Why Does The Snooze Button Give You Only 9 More Minutes of Sleep?

Editor's Note: A reader recently wrote to ask why snooze buttons on alarm clocks only give you nine more minutes of sleep. Our own Sandy Wood has tackled that topic, so I'm re-posting his explanation today.

By the time the snooze feature was added in the 1950s, the innards of alarm clocks had long been standardized. This meant that the teeth on the snooze gear had to mesh with the existing gear configuration, leaving engineers with a single choice: They could set the snooze for either a little more than nine minutes, or a little more than 10 minutes. But because reports indicated that 10 minutes was too long, allowing people to fall back into a "deep" sleep, clock makers decided on the nine-minute gear, believing people would wake up easier and happier after a shorter snooze. We'd tend to disagree with that logic, but, then, we must be in the lazy minority. Although today's digital clocks can be programmed to have a snooze of any length, most stick with nine minutes because that's what consumers expect.