"The Copernican revolution in man's ideas of the structure of the universe, the place of his own earth in it, and the methods and concepts appropriate for studying it is probably the most important turning point in the development of modern science and the European mind. Although Copernicus himself seems hardly to have realised the scope of the upheaval which he was starting, his book On the revolutions of the heavenly spheres, published when he was on his deathbed, is certainly one of the most significant in the history of European thought. It is important not only in the history of astronomy and cosmology but also in the history of mathematics. Although the mathematics involved would now scarcely be counted as advanced, the book was the most accomplished mathematical work published since the time of Ptolemy fourteen centuries before. The power and breadth of its treatment of the motions of the earth, moon and planets are still immensely impressive. Hitherto no English translation of the whole work has been readily accessible. Dr. Duncan has set out to convey the meaning and tone of Copernicus's words in a simple, straightforward style for English-speaking readers. The introduction and notes give the essential background for understanding the work"--Dust jacket.