Genre in the Mainstream: Time Travel Yes. Spaceship? No.

In the intersections between mainstream literature and genre fiction, certain fanciful concepts seem to translate better than others. Ghost stories drift in and out of a variety of genres, haunting us in Victorian romances, scaring us out of our wits in traditional horror, as well as showing up in contemporary urban fantasy.

The notion of a ghost might be the most mutable of all fantasy concepts, a survivor among genre tropes. But what else? Do certain imaginative ideas have a greater ability to sneak into mainstream literature than others? In terms of crossover potential, the conflict can be clearly defined between time travel and the space travel. “Regular” literature seems to like time travel a whole lot more than space travel. But why?

Ghosts are important in understanding why time travel crosses over into the mainstream more frequently than its cousin, space travel. As far back as Shakespeare’s Julius Caesar or Hamlet, ghosts are hogging a portion of the narrative spotlight. In older stories like these, ghosts tend to encourage living characters to do or not do something or warn them of some kind of past mistake or impending doom. In this way, ghosts are a bit like time travel insofar as they exist outside of a story in a non-linear way. While Hamlet can’t go back in time and literally talk to his father, his father can travel forward in time as a ghost and speak to Hamlet. When you tilt your head a certain way, ghosts are perpetual time travelers, traveling into a future beyond their deaths.

With this in mind, Charles Dickens’s A Christmas Carol represents two kinds of time travel as it features ghosts who drag a person into the past and into the future. Though Scrooge can’t actually effect the past Marty McFly style, the act of time traveling in his own timestream does alter his present, and in turn, create an alternate reality from the one depicted by the Ghost of Christmas Yet to Come. (One of the reasons why the Doctor Who episode “A Christmas Carol” works so well is because writer Steven Moffat essentially kept this thematic constraint the same.)

A shadow of time travel also exists in contemporary literature via historical fiction, particular historical fiction containing anachronisms. Julius Caesar infamously depicts a clock tower’s chimes, though there were no such clock towers in Ancient Rome. While this might have just been a mistake on Shakespeare’s part, it also may have been intentional, a way of messing with the temporal location of the story in order to make the drama more appealing. In fact, you might argue this single anachronism is what makes it totally acceptable for numerous Shakespeare narratives to be set in different time periods. Is this a form of time travel on the part of the author: the insinuation of contemporary concepts into a past world? Perhaps. Ernest Hemingway certainly makes use of a similar strategy in his short story/closet drama “Today is Friday.” In this one, three Roman soldiers drink at a bar and talk about the recent crucifixion of Jesus. The dialogue isn’t too different from the way characters sound in other Hemingway stories; they use words like “ain’t” and “guys” which I’m fairly certain don’t have direct Latin translations. The point is we’re not really reading historical fiction with Julius Caesar or “Today is Friday.” Instead, it’s like Shakespeare or Hemingway traveled back in time and then wrote down their approximation of what they witnessed.

Post-Mark Twain’s A Connecticut Yankee in King Arthur’s Court, time travel hasn’t left the pages of mainstream literature for long. In recent years it’s made a come back, cropping up in everything from Diana Gabaldon’s Outlander to Audrey Niffenegger’s The Time Traveler’s Wife. These books are almost certainly not aimed at science fiction and fantasy fans, nor was “Today is Friday” aimed at people who were really into Bible lore or Ancient Rome. Instead, these authors are smart like Hemingway and Shakespeare insofar as they know the idea of communicating with other times and the people in those times resonates with most every reader in some kind of deep-rooted way.

But spaceships are different. If the literary ancestors of time travel are ghosts and anachronisms, then I suppose the ancestors of spaceships would be sailing ships. But this is too literal, because while there are connections between the genre of military science fiction and naval narratives like C.S. Forester’s Hornblower books, that doesn’t really account for what spaceships are all about or what they represent in the zeitgeist. Spaceships are more fanciful on a subconscious level because in terms of how they’re used in fiction, a real world analog doesn’t really exist. Sure, humans have traveled in space, but not in the far-flung way depicted in science fiction. We can imagine a starship, but with much greater difficulty than we can imagine time travel. This is because a spaceships/starships not only exist in an imaginary future, but they also represent a setting. Spaceships aren’t just vehicles in science fiction narratives; they’re also homes for the characters. Mainstream literature prefers its settings to be literally on terra firma. A good example of this can be illustrated in the inverse, by talking about a science fiction novel which crosses over into the mainstream, Stranger in a Strange Land.

Heinlein doesn’t bother too much in this book explaining how or why the spaceships from Mars to Earth operate, it’s simply important that they do. Valentine Michael Smith just needs to get from Mars to Earth, and then the real story can get going. Instead of exiling a literary concept in a science fiction narrative, Heinlein took a science fiction thing and put it into a literary world. This partly works because Valentine Michael Smith is a human, but it also works because the book isn’t really about space travel or Mars at all. It’s about Earth. In Vonnegut’s The Sirens of Titan the flying saucers (also piloted by HUMAN Martians) only have an On/Off button to make them go. Though Vonnegut gives an in-universe reason for this simplistic functionality of the saucers (they were designed for a one-way journey) this example ultimately sums up how mainstream literature utilizes space travel. It’s simply a means to an ends, and not a story in it of itself.

Most of us haven’t actually ridden in space, and even those of us who have haven’t been to Mars (probably). But we have read history books, and we do know people who have lived in past worlds. On a very basic level we can physically conceive of time travel, at least as far as the human experience is concerned. Spaceships are more fantastical, almost like dragons from future. They’re fire-breathing beasts with a whole magical context of their own. And until our technology catches up to our imagination, spaceships may continue to fly only in the contexts of hard science fiction with an occasional crash-landing in the mainstream.

Unless of course you have a combination spaceship/time machine handy.

Ryan Britt is a staff writer for Tor.com.