Description

This simulation illustrates Kepler's Distance Law as applied to an eccentric circular orbit. The simulation shows two copies of Earth (blue and green), separated by some time delay, orbiting around the Sun in an eccentric circular orbit. The motion of these earths is determined by Kepler's Distance Law: that the speed of a planet is inversely proportional to the distance of the planet from the Sun. The simulation also highlights the area swept out by the Sun-earth line between the earth at these two times. Plots show how this area varies with time, as well as how the distance (to the blue planet) varies with time. The simulation can be used to demonstrate that Kepler's Distance Law closely approximates the more accurate Area Law (that the Sun-planet line sweeps out equal areas in equal times), since the distance law results in an approximately constant area (at least for small eccentricities).

Controls let the user speed up the simulation, change the eccentricity of the planet's orbit, or alter the initial angular separation (and thus the time delay) between the two earths.