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The Antikythera mechanism is an ancient artifact believed to be an early clockwork mechanism . It was discovered in a shipwreck off the Greek island of Antikythera, between Kythera and Crete, and has been dated to about 87 BC.
The wreck was discovered in 1900 at a depth of about 40m (140 feet), and many statues and other works were retrieved from it by sponge divers. On May 17 1902 archaeologist Spyridon Stais noticed that one of the pieces of rock had a gear wheel embedded in it.
The mechanism is the oldest surviving geared mechanism, made from bronze in a wooden frame, and has puzzled and intrigued historians of science and technology since its discovery. The most commonly accepted theory of its function is that it was an analog computer designed to track the movements of heavenly objects. Recent working reconstructions of the device support this analysis. The device is all the more impressive for its use of a differential gear, which was previously believed to have been invented in the 13th century AD.
The late Professor Derek De Solla Price, a science historian working at Yale University, published an article on the mechanism in Scientific American in June 1959 while the device was still only partially inspected. In 1973 or 1974 he published an analysis based on gamma ray imaging by Greek archaeologists. He claimed that the device had been built by a Greek astronomer, Geminus of Rhodes. His conclusion was not accepted by experts at the time, who believed that the Ancient Greeks had the theoretical knowledge but not the necessary practical skills.
A partial reconstruction was built by Australian computer scientist Allan George Bromley (1947-2002) of the University of Sydney and Sydney clockmaker Frank Percival. This project led Bromley to review Price's X-ray analysis and to make new, more accurate X-ray images that were studied by Bromley's student, Bernard Gardner, in 1993.
Later, a British orrery maker named John Gleave constructed a working replica of the mechanism. According to his reconstruction, the front dial shows the annual progress of the Sun and Moon through the zodiac against the Egyptian calendar. The upper rear dial displays a four-year period and has associated dials showing the Metonic cycle of 235 synodic months, which equals 19 solar years. A synodic month is the period between two new moons. The lower rear dial plots the cycle of a single synodic month, with a secondary dial showing the lunar year of 12 synodic months.
The original mechanism is kept in the National Archaeological Museum in Athens.
The Antikythera mechanism is occasionally interpreted as an anachronism by those attempting to prove the occurrence of time travel (see anachronism and time travel).
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