"Therefore, since it is the heavens that contain all things, it is not the heavens that move, but rather the earth, which is contained within the heavens, that moves."

"I consider it the chief duty of an astronomer to gather the observations of the heavenly bodies, and to explain their motions by hypotheses."

"Yet because the novelty of the undertaking, which I knew to be contrary to the accepted views of the common people, might be regarded as absurd, I long hesitated."

"For it is the duty of an astronomer to compose the history of the celestial motions from a careful and skillful study of the observations."

"The order of the planets is this: Saturn, Jupiter, Mars, Earth, Venus, Mercury."