The butterfly effect is the concept that small causes can have large effects. Initially, it was used with weather prediction but later the term became a metaphor used in and out of science.
In chaos theory, the butterfly effect is the sensitive dependence on initial conditions in which a small change in one state of a deterministic nonlinear system can result in large differences in a later state. The name, coined by Edward Lorenz for the effect which had been known long before, is derived from the metaphorical example of the details of a tornado (exact time of formation, exact path taken) being influenced by minor perturbations such as the flapping of the wings of a distant butterfly several weeks earlier. Lorenz discovered the effect when he observed that runs of his weather model with initial condition data that was rounded in a seemingly inconsequential manner would fail to reproduce the results of runs with the unrounded initial condition data. A very small change in initial conditions had created a significantly different outcome.
On this day in history, June 28, 1914, the driver for Archduke Franz Ferdinand, nephew of Emperor Franz Josef and heir to the Austro-Hungarian Empire, made a wrong turn onto Franzjosefstrasse in Sarajevo.
Just hours earlier, Franz Ferdinand narrowly escaped assassination as a bomb bounced off his car as he and his wife, Sophie, traveled from the local train station to the city’s civic city. Rather than making the wrong turn onto Franz Josef Street, the car was supposed to travel on the river expressway allowing for a higher speed ensuring the Archduke’s safety.
Yet, somehow, the driver made a fatal mistake and tuned onto Franz Josef Street.
The 19-year-old anarchist and Serbian nationalist, Gavrilo Princip, who was part of a small group who had traveled to Sarajevo to kill the Archduke, and a cohort of the earlier bomb thrower, was on his way home thinking the plot had failed. He stopped for a sandwich on Franz Josef Street.
Seeing the driver of the Archduke’s car trying to back up onto the river expressway, Princi seized the opportunity and fired into the car, shooting Franz Ferdinand and Sophie at point-blank range, killing both.
That small wrong turn, a minor perturbation to the initial conditions, or deviation from the original plan, set off the chain events that led to World War I.