Yesterday at the Usenix Technical Conference in San Diego, I listened to a delightful talk about the Antikythera Mechanism, a 2000-year-old bronze object recovered from a shipwreck in 1901 but only later recognized as an astronomical calculator.
The speaker, Diomidis Spinellis, has written a software emulation of the mechanism, allowing the viewer to see how the different sets of gears move. There’s a particularly ingenous pair of gears known as k1 and k2, which help represent the Moon’s elliptical orbit.