Pi seconds is a nanocentury



π seconds is a nanocentury

— Jon Bentley, quoting Tom Duff, Programming Pearls

No, this isn’t a mysterious and fundamental connection between circles and the solar system. Actually, it’s incorrect:

  • nanocentury ~3.15576 seconds
  • ratio of a circle’s circumference to its diameter ~3.14159

Rather, Tom Duff’s rule of thumb is a useful mnemonic. One year is roundabout 3.14×107 seconds. The accuracy of this figure is more than good enough for back of an envelope calculations. (Such calculations would be easier if we adopted a decimal time system — 100 seconds in a minute, 100 minutes in an hour, say — but time is one of the few currencies with internationally agreed denominations. I can’t see it changing, and 100 days in a year doesn’t make sense anyway.)