Clockwise is the fossil of a shadow. North of the tropics, the shadow on a sundial creeps round from west through north to east, and when people in Europe began building clocks with dials, they sent the hand the way the shadow had always gone. Had the first clock faces been made in Santiago or Sydney, where the shadow turns the other way, we would be calling the other direction clockwise and thinking it the natural one. There are a few dissenters: on the Jewish Town Hall in Prague, one dial has Hebrew letters for numbers and hands that run backwards, which is to say forwards, if you read from right to left. A good deal of what feels like the right way round is only the way the first shadow happened to fall.