Welcome to You Ask Andy

Elizabeth Drum, age 10 of Allentown, Pennsylvania, for her question:

How were the hours, minutes and seconds divided

This fascinating story takes us back thousands of years to the Magi of ancient Babylon. These wise men were astronomers and very talented with numbers. There in the desert region of Mesopotamia, they built tall pyramids for their patient stargazing. They also worked out a clever system of mathematics that survives to this day. It is the system of 60's we still use to divide the hours into minutes and the minutes into seconds.

Nature presented us with an enormous clock to check off the passing moments. It is .the immense dome of the heavens that spreads down from the top of the sky to meet the great circle of the horizon on every side. Its moving hands are the sun and the moon, the planets and the multitude of stars that pass overhead. The heavenly pointers, of course, appear to move overhead because the earth spins around on its axis. As it turns, it turns us around to face a vast circle of changing scenery, out there in the oceans of space that surround our globe on every side.

The heavenly parade marches around us once each calendar day. It glides at a steady pace and its moving pointers show us how to divide the big circle into hours, minutes and seconds. The wise Magi of ancient Babylon figures this out and based their time system on the Big Clock in the sky. This was more than 5,000 years ago. These early astronomers also charted the moving heavenly bodies in patient detail. They. also invented a number system or organize this work. The background for their charts was the great double dome, or sphere, of the day and night sky. And this curved sphere needed guidelines in circles and parts of circles.

These circles, naturally, are related to the passing of time. And the Magi used their clever way of dividing circles to mark the calendar day into smaller sections. Their favorite numbers were six and other numbers one gets by multiplying or dividing sixes. These include 12 and 24, 90 and 360. Their clever system divided a circle in 360 equal sections called degrees. We will divide every circle, large or small, in 360 degrees. And according to the Big Clock in the sky, a complete circle of the heavenly parade passes overhead with every calendar day.

The ancient Magi sectioned this celestial circle into their usual 360 degrees. They divided the big time circle into 24 sections, each having 15 degrees. These of course are the 24 hours in the calendar day. The favorite old number 60 divides each hour into minutes and each minute into seconds. Most of this neat system was worked out in ancient days by the patient astronomers of Mesopotamia. It still works as well as it always did and nobody has thought of a better way to mark off the passing moments.

Mathematicians rely on this old division of the circle in many other ways. We can draw lines from all the degree marks to the center of a circle, making 360 thin slices of pie. The pointed corners in the middle are angles, 360 angles in every circle large or small. A quarter circle gives a square cornered angle of 90 degrees. A pie slice with 60 degrees around the circle points in to form an angle of 60 degrees.

 

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