Galileo was a brilliant scientist who lived in the fifteenth and sixteenth centuries. It is thought that one day in 1581, in Pisa Cathedral, Galileo observed a lamp hung on a long chain. As he watched the lamp swing back and forth he noticed that it didn't matter whether the lamp swung a long way or a short way, it took the same amount of time to go back and forth. The time it takes a pendulum to complete one swing is called its period.
Pendulums are useful because they can accurately measure time.
We will answer that question much the same way Galileo did more than 500 years ago. Pendulums are mentioned in both Galileo's Dialogue Concerning Two Chief World Systems and his Dialogues Concerning Two New Sciences . The period is independent of the amplitude . The square of the period varies directly with the length. For one experiment described in Two New Sciences , string lengths of four or five yards are suggested.