CHAPTER II.. Greek Astronomy (from About 600 B.c. to About

GREEK ASTRONOMY (FROM ABOUT 600 B.C. TO ABOUT 400 A.D.), §§ 19-54 21-75

§§ 19-20. =Astronomy up to the time of Aristotle.= The Greek calendar: full and empty months: the octaeteris: Meton’s cycle 21

§ 21. The Roman calendar: introduction of the Julian Calendar 22

§ 22. The Gregorian Calendar 23

§ 23. Early Greek speculative astronomy: Thales and Pythagoras: the spherical form of the earth: the celestial spheres: the music of the spheres 24

§ 24. Philolaus and other Pythagoreans: early believers in the motion of the earth: Aristarchus and Seleucus 25

§ 25. Plato: uniform circular and spherical motions 26

§ 26. Eudoxus: representation of the celestial motions by combinations of spheres: description of the constellations. Callippus 27

§§ 27-30. Aristotle: his spheres: the phases of the moon: proofs that the earth is spherical: his arguments against the motion of the earth: relative distances of the celestial bodies: other speculations: estimate of his astronomical work 29

§§ 31-2. =The early Alexandrine school=: its rise: Aristarchus: his estimates of the distances of the sun and moon. Observations by Timocharis and Aristyllus 34

§§ 33-4. Development of spherics: the Phenomena of Euclid: the horizon, the zenith, poles of a great circle, verticals, declination circles, the meridian, celestial latitude and longitude, right ascension and declination. Sun-dials 36

§ 35. The division of the surface of the earth into zones 37

§ 36. Eratosthenes: his measurement of the earth: and of the obliquity of the ecliptic 39

§ 37. =Hipparchus=: his life and chief contributions to astronomy. Apollonius’s representation of the celestial motions by means of circles. General account of the theory of eccentrics and epicycles 40

§§ 38-9. Hipparchus’s representation of the motion of the sun, by means of an eccentric: apogee, perigee, line of apses, eccentricity: equation of the centre: the epicycle and the deferent 41

§ 40. Theory of the moon: lunation or synodic month and sidereal month: motion of the moon’s nodes and apses: draconitic month and anomalistic month 47

§ 41. Observations of planets: eclipse method of connecting the distances of the sun and moon: estimate of their distances 49

§ 42. His star catalogue. Discovery of the precession of the equinoxes: the tropical year and the sidereal year 51

§ 43. Eclipses of the sun and moon: conjunction and opposition: partial, total, and annular eclipses: parallax 56

§ 44. Delambre’s estimate of Hipparchus 61

§ 45. The slow progress of astronomy after the time of Hipparchus: Pliny’s proof that the earth is round: new measurements of the earth by Posidonius 61

§ 46. =Ptolemy.= The Almagest and the Optics: theory of refraction 62

§ 47. Account of the Almagest: Ptolemy’s postulates: arguments against the motion of the earth 63

§ 48. The theory of the moon: evection and prosneusis 65

§ 49. The astrolabe. Parallax, and distances of the sun and moon 67

§ 50. The star catalogue: precession 68

§ 51. Theory of the planets: the equant 69

§ 52. Estimate of Ptolemy 73

§ 53. The decay of ancient astronomy: Theon and Hypatia 73

§ 54. Summary and estimate of Greek astronomy 74