can we travel in wormhole

• Login/Register
• Solar System
• Exotic Objects
• Upcoming Events
• Deep-Sky Objects
• Observing Basics
• Telescopes and Equipment
• Astrophotography
• Space Exploration
• Human Spaceflight
• Robotic Spaceflight
• The Magazine

What are wormholes? An astrophysicist explains these shortcuts through space-time

What are wormholes and do they exist? – Chinglembi D., age 12, Silchar, Assam, India

Imagine two towns on two opposite sides of a mountain. People from these towns would probably have to travel all the way around the mountain to visit one another. But, if they wanted to get there faster, they could dig a tunnel straight through the mountain to create a shortcut. That’s the idea behind a wormhole.

A wormhole is like  a tunnel between two distant points  in our universe that cuts the travel time from one point to the other. Instead of traveling for many millions of years from one galaxy to another, under the right conditions one could theoretically use a wormhole to  cut the travel time  down to hours or minutes.

Because wormholes represent shortcuts  through space-time , they could even act like time machines. You might emerge from one end of a wormhole at a time earlier than when you entered its other end.

While scientists have no evidence that wormholes actually exist in our world, they’re good tools to help astrophysicists  like me  think about space and time. They may also answer age-old questions about what the universe looks like.

Fact or fiction?

Because of these interesting features, many science fiction writers use wormholes in novels and movies. However, scientists have been just as captivated by the idea of wormholes as writers have.

While researchers have never found a wormhole in our universe, scientists often see wormholes described in the solutions to important physics equations. Most prominently, the solutions to the equations behind Einstein’s  theory of space-time and general relativity  include wormholes. This theory describes the shape of the universe and how stars, planets and other objects move throughout it. Because Einstein’s theory has been tested many, many times and found to be  correct every time , some scientists do expect wormholes to exist somewhere out in the universe.

But, other scientists think wormholes can’t possibly exist because they would be too unstable.

The constant pull of gravity affects every object in the universe, including Earth. So gravity would have an effect on wormholes, too. The scientists who are skeptical about wormholes believe that after a short time the middle of the wormhole would  collapse under its own gravity , unless it had some force pushing outward from inside the wormhole to counteract that force. The most likely way it would do that is using what’s called “negative energies,” which would  oppose gravity  and stabilize the wormhole.

But as far as scientists know, negative energies can be created only in amounts much  too small  to counteract a wormhole’s own gravity. It’s possible that the Big Bang created teeny, tiny wormholes with small amounts of negative energies way back at the beginning of the universe, and over time these wormholes have  stretched out  as the universe has expanded.

Just like black holes?

While wormholes are interesting objects to think about, they still aren’t accepted in mainstream science. But that doesn’t mean they’re not real – black holes, which we astrophysicists know abound in our universe, weren’t accepted when scientists first suggested they existed, back in the 1910s.

Einstein first formulated his famous field equations in 1915, and German scientist Karl Schwarzschild found a way to mathematically describe black holes after  only one year . However, this description was so peculiar that the leading scientists of that era refused to believe that black holes could actually exist in nature. It took people 50 years to start taking black holes seriously – the term “black hole” wasn’t even coined  until 1967 .

The same could happen with wormholes. It may take scientists a little while to come up with a consensus about whether or not they can exist. But if they do find strong evidence pointing to the existence of wormholes – which they may be able to do by looking at odd movements in  star orbits  – the discovery will shape how scientists see and understand the universe.

Dejan Stojkovic , Professor of Physics,  University at Buffalo

This article is republished from  The Conversation  under a Creative Commons license. Read the  original article .

2024 Full Moon calendar: When to see the Full Moon and phases

Greenhouse gases could indicate alien life — if we ever find them

The fight against light pollution

What’s in this most recent hole NASA drilled on Mars? We might know soon

Gemini North celebrates its 25th birthday with a glorious photo of NGC 4449

Webb examines how planets form around Beta Pictoris

Soar through the Pillars of Creation with NASA’s stunning new video

In a first, JWST captures ultra-detailed image of aligned jets in the Serpens Nebula

Did we find signs of life on K2-18 b? Not yet, but we might.

December 1, 2015

12 min read

Can Time Travelers Reach the Past via Wormholes?

Astronauts already skip ahead in time, but the laws of physics seem to forbid going backward—or do they?

