In the famous science fiction short story "A Sound of Thunder" by Ray Bradbury, a man named Eckels books a place in an unusual hunting expedition through a company called Time Safari, Inc. He and a group of other travelers take a guided trip back in time sixty million years to hunt a Tyrannosaurus Rex. When they arrive, Mr. Travis, the guide, warns everyone to stay on the hovering path so that they don't disturb any plants or animals. If they do, they might change the future. The animals that the hunters are allowed to shoot are carefully pre-tracked and marked; they are selected because they would have died within minutes anyway.
When they spot the huge terrifying dinosaur, though, Eckels panics, inadvertently stepping off the path and crushing a single butterfly. That tiny difference is enough to unloose a chain of events so that by the time they get back to the future, it is irreparably changed.
A branch of chaos theory known as the "butterfly effect" posits that infinitesimal events...
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