James M. Shook
Redfort Township, Miss.
The same people who invented the wheel about 6,000 years ago: the Mesopotamians, who loved the number 60. It's a useful and easily divisible number, which made it ideal for both early mathematics and commercial trade. The Mesopotamians passed their base-60 numerical system to the ancient Egyptians, who used it to divide a circle into 360 degrees, Mary Blocksma writes in her book Reading the Numbers.
The 360-degree circle worked out great: The Egyptians loved perfect triangles, and exactly six of them fit into a circle. Therefore, six triangular slices of 60 degrees each made for a sensible 360-degree dissection of a circle. The Egyptians, who invented the degree symbol, also came up with the first calendar based on a 360-day year, which is only off by 5.25 days. Since then, the 360-degree circle has more than stood the test of time, it has made its mark on time itself: When time was first recorded on the face of a circle, it was an easy leap to divide hours into 60 minutes and minutes into 60 seconds.