The Triumph of Heliocentrism

• 1687: Newton's Philosophiae Naturalis Principia Mathematica showed how the concept of gravity, coupled with Galileo's laws of motion, explains Kepler's ellipses (GG +54).

• Newton's laws of motion:

• Every body in motion or at rest tends to stay in motion or at rest unless a force acts on it.
• Force is measured as mass times acceleration.
• F = ma
• Fgravity = G m1 m2 / d2 (explains Kepler’s laws!)

• For every action there is an equal and opposite reaction.