For decades, he hid his time-travel obsession. Now, he is challenging the assumptions that underpin our universe.

• After the death of his father, theoretical physicist Ronald Mallett embarked on a lifelong quest to build a time machine.
• Inspired by Albert Einstein’s concept of time dilation—wherein time moves differently based on your point of reference—he began studying black holes.
• The time travel theory Mallett has developed is mathematically sound, but just because it theoretically works doesn’t mean it will in practice.

Ronald Mallett’s 70-year-long obsession with time travel was borne out of tragedy, but also out of love. A theoretical physicist originally from the Bronx, Mallett was always a curious kid, and his father, Boyd, who worked in the city as a television repairman, nourished that desire for knowledge.

“He was a stickler about education—he’d give me toys like a gyroscope or radio set, and in order to get my allowance, I had to answer questions from my multiplication tables,” Mallett recalls. “For me, the sun rose and set with him.”

In 1955, Mallett’s father unexpectedly died at age 33 from a massive heart attack. A year later, Mallett came across a book that would change his life—a Classics Illustrated version of The Time Machine by H.G. Wells. “When I read that, it was like the sky opened up,” Mallett recalls. “If I could build a time machine and go back into the past, maybe I could see him again.”

Mallett immediately got to work, building his own makeshift time machine out of old television, radio, and bicycle parts. Naturally, it didn’t work, which he says is for the best as it “probably would’ve burned the house down.” Mallett continued to harbor this dream of time travel until eventually stumbling upon the work of Albert Einstein.

Nearly half a century before Mallett began exploring the famous German physicist’s work, Einstein mic-dropped some serious physics knowledge in the form of his Theory of General Relativity. Among many details in this science-altering theory, Einstein noted that time wasn’t as absolute as Newtonian physics had predicted, but instead was interwoven into the fabric of space (hence space-time). This meant that things like velocity and gravity could impact the “flow” of time. So if you were moving faster or closer to a massive object—whether a planet or a black hole—to some reference point, time actually passed more slowly.

Understanding what Einstein calls “time dilation” is the reason why we have GPS, and why all of us—whether traveling in a plane, driving a car, or just taking the elevator—in our own small and imperceptible ways, become time travelers. Yet all of these ideas leverage forward-moving time travel. If time was suddenly mutable as Einstein said, could someone conceivably go back in time?

Understanding what Einstein calls “time dilation” is the reason why we have GPS, and why all of us—whether traveling in a plane, driving a car, or just taking the elevator—in our own small and imperceptible ways, become time travelers.

Answering this question would consume Ronald Mallett’s entire academic life. After serving in the Air Force during the Vietnam War (and reading up on all the time travel material he could get his hands on, including mathematician Kurt Gödel’s own ideas on the matter), Mallet attended Penn State University on the G.I. Bill and eventually obtained his Ph.D. in physics. But as he began his academic career, Mallett kept his true interests close to his chest.

“Science fiction was not the popular thing it is now—kids who were interested in science fiction were considered a little suspect,” Mallett says. “People were already worried about me—I was depressed—and if I said I wanted to build a time machine, I didn’t know what the consequences would be.”

Instead, Mallett studied the next best thing—black holes. While Einstein’s work detailed the inner workings of time dilation as well as time’s relationship among gravity, mass, and light, solving some of these field equations seemed to, at least theoretically suggest, that time travel was possible in some extreme circumstances.

“If gravity can affect time, and light can create gravity, then light can affect time,” Mallet says. “It turns out that in Einstein’s theory, a rotating black hole … will actually take time and twist it into a loop.”

Astrophysicists refer to this phenomenon as a “closed timelike curve,” or CTC, a mathematical explanation that theoretically allows for time travel into the past. These ideas are what eventually led Mallett to construct his eponymous machine, a ring-laser device that theoretically creates what Mallett calls “twists in space.”

“Suppose you have a cup of coffee,” Mallett says. “Think of the coffee in the cup as empty space, and think of a spoon as a circulating light beam. You take the spoon, you stir the coffee around. ... Now suppose I put a coffee bean in the coffee and stir it around. The coffee will drag that coffee bean around, so if you put a subatomic particle in space and you turn on the circulating light beam, then what you would see is the subatomic particle would move around in empty space due to the fact that the space is dragging the bean around. That’s what I showed in my calculation.”

This would have the effect of essentially returning to a place in space and time you’ve already left, though with one big caveat—you could only go back into time to the point that you turned on this hypothetical time machine. Mallett first introduced these ideas with a paper published in the journal Physics Letters A. Of course, such a radical idea did come with some criticisms, some of which Mallett himself shares.

“This is the mathematics of it, but creating the device requires enormous amounts of energy—galactic levels of energy,” Mallett says, admitting that answers could lie in continuing advancements in quantum theory. “Einstein’s General Theory of Relativity definitely says that loops in time can be created by circulating beams of light. The question is if it can be done practically, that’s where I feel we’re going to have to go beyond classical general relativity to do that.”

In 2005, two physicists from Tufts University doused some cold water on Mallett’s plans for time travel, stating that “the CTCs occur at distances from the axis greater than the radius of the visible universe by an immense factor” among other issues. Other physicists, such as Nobel Prize-winning theoretical physicist Kip Thorne, have similarly stated that things like time travel and wormholes exist in scientific areas that even if theoretically feasible, “the experiment is so challenging that we can’t do it with human technology in this century.”

A time machine won’t be built in our lifetime, and it’s unlikelier still that ring lasers will be the aluminum-clad DeLorean of our hopes and dreams. But sometimes it takes unorthodox scientists like Mallett to help us traverse the ever present sci-fi bias in research, creating the freedom to investigate big questions about our universe that many may be too afraid to ask.

After all, as Einstein once said, “imagination is more important than knowledge.”