Born From a Rounding Error

In 1961, Edward Lorenz reran a weather simulation but rounded one input from 0.506127 to 0.506. The result diverged completely — a tiny change produced a totally different forecast. He published this as "Deterministic Nonperiodic Flow" in 1963, and chaos theory was born.

The name "butterfly effect" came from his 1972 talk: "Does the Flap of a Butterfly's Wings in Brazil Set Off a Tornado in Texas?" Mathematically, we cannot rule it out. Chaotic systems amplify small differences exponentially, so given enough time, even a tiny measurement error makes prediction impossible.