Occult, mysterious and ad hoc, energy should have no place in modern physics. Newton had no use for it. Motion, in the form of momentum, was enough for him.
Momentum kept the universe moving. But what causes the planets to orbit the sun and the moons orbit their planets? What is the watch-spring of the universe?
Leibniz believed that momentum was not enough. He wanted something to explain what made the ball roll down the hill; the arrow leap from the bow; the wind begin to blow on a still day. He wanted to find the force that gave life to motion.
Leibniz 1646 – 1716
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