Playground · Double Pendulum
Double pendulum
Two rods, one hinge, and pure deterministic chaos. The motion is fully determined by the starting angles — yet it's effectively unpredictable, because the tiniest difference in the start grows exponentially. Turn on the chaos twin to see it.
Sim time
0.0
Twin divergence
—
how far the nudged copy has drifted
How it's built
Vanilla JS on a <canvas>. The two coupled equations of motion (from the Lagrangian) are
integrated with RK4 at a small time-step, so energy stays sensible over long runs. The
chaos twin starts from an angle just 0.001 radians different — identical to
the eye, yet within seconds it peels away completely. That sensitivity to initial conditions is the same
reason the three-body problem, and the weather, resist long-term prediction.