Our digital civilisation, if you can call it that, runs on just two numbers – 0 and 1. The devices we call computers run on vast strings of ones and zeros. How? By having electrical currents that are either flowing or not. The tiny electronic switches that decide whether they’re on (1) or off (0) are called transistors. Once upon a time, these were tangible objects: I remember buying one with my pocket money in the 1950s for a radio receiver I was building. But rapidly they were reduced in size, to the point where electrical circuits using them could...