Lorenz discovered the effect when he observed runs of his weather model with initial condition data that were rounded in a seemingly inconsequential manner. Lorenz originally used a seagull causing a storm but was persuaded to make it more poetic with the use of butterfly and tornado by 1972. He noted that the butterfly effect is derived from the metaphorical example of the details of a tornado (the exact time of formation, the exact path taken) being influenced by minor perturbations such as a distant butterfly flapping its wings several weeks earlier.
The term is closely associated with the work of mathematician and meteorologist Edward Norton Lorenz. In chaos theory, the butterfly effect is the sensitive dependence on initial conditions in which a small change in one state of a deterministic nonlinear system can result in large differences in a later state. Over time the differences in the dynamics grow from almost unnoticeable to drastic. In each recording, the pendulum starts with almost the same initial condition. Experimental demonstration of the butterfly effect with different recordings of the same double pendulum.
