How to run for 60 minutes if you've already conquered a 30-minute run. A one-hour run is the perfect challenge for a strong beginner.

One “day” of 24 hours divided at noon into two 12-hour chunks — why 24 and 12? And each hour consists of 60 minutes with 60 seconds to a minute — why 60? Who thought that was a good idea?

Today, 5,000 years after the Sumerians first began using 60, we divide our days by hours, minutes and seconds. In recent years, we have changed how the units are measured.