A handful of great landmark books in the scientific renaissance forever changed how we look at our place in the universe. The first of these was Nicolaus Copernicus De Revolutionibus Orbium Coelestium, Libri VI (Six books on the revolutions of the heavenly spheres). Published in 1543, the year of the Polish astronomer s death, De Revolutionibus gave a revolutionary new blueprint for the planetary system. The earth, instead of resting solidly in the center of the cosmos, was set awhirl, spinning on its axis every twenty four hours and revolving around a distant, fixed sun. The new cosmology was not a clarion call from the stars, inevitable and proven by fresh Renaissance observations of the planets; instead it was something truly subtle and wonderful, a 'theory pleasing to the mind.' Chapter 10, with its famous sun centered diagram of the planetary system, was intended to convince not by physical or astronomical 'proof,' but by aesthetics, by the beauty of the explanation. Clearly the persuasion would be in the eye of the beholder. Each of Copernicus arguments concerns the planets, those heavenly bodies that moved against the fixed patterns of the distant stars. He demonstrated that the principal complications in the planetary motions could be elegantly explained by attributing movement to the earth itself. From a geometric point of view, Copernicus arguments were highly compelling, but to the great majority of his contemporaries, any claims for physical reality seemed ridiculous. If the earth were spinning daily on its axis, a stone thrown upward would surely land in another county. As the great Danish astronomer Tycho Brahe would say later in the sixteenth century, 'The Copernican arrangement nowhere offends the principles of mathematics, but it casts the earth, a lazy, sluggish body unfit for motion, into a movement as fast as the aetherial torches i.e., the stars themselves .' Commentary by Owen Gingerich, searchable English translation and Latin live text.