By Tim Folger

The famous writer H. G. Wells published his first novel, The Time Machine , in 1895, just a few years before Queen Victoria's six-decade reign over the U.K. ended. An even more durable dynasty was also drawing to a close: the 200-year-old Newtonian era of physics. In 1905 Albert Einstein published his special theory of relativity, which upset Isaac Newton's applecart and, presumably to Wells's delight, allowed something that had been impossible under Newton's laws: time travel into the future. In Newton's universe, time was steady everywhere and everywhen. It never sped up. It never slowed down. But for Einstein, time was relative.

Time travel is not merely possible—it has already happened, though not exactly as Wells imagined. The biggest journey through time so far, according to J. Richard Gott, an astrophysicist at Princeton University, was taken by Sergei K. Krikalev. Over the course of his long career, which began in 1985, the Russian cosmonaut spent 803 days in space. As Einstein proved, time passes more slowly for objects in motion than for those at rest, so as Krikalev hurtled along at 17,885 miles an hour onboard the Mir space station, time did not flow at the same rate for him as it did on Earth. While in orbit, Krikalev aged 1/48 of a second less than his fellow earthlings. Put another way, he traveled 1/48 of a second into the future.

The time-travel effect becomes easier to see as distances stretch longer and speeds creep higher. If Krikalev left Earth in 2015 and made a round-trip to Betelgeuse—a star that is about 650 light-years from Earth—at 99.995 percent the speed of light, then by the time he returned to Earth he would be only 10 years older. Sadly, everyone he knew would be long dead because 1,000 years would have passed on Earth; it would be the year 3015. “Time travel to the future, we know we can do,” Gott says. “It's just a matter of money and engineering!”

On supporting science journalism

If you're enjoying this article, consider supporting our award-winning journalism by subscribing . By purchasing a subscription you are helping to ensure the future of impactful stories about the discoveries and ideas shaping our world today.

Jumping a few nanoseconds—or even a few centuries—into the future is relatively straightforward, practical challenges aside. But going backward in time is harder. Einstein's special theory of relativity forbade it. After another decade of work, Einstein unveiled his general theory of relativity, which finally lifted that restriction. How someone would actually travel back in time, however, is a vexing problem because the equations of general relativity have many solutions. Different solutions assign different qualities to the universe—and only some of the solutions create conditions that permit time travel into the past.

Whether any of those solutions describes our own universe is an open question, which raises even more profound puzzles: Just how much tweaking of fundamental physics would it take to allow backward time travel? Does the universe itself somehow prevent such journeys even if Einstein's equations do not rule them out? Physicists continue to speculate, not because they imagine time travel to the past will ever be practical but because thinking about the possibility has led to some surprising insights about the nature of the universe we live in—including, perhaps, how it came to be in the first place.

A new way of looking at time With his special theory of relativity, Einstein made time malleable in a way that must have pleased Wells, who presciently believed that we inhabit a universe in which three-dimensional space and time are knit together into a four-dimensional whole. Einstein arrived at his revolutionary results by exploring the implications of two fundamental ideas. First, he argued that even though all motion is relative, the laws of physics must look the same for everyone anywhere in the universe. Second, he realized that the speed of light must be similarly unchanging from all perspectives: if everyone sees the same laws of physics operating, they must also arrive at the same result when measuring the speed of light.

To make light a universal speed limit, Einstein had to jettison two commonsense notions: that all observers would agree on the measurement of a given length and that they would also agree on the duration of time's passage. He showed that a clock in motion, whizzing past someone at rest, would tick more slowly than a stationary clock at the person's side. And the length of a ruler moving swiftly by would shorten. Yet for anyone who was traveling at the same speed as the clock and ruler, the passage of time and the length of the ruler would appear normal.

At ordinary speeds, the time-and-space-distorting effects of special relativity are negligible. But for anything moving at a hefty fraction of the speed of light (relative to the observer), they are very real. For example, many experiments have confirmed that the decay rate of unstable particles called muons slows by an order of magnitude when they are traveling at close to the speed of light. The speeding muons, in effect, are minuscule time travelers—subatomic Krikalevs—hopping a few nanoseconds into the future.

Gödel's strange universe Those speedy clocks and rulers and muons are all racing forward in time. Can they be thrown into reverse? The first person to use general relativity to describe a universe that permits time travel into the past was Kurt Gödel, the famed creator of the incompleteness theorems, which set limits on the scope of what mathematics can and cannot prove. He was one of the towering mathematicians of the 20th century—and one of the oddest. His many foibles included a diet of baby food and laxatives.

