By now you’ve probably seen a Predictor; millions of them have been sold by the time you’re reading this. For those who haven’t seen one, it’s a small device, like a remote for opening your car door. Its only features are a button and a big green LED. The light flashes if you press the button. Specifically, the light flashes one second before you press the button.

Ted Chiang, ‘What’s Expected of Us’, Nature, vol. 436 (July 7, 2005), p. 150