“Donnie Darko” offers a time travel lesson you won’t find elsewhere

In film, there are many ways to tell a story that involves time travel. Some movies, such as the Terminator franchise, simply include the phenomenon as a plot device, reckoning that the technical explanation is unimportant to the plot. Other times, as in Groundhog Day, characters get stuck in a time loop, only breaking out of it once a moral lesson is learned. Still others explore time travel in a scientific (or scientific-sounding) fashion, such as Back to the Future, Primer, or Everything Everywhere All at Once. Usually, time travel is introduced as a device to alter the past in order to bring about a superior outcome for those here in the present: a theme common to most time travel movies.

But every once in a while, a story comes along that subverts those expectations. In 2001, the film Donnie Darko (spoilers ahead) was released: a time travel story that begins both miraculously and ominously when Donnie leaves his bedroom on October 2, 1988, to go sleep in a field. (Starting on October 2, 2026, corresponding to the critical days of the events of the film set in 1988, a remastered version of the original movie will be rereleased in select theaters for three days.) A few hours later, a jet engine from an unidentified plane mysteriously crashes through his affluent family’s room, landing on his bed, where it would have killed him if he had remained there. Donnie is visited by Frank, the voice in his head manifesting as a man in a bunny suit, who compels him to leave his bed just a little bit earlier, and receives a mysterious message that, in precisely 28 days, 6 hours, 42 minutes, and 12 seconds, the world will end. The ensuing story does indeed involve time travel, but the lessons inside the story touch on much more than the underlying physics behind the idea of time travel.

Donnie Darko, as we’re introduced to him, is an outcast: both at home and at school. At home, his parents and sisters view him uneasily, as someone with mental illness (schizophrenia) who, despite being very intelligent, struggles at school and has been held back. Donnie’s older sister is politically active, advocating for Michael Dukakis’ 1988 presidential campaign, while Donnie’s affluent and more conservative father dismisses her astute observations and criticisms of the nature of America’s power structure.

At school, Donnie is frequently bullied, and often has deep, insightful thoughts about his assignments: something that makes him stand out among his classmates. There are only two teachers that Donnie has a well-established rapport with: his English literature teacher, whose challenging, thoughtful, and complex assignments often go over the heads of most students, and his science teacher, who initially feeds Donnie’s interest in deep scientific concepts that go beyond the standard curriculum. On the other hand, Donnie clashes with the school administrators and particularly the gym teacher, whose overly simplistic view of the world leads Donnie to intellectually embarrass her: something that leads her to retaliate against Donnie, but which doesn’t impact her attitude toward Donnie’s youngest sister, who gets the lead role in a performance of the gym teacher’s dance team, Sparkle Motion.

Over the course of the movie, Donnie exhibits a large amount of personal growth on many fronts, while becoming more social, taking initiative to learn more about what he’s curious about, and also bolder. Donnie approaches a girl that he’s interested in after engaging in his first targeted acts of violence and destruction at the urging of Frank. Frank often offers him guidance as to what to do next, and Donnie, who initially lets Frank’s voice direct his actions completely, begins to live a life that seems to pan out better than it had previously. Donnie forms closer bonds with his friends and classmates, is genuinely cared for by Gretchen, who becomes his girlfriend, is taken more seriously by his therapist and parents, and takes an interest in his education: an interest that his science and English teachers take note of.

When Donnie becomes curious about time travel, he approaches his science teacher after class. The teacher begins by telling Donnie about established science and then speculative extensions to it, leading Donnie to go pursue an education farther than what the school’s curriculum can provide. The notion of time travel in the film follows the most common thread as far as realistic scenarios for time travel go: through the idea of an Einstein-Rosen bridge, or a region of severely curved spacetime that connects one location, or event in spacetime, to another.

The idea of an Einstein-Rosen bridge dates back to the 1930s, when Albert Einstein, working with his student Nathan Rosen, had a profound realization: The presence of matter and energy can curve, deform, and distort the fabric of spacetime, and both positive and negative types of curvature are possible. A strong enough, massive enough, and dense enough region can create a pathological object: a black hole, for example. You can also have higher-dimensional objects than a zero-dimensional, point-like object such as a black hole:

• a cosmic string in one dimension,
• a domain wall in two dimensions,
• or a cosmic texture in three dimesions.

What Einstein and Rosen showed was that if you had either two such objects (like two black holes) with the right properties or a single object (for example, a cosmic string) that connected two separate locations in spacetime — including two distinct locations in space or two events at the same location in space but at different moments in time — you could create a “bridge” between those two events. It would be possible, if you could stabilize the bridge connecting those two events, to send matter through it: a portal from one point in space and time to another.

