The short story "A Sound of Thunder" is largely about unintended consequences. It is called the ripple effect or the butterfly effect. The story has entered our culture, because the butterfly effecf is referred to often by people. Many stories involving time travel also refer to the problems that can be caused by going back in time and changing the future. Consider the "Back to the Future" movie series, for example. In these movies, going back in time dramatically changes the future, and like in this story the future is far worse. In your personal life, you have probably made a choice that seemed small at the time, but had great consequences. Consider the legend of the man who gives up his seat on the plane, and then the plane crashes. Apparently this happened to Buddy Holly, a singer. Legend goes that it was a coin toss that resulted in his death.