Craig Nielsen, age 10, of Moraga, Calif., for his question:
WHY DOES A COMPASS HAVE 360 DEGREES?
This story goes back to the early days of numbers and figuring. And it is not likely to change when we convert to the metric system. The 360 degrees around a compass belong to circles and angles. And the ancient wizards who worked it all out did such a splendid job that no improvement is needed.
The modern metric system is based on 10s. But the parts of a circle are based on 6s. Clock faces are circles; so are the lines of latitude and longitude around the globe. A compass needle swings around a circle with 360 equal degrees, which is 6 times 60. Actually the first 360‑degree circles were invented long before latitudes and longitudes, clocks and compasses.
The first people who coped with circles were the magi, or wise men, who lived in ancient Mesopotamia, thousands of years ago. They were astronomers and perhaps the first real scientists of human history. Through untold centuries, they studied the heavens from the tops of tall buildings called ziggurats.
The sky above is like a great dome, and those early astronomers needed circles and parts of circles to divide and study it in sections. They also needed curves to chart the paths of the stars and other heavenly bodies. Above all, they needed a way to measure a circle, large or small.
Had they used a metric system based on 10s, they might have divided the basic circle into 100 or 1,000 equal degrees. However, their favorite number system was based on 6s rather than on 10s. It was a fine system for multiplying and dividing by 3, 9, 12 and 60. They used it to divide any circle into 360 equal degrees.
What's more, when you cut up a circle like a pie, the corners in the middle are angles. For example, a square corner is a right angle of 90 degrees‑‑which is a quarter of a 360‑degree circle. The sides of an angle point to different directions. And the whole purpose of a compass is to point out the way. So when the compass was invented, the old 360‑degree circle seemed just right for the job.
Since the compass needle points north, it seemed logical to set this direction at O degrees. East is a quartercircle toward the right, at 90 degrees. South, halfway around the circle, is 180 degrees. West is 270 degrees, turning to the right as far as three‑quarters of the way around the compass circle. And the whole thing dates back to the first astronomers who divided the circle to chart the skies.