By Jo Marchant Smithsonian Magazine http://www.smithsonianmag.com/history/decoding-antikythera-mechanism-first-computer-180953979/
After 2,000 years under the sea, three flat, misshapen pieces of bronze at the National Archaeological Museum in Athens are all shades of green, from emerald to forest. From a distance, they look like rocks with patches of mold. Get closer, though, and the sight is stunning. Crammed inside, obscured by corrosion, are traces of technology that appear utterly modern: gears with neat triangular teeth (just like the inside of a clock) and a ring divided into degrees (like the protractor you used in school). Nothing else like this has ever been discovered from antiquity. Nothing as sophisticated, or even close, appears again for more than a thousand years.
For decades after divers retrieved these scraps from the Antikythera wreck from 1900 to 1901, scholars were unable to make sense of them. X-ray imaging in the 1970s and 1990s revealed that the device must have replicated the motions of the heavens. Holding it in your hands, you could track the paths of the Sun, Moon and planets with impressive accuracy. One investigator dubbed it “an ancient Greek computer.” But the X-ray images were difficult to interpret, so mainstream historians ignored the artifact even as it was championed by fringe writers such as Erich von Däniken, who claimed it came from an alien spaceship. It wasn’t until 2006 that the Antikythera mechanism captured broader attention. That year, Mike Edmunds of Cardiff University in Wales and his team published CT scans of the fragments, revealing more details of the inner workings, as well as hidden inscriptions—and triggering a burst of scholarly research.
The Antikythera mechanism was similar in size to a mantel clock, and bits of wood found on the fragments suggest it was housed in a wooden case. Like a clock, the case would’ve had a large circular face with rotating hands. There was a knob or handle on the side, for winding the mechanism forward or backward. And as the knob turned, trains of interlocking gearwheels drove at least seven hands at various speeds. Instead of hours and minutes, the hands displayed celestial time: one hand for the Sun, one for the Moon and one for each of the five planets visible to the naked eye—Mercury, Venus, Mars, Jupiter and Saturn. A rotating black and silver ball showed the phase of the Moon. Inscriptions explained which stars rose and set on any particular date. There were also two dial systems on the back of the case, each with a pin that followed its own spiral groove, like the needle on a record player. One of these dials was a calendar. The other showed the timing of lunar and solar eclipses.
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