Changes to one part of a complex system can lead to dramatically different changes in other parts.

A minor change to the state of an object or event (such as the flap of a butterfly’s wings or a slightly different starting position of a double pendulum’s arms) can eventually, through countless compounding effects, cause a dramatic change later on (like the metaphorial Texan tornado or a different double pendulum pattern).

The double-rod pendulum is one of the simplest dynamical systems to demonstrate nonlinearity. Compared to a linear system of one arm swinging from a fixed position, two swinging arms attached to each other produce behaviours that are close to impossible to predict.

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