In 1637, when he was 73, Galileo had the idea of a mechanism that would keep the pendulum swinging by giving it pushes, an escapement, thus allowing it to be applied to clocks.
Since he was by then totally blind, he described the mechanism to his son Vincenzio, who drew a picture from his description.
Galileo's student and biographer, Vincenzo Viviani, describes the invention:[4] One day in 1641, while I was living with him at his villa in Arcetri, I remember that the idea occurred to him that the pendulum could be adapted to clocks with weights or springs, serving in place of the usual tempo, he hoped that the very even and natural motions of the pendulum would correct all the defects in the art of clocks.
But because his being deprived of sight prevented him making drawings and models to the desired effect, and his son Vincenzio came one day from Florence to Arcetri, Galileo told him his idea and several discussions followed.
Finally, they decided on the scheme shown in the accompanying drawing, to be put in practice to learn the fact of those difficulties in machines which are usually not foreseen in simple theorizing.The existing clocks of the time, which used the verge escapement with a crude balance wheel, were very inaccurate.