Betty Simon, age 12, of Fowler, Michigan, for her question:
Who thought of dividing the minute into 60 seconds?
This system was invented thousands of years ago and we are not likely to change it when we change our other figuring to the metric system. It is based on the circle, which is related to the clock dial and also to the rising and setting of heavenly bodies. The circle also is related to angled corners of every description. Adjusting the passage of time, plus all our convenient angles to the decimal system of ten would be just too much.
Our time divisions were invented by early astronomers, before the beginning of modern history. They were invented by the magi or wise men who lived in ancient Mesopotamia. Their flat land spread between the Tigris and Euphrates Rivers that flow toward the Persian Gulf. This was a fertile region where a settled civilization began to flourish at least 6,000 years ago.
The region was plundered by barbaric nomads and there were wars between rival communities. But the fertile fields yielded plenty of food and also time for other things besides scratching for a living. The Mesopotamians had leisure time to think and study, to pursue arts and hobbies and to satisfy their curiosity by observing nature. It so happened that their expanse of flat plain offered a stupendous view of the sky. They watched with wonder as the heavenly bodies moved across the celestial dome above their heads.
These early astronomers built tall pyramids called ziggurats, terraced with stairways to study the stars. They also invented a number system and a system of circles to make accurate observations of celestial motions. Their number system was based on multiples of six, just as the metric system is based on multiples of ten. Their circles and half circles recorded the passage of time, as they charted the motions of heavenly bodies across the sky.
They divided their basic circle into 360 equal segments or degrees. We still use them. A half circle spanning from horizon to horizon through the top of the sky is 180 degrees, a quarter circle is 90 degrees. These figures are multiples of six. The scholars of ancient Mesopotamia observed that during a day and night period, celestial circles pass once overhead. They used their favorite number again to divide this base period into 24 hour periods.
It was, you must admit, a neat and workable system. Hence, it was logical to use the six again to divide the hour into 60 minutes and the minute into 60 seconds.
When you know the handy circle's exact center, radius lines can be drawn to the circumference. The diameter is two radii, forming one straight line through the center. It divides the circumference into two halves of 180 degrees. A quarter circle encloses 90 degrees. The corner of this piece of pie gives us an angle of 90 degrees. A simi lar slice of 80 degrees gives a corner angle of 80 degrees, and so on. Through thou sands of years, this remarkable system has worked successfully to measure angles and the passing hours. No, we are not likely to remodel it to match the metric system.