HISTORY OF THE FROM THALES TO KEPLER BY J. L. E. DREYER, Ph.D. AUTHOR OF "TYCHO BRAHE" CAMBRIDGE: at the University Press 1906 IN PREFACE. N this book an attempt has been made to trace the history of man's conception of the Universe from the earliest historical ages to the completion of the Copernican system by Kepler in the seventeenth century. Among the various branches of physical science there is no other which in its historical development so closely reflects the general progress of civilisation as the doctrine of the position of the earth in space and its relation to the planetary system. In this we may follow man's gradual emancipation from primitive ideas during the rise of Greek philosophy and science, his relapse into those ideas during the ages following the destruction of the seats of Greek culture, and the rapid advance of knowledge after the revival of learning at the end of the Middle Ages. What chiefly induced me to write this book was the circumstance that a number of legends on subjects connected with the history of the cosmical systems have been repeated time after time, not only in works on the general history of science and literature like those of Hallam and Draper, but also in books dealing specially with astronomy. Among errors long ago refuted but still frequently produced in print may be mentioned that Thales knew the earth to be a sphere; that Pythagoras and his school taught the motion of the earth round the sun; that Plato taught the daily rotation of the earth and in his old age inclined to the heliocentric system; that the Egyptians knew that Mercury and Venus move round the sun; that the lunar variation was discovered by Abu'l Wefa; that King Alfonso the X. of Castille found the orbit of Mercury to be an ellipse (which has not been refuted before, so far as I know), and that Cusa and Regiomontanus anticipated Copernicus. On the other hand, some writers are inclined to belittle the knowledge of the Ancients, making out that Plato imagined the earth to be a cube and that the spheres of Eudoxus and the Ptolemaic and Tychonic systems are impossible and absurd. In order to enable the reader to check every statement made and to form his own opinion on every debatable point, I have given full references to the original authorities. The most recent and best editions have generally been used, though in the case of some of the patristic writers I have only been able to consult old editions. J. L. E. DREYER. ARMAGH OBSERVATORY, December 1905. CONTENTS. Pythagoras-Spherical figure of the earth--Philolaus and his system of the world-Later Pythagoreans, Hiketas and Ekphantus. His earlier works-System of spheres described in the Republic -The Timaus-The Soul of the World-Rotation of the heavens— The inferior planets-Did he teach the rotation of the earth?— PAGE |