planetary motion

The conditions under which this vivifying tide is received have their origin in the planetary motion.

The only reason for Kepler's angels was his ignorance of the causes of planetary motion.

But even he retained epicycles and excentrics, and could not explain the unequal orbits of planetary motion.

Accepting Kepler's laws as a statement of the facts of planetary motion, he deduced from them his theory of gravitation.

Kepler describes his sensations when he discovered the law of planetary motion.