Two identical pendulums, except one starts 0.001 radians off. Watch them diverge.
Approx. largest Lyapunov exponent: …
Estimated by tracking a hidden shadow copy of the left pendulum that is nudged back to a distance of 0.001 after every frame (Benettin's method). A positive value (per second) means nearby paths diverge exponentially, i.e. chaos. It is noisy at first and settles over a few dozen seconds. A single arm is a plain pendulum, so it stays near zero.