Nicholas Copernicus’ Revolutions

Abstract

I have to the best of my ability indicated how the assumed revolution of the earth influences and affects the planets’ apparent motion in longitude, and how it forces all these phenomena into a precise and necessary regularity. It remains for me to consider the movements which impart to the planets a deviation in latitude, and to show how the earth’s motion exercises control over these phenomena too, and prescribes rules for them also in this division. This division of the science is indispensable because the planets’ deviations [in latitude] produce no small modification in the risings and settings, first visibilities, occultations, and other phenomena which were explained in general above. Indeed, the planets’ true places are said to be known when their longitude is determined together with their latitudinal deviation from the ecliptic. What the ancient astronomers believed they had demonstrated here too by means of a stationary earth, I shall accomplish perhaps more compactly and more appropriately by assuming that the earth moves.