The Butterfly Effect

Many of us have heard of the butterfly effect but what does it mean? In short, the butterfly effect is a property of chaotic systems (such as the atmosphere) by which small changes in initial conditions can lead to large-scale and unpredictable variations in the future state of the system.

Mathematician and meteorologist Edward Lorenz noted that the butterfly effect is derived from the metaphorical example of the details of a tornado being influenced by minor perturbations such as a distant butterfly flapping its wings several weeks earlier. He discovered the effect while he was observing runs of his weather model with initial condition data that were rounded in a seemingly inconsequential manner. He noted that the weather model would not reproduce the same results of runs with the unrounded initial condition data. A very small change in initial conditions had created a greatly different outcome. The butterfly effect concept has since been used outside the context of weather science as a broad term for any situation where a small change is supposed to be the cause of larger consequences.

In a paper in 1963 given to the New York Academy of Sciences, Lorenz said that one meteorologist had remarked that if the theory were correct, one flap of a sea gull's wings would be enough to alter the course of the weather forever. Later, Lorenz used the more poetic butterfly in his speeches and papers. Although a butterfly flapping its wings has remained constant in the expression of this concept, the location of the butterfly, the consequences, and the location of the consequences have varied widely

The phrase refers to the idea that a butterfly's wings might create tiny changes in the atmosphere that may change the course, speed or even prevent the tornado. The butterfly itself does not cause the tornado but it is part of an interconnected web of conditions that lead to the tornado. One set of conditions leads to a tornado, while the other set of conditions does not.

In reality, the theory is much more complex than one simple idea. It has many mathematical discoveries and equations that it encompasses. We still cannot predict beyond a certain finite time horizon, no matter how accurate our initial conditions are.