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Mathematicians Show Single Ball Can Theoretically Perform Any Computation
Developing
In Short: Mathematicians Eva Miranda of the Polytechnic University of Catalonia in Spain and Isaac Ramos of ETH Zürich in Switzerland have demonstrated that a single ball bouncing around a specially shaped two-dimensional billiard table can simulate a universal Turing machine.

Mathematicians Eva Miranda of the Polytechnic University of Catalonia in Spain and Isaac Ramos of ETH Zürich in Switzerland have demonstrated that a single ball bouncing around a specially shaped two-dimensional billiard table can simulate a universal Turing machine.
A universal Turing machine is capable of simulating any other Turing machine, meaning it can perform any computation that can be expressed as an algorithm.
Miranda and Ramos's work builds on previous research that showed complex computations could be performed using multiple balls.
Their breakthrough lies in showing that even a single ball can achieve this level of computational power.
The billiard table used in their model is a mathematical abstraction where the ball's position encodes information, and the shape of the walls determines how that information is processed.
According to Miranda, the goal was to understand the minimal geometric mechanism that allows a physical system to perform universal computation.
This research highlights the surprising computational capabilities of simple physical systems.
The findings suggest that even seemingly simple systems can have profound computational potential.
What's still developing
- It's hard to imagine a system of physics simpler than a billiard table.
- Send a ball across the table, and its path follows a simple rule: It travels in a straight line until it hits a wall, then bounces away at the same angle it came in.
- Yet even a system this simple can, at least in theory, reproduce any computation that can be performed by a much more sophisticated computer.
- It's a mathematical model of computation devised by British mathematician Alan Turing in 1936.
- In their mathematical 'billiard' – the word they use to describe their system – the ball's position can encode information, while the carefully designed shape of the walls determines what happens to that information next.
