Galileo Galilei (1564-1642) built several telescopes and observed the movements of the Moon and planets. He was the first person to discover that the surface of the Moon is rough and cratered, and not smooth as had been supposed for centuries. He also found that he could use the swing of a pendulum to measure time.
Galileo got into trouble with the authorities when he claimed that the Earth moved around the Sun, rather than the Sun moving around the Earth. This idea was thought to be a threat to biblical teaching, and Galileo was placed under house arrest for the remainder of his life.
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