The dream of time travel probably arose out of a desire to go back and correct one’s past mistakes—or to visit the future and subsequently return to take advantage of foreknowledge. The concept intrigues historians and archaeologists for obvious reasons. Science fiction has explored the possibility of time travel many times, as well as the pitfalls of visiting the past and impacting the future.
Technically, time travel—of the “into the future” sort—is within the realm of possibility. In fact, it happens all the time—just on such a small scale that no one notices. Given that a starship engine could be developed that accelerates a ship to relativistic speeds at which time dilation occurs, time travel can be achieved simply by achieving 90% of the speed of light for a short time, then returning to one’s point of origin. For every minute you spend flying at 90% the speed of light, 2.3 minutes pass everywhere else. Travel at relativistic speeds long enough and you could return to a time predating the rise of human civilization!
Traveling into the future isn’t a very useful ability if one has no way back—which is where the concept of traveling into the past breaks down. The principle of causality rather logically argues that an effect cannot occur before its cause—meaning, in this case, that one cannot arrive in the past via the use of a time machine before that time machine is invented.