desk comments, "We don't want anyone going who'll panic at the first shot. Six Safari leaders were killed last year, and a dozen hunters." The moment when Eckels sees the massive dinosaur, he panics and runs off the Path.

Once Eckels and the other members of the Time Safari crew arrive in the past, Travis issues a warning about the importance of staying on the hovering Path. Travis explains that the Path is anti-gravity and says,

Doesn't touch so much as one grass blade, flower, or tree. It's an anti-gravity metal. Its purpose is to keep you from touching this world of the Past in any way. Stay on the Path. Don't go off it. I repeat. Don't go off. For any reason! If you fall off, there's a penalty.

Travis's remarks about the Path and the penalty attached to stepping off it foreshadows Eckels's tragic mistake.

In addition to Travis's warning regarding the importance of staying on the Path, Travis also explains the implications of accidentally disturbing the past and dramatically changing the future. Travis elaborates on the "chaos theory," also known as the "butterfly effect," which is when a small change in the past is multiplied exponentially and alters the trajectory of human history. Travis's explanation foreshadows the outcome of Eckels accidentally stepping on a prehistoric butterfly. After Eckels runs off the Path and steps on a prehistoric butterfly, they travel back to the present, where Deutscher is the president and the United States is a dystopia.

The most obvious foreshadowing is when Travis warns Eckles about leaving the path. He states that even if Eckles stepped on and killed a mouse it could result in mice dying out, which in turn could effect other animals who rely on mice for food. Billions could be destroyed by the killing of just one animal.

However, there are more subtle hints littered throughout the story. At the very beginning, the reader can detect the nervous disposition of the main character Eckles when the author states that "Warm liquid gathered in Eckels' throat. He swallowed and pushed it down." Eckles than gives an indication of the danger of the situation he's putting himself in by saying, "Don't I get some kind of document promising that I will come back alive?" The reply by the office, "we promise nothing," is equally ominous.

In fact, the entire end of the story is summarized in the first page. First, the official says that Eckles would face government action if he doesn't follow his guide's orders, and second, they talk about what would have happened if Deutscher instead of Keith was elected. "We're lucky. If Deutscher had gotten in, we'd have the worst kind of government."

The aggression of Travis and how serious he takes his job is foreshadowed from the moment Eckles meets him. Travis first of all talks to him angrily about what would happen if he went off the path and then he shouts at Eckles when Eckles jokingly points his gun at an animal.

Finally, Eckles outlines just precarious it is to travel back in time.

In sixty million years, Election Day over. Keith made President. Everyone celebrating. And here we are, a million years lost, and they don't exist. The things we worried about for months, a lifetime, not even born or thought of yet.

Probably the most important and critical example of foreshadowing to be found in "A Sound of Thunder," is the scene in which the hunting expedition first arrives in the distant past, and Travis goes over the protocols, as well as the existential threat that time travel represents. This scene ultimately sets the stage for everything that will follow in the story.

Here we find Travers' instructions to stick to the path, as a way of protecting the timeline. As he says it, to "touch so much as one grass blade, flower, or tree" is forbidden. He then proceeds to describe the existential dangers that time travel involves, and the ways that even the smallest, most apparently insignficant, changes can have catastrophic implications on the larger timeline. He uses as his example a single mouse, killed before its time: on its own, it might not seem like a dramatic change, but in effect you have not just killed that mouse, but also every mouse that has descended from that initial mouse, which would have impacted the predators of those mice, and so on down the line. As he puts it, to step off the path and risk even the smallest, most apparently insignificant impact this far back in time, is to risk unseen, catastrophic damage to all of history.

This scene proves prophetic, because Travers' warnings are precisely what come to pass later in the story. Eckels panics in the face of the Tyrannosaurus, leaves the path, ends up stepping on a butterfly, and proceeds to change the course of history.

