CHAPTER IV.

COPPERNICUS (FROM 1473 A.D. TO 1543 A.D.), §§ 70-92 92-124

§ 70. The Revival of Learning 92

§§ 71-4. Life of _Coppernicus_: growth of his ideas: publication of the _Commentariolus_: _Rheticus_ and the _Prima Narratio_: publication of the _De Revolutionibus_ 93

§ 75. The central idea in the work of Coppernicus: relation to earlier writers 99

§§ 76-9. The =De Revolutionibus=. _The first book_: the postulates: the principle of _relative motion_, with applications to the apparent annual motion of the sun, and to the daily motion of the celestial sphere 100

§ 80. The two motions of the earth: answers to objections 105

§ 81. The motion of the planets 106

§ 82. The seasons 108

§ 83. End of first book. _The second book_: decrease in the obliquity of the ecliptic: the star catalogue 110

§ 84. _The third book_: precession 110

§ 85. _The third book_: the annual motion of the earth: _aphelion_ and _perihelion_. _The fourth book_: theory of the moon: distances of the sun and moon: eclipses 111

§§ 86-7. The _fifth_ and _sixth_ books: theory of the planets: _synodic_ and _sidereal periods_ 112

§ 88. Explanation of the stationary points 118

§§ 89-90. Detailed theory of the planets: defects of the theory 121

§ 91. Coppernicus’s use of epicycles 122

§ 92. A difficulty in his system 123