The Antikythera mechanism is a 2,000-year-old computer – Updated by Brian Resnick May 17, 2017, 12:00am EDT

115 years ago, divers found a hunk of bronze off a Greek island. It changed our understanding of human history.

Exactly 115 years ago today, divers looking for sponges discovered the wreck of a 2,000-year-old vessel off the Greek island Antikythera. Scattered among the wreck’s treasures — beautiful vases and pots, jewelry, a bronze statue of an ancient philosopher — was the most peculiar thing: a series of brass gears and dials mounted in a case the size of a mantel clock. Archeologists dubbed the instrument the Antikythera mechanism. The genius — and mystery — of this piece of ancient Greek technology, arguably the world’s first computer, is why Google is highlighting it today in a Google Doodle.

What is the Antikythera mechanism?

At first glance, the piece of brass found near the wreck looks like something you might find in a junkyard or hanging on the wall of a maritime-themed dive bar. What remains of the mechanism is a set of rusted brass gears sandwiched into a rotting wooden box.

The front side of the Antikythera mechanism.
Wikimedia Commons
The backside.
Wikimedia Commons

But if you look into the machine, you see evidence of at least two dozen gears, laid neatly on top of one another, calibrated with the precision of a master-crafted Swiss watch. This was a level of technology that archeologists would usually date to the 16th century, not well before the first.

But a mystery remained: What was this contraption used for?

The world’s first mechanical computer?

To archeologists, it was immediately apparent that the mechanism was some sort of clock, calendar, or calculating device. But they had no idea what it was for. For decades, they debated: Was the Antikythera a toy model of the planets? Or perhaps it was an early astrolabe (a device to calculate latitude)?

In 1959, Princeton science historian Derek J. de Solla Price provided the most thorough scientific analysis of the contraption to date. After a careful study of the gears, he deduced that the mechanism was used to predict the position of the planets and stars in the sky depending on the calendar month. A main gear would move to represent the calendar year, and would, in turn, move many separate smaller gears to represent the motions of the planets, sun, and moon.

So you could set the main gear to the calendar date and get approximations for where those celestial objects would be in the sky on that date.

And Price declared in the pages of Scientific American that it was a computer: “The mechanism is like a great astronomical clock … or like a modern analogue computer which uses mechanical parts to save tedious calculation.”

It was a computer in the sense that you, as a user, could input a few simple variables and it would yield a flurry of complicated mathematical calculations. Today the programming of computers is written in digital code — series of ones and zeros. This ancient clock had its code written into the mathematical ratios of its gears. All the user had to do was enter the main date on one gear, and through a series of subsequent gear turns, the mechanism could calculate things like the angle of the sun crossing the sky. (For some reference, mechanical calculators — which used gear ratios to add and subtract — didn’t arrive in Europe until the 1600s.)

Scientists have learned even more about how the Antikythera mechanism works

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