Nicolaus Copernicus

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

Near the sun is the center of the universe.

Accordingly, since nothing prevents the earth from moving, I suggest that we should now consider also whether several motions suit it, so that it can be regarded as one of the planets. For, it is not the center of all the revolutions.

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

The massive bulk of the earth does indeed shrink to insignificance in comparison with the size of the heavens.

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.

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

For a traveler going from any place toward the north, that pole of the daily rotation gradually climbs higher, while the opposite pole drops down an equal amount.

The earth also is spherical, since it presses upon its center from every direction.

First of all, we must note that the universe is spherical.

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

Therefore, in the course of the work I have followed this plan: I describe in the first book all the positions of the orbits together with the movements which I ascribe to the Earth, in order that this book might contain, as it were, the general scheme of the universe.