《费曼物理学讲义》书摘

Any great discovery of a new law is useful only if we can take more out than we put in. Now, Newton

usedthe second and third of Kepler’s laws to deduce his law of gravitation. What did hepredict?First, his analysis of the moon’s motion was a prediction because it connected the falling of objects on the earth’s surface with that of the moon. Second, the question is,is the orbit an ellipse?We shall see in a later chapter how it is possible to calculate the motion exactly, and indeed one can prove that it should be an ellipse, so no extra fact is needed to explain Kepler’sfirstlaw. Thus Newton made his first powerful prediction.

http://www.feynmanlectures.caltech.edu/I_07.html