Kepler stated 3 laws that today form the basis for understanding orbits.
- Planets move in elliptical orbits around the Sun.
- Planets move faster the nearer they are to the Sun.
- There is a relationship between the distance of a planet and the time it takes to orbit the Sun.
Law #1. Planets move in elliptical orbits around the Sun.
They do not move in circular orbits. Before Kepler astronomers did not recognise this and so their computations were flawed.
An ellipse is an oval shape with two foci (a focus). The Sun is at one focus and the other is in space.
- Bill Drennon, Central Valley Christian High School Animated Kepler's Laws
- Davidson's WebPhysics Animations
- UBC's Interactive Mathematics Interactive Simulator