These Einstein-Rosen bridges have been more thoroughly developed in the latter half of the 20th century and throughout the first quarter of the 21st century, culminating in what we call a modern-day wormhole. Forms of exotic matter with negative energy density could create a traversable wormhole, as could sufficiently high-charge, low-mass matter that prevents the formation of a charged (Reissner-Nordstrom) black hole. Alternatively, extra-dimensional formulations of gravity, such as those suggested by string theory, could admit traversable wormholes as well.

One intriguing way to make a wormhole that results in time travel is to first create a stable wormhole, and then, at one (and only one) of the two openings, accelerate it close to the speed of light. As the accelerating wormhole travels rapidly through space, it experiences a slower motion through time. If someone then entered the end of the wormhole that didn’t undergo the acceleration, they would emerge from the other end of the wormhole at an earlier time: up to a minimum time of the moment the wormhole was first created. Through a mechanism such as this, it would become physically possible to do as Donnie Darko does: travel back in time by 28 days, 6 hours, 42 minutes, and 12 seconds.

One of the pioneers of this idea — of using a traversable wormhole, where one end is accelerated to create a significant time difference between the two ends — to travel back in time is physicist Ronald Mallett. Back in 1955, Ronald’s father died of a heart attack when Ronald was only 10, leaving him devastated. Then, the next year, he read an illustrated version of H.G. Wells’ classic science fiction story The Time Machine, leading him to resolve to travel back in time to see his father again and save his life. Mallett went on to become a physics professor who specialized in General Relativity, and he eventually concocted a scheme that could lead to travel back in time to the past in a fashion very similar to what’s been described here.

In Mallett’s case, which is excellently laid out in his book Time Traveler: A Scientist’s Personal Mission to Make Time Travel a Reality, his whole motivation for traveling back in time is to see his father again, to potentially save his father’s life, and to soothe the child version of himself that was so distraught in the aftermath of the loss of his father.

If he were to succeed, however, one would have to wonder: What would have become of the Ronald Mallett who lived in this timeline? The one who was inspired to become a physicist, to study relativity, to invent his solution for a traversable wormhole, and who spent his life attempting to solve such a difficult problem? If he succeeded, an entirely different timeline would have been written: one where his father lived, and one where his entire life would have unfolded quite differently. It’s like pondering a branch of the multiverse that our Universe didn’t follow: the ultimate cosmic game of “what if” as far as the road not taken is concerned.

There’s an idea — popular in philosophy of physics circles, although less so in pure physics circles — known as the block Universe theory, where all of reality at all times, past, present, and future, all coexist equally. This philosophy, also known as eternalism, stands in contrast to presentism, where only the “now” exists, and the past is written, but the future remains unwritten. This philosophical idea was popular in the early days of Einstein’s relativity, but the discovery of quantum physics rendered it very questionable. After all, quantum physics showed us that the state of a quantum system does not inherently exist with a single, predetermined outcome, but rather exists as a superposition of all possible outcomes until the moment that a measurement (or sufficiently energetic interaction) occurs.

Only at that moment does the quantum state get determined, with quantum principles like interference, superposition, and quantum uncertainty all playing a role in the probability distribution that describes the potential outcomes that can occur. The “block Universe” view and quantum physics can be reconciled through a scenario known as the evolving block Universe, where the past is written, the present can be either a determinate or indeterminate state depending on what has/hasn’t been measured, but the future is wholly indeterminate: only describable in probabilistic terms. For example, a single radioactive atom may or may not have already decayed, but until a measurement is made, the outcome cannot be determined.

In Donnie Darko, Donnie sees a feature emerging from each person’s chest that’s in his vicinity: a visual cue to their future trajectory, which appears to be already predetermined, suggesting that outcomes for future situations are already assured. Donnie receives instructions from Frank and feels compelled to follow them. Donnie leaves his bedroom and doesn’t die when the jet engine falls, floods the school and winds up walking Gretchen home, leading Gretchen to become his (first) girlfriend, and burns down the house of a grifting self-help guru who has poisoned the minds of several teachers and administrators at his school, exposing the guru as a pedophile in the process.

