The Gears of Heaven

The most sophisticated machine to survive from the ancient world was found by men who were looking for sponges.

In the spring of 1900 a boat of sponge divers from the island of Symi put in behind Antikythera, a rock between Crete and the Peloponnese, to wait out a storm. One of them went down, came back up, and described a seabed covered in corpses and horses. They were bronze and marble statues, the cargo of a ship that sank around 70-60 BC. Over the following year the same divers excavated it in brass helmets and canvas suits at fifty metres and more, with a Greek navy ship standing by. It was the first excavation of an ancient shipwreck ever attempted, carried out before anyone understood decompression sickness. One diver died. Two were paralysed. Among the statues they raised were a few lumps of corroded bronze that nobody looked at closely.

In May 1902 one of those lumps cracked as it dried, and an archaeologist named Valerios Stais saw a gearwheel in the crack. Working out what it belonged to took the rest of the century and, finally, a CT scanner trucked to Athens. The answer: 82 fragments of a hand-cranked bronze model of the heavens. Turn the handle and its pointers showed the sun and moon in the zodiac, the phase of the moon, the date in a nineteen-year calendar, the 223-month cycle that predicts eclipses, and where you stood in the four-year round of the great Greek games, from Olympia down to the minor festivals at Dodona and on Rhodes. Some 3,400 characters of engraved text turn out to be its instructions.

The headline calls it the first computer. It is not one, and it does not need to be. What it is raises a harder question: nothing like it survives from the thousand years that followed. Either the Greeks built one astonishing machine and stopped, or they built many and lost them all. This book follows the wreck, the machine and the science that made it, and treats that disappearance as the real mystery.

What you'll learn:

• How sponge divers excavated a shipwreck in 1900-01, and what it cost them
• What the ship carried, where it was going, and why the Antikythera Youth came out of the same sand
• Jacques Cousteau's return, and the excavation that has been raising finds since 2012
• How five generations read the fragments, from gamma rays to microfocus tomography, and what each got wrong
• The pin-and-slot device that makes the moon speed up and slow down
• Why the numbers in the gears are Babylonian and the engineering is Greek
• Archimedes' sphere, Posidonius's sphere, and the genre historians refused to believe in until 1902
• Which claims rest on the fragments, which on the scans, and which are reconstruction, including the 2021 planetary model
• Why bronze does not survive, and whether the medieval clockmakers were heirs or reinventors

This book is for you if:

• You have seen the ancient computer headline and want the version that is neither hype nor dismissal
• You read narrative history of science and want the detective story told with its evidence showing
• You are drawn to shipwrecks, divers and the things the sea gives back
• You want to know what Greek science actually achieved, and how much of it we lost

It was never impossible. It was only alone.