Telling the Time
In the old days people told the time by the size of the shadow cast on the ground by a post. Sun-dials which developed from this primitive method are used as decorations in gardens today.
A burning rope with knots at regular intervals was another ancient method of telling the time. It took the fire the same amount of time to reach each knot.
One more method of telling the time was a sand glass measuring minutes, hours, etc., by the amount of time it took the sand to run into the lower glass.
Water clocks work on a similar principle, using water instead of sand.
Later mechanical clocks were made, but the first ones kept time so badly that it was not worth putting a minute-hand on them.
Galileo, the great scientist, born 400 years ago, showed what a perfect timekeeper a pendulum was. So clocks were controlled by a pendulum and they were correct to a second.
You can try making a pendulum. Tie a piece of cotton, two feet long, to a big button. Let it hang from a table while you hold down the other end of the cotton with a book.
Start swinging the cotton and look at the second hand of a watch to see how long it takes to do twenty movements. Do this with small swings, then with bigger ones.
You will find almost no difference in time. Big swing or small, it takes the pendulum the same amount of time.
That is why the pendulum is used to control the speed at which the wheels of the clock go round.
1. how long it takes to do twenty movements — сколько времени уходит на 20 колебаний
2. they were correct to a second — они показывали время с точностью до секунды
3. shadow – тень
4. Sun-dials – солнечные часы
5. to develop – развивать
6. to burn – гореть
7. rope – канат
8. knot – узел
9. ancient – древний
10. a sand glass measuring – песочные часы
11. a similar principle – тот же принцип
12. pendulum – маятник
13. speed – скорость
14. swing – колебание
15. wheel – колесо
Answer the questions:
1. How did people tell the time in the old days?
2. How did people use the fire?
3. Were the first mechanical clocks good?
4. Who showed what a perfect timekeeper a pendulum was?
5. How can we make a pendulum?
Say "true" or "false". If "false", give the right answer.
1. In the old days people told the time by the pendulum.
2. The first mechanical clocks were very good.
3. It was Newton who showed what a perfect timekeeper a pendulum was.
4. A burning rope with knots at regular intervals was another ancient method of telling the time.
5. Water clocks work on a similar principle as in a burning rope with knots.
6. You can not try making a pendulum by yourselves.
7. The pendulum is used to control the speed at which the wheels of the clock go round.
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