Pendulum clocks

Galileo's discoveries led to the development of accurate pendulum clocks.

Galileo is said to have discovered that pendulums keep remarkably good time while watching lamps swing in the Pisa cathedral as a young medical student. He noticed that the period of a pendulum (the time of one swing) remained almost exactly the same, even as the lamp lost energy and the size of the swing became smaller.

As an old man, Galileo realised this meant pendulums could be used to build a clock. Galileo's son Vincenzio, and Galileo's last student, Vincenzio Viviani, completed his design for a pendulum clock.

Years later, Christiaan Huygens discovered how to make pendulums swing exactly by making them swing between two curves called cycloids.

Huygens also developed Galileo's work by actually building a clock. Huygens' pendulum clocks were accurate to better than one minute per day. Huygens also invented the spring-powered clock that eventually solved the problem of determining longitude at sea.

Galileo's first discovery about pendulums allowed clocks to be made. His next discovery about pendulums suggested a new theory about the way things fall.