Trigonometry and Spherical Astronomy

Abstract

In the first eleven chapters of Book I, Copernicus sets out a general description of the planetary system and of the movement of the earth. It is here that he presents his principal arguments for the heliocentric theory and attempts to answer astronomical and physical objections to the motion of the earth. These chapters are so well known, and have been commented upon at such length by so many historians and philosophers, who have devoted particular attention to just this part of Copernicus’s work, that anything we might have to say, after the hundreds if not thousands of pages that have already been written, would be bringing owls to Athens.¹ Therefore, we shall pass immediately to the more practical, if less celebrated, expositions of trigonometry and spherical astronomy that occupy the greater part of Books I and II. It is of course true that Copernicus made no original contributions to either subject, but his presentation is on the whole admirable, and the rest of his work is either unintelligible, or of severely reduced intelligibility, without them.