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.

Nicolaus Copernicus

To know that we know what we know, and to know that we do not know what we do not know, that is true knowledge.

Nicolaus Copernicus

Mathematics is written for mathematicians.

Nicolaus Copernicus

Finally we shall place the Sun himself at the center of the Universe.

Nicolaus Copernicus

Of all things visible, the highest is the heaven of the fixed stars.

Nicolaus Copernicus

For I am not so enamoured of my own opinions that I disregard what others may think of them.

Nicolaus Copernicus

At rest, however, in the middle of everything is the sun.

Nicolaus Copernicus

Those things which I am saying now may be obscure, yet they will be made clearer in their proper place.

Nicolaus Copernicus

I am aware that a philosopher's ideas are not subject to the judgment of ordinary persons, because it is his endeavour to seek the truth in all things, to the extent permitted to human reason by God.

Nicolaus Copernicus

For it is the duty of an astronomer to compose the history of the celestial motions through careful and expert study.

Nicolaus Copernicus

I can easily conceive, most Holy Father, that as soon as some people learn that in this book which I have written concerning the revolutions of the heavenly bodies, I ascribe certain motions to the Earth, they will cry out at once that I and my theory should be rejected.

Nicolaus Copernicus

Therefore, when I considered this carefully, the contempt which I had to fear because of the novelty and apparent absurdity of my view, nearly induced me to abandon utterly the work I had begun.

Nicolaus Copernicus

So far as hypotheses are concerned, let no one expect anything certain from astronomy, which cannot furnish it, lest he accept as the truth ideas conceived for another purpose, and depart from this study a greater fool than when he entered it.

Nicolaus Copernicus

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.

Nicolaus Copernicus

Those who know that the consensus of many centuries has sanctioned the conception that the earth remains at rest in the middle of the heavens as its center, would, I reflected, regard it as an insane pronouncement if I made the opposite assertion that the earth moves.

Nicolaus Copernicus

Moreover, since the sun remains stationary, whatever appears as a motion of the sun is really due rather to the motion of the earth.

Nicolaus Copernicus

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

Nicolaus Copernicus

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

Nicolaus Copernicus

I shall now recall to mind that the motion of the heavenly bodies is circular, since the motion appropriate to a sphere is rotation in a circle.

Nicolaus Copernicus

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.

Nicolaus Copernicus

Near the sun is the center of the universe.

Nicolaus Copernicus