TO THE READER CONCERNING THE HYPO-

THESES OF THIS WORK.

A historiated woodcut initial 'N' depicting a scholar or astronomer seated at a desk with books or manuscripts, possibly in a study.

I do not doubt that certain learned men—now that the report has spread regarding the novelty of the hypotheses hypotheses: in this context, the fundamental assumptions or mathematical models used to explain planetary paths of this work, which posits a moving Earth and a stationary Sun at the center of the universe—will be strongly offended, and think that the liberal arts original: "disciplinas liberales"; the traditional core curriculum of education including geometry and astronomy., established correctly long ago, ought not to be thrown into confusion. But if they wish to weigh the matter exactly, they will find that the author of this work has committed nothing that deserves blame. For it is the astronomer’s unique task to gather the history of the celestial motions through diligent and skillful observation. Then, since he cannot by any means reach the true causes or hypotheses [behind them], he must devise and invent whatever kind of assumptions he can, so that, by assuming them, these same motions can be correctly calculated from the principles of geometry, for both the future and the past. This craftsman A respectful reference to Copernicus. has excellently performed both of these tasks. For it is not necessary that these hypotheses be true, nor even probable; rather, this one thing is sufficient: if they provide a calculation consistent with observations. Unless, perhaps, someone is so ignorant of geometry and optics that they take the epicycle: a small circle whose center moves around the circumference of a larger one, used in ancient astronomy to explain why planets seem to speed up or slow down of Venus to be probable, or believes it to be the reason why the planet sometimes precedes the Sun and sometimes follows it by forty degrees or more. For who does not see that, if this is assumed, it necessarily follows that the diameter of the star In the 16th century, planets were often called "wandering stars." would appear more than four times larger, and its body more than sixteen times larger, at perigee: the point in an orbit closest to Earth original Greek: "περιγείῳ" than at apogee: the point in an orbit farthest from Earth original Greek: "ἀπογείῳ"? Yet the experience of every age contradicts this. There are other things in this discipline no less absurd, which there is no need to examine for the time being. For it is clear enough that this art is entirely and simply ignorant of the causes of the apparent irregular motions. And if the astronomer devises any through invention—as he certainly devises many—he does not do so in order to persuade anyone that it is so, but only so that they may correctly set up a calculation. Moreover, since various hypotheses sometimes offer themselves for one and the same motion (as in the motion of the Sun, both eccentricity and the epicycle), the astronomer will primarily seize upon that which is easiest to grasp. The philosopher, perhaps, [will seek] probability mo-