SHEILA TERRY / SCIENCE PHOTO LIBRARY SHEILA TERRY / SCIENCE PHOTO LIBRARY
Galileo Galilei (1564-1642), Italian scientist, observing the pendulum-like swinging of a lamp in Pisa Cathedral, Italy, in 1582. Galileo made these observations while he was a medical student in Pisa. He noted that the lamp took the same time to do one swing, regardless of how far it had to swing. This led him to perform experiments which showed that the period of a pendulum's swing depends on its length, allowing it to be used as a timing device. Galileo used pendulums to monitor a person's pulse rate and to regulate clocks.
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