A double pendulum consists of two pendulums with the rod on the lower pendulum hanging from the bob of the other. It is a classic example of a chaotic system in which what the system does depends very sensitively on the initial conditions. You can learn more about the physics on the double pendulum on our wiki or see the resulting fractal in greater detail with our fractal explorer.
We can ask a simple question: if we start with the two pendulums making a particular angle with the vertical, how long will it be before either pendulum flips through the vertical? In the picture, green is a short time, followed by red, purple, blue and white.