However, things take a darker turn. Donnie’s English teacher, who assigned the most intellectually challenging material we see in the film, gets fired over an insignificant controversy involving the choice of a Graham Greene short story. His science teacher, who encouraged him, tells Donnie that “he could get fired” if he continued to discuss the topic of time travel with him. Donnie reads a book called The Philosophy of Time Travel — written by Roberta Sparrow, an elderly former science teacher now known as “Grandma Death” for routinely and futilely checking her mailbox while oblivious to oncoming cars on the road — to learn more about time travel. Meanwhile, the gym teacher who was supposed to take Donnie’s sister’s dance troupe to a faraway competition, instead is organizing the defense of the grifting guru against the (undeniably true) allegations of pedophilia. Donnie’s mother takes her instead (guilted into it by the infamous line, “sometimes I doubt your commitment to Sparkle Motion”), set to fly back the next morning.

Upon visiting Roberta’s mailbox for the final time the day before the timetable is set to expire, Donnie sees a car driven by Frank run over his girlfriend Gretchen. Instead of listening to Frank when Frank emerges from the car, Donnie shoots him, seemingly signifying Donnie’s rejection of Frank’s guidance. The next morning, Donnie’s mother and sister are flying back on an airplane when suddenly the plane begins shaking. It becomes clear that the engine that initially fell through Donnie’s bedroom ceiling comes from that very plane. Donnie returns, with Gretchen’s body, to the location we first find him in: in the field he slept in 28 days, 6 hours, 42 minutes, and 12 seconds earlier.

In the next moment, “the end” comes, just as was foretold by Frank. Donnie time travels back to the start of the story, but instead of leaving his bed, he remains there: sleeping soundly with a smile on his face. Instead of all of the personal growth we’ve seen in Donnie and the positive effects he’s had on others at school and elsewhere in the world — including exposing a child abuser, making a meaningful connection with Gretchen, helping his friends stand up to bullies — Donnie uses time travel for the opposite purpose of most science fiction stories: to give up on the hope of creating a better future and choosing to end his own life instead. The entire story we saw, from the moment the jet engine crashes through his ceiling until the full 28 days, 6 hours, 42 minutes, and 12 seconds elapse, becomes a branch of the multiverse that was not taken, with Donnie dying instantly instead.

It leads me to ponder a question that doesn’t usually arise in time travel stories: Is death the only way that anyone experiences time travel? Did the entire movie tell of a timeline that never actually existed, but instead represented a non-physical branch of the multiverse: one that would only have been possible had things turned out differently than they actually did?

Tragedies, such as death, are often used as the motivating factor for a time travel story, with the idea usually being to travel back in time to prevent the outcome of death (or many deaths), with the protagonist learning lessons about themselves as they improve their own life and the lives of others around them. In Donnie Darko, however, all of those improvements are undone by Donnie’s time traveling, and his choice to remain in his bed not only leads to his own demise, but leads to:

• the grifting, pedophilic guru remaining rich, influential, and powerful,
• the school remaining corrupt and afraid of any education that engages critical thought,
• Gretchen remaining alone, without love in her life, and in danger,
• and where bullies continue to terrorize Donnie’s schoolmates.

Instead, we’re left with Roberta Sparrow’s chilling words to Donnie Darko: “Every living creature on Earth dies alone,” and the darkly haunting song “Mad World,” playing as the final tragedy of the film, and its aftermath, unfolds.

Perhaps there is no time travel. Perhaps the version of reality we know — where all of the tragedies that weren’t avoided could never have been avoided — is the only one there is, was, or could be. After all, Einstein’s General Relativity and quantum physics have something in common: They have many mathematical solutions and offer many possible outcomes for any initial physical setup. But in our reality, only one outcome to any observation or experiment ever actually occurs.

On June 28, 2009, Stephen Hawking threw a now famous “reception for Time Travellers” at the University of Cambridge. For hours, Hawking was alone in a grand reception hall, with flutes of champagne, a wide variety of snacks and foodstuffs, and balloons and many other decorations. Only the next day, on June 29, did the invitations go out. Hawking stated that he hoped that the invitations would survive for potentially thousands of years, and that if time travel were ever developed, someone would travel back to his party and attend. Alas, Hawking himself called the empty reception hall “experimental evidence that time travel is not possible,” although perhaps it will someday become so: just not all the way back to 2009.

If time travel to the past did occur, events that have already been written here, in the present, could be altered, and perhaps that paradox alone is enough to render time travel to the past an impossibility. But until it’s proven to be so, physicists — and storytellers of all types — will be compelled to consider it as a fascinating avenue for exploration of what could be. After all, time travel to the future is mandated by all we know about physics. If travel to the past is possible as well, the impact it could have on the Universe, as well as the trajectory of human civilization, is immeasurable.

This article is featured on Big Think.