There are several instances of foreshadowing in Bradbury's "A Sound of Thunder":

1. The title itself acts as a prediction since thunder often precedes a storm, which can be a dangerous occurrence.
2. As he enters the Time Safari, Inc. office in order to pay for his trip Eckels's nervousness is apparent as he is described in this manner: "Warm phlegm gathered in Eckels' throat; he swallowed and pushed it down." (His lack of nerve serves as a predictor of what he later does.)
3. The words of the official also foreshadow future events: 

If you disobey instructions, there's a stiff penalty of another ten thousand dollars, plus  possible government action, on your return.

4. Eckels's conversation with the man-behind-the-desk hints at how easily circumstances can be altered by time. After Eckels looks at the Time Machine, he remarks, 

"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."

The man agrees, saying that the other candidate, Deutscher would have instituted a dictatorship. He adds that before the election, people called, wondering if they could go live in 1492 if Deutscher were to win. But, he adds, the company only does safaris.This foreshadows the change of time that Eckels causes, giving Deutscher the election, after all.

5. The man's warning to Eckels, "We don't want anyone going who'll panic at the first shot. Six Safari leaders were killed last year, and a dozen hunters" also foreshadows the panic that Eckels does feel when he sees the Tyrannosaurus Rex.

6. The guides' strict warning to Eckels to not stray from the Gravity Path because Time can, then, be altered certainly suggests the grave mistake of stepping on a butterfly that Eckels makes.

Foreshadowing refers to a technique by which writers give advance hints about key plot points which will emerge later on within the story. Bradbury's "A Sound of Thunder" follows Eckels, a time traveller, as he goes back into the Cretaceous to hunt a dinosaur only to inadvertently rewrite human history.

This short story begins in the future society which the time travelers themselves come from (and which will later be recreated as a result of Eckels's actions in the distant past). At this point in the story, Bradbury provides several details that will become important later on. Even the story's first paragraph does much to set up the transformations to come. The story begins with Eckels staring at a sign. It reads:

TIME SAFARI, INC.
SAFARIS TO ANY YEAR IN THE PAST.
YOU NAME THE ANIMAL.
WE TAKE YOU THERE.
YOU SHOOT IT.

Later, we learn about recent election results and how one candidate, Keith, defeated his opponent, Deutscher. Eckels is a supporter of Keith's, and a Time Safari Employee describes Deutscher as an authoritarian, stating:

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.

These details might seem incidental at first until Eckels returns from his time in the past. In that moment, their full importance within the narrative becomes clear. By describing the world as it had been, Bradbury can contrast it with the world Eckels creates. The sign we observe in the story's beginning returns, but now it reads:

TYME SEFARI INC.
SEFARIS TU ANY YEER EN THE PAST.
YU NAIM THE ANIMALL.
WEE TAEK YU THAIR.
YU SHOOT ITT.

The world has changed in other ways as well, with the election results having reversed (with Deutscher defeating Keith). Meanwhile, the Time Safari employee who had previously been a critic of Deutscher is now described as a supporter instead. Bradbury writes:

The man behind the desk laughed. "You joking? You know damn well. Deutscher, of course! Who else? Not that damn weakling Keith. We got an iron man now, a man with guts, by God!

Additionally, note how the mechanism by which Eckels rewrites history is established ahead of time by Bradbury through a conversation between Eckels and Travis. Here, Travis describes the potentially catastrophic consequences of killing a single mouse and the ripple effects that could result from apparently insignificant changes. As Travis insists:

The stamp 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.

What Travis is warning about is precisely what occurs later in the story. Eckels, panicked by his encounter with the Tyrannosaurus, inadvertently steps on a butterfly. From that change, all of history is rewritten.

Foreshadowing is a literary device that writers use to drop hints about what is going to occur within a particular story.  

Ray Bradbury's "A Sound of Thunder" is full of foreshadowing. Early in the story, the characters discuss how glad they are that Keith won the election. They briefly discuss what the ramifications might have been like if Deutscher had won the election. That discussion foreshadows the end of the story. Eckels's mistake changes the election results.  

The following exchange is also a good example of foreshadowing in the story.

"A Tyrannosaurus Rex. The Tyrant Lizard, the most incredible monster in history. Sign this  release. Anything happens to you, we're not responsible. Those dinosaurs are hungry." 

