In 1901, divers working a Roman-era shipwreck off the Greek island of Antikythera brought up a corroded lump of bronze. It took most of a century to understand what it was: a geared astronomical calculator more than two thousand years old, and the oldest known analog computer.
The idea
Analog computation. The mechanism represented astronomical cycles as the continuous turning of gears, a physical model standing in for the mathematics of the heavens, the opposite of digital, discrete counting.
A calculator of the heavens
The mechanism is an ancient Greek hand-powered device, built in the late second or early first century BC. Turning a crank drove a train of dozens of bronze gears, and it could be used to predict astronomical positions and eclipses decades in advance. For sheer miniaturization and complexity it has no known equal for over a thousand years afterward.
Analog, not digital
The mechanism did not count in digits. It modeled. The ratios of its gear teeth embodied the ratios of the astronomical cycles, so advancing the crank advanced a working model of the cosmos. That is the essence of analog computation: a physical system arranged so that its behavior mirrors the mathematics you want to solve. The much later naval rangekeeper solved its targeting problem the same way, with gears and cams, two millennia on.
Why it matters
The Antikythera mechanism plants the analog-versus-digital distinction at the very beginning of the story. For most of history, to compute meant to build a physical analog of a problem. The digital, stored-program machine that came to dominate is, in the long view, the newcomer.
Related Notes
- The Ford Rangekeeper, analog computation two thousand years later
- Al-Khwarizmi and the Algorithm, the other ancient root of computing
- Von Neumann Architecture, the digital model that displaced analog
- History of Computing, the section index
Sources
- “Antikythera mechanism,” Wikipedia. https://en.wikipedia.org/wiki/Antikythera_mechanism . Supports the device as an ancient Greek hand-powered mechanism built in the late second or early first century BC, described as the oldest known analogue computer, able to predict astronomical positions and eclipses decades in advance using a complex system of bronze gears.