We all know what computers are, right? They sit on our desks and in our pockets, and put the smarts into everything from cars to washing machines.
That's not wrong – and yet it's not entirely right.
At its most basic, a computer takes information as an input, transforming it according to some predetermined rules into a different output. The digital electronic computers that rule our world do this using little pulses of electric current. But there's no reason it has to be that way. "An abacus allows us to compute by moving stones around," says Peter Bentley at University College London. "If you can do that, I struggle to think of anything you cannot compute with."
Sundials convert shadows to time, the liver regulates chemical outputs according to inputs, even rocks store mineral compositions for later breakdown and release: all of these things fit ...
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