 In 1612 , having determined the orbital periods of Jupiter 's satellites , Galileo proposed that with sufficiently accurate knowledge of their orbits , one could use their positions as a universal clock , and this would make possible the determination of longitude . He worked on this problem from time to time during the remainder of his life ; but the practical problems were severe . The method was first successfully applied by Giovanni Domenico Cassini in 1681 and was later used extensively for large land surveys ; this method , for example , was used to survey France , and later by Zebulon Pike of the midwestern United States in 1806 . For sea navigation , where delicate telescopic observations were more difficult , the longitude problem eventually required development of a practical portable marine chronometer , such as that of John Harrison . Late in his life , when totally blind , Galileo designed an escapement mechanism for a pendulum clock ( called Galileo 's escapement ) , although no clock using this was built until after the first fully operational pendulum clock was made by Christiaan Huygens in the 1650s . 
