One of the futurist Paul Saffo’s rules of forecasting is: look for the S curves. When you can’t get the temperature in the shower just right—first it’s too cold, and then it quickly shifts to too hot—blame the S curve. When you make popcorn, watch the S curve’s progress: at first nothing happens, then a few kernels pop, then a bunch more, then the bulk of them in a sudden burst of fireworks, then a few more, and then it’s ready to eat. Every motion of your muscles follows an S curve: slow, then fast, then slow again.
