| kepler | (n) German astronomer who first stated laws of planetary motion (1571-1630), Syn. Johannes Kepler, Johan Kepler |
| kepler's first law | (n) a law stating that the orbit of each planet is an ellipse with the sun at one focus of the ellipse |
| kepler's law | (n) (astronomy) one of three empirical laws of planetary motion stated by Johannes Kepler, Syn. Kepler's law of planetary motion |
| kepler's second law | (n) a law concerning the speed at which planets travel; a line connecting a planet to the sun will sweep out equal areas in equal times, Syn. law of equal areas, law of areas, Example: Kepler's second law means that a planet's orbital speed changes with its distance from the sun |
| kepler's third law | (n) a law stating that the ratio of the square of the revolutionary period (in years) to the cube of the orbital axis (in astronomical units) is the same for all planets, Syn. harmonic law |
