I have to admit, I’m a sucker for a great time travel story. Whether it’s Star Trek, H.G. Wells or The Terminator, there’s something about the confusion, impossibility and theoretical consequences of traveling backwards and forward through time that engages and excites the imagination. However, not all time travel stories are created equal, and there are many different theories (fictional and real) on exactly how time travel might work, if it were possible. I’m not going to debate whether time travel is actually possible or not – Stephen Hawking’s party for time travelers may have unfortunately proved this – but rather examine the elements that make for an exciting and mind-bending time travel story, within which universe time travel – according to the rules set forth in the story – is entirely possible.

Paradox

Let’s get the obvious out of the way first: one of the most intriguing aspects of time travel stories is the concept of temporal paradoxes – the notion that by going (specifically) back in time, you can cause an event that would, in one way or another, prevent you from going back in time. The most famous of these is the grandfather paradox: if you go back in time and murder your grandfather before your father was born, you would never have existed, and therefore couldn’t have gone back in time to commit the murder.

There are a number of stories that deal with this – and other – paradoxes in wonderfully inventive ways. One of my favorites is Futurama’s feature-length episode, Bender’s Big Score. In it, a ‘time code’ is discovered (on main character Fry’s butt cheek, of all places) that allows for one-way backwards time travel (the traveler can go back in time to any point in history, but cannot return without waiting it out). A group of scammers get hold of the time code and use it to pull off heists in the past – all by using the robot, Bender, who can commit the crime, then simply wait out the centuries in the basement until bringing the pilfered goods at just the right moment.

The paradox presented in this episode is that of time duplicates: the more you use the code, the more copies of you end up in history, leading to the possibility of encountering yourself, and even killing yourself (or, in one somewhat disturbing scene, making out with yourself). This is corrected, humorously enough, by introducing a concept called the ‘doom-field’; the time code corrects all paradoxes by ‘dooming’ any time duplicates to death or destruction. This leads to some rather emotional moments, as Fry ends up going back in time to relive life in the 20th century, only to discover that his arch-nemesis, Lars, is not who he seems to be.

There are, of course, countless other paradoxes presented by the concept of time travel, and each story deals with it in interesting ways; some embrace the paradox, using it as a reason for everything to have happened in the first place, while others try to find a way around the paradox, but it’s one of the key aspects of any decent time travel story.

Fish-Out-Of-Water

Another major component of time travel stories, whether used for serious plot devices or simply for humor, is the idea that by traveling to another point in time – whether the past or the future – the traveler will find themselves woefully unprepared to deal with life in that other time. In cases where the traveler finds themselves in the past, we usually see a technologically advanced character in a position of superiority to the inferior technology of the past; when the reverse is the case, we usually see the character marvel incomprehensibly at the newness of imagined future technology.

One of the earliest examples of a going-to-the-past time travel story is Mark Twain’s A Connecticut Yankee in King Arthur’s Court, where the protagonist is hit over the head and awakens in 6th-century England, around the time of King Arthur and the Knights of the Round Table. Whilst the story itself is something of a satire, the concept of an advanced character in a primitive setting is inventive (for the time). It helps that the main character, Hank, is an engineer, and therefore able to recreate the technology of the 19th century without additional aid, but a famous moment comes partway through the story when he is challenged to joust a fellow knight; rather than go through with the contest and potentially get killed himself, he fashions a rudimentary gun and simply shoots his opponent.

Of course, traveling to the past is entertaining in that we get to feel superior to our ancestors; traveling to the future, however, is an opportunity to engage both the author and the reader’s imagination and see how we would feel if presented with significantly more advanced technology than currently exists. To some extent, sci-fi shows such as Star Trek, set entirely in the future, are an example of this, but the fish-out-of-water concept specifically comes in when a character from the past is introduced. Star Trek has actually done this several times, but one of my favorites is the episode Relics, where Scotty, the engineer from the original series, finds himself aboard the Enterprise-D after almost a century of suspended animation.

This episode specifically plays on the notion that technology advances rapidly, and that we as humans are inevitably going to feel left behind, whether due to age or other advancements. Scotty, once-revered as a wizard of engineering, suddenly finds himself unable to do even the ‘simplest’ things (such as changing the dilithium crystals required for warp drive), because advancements in the century he was absent rendered most of his knowledge completely obsolete. It’s an interesting take that doesn’t really deal with time travel specifically, but more so deals with the the idea that human technology will one day advance beyond us all, and that what is incomprehensible today will one day be commonplace knowledge.

Causality

Perhaps connected to the idea of paradox, causality is also an important aspect of time travel stories, inasmuch as traveling back in time to cause an event is just as important a notion as going back in time to prevent one. Coming out of the blue as it did in 1984, seemingly billed as a simple action vehicle for Arnold Schwarzenegger, one of the best examples of this is the movie (and subsequent franchise) The Terminator. In it, the infamous titular villain is sent back in time from a future in which machines have taken over the world, on a mission to enact a grandfather paradox: killing the mother of the leader of the human resistance, meaning that John Connor would never be born, thus ensuring the victory of the machines.

However, The Terminator takes this a step further by introducing a second character sent back in time, Kyle Reese: a human, knowing the machines’ plot, is sent to stop the terminator before it can kill Sarah Connor. IN doing so, Kyle falls unexpectedly in love with Sarah Connor, and without knowing it, fathers her son: John Connor. In other words, the human savior would not have been born at all if the machines’ plot to kill his mother had not been hatched – which it wouldn’t have been, had it not already happened. It’s actually really quite confusing.

In this instance, we see an example of causality: in going back in time, Kyle caused an event to happen (the conception of John Connor) that ensured he would eventually have to go back in time to cause it to happen. In real life, causality usually only goes one way: we do a thing, which in turn causes another to happen. When the ability to travel into the past is introduced, things get funky: we can cause things that have already happened, leading into the time where we go back to cause it to happen again (an almost never-ending loop).

There are quite a few other aspects of time travel that I haven’t gone into, such as multiple timelines (see Back to the Future), but these are some of the aspects that intrigue me the most, and are most likely to get me hooked when reading/watching a time travel story. What are your favorite time travel movies, shows and books? Are there aspects discussed in them that I haven’t mentioned? What makes them so appealing to you? Let me know in the comments!