Is It Actually Possible To Travel Through Time?

25.10.2026, 12:16

The scientists gave an unexpected answer.

Jumping into the future, going back to the past to set things right—time travel fascinates not only science fiction writers but also physicists. But what does science actually say about this? Will we ever be able to build a real time machine—to travel back to ancient times or visit our great-great-grandchildren?

To answer this question, we first need to understand how time itself works. But physicists haven’t even come close to answering this question yet, writes Futura. Still, there’s one thing we can say with certainty. Traveling to the future is achievable. But traveling to the past is either incredibly difficult or simply impossible.

It all begins with Albert Einstein’s theories of relativity. They describe space, time, mass, and gravity. And the main conclusion from them is this: time does not flow at a constant rate. It can speed up or slow down—depending on the circumstances.

And this is precisely where time travel ceases to be science fiction and becomes a scientific fact—with serious real-world implications, according to Emma Osborne, an astrophysicist at the University of York.

How Physics Allows Us to Travel into the Future

Time passes more slowly when you’re moving very fast. But for this effect to be noticeable, you must approach the speed of light. Hence the famous “twin paradox”: the twin who becomes an astronaut and travels into space at a speed close to the speed of light ages more slowly than the one who stays on Earth.

If you were to take such a trip and return home, you would actually be younger than your twin, summarizes Vlatko Vedral—a quantum physicist at the University of Oxford. Twins Scott and Mark Kelly experienced this firsthand—although the months Scott spent in space were nowhere near the speed of light.

Gravity has a similar effect. Time slows down in strong gravitational fields—for example, near a black hole. Your head ages faster than your legs. That’s because Earth’s gravity is stronger at ground level.
This phenomenon is precisely what forms the basis of the plot of the movie *Interstellar*. In space, clocks run faster than clocks on Earth—and they have to be constantly adjusted. Without such adjustments, navigation systems would be off by about 10 kilometers a day.

That’s why the theory of relativity makes traveling into the future possible. And you don’t even need some kind of fancy “machine.” You just need to travel at a speed close to the speed of light—or spend time near a very strong gravitational field. Essentially, it’s the same thing.

The result will be the same. You’ll experience a relatively short span of subjective time. Meanwhile, for the rest of the universe, decades or even centuries will pass. If you want to see the world several hundred years from now—here’s how. But coming back is a whole different story. And not a particularly happy one.

The Difficulties of Returning to the Past

Is it even possible? Barack Shoshani—a theoretical physicist at Brock University in Canada—is not optimistic. “What we have right now is not enough facts and, perhaps, not enough theories,” he said. The theory of relativity offers some very theoretical paths—but nothing concrete.

As noted by Katie Mack—a theoretical cosmologist at the Perimeter Institute—people are bending over backward trying to reshape spacetime to make travel into the past possible.

One option is to create what’s known as a “closed timelike curve.” This is a path through space and time that loops back on itself. Mathematician Kurt Gödel described this as far back as 1949. But there’s a problem. “We have no data on whether such things exist anywhere in the universe,” emphasized Vlatko Vedral.

In other words, this is pure theory with not a shred of evidence. Even with technologies far superior to our own, we would hardly ever be able to intentionally create such a curve, added philosopher Emily Adlam. And would we really want that? As Vedral points out, you would literally be repeating the same events over and over again.

Another scenario was proposed by physicist Richard Gott in 1991

Two “cosmic strings” crossing in opposite directions would form closed loops around themselves. But where are these hypothetical objects? They have never been detected. And, according to Katie Mack, “we have no reason to believe that cosmic strings exist. Or that they cross paths so conveniently.”

There is another phenomenon that, apparently, is allowed by the theory of relativity—the so-called wormholes. Theoretically, spacetime can be curved like a sheet of paper. This would make it possible to “dig a tunnel” between two distant points. “Wormholes are theoretically possible in general relativity,” confirms Vedral.
But this is where the complications begin. First, there is no evidence that they exist. Mathematics shows that they could exist. But their physical existence is an entirely different matter, points out Emma Osborne. Also, they would be extremely fleeting.

They are often described as two connected black holes. They would generate such strong gravitational fields that they would collapse under their own weight. And finally—they would be microscopic. Too tiny for a human—or even a bacterium—to pass through them.

Quantum Mechanics and Other “Wild” Theories

Quantum mechanics introduces a whole new set of paradoxes. It describes an incredibly small world. There, physics openly mocks our human intuition. One of its strangest observations is nonlocality.

That is, a change in the state of one particle can instantly affect another. Einstein called this “spooky action at a distance.” This has been proven time and again in experiments—and even earned a Nobel Prize.

Many physicists feel very uncomfortable with this nonlocality, notes Emily Adlam. After all, any instantaneous effect would mean that information is transmitted faster than the speed of light. And that is considered impossible. Some propose alternative interpretations—to do away with nonlocality.

But these “undermine” our very conception of time. Instead of instantaneous nonlocal effects, the influence could be directed toward the future. And there—eventually—it would turn around and travel into the past. From the outside, it would still appear instantaneous, she explains.
This is how the concept of retrocausality arises. It’s when future events influence the past. Not all physicists accept it. Many believe it is just as troubling as nonlocality itself—if not more so.
But even if retrocausality were real, it wouldn’t turn us into time travelers. As Adlam states: “Retrocausality is still not quite the same thing as time travel.” First of all, observations of nonlocality apply only to a tiny handful of particles. Scaling this up to human size—or even to something as large as a sheet of paper—is a massive challenge.
Furthermore, sending a message to the past is still impossible. Retrocausality is “hidden” in a very specific way by how it works. In a typical experiment, the result obtained by one researcher would depend on a later measurement by another researcher.

But only if that second experiment erased all traces of the first. In other words, you could, in a sense, send a signal into the past. But only by destroying all records of what happened, says Adlam. This is definitely not how you could send yourself last year’s lottery numbers.
According to our current understanding of the universe, we can potentially travel into the future. But rewinding to the past is something that lies beyond our reach. The only loophole that remains is that our theories themselves are incomplete. The theory of relativity and quantum mechanics each work brilliantly in their own fields. But they are incompatible. And after decades of searching for a theory to unify them, we still don’t have one.

As Barak Shoshani sums it up: “Until we have that theory, we can’t be sure of anything.”

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