A diagram that shook the world, in chapter 10 of Book I of Copernicus' On the Revolutions (De revolutionibus orbium coelestium). The book was published in 1543 in Nuremberg as Copernicus lay on his deathbed, and was dedicated to Pope Paul III. The second edition was printed in Basel in 1566, and the third in Amsterdam in 1617.
In the Copernican system the Earth is given three distinct motions: a daily axial rotation, an annual rotation about the Sun, and a third motion related to precession. As acknowledged by Copernicus himself in the introduction of his book, the heliocentric hypothesis goes back to antiquity, in fact with Aristarchus of Samos (ca. 310-230 BC; In De Revolutionibus Copernicus mentions Philolaus, in reference to the Pythagorean school in general), and the hypothesis of the Earth's axial rotation at least to Heraklides of Pontus (ca. 388-310 BC).
Contrary to a common opinion still perpetuated today in some introductory astronomy textbooks, Copernicus did not eliminate Ptolemy's epicycles from planetary theory; in fact, his mathematical model of planetary motion contains about as many epicycles as the version of the ptolemaic model in use at the time. What Copernicus did eliminate was the equant, so that his model involved only perfectly regular circular motions.
Copernicus, N., On the Revolutions, edited and translated by E. Rosen, The Johns Hopkins University Press, 1992.
Kuhn, T.S. 1957, The Copernican Revolution, Harvard University Press.
Gingerich, O. 1993, The Eye of Heaven, American Institute of Physics.
-Written and last revised 29 December 1997 by paulchar@ucar.edu.
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