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Rosanne Morello, age 12, of Houston, Texas, for hex question:

How did they calculate time in ancient days?

It's fun to imagine what life was like in ancient days. But none of us want to go back and live perhaps 10',000 years ago, when people began to notice that time passes by. We have clocks to tick off the moments and calendars to note the dates. Our early ancestors had to figure out ways to do these things for themselves. And their inventions led step by step to our convenient clocks and calendars.

The earliest peoples wandered the world in search of food, hunting catchable animals and gathered edible plants. We cannot say what first made them notice that time was passing. Perhaps they saw children grow bigger and adults become aged. These things would make them aware of the relentless march of time. This awareness would make them want to measure how fast it went.

These wanderers lived outdoors, where the heavenly bodies pass overhead in plain sight. They noticed the changing phases of the moon and the different starry constellations that change with the changing seasons. We base our modern time system on these heavenly motions. And early wanderers also consulted that big basic clock in the sky. The stars told them the changing seasons, the changing moon gave them the lunar month.

The time of day became more important when they    settled down to herd their own cattle and grow their own crops. This    called for regular daily chores and regular daily meals, It was    logical to clock these schedules by the sun's journey over the daytime sky. The sun divided their day in half when it reached its highest    point overhead.

The first man made time keeping devices used the differing shadows cast by the traveling sun. It started as a sturdy stick set upright in the ground. Its shadow pointed a moving finger    westward in the morning and eastward in the afternoon. When its shadow was shortest, it showed the moment of mid day.

Eventually, early astronomers partitioned the circle and used it to divide the day into hours, minutes and seconds. At last it was possible to invent devices to mark off periods of passing time  ¬during the day or night. There were many such inventions, but basically all of them relied on something that progresses at a steady rate.

In ancient times, one popular time keeper was a tall candle marked in inches. As it burned down inch by inch, it marked the passage of the passing hour. One device measured time by the drip dripping of water from one container into another. And another measured time by how long it takes sand to sift between two glass globes. We still use this clever bygone invention    and call it an egg timer.

 

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