Gödel presented this model universe as a gift to Einstein on his 70th birthday. The universe Gödel described to his skeptical friend had two unique properties. It rotated, which provided centrifugal force that prevented gravity from crunching together all the matter in the cosmos, and thus created the stability Einstein demanded of any cosmic model. But it also allowed for time travel into the past, which made Einstein deeply uneasy. In Gödel's cosmos, space travelers could set out and eventually reach a point in their own past, as if the travelers had completed a circuit around the surface of a giant cylinder. Physicists call these trajectories in spacetime “closed timelike curves.”

A closed timelike curve is any path through spacetime that loops back on itself. In Gödel's rotating cosmos, such a curve would circle around the entire universe, like a latitude line on Earth's surface. Physicists have concocted a number of different types of closed timelike curves, all of which allow travel to the past, at least in theory. A journey along any of them would be disappointingly ordinary, however. Through the portholes of your spaceship, you would see stars and planets—all the usual sights of deep space. More important, time—as measured by your own clocks—would tick forward in the usual way; the hands of a clock would not start spinning backward even though you would be traveling to a location in spacetime that existed in your past.

“Einstein was already aware of the possibility of closed timelike curves back in 1914,” says Julian Barbour, an independent theoretical physicist who lives near Oxford, England. As Barbour recalls, Einstein said, “My intuition strives most vehemently against this.” The curves' existence would create all kinds of problems with causality—how can the past be changed if it has already happened? And then there is the hoary grandfather paradox: What happens to a time traveler who kills Granddad before Granddad meets Grandma? Would the demented, now parentless traveler ever be born?

Fortunately for fans of causality, astronomers have found no evidence that the universe is rotating. Gödel himself apparently pored over catalogs of galaxies, looking for clues that his theory might be true. Gödel might not have devised a realistic model of the universe, but he did prove that closed timelike curves are completely consistent with the equations of general relativity. The laws of physics do not rule out traveling to the past.

An annoying possibility Over the past few decades cosmologists have used Einstein's equations to construct a variety of closed timelike curves. Gödel conjured an entire universe that allowed them, but more recent enthusiasts have warped spacetime only within parts of our universe.

In general relativity, planets, stars, galaxies and other massive bodies warp spacetime. Warped spacetime, in turn, guides the motions of those massive bodies. As the late physicist John Wheeler put it, “Spacetime tells matter how to move; matter tells spacetime how to curve.” In extreme cases, spacetime might bend enough to create a path from the present back to the past.

Physicists have proposed some exotic mechanisms to create such paths. In a 1991 paper, Gott showed how cosmic strings—infinitely long structures thinner than an atom that may have formed in the early universe—would allow closed timelike curves where two strings intersected. In 1983 Kip S. Thorne, a physicist at the California Institute of Technology, began to explore the possibility that a type of closed timelike curve called a wormhole—a kind of tunnel joining two different locations in spacetime—might allow for time travel into the past. “In general relativity, if you connect two different regions of space, you're also connecting two different regions of time,” says Sean M. Carroll, a colleague of Thorne's at Caltech.

The entrance into a wormhole would be spherical—a three-dimensional entrance into a four-dimensional tunnel in spacetime. As is the case with all closed timelike curves, a trip through a wormhole would be “like any other journey,” Carroll says. “It's not that you disappear and are reassembled at some other moment of time. There is no respectable theory where that kind of science-fiction time travel is possible.” For all travelers, he adds, “no matter what they do, time flows forward at one second per second. It's just that your local version of ‘forward’ might be globally out of sync with the rest of the universe.”

Although physicists can write equations that describe wormholes and other closed timelike curves, all the models have serious problems. “Just to get a wormhole in the first place, you need negative energy,” Carroll says. Negative energy is when the energy in a volume of space spontaneously fluctuates to less than zero. Without negative energy, a wormhole's spherical entrance and four-dimensional tunnel would instantaneously implode. But a wormhole held open by negative energy “seems to be hard, probably impossible,” Carroll says. “Negative energies seem to be a bad thing in physics.”

Even if negative energy kept a wormhole open, just when you would be on the verge of turning that into a time machine, “particles would be moving through the wormhole, and every particle would loop back around an infinite number of times,” Carroll says. “That leads to an infinite amount of energy.” Because energy deforms spacetime, the entire thing would collapse into a black hole—an infinitely dense point in spacetime. “We're not 100 percent sure that that happens,” Carroll says. “But it seems to be a reasonable possibility that the universe is actually preventing you from making a time machine by making a black hole instead.”

