In Ray Bradbury's celebrated short story "A Sound of Thunder," Eckels signs up to participate in a Time Safari, where he will have the rare opportunity to travel sixty million years back in time to hunt a dinosaur. Once Eckels, several other hunters, and the safari guides arrive back in time, Travis instructs them to remain on the floating path. Travis proceeds to emphasize the importance of remaining on the path so that the travelers do not touch or alter the environment of the past in any way, shape, or form.

He explains to the hunters that they do not belong in the past, and accidentally killing a seemingly insignificant animal could destroy an important link in a growing species. Travis then uses the example of accidentally killing one mouse, which means all the future families of the one particular mouse are destroyed. By killing a single mouse, billions of future mice cease to exist, which adversely affects the fox and lion population. Once the lion and fox populations are affected, "insects, vultures, infinite billions of life forms are thrown into chaos" and will also cease to exist. Travis proceeds to elaborate on this theory by telling Eckels,

By stepping on one single mouse. So the caveman starves. And the caveman, please note, is not just any expendable man, no! He is an entire future nation. From his loins would have sprung ten sons. From their loins one hundred sons, and thus onward to a civilization. Destroy this one man, and you destroy a race, a people, an entire history of life. It is comparable to slaying some of Adam's grandchildren. The stomp of your foot, on one mouse, could start an earthquake, the effects of which could shake our earth and destinies down through Time, to their very foundations.

Essentially, killing one mouse could set off a chain reaction that dramatically alters the course of human history, which is exactly what happens when Eckels accidentally kills a prehistoric butterfly.