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 spheres-that illustrated the "wandering" of the sun, the moon, and the planets...
commonly used to study the heavens. Shortly after the construction of Archimedes" sphere, Ctesibus built the first clepsydra. Although it is possible to observe the time on an armillary sphere, it is quite difficult to perpetually mimic the motion of the sun around the earth. The invention of stereography by Hipparchos made the construction of a dynamic representation of the heavens possible through the combination of planispheric projections with the clepsydra. The anaphoric clock and its cousin, the astrolabe, not only helped Ptolemy create the extensive catalogue in the Almagest, but also established the foundation of modern time keeping.