Unlike black holes, which are a natural consequence of general relativity, wormholes and closed timelike curves in general are completely artificial constructs—a way of testing the bounds of the theory. “Black holes are hard to avoid,” Carroll says. “Closed timelike curves are very hard to make.”

Even if wormholes are physically implausible, it is significant that they fit in with the general theory of relativity. “It's very curious that we can come so close to ruling out the possibility of time travel, yet we just can't do it. I also think that it's annoying,” Carroll says, exasperated that Einstein's beautiful theory might allow for something so seemingly implausible. But by contemplating that annoying possibility, physicists may gain a better understanding of the kind of universe we live in. And it may be that if the universe did not permit backward time travel, it never would have come into existence.

Did the universe create itself? General relativity describes the universe on the largest scales. But quantum mechanics provides the operating manual for the atomic scale, and it offers another possible venue for closed timelike curves—one that gets at the origin of the universe.

“On a very small scale (10−30 centimeter) you might expect the topology of spacetime to fluctuate, and random fluctuations might give you closed timelike curves if nothing fundamental prevents them,” says John Friedman, a physicist at the University of Wisconsin–Milwaukee. Could those quantum fluctuations somehow be magnified and harnessed as time machines? “There's certainly no formal proof that you can't have macroscopic closed timelike curves,” Friedman says. “But the community of people who have looked at these general questions would bet pretty heavily against it.”

There is no doubt that the creation of a loop in spacetime on either a quantum scale or a cosmic one would require some very extreme physics. And the most likely place to expect extreme physics, Gott says, is at the very beginning of the universe.

In 1998 Gott and Li-Xin Li, an astrophysicist now at Peking University in China, published a paper in which they argued that closed timelike curves were not merely possible but essential to explain the origin of the universe. “We investigated the possibility of whether the universe could be its own mother—whether a time loop at the beginning of the universe would allow the universe to create itself,” Gott says.

Just as in standard big bang cosmology, Gott and Li's universe “starts” with a bout of inflation, where an all-pervasive energy field drove the universe's initial expansion. Many cosmologists now believe that inflation gave rise to countless other universes besides our own. “Inflation is very hard to stop once it gets started,” Gott says. “It makes an infinitely branching tree. We're one of the branches. But you have to ask yourself, Where did the trunk come from? Li-Xin Li and I said it could be that one of the branches just loops around and grows up to be the trunk.”

A simple two-dimensional sketch of Gott and Li's self-starting universe looks like the number “6,” with the spacetime loop at the bottom and our present-era universe as the top stem. A burst of inflation, Gott and Li theorized, allowed the universe to escape from the time loop and expand into the cosmos we inhabit today.

It is difficult to contemplate the model, but its main appeal, Gott says, is that it eliminates the need for creating a universe out of nothing. Yet Alexander Vilenkin of Tufts University, Stephen Hawking of the University of Cambridge and James Hartle of the University of California, Santa Barbara, have proposed models in which the universe does indeed arise out of nothing. According to the laws of quantum mechanics, empty space is not really empty but is filled with “virtual” particles that spontaneously pop into and out of existence. Hawking and his colleagues theorized that the universe burst into being from the same quantum-vacuum stew. But in Gott's view, the universe is not made out of nothing; it is made out of something—itself.

A cosmic chess game For now, there is no way to test whether any of those theories might actually explain the origin of the universe. The famed physicist Richard Feynman compared the universe to a great chess game being played by the gods. Scientists, he said, are trying to understand the game without knowing the rules. We watch as the gods move a pawn one space forward, and we learn a rule: pawns always move one space forward. But what if we never saw the opening of a game, when a pawn can move two spaces forward? We might also assume, mistakenly, that pawns always remain pawns—that they never change their identity—until we see a pawn transformed into a queen.

“You would say that's against the rules,” Gott says. “You can't change your pawn into a queen. Well, yes, you can! You just never saw a game that extreme before. Time-travel research is like that. We're testing the laws of physics by looking at extreme conditions. There's nothing logically impossible about time travel to the past; it's just not the universe we're used to.” Turning a pawn into a queen could be part of the rules of relativity.

