Two thousand years ago, the Greeks built a mechanical computer to calculate eclipse dates with surprising accuracy. A modern-day historian has created a working replica of the device using Lego Technic building blocks.
The ancient computing device, known in the modern day as the Antikythera mechanism, was discovered underwater in 1901. X-ray tomography only recently revealed its purpose, which was to predict eclipses of heavenly bodies using complex gear ratios.
Andrew Carol, a software engineer who had previously created a replica of Charles Babbage's Difference Engine, was asked by a journalist to create the Antikythera replica as well. Carol did so using about 1500 Lego pieces and about 100 gears. The available gearing in the Lego set forced him to use a different complement of sizes than were used in the original, but the result is functionally equivalent. Gear ratios such as 19:5 are nontrivial to create and needed multiple stages that feed into one another. A central drive mechanism provides rotational energy to all the other gear sections, and the output drives two indicator dials that predict an eclipse whenever their needles align.
Articles on the PC World and New Scientist web sites discuss the device, and the New Scientist article includes a video that explains how the Lego re-creation works.
Sabine Berard contributed to this SCAtoday.net article as well.