There are a number of different forms of pendulum. The main characteristic being that when the mass is displaced from it's position of rest it will oscillate at a fixed frequency.
- 1581 Galileo uses his pulse to time the swinging of the lamps in the cathedral at Pisa. He concludes that the time for a lamp to swing does not depend on the angle through which it swings. This observation eventually leads to the development of pendulum clocks.