The earth together with its surrounding waters must in fact have such a shape as its shadow reveals, for it eclipses the moon with the arc of a perfect circle.

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.

Therefore, having obtained the opportunity from these sources, I too began to consider the mobility of the earth.

In so many and such important ways, then, do the planets bear witness to the earth's mobility.

Pouring forth its seas everywhere, then, the ocean envelops the earth and fills its deeper chasms.

We regard it as a certainty that the earth, enclosed between poles, is bounded by a spherical surface.

In the midst of all dwells the Sun. For who could set this luminary in another or better place in this most glorious temple, than whence he can at one and the same time brighten the whole.