Such wildly speculative ideas may be closer to philosophy than to physics. But for now, quantum mechanics and general relativity—powerful, counterintuitive theories—are all we have to figure out the universe. “As soon as people start trying to bring quantum theory and general relativity into this, the first thing to say is that they really have no idea what they're doing,” says Tim Maudlin, a philosopher of science at New York University. “It's not really rigorous mathematics. It's one piece of mathematics that sort of looks like general relativity and another little piece of mathematics that sort of looks like quantum theory, mixed together in some not entirely coherent way. But this is what people have to do because they honestly don't know how to go forward in a way that makes sense.”

Will some future theory eliminate the possibility of time travel into the past? Or will the universe again turn out to be far stranger than we imagine? Physics has advanced tremendously since Einstein redefined our understanding of time. Time travel, which existed only in the realm of fiction for Wells, is now a proved reality, at least in one direction. Is it too hard to believe that some kind of symmetry exists in the universe, allowing us to travel backward in time? When I put the question to Gott, he replies with an anecdote:

“There's a story where Einstein was talking to a guy. The guy pulled a notebook out and scribbled something down. Einstein says, ‘What's that?’ The guy says, ‘A notebook. Whenever I have a good idea, I write it down.’ Einstein says, ‘I've never had any need for a notebook; I've only had three good ideas.’”

Gott concludes: “I think we're waiting for a new good idea.”

Tim Folger is a freelance journalist who writes for National Geographic , Discover , and other national publications.

Travel through wormholes is possible, but slow

A Harvard physicist has shown that wormholes can exist: tunnels in curved space-time, connecting two distant places, through which travel is possible.

But don't pack your bags for a trip to other side of the galaxy yet; although it's theoretically possible, it's not useful for humans to travel through, said the author of the study, Daniel Jafferis, from Harvard University, written in collaboration with Ping Gao, also from Harvard and Aron Wall from Stanford University.

"It takes longer to get through these wormholes than to go directly, so they are not very useful for space travel," Jafferis said. He will present his findings at the 2019 American Physical Society April Meeting in Denver.

Despite his pessimism for pan-galactic travel, he said that finding a way to construct a wormhole through which light could travel was a boost in the quest to develop a theory of quantum gravity.

"The real import of this work is in its relation to the black hole information problem and the connections between gravity and quantum mechanics," Jafferis said.

The new theory was inspired when Jafferis began thinking about two black holes that were entangled on a quantum level, as formulated in the ER=EPR correspondence by Juan Maldacena from the Institute for Advanced Study and Lenny Susskind from Stanford. Although this means the direct connection between the black holes is shorter than the wormhole connection -- and therefore the wormhole travel is not a shortcut -- the theory gives new insights into quantum mechanics.

"From the outside perspective, travel through the wormhole is equivalent to quantum teleportation using entangled black holes," Jafferis said.

Jafferis based his theory on a setup first devised by Einstein and Rosen in 1935, consisting of a connection between two black holes (the term wormhole was coined in 1957). Because the wormhole is traversable, Jafferis said, it was a special case in which information could be extracted from a black hole.

"It gives a causal probe of regions that would otherwise have been behind a horizon, a window to the experience of an observer inside a spacetime, that is accessible from the outside," said Jafferis.

To date, a major stumbling block in formulating traversable wormholes has been the need for negative energy, which seemed to be inconsistent with quantum gravity. However, Jafferis has overcome this using quantum field theory tools, calculating quantum effects similar to the Casimir effect.

"I think it will teach us deep things about the gauge/gravity correspondence, quantum gravity, and even perhaps a new way to formulate quantum mechanics," Jafferis said.

The presentation, "Traversable wormholes" will took place on Saturday, April 13. ABSTRACT: http://meetings.aps.org/Meeting/APR19/Session/B02.2

• Black Holes
• Astrophysics
• Space Probes
• Space Exploration
• Introduction to general relativity
• Spitzer space telescope
• Presentism (philosophy of time)
• Albert Einstein
• Gravitational wave
• Barred spiral galaxy

Story Source:

Materials provided by American Physical Society . Note: Content may be edited for style and length.

Cite This Page :

Explore More

• Better Wearable Devices
• Dampening the 'Seeds' of Hurricanes
• Carbonate and World of Ancient Romans
• Age of Puberty in Girls and Weight Gain
• Dinos and Sixty-Million-Year-Old Grape Seeds
• 'World Record' for Data Transmission Speed
• Youth Sports Linked to Better Mental
• Better Mobile Device Performance
• Light-Controlled Fake Maple Seeds for Monitoring
• Climate: Projected Loss of Seagrasses

Trending Topics

Strange & offbeat.

