Everyone knows a steps fanatic. She glows with mastery. She is potentially adding years to her life. There is a giant math problem looming over her day, which she takes enormous pleasure in methodically attacking: How will she get to 15,000 steps? If it is raining, she walks on a treadmill in a windowless room.

The steps, of course, are not just steps. She is accruing immortality. She is winning. She is beating the sedentary, the paunchy, the person who is curled up on a couch reading a book when they look up and it is dark. There are a lot of people under the sun to get more steps than.