Orbital Simulator -- Classroom Activity The simulator at http://observe.arc.nasa.gov/nasa/education/reference/orbits/orbit_sim.html allows students to investigate Kepler's three laws of planetary motion.  Ask students to work in small groups to explore the simulator, and to keep a record of what they do.  On the Third Law simulation, bear in mind that the relationship (period squared) ~ (radius cubed), when translated into mean orbital speed, becomes (speed squared) ~ (1/radius), so a smaller radius implies a higher speed.  The following are possible questions for classroom discussion:  A. First simulator: The Law of Ellipses: At what point does the satellite move the fastest? At what point does the satellite move the slowest? The Earth is at one focus of the ellipse.  What is at the other focus? What does the orbit look like if the eccentricity is set at one of the values for a planet about the Sun? B. Second simulator: The Law of Areas: Which end of the ellipse is the yellow section thinnest on? Which is it the thickest? The yellow section shown will always be the same area, although sometimes it is thinner and sometimes it is thicker.  How can this be the same area, yet have a different shape? (You might have to demonstrate conservation using the same amount of liquid in two differently shaped cups.) C. Third simulator: The Harmonic Law: How does the period of revolution of the Shuttle compare with that of a geosynchronous satellite?  With the period of the Moon? While the space shuttle orbits the earth, it doesn’t speed up or slow down by accelerating like a car.  Instead, it moves to a higher or lower orbit.  What does it need to do if it wants to speed up? What does it need to do to slow down?