Eckels flushed angrily. "Trying to scare me!" 

At this point in the story, Eckels is full of confidence in himself. He comes off as brash and cocky; however, Eckels becomes completely terrified the moment that he sees the dinosaur.  

Once the group of hunters is in the past, I feel that there is one more significant piece of foreshadowing. The safari leaders specifically emphasize the importance of staying on the path.

"Stay on the Path. Don't go off it. I repeat. Don't go off. For any reason!"

Unfortunately, Eckels's fear gets the better of him, and without realizing what he is doing, he steps off of the path, kills a butterfly, and changes the results of the election.

You can predict the ending based on the comments about changing the future and the discussion of who is president.

You can make a prediction that the men are going to change the future from the fact that such a big deal is made about how careful they have to be because it is easy to change the future.  In the beginning of the story, they discuss who the president is.  This is a text clue that foreshadows the ending, when another man is chosen president.

“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, antiChrist, 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. …”

This foreshadows the ending when Deutscher is president.  In the present, Keith has been elected and they are happy because certain people feel that Deutscher would be a tyrant.  At the end of the story we will see the spelling on the sign is different and Deutscher is president.

Another example of foreshadowing is the caution about how easy it is to change the future by changing something in the past.  The government regulates time travel carefully, we are told.  There is a special path, and you do not step off that path!

“We don’t want to change the Future. We don’t belong here in the Past. The government doesn’t like us here. We have to pay big graft to keep our franchise. A Time Machine is finicky business. Not knowing it, we might kill an important animal, a small bird, a roach, a flower even, thus destroying an important link in a growing species.”

These text clues indicate that someone is going to step off the path to change the future.  All of that talk about not changing anything in the future definitely foreshadows Eckels stepping off the path onto the butterfly.  He changes the future, just like we have been warned against.

There are, indeed, several hints of things to come in Bradbury's short story. When Eckels arrives at the Time Safari, Inc., he swallows hard and "a warm phlegm gathered" in his throat. Evidently, he is nervous about his trip to hunt the Tyrannosaurus Rex. When he asks if the safari guarantees that he will return, the official tells him that his company has no guarantee upon anything but "the dinosaurs." He also adds,

If you disobey instructions, there's a stiff penalty of another ten thousand dollars, plus possible government action, on your return."

And, as Eckels looks around, he notices

a sound like a gigantic bonfire burning all of Time, all the years and all the parchment calendars, all the hours piled high and set aflame.

Here are suggestions that something serious may happen with the manipulation of "Time" if things do not go as calculated. As he waits, Eckels talks about the recent election, grateful that the man who has won the presidential election is in office since his opponent would have created a dictatorship. The official assures him that all he has to worry about is shooting his dinosaur.

The foreshadowing here is that the outcomes of the present time may change, Eckels may have trouble shooting his dinosaur, and he may have to pay a penalty for disobeying instructions.

"A Sound of Thunder" concerns a group of hunters on a time safari - they use a time machine to travel into the distant past, in order to hunt animals that are extinct in the modern era. In this setting, the concept of foreshadowing becomes a bit confused - normally it is taken to refer to things that will happen in the future, but because this story takes place in various times, it's easier to think of foreshadowing as a reference to the future of the narrative, rather than the timeline itself.

I think the most significant foreshadowing that takes place in this story is the response Eckels receives to one of his questions. When he hears that the safari group has already scouted out his tyrannosaurus by using the time machine to go into the past, track the tyrannosaur, and see how it would have normally died, he assumes that they must also be able to use the machine to watch the safari take place, and see what its outcome was. Eckels is concerned about whether everyone survives, since he is strongly warned about the number of people who have died on safaris recently.

In response to Eckels' question, the safari leader, Travis, and his assistant Lesperance give each other "a look". On first impressions, this seems to suggest that they did observe the outcome of the expedition, and the shared look is a means of reassuring each other and looking for support when admitting that not everyone survives (most likely, not Eckels). While this is not, in fact, the case, and the two are probably just irritated at Eckels' oblivious questions, it nevertheless implies, based on body language alone, that Eckels will not survive the trip.