Embrace chaos by making your own double pendulum fidget spinner

If the novelty of holding an elaborate bearing (possibly connected to some motion-sensitive LEDs) is wearing thin, have no fear: with a 3D printer and a little ingenuity, you can make your own double-pendulum fidget spinner, a chaotic system that is intensely sensitive to initial conditions, such that it becomes very hard to predict the motion of the pendulum when you set it to swinging. (more")