HPS 322 Michael J. White History of Science Fall semester, 2013 Some of the Major Players in Ancient Greek (Ptolemaic) Astronomy $ Eudoxus (of Cnidus) and Callippus (of Cyzicus) (both 4th century B.C.) B responsible for use of homocentric (concentric) spheres as (rough) qualitative and quantitative model of celestial motion. $ Aristotle (4th century B.C.) B adaptation of homocentric-sphere model as a cosmological (‘physical’) model using back-rolling or counteracting spheres. Aristotle’s model was intended not to be ‘merely’ a contribution to positional astronomy but an account of celestial mechanics (celestial cosmology). $ Apollonius (of Perga) (3rd century B.C.) B important mathematician (who did foundational work on conic sections) credited with introducing the mechanisms of deferents and epicycles and of eccentrics and with demonstrating their mathematical equivalence. $ Aristarchus (of Samos) (3rd century B.C.) B responsible for principal ancient heliocentric cosmology of Greek antiquity with earth rotating diurnally on axis and revolving (in a circle) around central stationary sun; famous calculations of sizes and distances of sun and moon (based on geocentric assumptions). $ Eratosthenes (of Cyrene) (3rd century B.C.) B wrote a treatise On the Measurement of the Earth, in which he produces and estimate of the earth’s (vertical) diameter based on observations taken at Alexandria and at Syene in Egypt. $ Hipparchus (of Nicaea) (2nd century B.C.) B developed qualitatively and quantitatively accurate model of motion of moon and sun; recognized the phenomenon of precession of the equinoxes; first to make extensive use of trigonometry in astronomy. $ Ptolemy (Claudius Ptolemaeus) (2nd century A.D.) B culminated and refined the ancient Greek tradition of positional astronomy producing quite respectable qualitative and quantitative models of planetary motion. His principal work (Almagest, an Arabic corruption of the Greek hê megistê syntaxis, literally translated as “The Greatest Treatise”) was largely quite technical; it became the standard work on astronomy for over a thousand years..