HIPPARCHUS

born , Nicaea, Bithynia died after 127, BC, Rhodes? also spelled Hipparchos Greek astronomer and mathematician who discovered the precession of the equinoxes, calculated the length of the year to within 6 1/2 minutes, compiled the first known star catalog, and made an early formulation of trigonometry. Additional reading J.L.E. Dreyer, History of the Planetary Systems from Thales to Kepler (1906; reprinted as A History of Astronomy from Thales to Kepler, 1953), a readable but scholarly book in which the work of Hipparchus is clearly set out; George Sarton, A History of Science, vol. 2, Hellenistic Science and Culture in the Last Three Centuries B.C. (1959), a volume containing an excellent well-written rsum of Hipparchus and his achievements; Ptolemy, The Almagest, reprinted in an English translation in "Great Books of the Western World," vol. 16 (1952), the main original source of references to the astronomical work of Hipparchus.