In this activity, a translucent, half-ellipsoid-shape, molded acrylic polystyrene object—known as a “rattleback”—is placed on an overhead projector or under a document camera and is observed to spin freely if pushed in a counterclockwise direction. When spun in a clockwise direction, it slows down quickly, starts to rock in a vertical direction, and reverses to its “natural” counterclockwise rotation. Similarly if the rattleback is pushed down on either end, the resulting rocking motion changes to rotation in the “preferred” direction of movement. The science concepts addressed in this activity include the nature of science (i.e. evolution of theories) center of gravity, friction, rotational dynamics, stability, and inertia and conservation of energy.