Isaac Newton

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1. 01

   An object stays at rest or keeps moving steadily unless something pushes it, and the same force pulling an apple down also keeps the Moon in orbit.

   Philosophiae Naturalis Principia Mathematica · 1687

   An object stays at rest or moves uniformly if no net force acts on it.

   Newton realized gravity does not stop at your roof. It pulls an apple from a tree and the Moon overhead the same way. The difference is speed: the Moon moves sideways so fast that it keeps falling toward Earth without ever hitting it. He linked sky and ground with one set of rules.

   “Every body perseveres in its state of rest, or of uniform motion in a right line, unless it is compelled to change that state by forces impressed thereon.”

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