Telling time

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Long ago when people wanted to know the time,they looked at the position of the sun during the day or the stars at night. Then people learned to tell time by the length of a shadow. When they put a stick in the ground,the shadow moved with the sun. This was sundial. Egypt had the first sandials 3,500 years ago. Today we sometimes see them in gardens or parks.

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Water clocks are also very old. the simplest kind was just a bottle with water that dripped slowly whrough a hole in bottom. Then there was the hourglass in which sand runs from one part to the other in an hour.  Then about 1,000 years ago people began make the first real clocks that could tell time in minutes and seconds,and about 500 years ago the first watches. Today scientists need accurate clocks. They invented first the electric and then the quartz crystal clock.

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