Chaotic planetary orbits. Animation showing how the motion of an object in the gravity field of more than one other object is chaotic (unpredictable) in nature. Tiny variations in the initial parameters (location and and velocity) cause large and arbitrary changes in the orbit. In this simulation, several thousand spheres move in the gravity field of four spheres (planets, blue). At the start, the difference in the position between neighbouring spheres is only one ten-millionth of their radius. However, after few seconds of motion, the paths of the different spheres diverge and finally become completely chaotic by the end of the animation.