American mathematician and meteorologist Edward Norton Lorenz (1917–2008) came up with chaos theory as a way of explaining the unpredictable way in which mathematical and natural systems (including weather) behave. The idea was that even the tiniest changes in initial conditions of a complex, dynamic system can lead to huge, measurable effects over time. As a colorful metaphorical illustration of this concept, he posed that a single butterfly flapping its wings in Brazil could be the instigator of a tornado in Texas. He called this the “butterfly effect.”