"Thus, the sun, although it is the center of the world, is not the center of the universe."

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

"The universe is a harmonious system, and all its parts are in perfect accord."

"The Sun, the Moon, and the five wandering stars are all governed by the same laws."

"For the Earth, which is a planet, must therefore move in a circle around the Sun."