It News: The Four Rules of Time-Travel Movies

The Four Rules of Time-Travel Movies

By STEVE KNOPPER
September 20, 2012

In the middle of the coming movie "Looper," Bruce Willis, a retired hit man from the future, sits in a diner and offers some wisdom: "I don't want to start talking about time travel," he snarls. "Because if we start talking about time travel, we're going to be here all day, making diagrams with straws."

Mr. Willis's character is explaining one of the ironclad rules of time-travel movies: Don't get too bogged down with scientific details. "Time travel doesn't make sense," says "Looper" director Rian Johnson. "All you can do is construct a system for it."

"Looper," a thriller about time-traveling mob victims which opens next week, is the latest in a long list of books, movies and TV shows wrestling with the complexities of time travel. From H.G. Wells's "The Time Machine" in 1895 to L. Sprague de Camp's 1956 "A Gun for Dinosaur," time-travel stories often present headache-inducing puzzles and contradictions that can easily trip up the best storytellers.

Shane Carruth's 2004 film "Primer," for example, is so complex and methodical that fanatical bloggers have posted flow charts containing thousands of words of plot summary. "Even if you dig into that deeply enough, you're going to find stuff that doesn't make sense," says Mr. Johnson, the "Looper" director, who is a "Primer" fan.

One of the first time travel stories, Norwegian Johan Wessel's 1781 comedic novel "Anno 7603," mostly skitters over any scientific snarls, focusing on a couple who visit the past with the help of a fairy, according to physicist Paul J. Nahin's book "Time Machines: Time Travel in Physics, Metaphysics and Science Fiction."

Mark Twain's "A Connecticut Yankee in King Arthur's Court" in 1889 cleverly explains his hero's Camelot journey as a hazy dream. And Cecil B. DeMille's 1925 film "The Road to Yesterday" is also basically free of story contradictions. (The wife's frigidity toward her husband turns out to be the result of an injustice committed in an earlier time, when he was a knight and she was a gypsy about to be burned at the stake, according to the IMDb movie database.)

By 1944, René Barjavel's French sci-fi novel "Le Voyageur Imprudent" has already discovered the perils of the grandfather paradox: If a time traveler kills off his grandfather when he visits the past, can he still exist in the present?

Today's time-travel movies generally follow the blueprint of entertainment-above-science, often farcically ignoring the contradictions caused by time-travel storytelling.

"Bill and Ted's Excellent Adventure" in 1989 brought historical dudes, such as Genghis Khan and Abraham Lincoln, to modern-day California. They made no mention of what they'd do with the future knowledge once they returned. The characters in 2010's "Hot Tub Time Machine" deliberately fiddle with their own pasts to improve their futures, and the movie leaves many of its strings untied.

Writers have names for all the pitfalls such stories can induce. In addition to the grandfather paradox, the "butterfly effect" is based on a scientific theory that a butterfly flapping its wings a certain way can lead to an epochal event; thus, altering what the butterfly does in the past can drastically change the present. The duplication paradox emerges when time travelers exist in the same time and place as their past or future selves.

Some movies and TV shows ("The Butterfly Effect," "Lost," "Primer") agonize over these plot inconsistencies, trying to tie up every conceivable loose end. Others ("Bill and Ted's Excellent Adventure," "Midnight in Paris," "Safety Not Guaranteed") happily ignore the finer points of physics.

In "Looper," the mob sends condemned men 30 years into the past so that hired killers (such as Joe, played by Joseph Gordon-Levitt) can blow them away with giant guns. Everything proceeds in orderly, if grim, fashion, until one day the mob sends Joe's future self (Mr. Willis) to be executed ("closing the loop") and Young Joe allows Old Joe to escape.

Like "Terminator," one of Mr. Johnson's time-travel inspirations, "Looper" establishes the science, mostly via expository voice-overs by Mr. Gordon-Levitt, then spends much of the movie avoiding it.

