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Explanation for
Kepler’s Laws

•Momentum keeps the planets moving – you do not need some
force to do this.

•Gravity provides the force which makes orbits curve

–Gravity of Sun curves orbits of Planets

–Gravity of Earth curves orbit of moon (and also makes
objects on earth fall
downward)

•“Conservation of Angular Momentum” explains why motion
is faster when closer to
the sun.

•The inverse square law of gravity explains P2 µ a3 and the details of why the orbits are ellipses.