A mechanical machine that can solve the same algorithms as a modern computer has been built out of wood and scrap metal, says software engineer Jim MacArthur.

The machine is a close physical model of the theoretical Turing machine — a device first described by Alan Turing in 1937 as a thought experiment to understand the limits of mechanical computation.

According to the theory, the machine performs calculations using a set of rules to manipulate symbols on an infinite strip of tape. Instead of tape, this machine’s memory uses ball bearings placed on a steel grid. A ball can represent one of five different symbols based on its position on the grid. The machine reads and writes data by repositioning the balls into different cells.

“Since you can see this computer working, it could be useful for educational purposes,” says MacArthur.