The Butterfly Effect is a theory developed by the mathematician and chaos theorist Edward Lorenz. While studying weather patterns Lorenz developed the Lorenz attractor, which defined his theory; the sensitive dependence on initial conditions in which a small change in one state of a deterministic non-linear system can result in large differences in a later state.

Lorenz’s theory is derived from the metaphorical example of the details of a tornado (exact time of formation, exact path taken) being influenced by minor perturbations such as the flapping of the wings of a distant butterfly occurring several weeks earlier. A very small change in initial conditions had created a significantly different outcome.