Some hold that the expression "butterfly effect" was

inspired by one of the most famous science-fiction stories by Ray Bradbury: A Sound of Thunder (in                               R is for Rocket  1952), which imagines that in the future, thanks to a time machine , temporal safaris are organised for tourists. In a remote prehistoric age a hiker from the future treads on a butterfly, and this sets off a chain of appalling consequences for human history

Alan Turing, in an essay of 1950, anticipated this idea:

 

«The displacement of a single electron by a billionth of a centimetre at one moment might make the difference between two very different events, such as a man being killed a year later by an avalanche, or escaping.»                              (Alan Turing, Computing Machinery and Intelligence, 1950)

All things considered, then, a single action can shape the future unpredictably: in the metaphor of the butterfly, the idea is that a simple movement of air molecules generated by the beating of the insect's wings may cause a chain of movements of other molecules until a hurricane is unleashed, perhaps thousands of kilometres away