• The Magazine
• Stay Curious
• The Sciences
• Environment
• Planet Earth

If Wormholes Exist, Could We Really Travel Through Them?

Wormholes could offer a path to the most distant places in the universe..

Wormholes make the best shortcuts in the universe. That’s true in a literal sense, since the theoretical things can connect distant corners of the cosmos (or even different universes), allowing a traveler to go someplace without having to visit everywhere in between.

But wormholes also present the perfect way for writers to get around that pesky speed of light, the universe’s speed limit and impediment to fast travel through the cosmos. If characters in science fiction aren’t taking months or years to travel between worlds, a wormhole is likely the reason.

Too bad, then, that as far as we know, the things don’t exist.

Historical Holes

Oh, wormholes  could  exist. We just don’t know whether they actually  do . Or, for that matter, if they’d be useful to us as potential shortcuts.

But ever since Albert Einstein published his  general theory of relativity , we’ve had the  mathematical language for describing and imagining  these fantastical structures. Back then, though, scientists referred to them as “one-dimensional tubes” and simply “bridges” — in fact, the term “ Einstein-Rosen bridge ” is still used semi-interchangeably with “wormhole” (the “Rosen” being Israeli physicist  Nathan Rosen ).

It was American physicist John Wheeler who coined the  vermicular  vernacular in  a 1957  Annals of Physics  paper : “This analysis forces one to consider situations,” he wrote, “where there is a net flux of lines of force, through what topologists would call ‘a handle’ of the multiply-connected space, and what physicists might perhaps be excused for more vividly terming a ‘wormhole’.”

Tantalizing Physics

It’s a lucky thing, because that vivid name helps describe just what the heck we’re talking about. The curvature of space and lines of force might not mean much to most people, but who can’t imagine a worm eating its way through an apple or piece of timber? The resulting tunnel, connecting one part of the surface with another more distant part, is the perfect metaphor for something that can connect otherwise remote locations in the universe.

And, because Einstein also showed that space and time are fundamentally interconnected, traveling through a wormhole might not only take us to another far-away  place , but it could even serve as a  shortcut to another  time .

No wonder, then, that they’ve become  so popular in science fiction . In real life,  the speed of light is the end of the line : Nothing with mass can ever accelerate faster. That means sunlight takes  over 5 hours to get to Pluto  and  years  to reach other star systems. And it’s the rare story that benefits from forcing its characters to sit around waiting years to get anywhere.

Wormholes, thus, are the perfect way to bypass Einstein’s speed limit, and get your heroes and villains to travel the galaxy in a reasonable time frame. Plus, they allow for the element of time travel to enter the story, all without breaking any laws of physics.

So, the real question is: Can actual people take advantage of wormholes too? The answer is… maybe?

Wither Wormholes?

The first problem for any explorer determined to survey a wormhole is simply finding one. While Einstein’s work says they can exist, we  don’t currently know of any . They may actually be impossible after all, forbidden by some deeper physics that the universe obeys, but we haven’t discovered.

The second issue is that, despite years of research, scientists still aren’t really sure how wormholes would work. Can any  technology ever create and manipulate them , or are they simply a part of the universe? Do they stay open forever, or are they only traversable for a limited time? And perhaps most significantly, are they stable enough to allow for human travel?

The answer to all of these: We just don’t know.

But that doesn’t mean scientists aren’t working on it. Despite the lack of actual wormholes to study, researchers can still model and test Einstein’s equations. NASA’s conducted legitimate wormhole research  for   decades , and a team  described just this year  how wormhole-based travel might be more feasible than previously thought.

That research concerned one of the most popular conceptions of wormholes, with black holes serving as one of the openings. But black holes are  famously dangerous , possibly stretching apart anyone who approaches too close. It turns out, though, that some black holes might allow objects to pass through relatively easily. This would allow a traveler to explore the space beyond, and thus eliminate one of the biggest hurdles to entering such a wormhole. But again, that’s only if they exist in the first place.

So, until we either find an actual wormhole to study, or realize that they can’t help us explore the universe, we’ll have to do it the old fashioned way: By taking rockets the long way around, and taking our minds on fictional adventures.

