A Greek Computer From 200 BC

In April 1900, Greek sponge divers sheltering from a storm dropped anchor near the tiny island of Antikythera and dove on a Roman-era wreck. Among the bronze statues and amphorae they hauled up was a corroded lump the size of a shoebox. Nobody paid it much attention until two years later, when a museum curator noticed gear teeth poking through the green crust.

Decades of guesses followed: an astrolabe, a planetarium, a fake. The real answer required CT scanners. A 2006 imaging project led by Cardiff University and the National Archaeological Museum of Athens mapped 30 interlocking bronze gears, the smallest of them barely a centimeter across, and read inscriptions that had been hidden under sea-floor crud for two thousand years.

The device is an analog computer. Turn a crank on the side and the gears rotate dials that show the position of the sun and moon, the phase of the moon, the dates of the four major Panhellenic games (including the Olympics), and the timing of solar and lunar eclipses years in advance. It tracked a luni-solar calendar that uses a 19-year Metonic cycle.

Nothing of comparable mechanical complexity survives from the next thousand years. Clockmakers in 14th-century Europe were just catching up to what some Hellenistic engineer — possibly working in the school of Hipparchus on Rhodes around 150 to 100 BC — had already built.

It's the kind of object that quietly rearranges your sense of when history started.