A Brief History of Clocks: From Thales to Ptolemy The clock is one of the most influential discoveries in the history of western science. The division of time into regular, predictable units is fundamental to the operation of society. Even in ancient times, humanity recognized the necessity of an orderly system of chronology. Hesiod, writing in the 8th century BC., used celestial bodies to indicate agricultural cycles: "When the Pleiads, Atlas’ daughters, start to rise begin your harvest; plough when they go down" ( Hesiod 71). Later Greek scientists, such as Archimedes, developed complicated models of the heavens—celestial s