Yet the widespread planetary theories, advanced by Ptolemy and most other astronomers, although consistent with the numerical data, seemed likewise to present no small difficulty. For these theories were not adequate unless they also conceived certain equalizing circles, which made the planet appear to move at all times with uniform velocity neither on its deferent sphere nor about its own epicycle's center.
Nicolaus CopernicusFinally we shall place the Sun himself at the center of the Universe. All this is suggested by the system of procession of events and the harmony of the whole Universe, if only we face the facts, as they say, "with eyes wide open."
Nicolaus CopernicusThe strongest affection and utmost zeal should, I think, promote the studies concerned with the most beautiful objects, most deserving to be known.
Nicolaus CopernicusTherefore, having obtained the opportunity from these sources, I too began to consider the mobility of the earth.
Nicolaus CopernicusIn so many and such important ways, then, do the planets bear witness to the earth's mobility.
Nicolaus CopernicusIn first place we must observe that the universe is spherical. This is either because that figure is the most perfect, as not being articulated, but whole and complete in itself; or because it is the most capacious and therefore best suited for that which is to contain and preserve all things.
Nicolaus Copernicus