What is the oldest known mechanical analog computer?

The Antikythera mechanism is the oldest known mechanical analog computer.

The device is a complex geared instrument made in ancient Greece, probably during the second or early first century BCE. It was recovered in 1901 from a Roman-era shipwreck near the Greek island of Antikythera, along with statues and other valuable cargo.

Researchers have reconstructed its functions from surviving bronze fragments and inscriptions. Its gear trains could model astronomical cycles, display positions of the Sun and Moon, predict eclipses and track the timing of athletic games, including the Olympic Games. The mechanism used sophisticated engineering far earlier than comparable surviving devices.

The original object is badly corroded and incomplete, so scholars continue to refine interpretations of its display and gearing. It is not a modern computer with electronic components; “analog computer” describes its use of physical quantities and mechanical relationships to represent calculated astronomical cycles.