 Galileo 's theoretical and experimental work on the motions of bodies , along with the largely independent work of Kepler and René Descartes , was a precursor of the classical mechanics developed by Sir Isaac Newton . Galileo conducted several experiments with pendulums . It is popularly believed ( thanks to the biography by Vincenzo Viviani ) that these began by watching the swings of the bronze chandelier in the cathedral of Pisa , using his pulse as a timer . Later experiments are described in his Two New Sciences . Galileo claimed that a simple pendulum is isochronous , i.e. that its swings always take the same amount of time , independently of the amplitude . In fact , this is only approximately true , as was discovered by Christiaan Huygens . Galileo also found that the square of the period varies directly with the length of the pendulum . Galileo 's son , Vincenzo , sketched a clock based on his father 's theories in 1642 . The clock was never built and , because of the large swings required by its verge escapement , would have been a poor timekeeper . ( See Engineering above . ) 
