Laws of Calorie Counting

摘要

Gazing into our quiet street, we see a scrap of paper ruffle in the breeze or a little water creep along the gutter. Those motions have clear causes: wind and gravity. But the local raccoon that hunts by night and the car that rolls past are distinct. The forces that impel both are mustered internally: timed muscular contractions lift and plant paws, and a stream of explosions turns the wheels. Each self-mover draws on a diet of energy, the one scraps of food, the other gasoline.