When Galileo was in church in Pisa he started watching the light hanging from the ceiling. It was swinging.
He was interested in how it was moving. Sometimes the wind would blow and it would swing more, then gradually it would slow down.
So he began experimenting with pendulums. He tried changing the size of the swing, the weight at the end of the string and the length of the string, and each time measured how long the swing took.
We used a timer to time ten swings of a pendulum.
We tried it with a big swing and with a little swing and found that the time the swings took was almost the same.
Galileo found the same thing and used the sameness of the pendulum swing to design a clock that would keep steady time: a pendulum clock. This was the beginning of pendulum clocks:
Here it is, made out of cardboard by J. E. Johnson:
|How the pendulum gives the tick tock of the clock|
|The design built|
Pendulum clocks meant that people could measure time accurately at last. Before they could measure to the hour, now they could measure to the minute, the second even. Galileo's discovery changed the world.