More stars in the north are seen not to set, while in the south certain stars are no longer seen to rise.

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

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.

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

Mathematics is written for mathematicians.

Mathemata mathematicis scribuntur.

Perhaps there will be prattlers who, although completely ignorant of mathematics, nevertheless take it upon themselves to pass judgment on mathematical questions, and on account of some passage in Scripture, badly distorted to their purpose, will dare to censure and assail what I have presented here.

Not only the phenomena of the others followed from this, but also it so bound together both the order and magnitude of all the planets and the spheres and the heaven itself, that in no single part could one thing be altered without confusion among the other parts and in all the universe.

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.

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

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.

So, influenced by these advisors and this hope, I have at length allowed my friends to publish the work, as they had long besought me to do.

Although all the good arts serve to draw man's mind away from vices and lead it toward better things, this function can be more fully performed by this art, which also provides extraordinary intellectual pleasure.

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

If there should chance to be any mathematicians who, ignorant in mathematics yet pretending to skill in that science, should dare, upon the authority of some passage of Scripture wrested to their purpose, to condemn and censure my hypothesis, I value them not, and scorn their inconsiderate judgement.

De Revolutionibus Coelestibus.

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

Near the sun is the center of the universe.

The strongest affection and utmost zeal should, I think, promote the studies concerned with the most beautiful objects, most deserving to be known.

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

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.