Debunking the Butterfly Effect

These days we are all familiar with the concept of the “butterfly effect.” The usual formulation goes something like this: when a butterfly flaps its wings in one part of the world (often the Amazon jungle) it can cause a hurricane in another part of the world. The colossal disparity in magnitude between cause and effect embodied in the idea has fired the collective imagination around the globe.

Butterflies surround a glowing ball of energy

At the level of our lives, the famous butterfly effect is largely an urban myth. (Image: Thomas Cotterill)

The butterfly effect was “discovered” in 1961 by MIT meteorologist Edward Lorenz. He was working at the time as an assistant professor in MIT’s department of meteorology where one of his projects involved an early computer program designed to simulate weather. As so often happens in science, his discovery was accidental. Looking to save some input time, he rounded one of a dozen numbers representing atmospheric conditions from .506127 down to .506. To his amazement, the tiny reduction utterly transformed his long-term forecast. Lorenz wrote about the experience in a 1972 paper titled, “Predictability: Does the Flap of a Butterfly’s Wings in Brazil Set Off a Tornado in Texas?” The title was imaginative, intriguing, and provocative. A completely new idea was born. Vast opportunities for exciting scientific speculation suddenly sprang into being.

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