Why is "The Sound of Thunder" considered a science fiction

The short story "A Sound of Thunder" is considered a science fiction story for many reasons. For example, most all of science fiction stories are set in the future. "A Sound of Thunder" is set in the year 2055. Also, science fiction stories deal with the affect of technology and the impact on society. In "A Sound of Thunder", the time machine created the ability to travel back in time; however, through out this story it shows you how if you change one little thing in the past in changes the outcome of what is happening in the present. The hypothetical invention of a time machine is very common within science fictional stories.