A Sound of Thunder

"A Sound of Thunder" is a science fiction short story by American writer Ray Bradbury, first published in Collier's magazine on June 28, 1952, and later in Bradbury's 1953 collection The Golden Apples of the Sun.

Plot summary
In the year 2055, time travel has become a practical reality, and the company Time Safari Inc. offers wealthy adventurers the chance to travel back in time to hunt extinct species such as dinosaurs. A hunter named Eckels pays $10,000 to join a hunting party that will travel back 65 million years to the Late Cretaceous period, on a guided safari to kill a Tyrannosaurus rex. As the party waits to depart, they discuss the recent presidential elections in which a far-right candidate, Deutscher, has been defeated by his opponent Keith, to the relief of many concerned.

When the party arrives in the past, Travis, the hunting guide, and his assistant warn Eckels and the two other hunters about the necessity of minimizing the events they change before they go back, since even the smallest alterations to the distant past could snowball into catastrophic changes in history. Travis explains that the hunters are obliged to stay on a levitating path to avoid disrupting the environment, any deviation will be punished with hefty fines and prosecution, Time Safari scouts had been sent back to select and tag prey whose death will have minimal effect on the future prior to the hunt, and the time machine "steps aside" to prevent people from encountering themselves in the past.

Although Eckels is initially excited about the hunt, when the monstrous Tyrannosaurus approaches, he loses his nerve. Travis tells him to go back to the time machine, but Eckels panics, steps off the path, and stumbles into the forest. The other four shoot and kill the dinosaur and see that Eckels has found his way back to the time machine. Travis threatens to leave him in the past before ordering him to remove the bullets from the dinosaur's body, as they cannot be left behind.

Upon returning to 2055, Eckels and the rest of the party notice major changes; English words are now spelled phonetically, and worst of all, Deutscher has won the election to the approval of the pro-fascist populace. Looking at the mud on his boots, Eckels finds a crushed golden butterfly, whose death has apparently changed the nature of the alternative present to which the safari has returned. He frantically pleads to undo the damage, and the story ends on a gunshot fired by Travis.

Adaptations
A comic-book version appeared in issue #25 of EC Comics's Weird Science-Fantasy (1954), adapted by Al Feldstein with art by Al Williamson and Angelo Torres.

The story was adapted for the first issue of Topp's Publishing's Ray Bradbury Comics (1993) with art by Richard Corben.

The story was adapted for the fourth season episode six of The Ray Bradbury Theater on October 8, 1989, starring Kiel Martin.

A film adaptation of the same name starring Ben Kingsley, Edward Burns, and Catherine McCormack was released in 2005. Famed film critic Roger Ebert stated that while he "cannot endorse it, [he] can appreciate it" as a film that is bad because it "want[s] so much to be terrific that [it] explode[s] under the strain."

A Game Boy Advance video game based on the film was also released. It was finished in time for the film's planned 2003 release, delayed along with it, and ultimately released in February 2005. Planned console ports were canceled.

The story is parodied in the Time and Punishment section of The Simpsons episode "Treehouse of Horror V."

The story is referenced in a brief scene at the beginning of the Doctor Who episode "Space Babies."

Influence
"A Sound of Thunder" is often credited as the origin of the term "butterfly effect", a concept of chaos theory in which the flapping of a butterfly's wings in one part of the world could create a hurricane on the opposite side of the globe. The term was actually introduced by meteorologist Edward Norton Lorenz in the 1960s. However, Bradbury's concept of how the death of a butterfly in the past could have drastic changes in the future is a representation of the butterfly effect and is used as an example of how to consider chaos theory and the physics of time travel.