• black holes

Already a subscriber?

Register or Log In

Keep reading for as low as $1.99!

Sign up for our weekly science updates.

Save up to 40% off the cover price when you subscribe to Discover magazine.

This page has been archived and is no longer updated

The Missing Piece: Are Wormholes the Key to Time Travel?

Time travel -- it's a concept we're all too familiar with. From Hollywood Movies (shout out to Back to the Future) to theoretical physics, many theories have circulated regarding the bewildering topic of time travel. However, recently students at the California Institute of Technology1 have shed new light on a relatively dated theory: that wormholes may be the missing piece in the seemingly unsolvable puzzle behind time travel. So, step aside Doc Brown, because we're going to explore how a unique and mysterious part of our universe- the wormhole- connects to traveling through time!

Just like many principles in Physics, this concept finds its base in Einstein's Theory of General Relativity (for some background on this topic, view our previous blog post, "What happens to Matter inside a Black Hole?"). Basically, the theory attributes the characteristics of a wormhole to its incredibly high velocity. Similar to a black hole, a wormhole would compress an entering object to the size of a singularity and accelerate it to immeasurable speeds through the "throat" of the wormhole to the other side of the funnel. So, for now, think of a wormhole as a black hole that has a start and end point.2

Now, this is where the physics becomes complex. We know that a wormhole can basically "teleport" compressed objects at super speeds from one end to another, but how does that explain the time travel aspect? Well, the concept of time dilation can explain that. Time dilation is the relative difference in the passage of time between two entities due to a stark difference in either gravity or relative velocity. In the case of the wormhole, both are in play, which only compounds the effects. For a tangible example to grasp, let's look to the astronauts aboard the International Space Station. After 6 months aboard the ISS (where there is less gravity, but greater velocity of movement), these astronauts have actually aged .007 seconds less than the crew stationed on Earth.3 While this seems insignificant, we have to remember that because the velocity is increased but the gravity is decreased, each is actually mitigating the effects of the other. However, in a wormhole, where the effects of both gravity and velocity are exponentially amplified AND working in tandem, their relativistic effects are enormous.4

This graphic portrays an accurate depiction of velocities' effect on time dilation: http://upload.wikimedia.org/wikipedia/commons/7/72/Nonsymmetric_velocity_time_dilation.gif

Now that we have an understanding of time dilation, we want to leave you with this example. Imagine two test subjects at each side of a wormhole in the year 1995. One mouth of the wormhole has been accelerated to a point where relativistic effects (i.e. time dilation) apply significantly and the other mouth is stationary. When the two subjects pass through their respective mouths, they end up at where their counterpart stood... but at different times! The accelerated mouth would land its test subject in, let's say, 2000. However, the stationary mouth would place its test subject in a later year - we'll call it 2005- since the accelerated mouth exists in a different time caused by time dilation. The time travel becomes evident when we consider the following: what if the test subject who landed in 2005 stepped back into the mouth? They would end up in the year 2000, or 5 years in the past! A bit of manipulation, therefore, could technically transport this subject to any point in time between 2000 and 2005.5

Unfortunately, scientists have been unable to totally grasp how we could adapt the power of a wormhole into time machine-esq technology. We have yet to even theorize how we could accelerate a wormhole to relativistic speeds. Given that this is another theoretical aspect of our known universe, testing is extremely limited and all postulates have very little opportunity for tangible proof. What is certain, though, is that the advances we've made thus far in the field have brought us several pieces closer to solving the time traveler's puzzle!

Email your Friend

• January 23, 2014 The Search for the God Particle
• January 21, 2014 Can We Make the Jump?
• September 07, 2013 An Enlightening View of Solar Eclipses
• September 02, 2013 Sunny Side Down: The Future Destruction of the Sun
• August 28, 2013 The Missing Piece: Are Wormholes the Key to Tim...
• July 30, 2013 What Happens to Matter Inside a Black Hole?

© 2014 Nature Education

• Press Room |
• Terms of Use |
• Privacy Notice |

Human-Safe Wormholes Could Exist in the Real World, Studies Find

Pack your bags. We’re going to another galaxy.

• Two separate studies published in Physical Review Letters D propose new theories for how to construct a traversable wormhole.
• Wormholes, also known as Einstein-Rosen bridges, are commonly used in sci-fi stories as a way to quickly zip between distant parts of the universe .

