In the offices of Time Safari, Inc., a hunter named Eckels has contracted to travel back to pre-historic times so that he can shoot a Tyrannosaurus Rex. While he is in the office prior to his departure back in time, he is instructed that he must follow all rules or risk a $10,000,00 fine. One of these rules is that he must remain at all times on the anti-gravity metal path created by the company. Mr. Travis, one of the hunting guides, strictly instructs Eckels that while they are in the time machine not to stray from this metal path under any conditions. When Eckels asks him the reason for this strict rule, Travis replies that in the first place, the government does not approve of Time Safari, Inc.:
"We don't want to change the Future. We don't belong here in the Past..... 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."
Travis further explains,
Crushing certain plants could add up infinitesimally. A little error here would multiply in sixty million years, all out of proportion.
In essence, Travis speaks of what is known now as the balance of nature; by removing one species from the environment, others can then be harmed in some way. This is what is sometimes called "The Butterfly Effect." For this reason, the anti-gravity path has been created by Time Safari, Inc.