Chaos Theory

It's the birthday of Edward Norton Lorenz, born in West Hartford, Connecticut, in 1917. He started out as a mathematician, but turned to meteorology during World War II. In an attempt to explain why it's so difficult to make a long-range weather forecast, he spawned chaos theory, one of the 20th century's most revolutionary scientific ideas.

 Chaos theory is sometimes known as "the butterfly effect," a term coined by Lorenz in an attempt to explain how small actions in a dynamic system like the atmosphere could trigger vast and unexpected changes. He discovered the effect in the early 1960s while entering values into a computer weather prediction program; instead of entering the number to the full six decimal places, he rounded it to three to save time, and the resulting weather pattern was completely different. He first framed it as the effect a seagull's wing has on the formation of a hurricane, but he changed it to the more poetic butterfly in his 1972 presentation, "Does the flap of a butterfly's wings in Brazil set off a tornado in Texas?"

Though the term dates back to 1972, the concept actually predates Lorenz's discovery. Science fiction writers had been playing around with the idea for several years in their time-travel stories: Usually the hero goes back in time and makes some seemingly insignificant choice that ends up changing the course of history. Writer's Almanac