The Butterfly Effect.

Of course, a single act like the butterfly flapping its wings cannot cause a typhoon.

Small events can, however, serve as catalysts that act on starting conditions.

In an experiment to model a weather prediction, Edward Lorenz ( a meteorologist and a mathematician) entered the initial condition as 0.506, instead of 0.506127.

The result was surprising: a somewhat different prediction. From this, he deduced that the weather must turn on a dime. A tiny change in the initial conditions had enormous long-term implications. 

He theorized that weather prediction models are inaccurate because knowing the precise starting conditions is impossible, and a tiny change can throw off the result. To make the concept understandable to non-scientific audiences, Lorenz began to use the butterfly analogy.

A butterfly has the potential to create tiny changes which, while not creating a typhoon, could alter its trajectory.

A flapping wing represents the minuscule changes in atmospheric pressure, and these changes compound as a model progresses. Given that small, nearly imperceptible changes can have massive implications in complex systems, Lorenz concluded that attempts to predict the weather were impossible. 

he butterfly effect is somewhat humbling—a model that exposes the flaws in other models. It shows science to be less accurate than we assume, as we have no means of making accurate predictions due to the exponential growth of errors.