Force Vector Field of the Restricted 3-body system

     The "restricted 3-body problem" involves 5 Lagrange points in the system of two orbiting primary masses. The Lagrange points are unstable equilibrium points for motionless masses (masses not moving relative to the rotating frame of the two primaries).
     The effect of the gravitational attractions of the two primaries, as well as the non-inertial forces created by observing the system from within the moving frame, creates a net force inside this frame that relates to the position of any third small mass. The physlet to the right is used to illustrate that force by creating a "vector field" showing the strength (via the colors of the arrows) and the direction of the forces at points in the "grid" of the plane.
     You can use the radio buttons below to select different systems to watch (different pairs of gravitational objects), as well as different areas of the rotating plane to watch - so you can zoom in and see the vector field more closely near the Lagrange points.