40 SCIENCE AND THE HUMAN MIND 



string, presenting its inhabited outer face successively 

 to each part of the surrounding sky. 



In the fourth century before Christ, geographical 

 discovery was advanced greatly, especially by the 

 voyages of Pythias round Britain towards the north 

 polar seas. The knowledge thus gained of the varia- 

 tion with latitude of day and night, etc., led to the 

 simpler conception of the revolution of the earth on 

 its own axis, while Aristarchus of Samos (280-250 B.C.) 

 held that the sun was larger than the earth, formed 

 the true centre of our system, and was one among the 

 countless fixed stars of heaven. But this heliocentric 

 theory was too much in advance of the time to carry 

 general assent. The mass of mankind, even the 

 majority of philosophers, still considered the centre 

 of the Universe to be the earth, whether as a floating 

 ball round which the heavens revolved, or even as 

 the fixed, stable, bottomless solid it seemed to the 

 senses. The centuries from the days of Aristarchus 

 to those of Copernicus had to pass before enough 

 evidence accumulated to force men to revive the 

 speculative view of Aristarchus, and to establish it in 

 the light of all the new evidence as the universally 

 accepted theory of science. 



The authority of Aristotle was too great for the new 

 theory of Aristarchus, and, about 130 B.C. Hipparchus, 

 the inventor of trigonometry, developed the geocentric 

 theory into a form which, expounded by Ptolemy of 

 Alexandria (fl. 127-151 A.D.), held the field till the 

 sixteenth century of our era. 



The theory of Hipparchus, though erroneous in its 

 underlying assumption and in its results, was founded 

 on sound methods of induction. Accepting the earth 



