Chapter II

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