Quantifying the Rise and Fall of Complexity in Closed Systems: The Coffee Automaton

Editorial record

Plain-language summary

A cup of coffee with cream starts simple, passes through an intricate swirling phase, and ends simple again, fully mixed. Entropy only increases, so it cannot be what makes the middle stage interesting. Aaronson, Carroll and Ouellette simulate the mixing and measure the size of the compressed, blurred picture of each state, which rises and then falls just as intuition suggests. The work is a small, concrete attempt to define the kind of structure that intelligence and learning may be about, and it is why the paper appears on reading lists about compression and understanding.