1. Planets Along the Ecliptic

2. Retrograde Motion

3. Retrograde Motion Explained

4. Solar System Geometry

5. Circles vs. Ellipses

6. Kepler’s First Law of Planetary Motion

7. Kepler’s Second Law of Planetary Motion

8. Kepler’s Third Law of Planetary Motion

9. Sir Isaac Newton

10. Newton’s Law of Gravitation

11. Kepler’s Laws Explained All three of Kepler’s law can be explained by Newton’s gravity Ellipses are special cases: bound orbits 2 nd law follows from central force and conservation of angular momentum Newton’s form of Kepler’s 3 rd law: p 2 = 4  2 a 3 G(M 1 +M 2 )