The idea of an astronomical clock is ancient. Although not a clock in the traditional sense, the 2nd century BC Antikythera mechanism of ancient Greece was used to calculate the positions of the sun, moon, and stars at any given point by use of complex mechanical gears. European astronomical clocks are probably descended from the technology of the Antikythera mechanism. As Cicero later wrote in the 1st century BC, Archimedes and Posidonius's orrery achieved virtually the same thing.