AUTHOR’S PREFACE.

...the motions of the world's spheres, than those who profess mathematics in the schools had proposed. And indeed, I first found in the writings of Cicero that Nicetus Copernicus likely means Hicetas of Syracuse, a 4th-century BCE philosopher mentioned by Cicero as believing the Earth rotates. had held the opinion that the Earth moves. Later, I also discovered in Plutarch that others were of the same opinion; I have decided to set down his words here so they may be available to all:

original: "οἱ μὲν ἄλλοι μένειν τὴν γῆν, Φιλόλαος δὲ Πυθαγόρειος κύκλῳ περιφέρεσθαι περὶ τὸ πῦρ κατακυκλῳ λοξὸν ὁμοιοτρόπως ἡλίῳ καὶ σελήνῃ. Ἡρακλείδης ὁ Ποντικός ϗ Ἔκφαντος ὁ Πυθαγόρειος κινεῖσι μὲν τὴν γῆν οὐ μήν γε μεταβατικῶς, τροχοῦ δίκην ἐζωνισμένην ἀπὸ δυσμῶν ἐπὶ ἀνατολὰς, περὶ τὸ ἴδιον αὐτῆς κέντρον."

Others say that the Earth stands still, but Philolaus the Pythagorean says that it moves around the central fire in an oblique circle, much like the Sun and the Moon. Heraclides of Pontus and Ecphantus the Pythagorean also grant the Earth motion, not by moving it from its place, but by turning it like a wheel on its axle from west to east around its own center.

Taking this as an opportunity, I too began to think about the mobility of the Earth. And although the opinion seemed absurd, yet because I knew that others before me had been granted the liberty to imagine whatever circles they pleased to demonstrate the phenomena The observed movements of celestial bodies. of the stars, I thought it might easily be permitted to me as well to test whether, by attributing some motion to the Earth, more solid demonstrations than those of my predecessors could be found regarding the revolution of the celestial spheres.

And so, assuming the motions which I attribute to the Earth later in this work, I finally discovered through long and frequent observation that if the motions of the other wandering stars The planets. are compared to the circulation of the Earth, and calculated according to the revolution of each star, not only do their observed appearances follow from this, but also the order and magnitudes of all the stars and spheres. Indeed, it binds heaven itself together so closely that in no part of it can anything be shifted without causing the confusion of all the other parts and of the entire universe.

Therefore, in the progress of this work, I have followed this order: in the first book, I describe all the positions of the spheres along with the motions I attribute to the Earth, so that this book contains the general constitution of the universe, as it were. In the remaining books, I then compare the motions of the other stars and all the spheres with the mobility of the Earth, so that it can be understood to what extent the motions and appearances of the other stars and spheres can be saved To "save the appearances" meant to create a mathematical model that accurately predicted observations, even if the physical reality of the model was debated. if they are compared to the Earth’s motions. Nor do I doubt that ingenious and learned mathematicians will agree with me, if—as this...