THE DEVELOPMENT OF A TRULY HELIOCENTRIC VIEW
Although the shift from the geocentric to heliocentric worldview is almost universally attributed to Copernicus, his system was not in fact characterized by the sun being exactly at the center. The sun certainly was not the dynamic center of the universe, nor even the geometrical center (the dynamic center refers to a body's function or activity, whereas the geometrical center refers to the position or location of a body). It is highly doubtful whether the sun occupies the center even in book 1 of DR because Copernicus betrayed clear signs of wavering, as in chapter 10: "Circa ipsum (solem) esse centrum mundi," which Rosen translates as "Near the sun is the center of the universe."1 The use of circa clearly shows that the sun does not occupy the central position of the universe. Later in the same chapter, however, Copernicus wrote: "In medio vero omnia residet sol" ("in the middle of everything is the sun").2 Even in book 1 Copernicus was not very consistent, although some scholars 3 still argue that in book 1 the sun is taken as the center of the universe (as we shall see, these scholars simply are not quite accurate).
The Copernican system was not truly heliocentric even from a geometrical point of view. Rather, the sun, like a lamp illuminating the surrounding space, illuminated the universe but did not govern