Caption: "A double pendulum (AKA double compound pendulum) in a long exposure photograph, tracked with an light-emitting diode (LED) light at its end. (Slightly edited.) The image illustrates chaos which is super sensitivity to initial conditions plus dynamical evolution. If the image maker had started the oscillations with even slightly different initial conditions, the track would eventually look wildly different in detail though qualitatively similar to what the image shows. Of course, friction in the pivot points and air drag means that the final condition will be the same for all initial conditions. The double pendulum will be at rest hanging straight down.