The Escapement
In 1641, Galileo was blind and he only had months to live. He
designed a pendulum-based escapement. (An escapement controls the "escape" of energy from a wound spring or raised weights.) Verge escapements had been around for hundreds of years for foliot (weight-driven) clocks but were not correct or inaccurate because of the wide swing required for it to work properly. Robert Hooke came up with the eventual solution to this problem with the anchor escapement, which fixed the swing amplitude and reduced the amplitude required.