Antikythera Mechanism showcases ingenuity of Greek engineers with this ancient computing marvel

The Antikythera Mechanism is a hand-powered Greek device, built roughly 2,100 years ago, as mentioned in an article published in Scientific American in 2022 named 'An Ancient Greek Astronomical Calculation Machine Reveals New Secrets'. It used interlocking bronze gears to track the sun, moon, and planets. It also predicted eclipses, followed the moon's phases, and showed the dates of the ancient Olympics.It is called one of the most technologically advanced instruments known from antiquity, and it's often described as the world's first analogue computer.

That explains the first half of the title: you set a date, turn a crank, and the gears do the math. The second half is about what experts believed before 1901. Back then, Greek craftsmen were thought to have made only simple fixed gears, the kind found in windmills and watermills.

This device had gears mounted on other gears, called epicyclic gears, with teeth carved about a millimetre long.