The characters who travel back in time arrive in the threatening prehistoric forest and confront the dangerous dinosaur, which threatens their lives.

Travis's dispute with Eckels is an example of another external conflict, man vs. man conflict. After Eckels panics and runs off the hovering path, Travis tries to leave him in the past for jeopardizing the Time Safari company and threatening to change the history of the world. Once they return to the present, Travis threatens to kill Eckels when he realizes that the United States is a dystopia because of Eckles's actions.

Another external conflict in the story is a man vs. society conflict, which concerns the way Eckels's tragic accident significantly impacts the presidential election and society at large. By stepping on a prehistoric butterfly, Eckels changes the future and affects the election results. When he returns to the present, Eckels discovers that Deutscher has won the election and transformed the United States into a dystopia.

The internal conflict in the story concerns Eckels's personal struggle to remain calm in the face of danger. When Eckels sees the massive Tyrannosaurus Rex for the first time, he panics and says,

It can't be killed ... We were fools to come. This is impossible.

Eckels completely loses his composure and sprints away from the dinosaur as fast as he can. Eckels's inability to control his emotions and stay relaxed is considered a man vs. self internal conflict.

"A Sound of Thunder" by Ray Bradbury is a quick moving, suspenseful short story. Conflict adds tension to any short story, and this one is no exception. There are four types of conflict:

External

1. Man Vs. Man -- During their trip back in time, Eckels panics when he sees the dinosaur and steps off the path, a huge mistake that could alter time. Travis, the tour guide, is furious with Eckels and threatens to leave him back in the past. He states:

"Stay out of this!" Travis shook his hand away. "This fool nearly killed us. But it isn't that so much, no. It's his shoes! Look at them! He ran off the Path. That ruins us! We'll forfeit! Thousands of dollars of insurance! We guarantee no one leaves the Path. He left it. Oh, the fool! I'll have to report to the government. They might revoke our license to travel. Who knows what he's done to Time, to History!"

This Man Vs. Man conflict adds tension between the two main characters of the story and adds to the suspense the reader feels as to what they will find when they return to present day. 

2. Man Vs. Nature -- This is the conflict that Eckels feels with the dinosaur he encounters in the past. It is huge - far bigger than he expected and he loses his nerve. Aside from the physical battle between the men and the dinosaur, this conflict also overlaps with Eckels internal conflict, man vs. self. 

3. Man Vs. Society -- This conflict is what makes the novel interesting; it begins as a sort of backdrop, seemingly unimportant, but by the end of the novel, Eckels' worst fear comes true and Deutscher is President. At the beginning of the story, Eckels states:

"Makes you think, If the election had gone badly yesterday, I might be here now running away from the results. Thank God Keith won. He'll make a fine President of the United States." "Yes," said the man behind the desk.

"We're lucky. If Deutscher had gotten in, we'd have the worst kind of dictatorship. There's an anti everything man for you, a militarist, anti-Christ, anti-human, anti-intellectual. People called us up, you know, joking but not joking. Said if Deutscher became President they wanted to go live in 1492. Of course it's not our business to conduct Escapes, but to form Safaris. Anyway, Keith's President now.

This sets up another external conflict that reappears again at the end of the story. 

Internal

4. Man Vs. Self -- This conflict is really the turning point of the story: Eckels loses his nerve and panics, veering off the path and rewriting history. When he sees the dinosaur, he states:

"Get me out of here," said Eckels. "It was never like this before. I was always sure I'd come through alive. I had good guides, good safaris, and safety. This time, I figured wrong. I've met my match and admit it. This is too much for me to get hold of."

He has a moment of realistic observation when he sees this dinosaur and is legitimately frightened. His veering off the path is what causes the change in the future. 

This excellent short story explores the ethics and dangers of time travel by offering us as spectators the ultimate safari showdown between man and dinosaurs. Clearly, therefore, the external conflict is the conflict betweel Eckels and the other men and the Tyrannosaurus Rex they hope to kill. However, more interestingly, the internal conflict that goes on inside of Eckels is with his own fear and sense of futility as he sees the dinosaur come striding towards him:

It can't be killed... We were fools to come. This is impossible.

Note how what Eckels says here captures his thoughts that trying to kill such a beast is ludicrous because of its size and power. As he sees the dinosaur, Eckels realises that he has bitten off more than he can chew, and fear wins out as he retreats from the creature bearing down on him.