Kepler's laws of planetary motion
(i) The orbit of each planet is an ellipse with the Sun at one focus.
(ii) The line joining a planet and the Sun sweeps out equal areas in equal times.
(iii) The squares of the times taken by the planets to complete an orbit are proportional to the cubes of the lengths of the major axes of their orbits.
These laws were formulated by Kepler, based on observations, but each can be deduced from Newton's inverse square law of gravitation.
http://astro.unl.edu/naap/pos/animations/kepler.swf
• Animation which illustrates all three laws.
- rectangle
- rectangular
- rectangular distribution
- rectangular hyperbola
- rectangular number
- rectilinear motion
- recurrence relation
- recurrent
- recurring decimal
- recursion theory
- reduce
- reduced echelon form
- reduced set of residues
- reductio ad absurdum
- reduction formula
- redundancy
- redundant
- re-entrant
- reflection
- reflex angle
- reflexive relation
- reflexive space
- Regiomontanus
- region
- regression