"I did spend quite a lot of work coming up with an intricate and—for a time-travel movie, at least—very tight set of rules," Mr. Johnson says. "But then I gave myself permission to say, 'Let's see the effect of those rules on screen but not explain them to the audience.' "

What follows are four time-honored rules of movie time travel:

1. Change only the fictional characters' histories.
At no point in 1955 does Marty McFly of "Back to the Future" assassinate President Eisenhower, introduce the Apple computer or invest in the stock market. (He does inadvertently teach Chuck Berry how to invent rock 'n' roll guitar, but that's another story.) "We can't change the history that everybody else has. We can only change the history of the McFly family," says Bob Gale, who co-wrote the 1985 classic with Robert Zemeckis. "That was our trick. That's how we got away with what we got away with."

2. Use the alternate-reality loophole.
Before creating last year's "Source Code," starring Jake Gyllenhaal as a soldier who inhabits a commuter's body to repeatedly relive a bombing event on a train, screenwriter Ben Ripley read a little about physics and the theoretical realities of time travel. He also remembered one of his favorite movies, "Groundhog Day." And he found his loophole.

"There seemed to be a willingness on the part of science to contemplate the existence of parallel realities—perhaps an infinite number of them," Mr. Ripley says.

Thus, Mr. Gyllenhaal's Sgt. Colter Stevens could continually return to the past and do all sorts of things, happy or sad, without affecting the present. "It was kind of freeing," Mr. Ripley says. "He could change anything and not experience the consequences—that was one of the rules we set down in telling the story, and we never broke it."

3. Inconsistencies be damned.

Long after the release of "Time After Time," the 1979 movie in which Jack the Ripper travels to the future using H.G. Wells's time machine, screenwriter Nicholas Meyer woke up in the middle of the night. Why, he wondered anxiously, didn't Mr. Wells just travel 24 hours back in time to stop the murderer from entering his machine in the first place?
Ordinarily, Mr. Meyer wouldn't have lingered on that question. His movie-time-travel philosophy boils down to: Don't worry about it. If the audience loves the film while watching it, who cares whether inconsistencies come up later? Certainly fans of "Star Trek IV," which Mr. Meyer co-wrote, dealing with the Enterprise's transportation of whales from 1980s Earth to the future, was not scientifically airtight.

"You take a look at 'A Midsummer Night's Dream'—do you have to believe in fairies to make the whole thing work?" Mr. Meyer asks.

In retrospect, he would have added expository dialogue—a landlady saying, "Why don't you wait at the bottom of the stairs for the murderer to show up?" and Mr. Wells responding, "What if I can't stop him? The guy's carrying around a bunch of knives and he's stronger than me."

Does Mr. Meyer regret not thinking of this solution earlier? "Of course I regret it!" he says. "I can't live with myself."
4. Don't kill your grandfather.

In "Looper," one of the characters declares, "So I changed it"—and corrects not only his own timeline but the timeline of everybody else in the film. That would never have taken place on "Lost." For the ABC series' screenwriters, "Back to the Future" was a cautionary tale: "Doc Brown comes back and says, 'Marty, you've got to come back to the future, there's something wrong with your kids!'—he fixed one thing, but there is now another problem as a result of doing this," says co-creator Damon Lindelof. "Every great time-travel story is, you go back to fix something, but you end up creating something much worse, and you're just fighting to get back to square one, if you're lucky."

So when Sayid, traveling through the past, encounters young Ben, knowing he will one day grow up and torment the island castaways, he shoots him. But Ben survives.

"We employed this rule—'whatever happened, happened,' " Mr. Lindelof says, referring also to the title of a crucial 2009 episode. "The past was fixed. You couldn't go back and kill your grandfather and create a paradox—something will not let that happen."

Even with this rule, though, the labyrinthine details of this aspect of "Lost" nearly drove Mr. Lindelof and his fellow screenwriters insane. "I wish I could have traveled back in time," he says, "and never have done time travel."