate it," says Andrew Ramsey, computer tomography specialist with X-Tek, based in Tring, U.K. "The system for that is a small room."

"It's sort of like an electron microscope: we shine our beam onto a metal target, which produces the X-rays, and we use those to create the image," Ramsey says.

The difference from a medical X-ray is it's all real-time and digital, no film. Each scan of the Mechanism resulted in 1,500 to 3,000 separate images, each 2,000 x 2,000 pixels. A computer converts the image into a digital photo and stores it, and then creates a 3-D volume, which cubes the number of pixels. The X-Tek crew ended with 600GB of data. "We were going out to buy hard disks every other day," Ramsey recalls.

The X-Tek system creates super thin slices of the object, which can be viewed via computer from any direction. It was hoped that the X-rays would let researchers in effect peel away the compressed wheels and dials and get an accurate count of the teeth.

But they suddenly found they could do more: the X-rays exposed writing on surfaces mashed together in the Mechanism, and never before seen.

"I was sitting there, taking a virtual slicing plane and moving it into the volume" of one bronze plate of the Mechanism, Ramsey recalls. "I'm rotating it when I see a letter." The letters, 3 to 4 millimeters high, are punched into the bronze plates. "You have to move the [X-ray] slice slowly through the plate, to piece together the full depth of the letter," Ramsey says. "It's a very painstaking process."

He declines to be specific about what the writing says. "But it was basically an instruction manual on using the mechanism, and what its purpose was," he says.

Despite the panoply of brain and technology power brought to bear on the device, much of what drives all of the participants seems to be something more basic, something common to all human beings: the thrill of discovery.

"I felt a bit like Indiana Jones, actually," Ramsey says.

Got a suggestion for a Wider Net story? An offbeat network industry-related topic? A fascinating personality we should profile? Contact Bob Brown with your ideas at bbrown@nww.com.

Learn more about this topic

slide showSee a slideshow about the mechanism

Pictures of fragments, imaging software results and X-ray gear.

UPDATE: More details of the calculator released.

Antikythera Mechanism Research Project

The group's site.

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