It was Kepler, THEN Newton. Get your history right.

There are two common falsities of the history of gravity which are purported by school teachers:

  1. That Newton, upon being hit by a renegade apple, found the equation F = - \gamma {m_1}{m_2}/{q^2} traced out by the seeds inside the fruit which, as he immediately realized, describes the motion of the planets.
  2. That Newton postulated the law of gravity and then used it to proved Kepler’s laws of planetary motion.

The first falsity is ridiculous and is rejected by anyone with half-a-brain. The second falsity, however, is held dear by many people even at the University level. This is not true.

Our freshman physics books may include a statement such as “Kepler’s laws of planetary motion can be derived from Newton’s laws of gravity.”  Some of them even derives Kepler’s laws. Of course, they are not lying. However, they leave the impression that Isaac Newton did precisely that. That is, he started with his  law of gravity that he found in his apple and then went to prove Kepler’s laws of planetary motion.

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