Newton and Kepler's Laws

Newton’s First Law

an object at rest will stay at rest unless acted on by an outside force

Newton’s Second Law

an object will not change direction unless acted upon by an outside force

Newton’s Third Law

for every action, there is an equal and opposite reaction

Kepler’s First Law

each planet's orbit about the Sun is an ellipse

Kepler’s Second Law

A radius vector joining any planet to the Sun sweeps out equal areas in equal lengths of time

Kepler’s Third Law

P² = a³