Sci-fi writers have long leaned on the wormhole as an important plot device. It’s a quick way to get characters from Point A to Point B across vast distances in spacetime in a matter of seconds. But are wormholes real?

🐛 You love weird science. So do we. Let’s nerd out over it together.

Theorists like Albert Einstein and Kip Thorne have been pondering the existence of these spacetime portals for decades, but so far, no one has been able to provide physical evidence of their existence until recently.

Two March 2021 studies, published in the journals Physical Review Letters and Physical Review D , propose wormholes safe enough for humans to travel through could exist in the real world after all. A third study published to the preprint server arXiv in September 2021 considers using a slightly different concept of gravity to allow safe passage through a wormhole.

One of the main arguments against the existence of wormholes suggests the portal’s narrowest part, or neck, would likely collapse under the weight of its own gravity . Some theorists say one way to sidestep this issue and prevent gravitational collapse would be to fill the wormhole with an exotic form of matter that has negative mass. But this solution isn’t a cosmological silver bullet—such a form of matter is purely theoretical.

In the first paper , an international trio of researchers led by Jose Blázquez-Salcedo of the Complutense University of Madrid has proposed an alternative way to prevent the collapse of a fragile wormhole’s neck—one that doesn’t need exotic matter to keep the wormhole propped open.

Instead, the researchers’ theoretical models, which ponder the possibility of microscopic wormholes, draw from three theories to harness the power of elementary particles : relativity theory, quantum theory, and electrodynamics.

These scientists suggest tweaking the mass and charge of fermions —fundamental building blocks of matter—could keep the cosmic thruway open. This would only work if the ratio of the total charge of the fermions to the total mass of everything inside the wormhole is greater than the practical limit set by black holes .

Now, there’s a catch: Blázquez-Salcedo and his team are talking about microscopic wormholes. They’re not exactly traversable by humans, but this is certainly one small step in a new theoretical direction.

The second paper , however, which comes from Juan Maldacena of the Institute for Advanced Study in New Jersey and Alexey Milekhin from Princeton University, does explore the theoretical existence of wormholes large enough for spacetime-surfing humans to squeeze through.

In this case, Maldacena and Milekhin have devised a wormhole that forms in five-dimensional spacetime, also known as the Randall-Sundrum model. These wormholes would look like intermediate-mass black holes to the untrained observer, the authors say.

If you hopped in this kind of wormhole, you’d experience up to 20 Gs of acceleration—an uncomfortable, albeit survivable, amount. But the authors acknowledge some practical limitations with this theory. For example, the wormhole has to be extremely clean—i.e., free from errant particles:

If particles that fall into the wormhole scatter and lose energy then they would accumulate inside, contributing some positive energy that would eventually make the wormhole collapse back into a black hole.

The last place anyone traveling through space wants to end up is at the center of a black hole. The wormhole also has to be extremely cold, the researchers write. And then there’s the small problem of actually generating the wormhole in the first place. Maldacena and Milekhin are still working on figuring out how to form one.

Needing negative energy or negative mass (exotic matter, in other words) to construct your wormhole is too much trouble. Instead, you need to tweak your understanding of gravity, according to João Luís Rosa, a physicist at University of Tartu, in Estonia. His paper on the arXiv preprint server discusses the use of a model called “generalized hybrid metric-Palatini gravity.” This concept is based on general relativity , but matter and energy, and space and time, have slightly different relationships than those predicted by general relativity. So, you would be able to build a stable wormhole by layering the entrance with double thin shells of regular matter—no exotic matter needed.

After all this fact-or-fiction speculation, what’s the good news? Theoretically, your cross-galaxy trip would only take less than a second. But if your family and friends are tracking your journey from outside the wormhole, they’ll be waiting a long time for it to end. From their perspective, your trip would last tens of thousands of years.

Looks like you’ll have to find your own ride home.

Correction, March 12, 2021: A previous version of this article mistakenly clipped short a quote from the article “Humanly traversable wormholes.” We regret the error.

Jennifer Leman is a science journalist and senior features editor at Popular Mechanics, Runner's World, and Bicycling. A graduate of the Science Communication Program at UC Santa Cruz, her work has appeared in The Atlantic, Scientific American, Science News and Nature. Her favorite stories illuminate Earth's many wonders and hazards.

.css-cuqpxl:before{padding-right:0.3125rem;content:'//';display:inline;} Deep Space .css-xtujxj:before{padding-left:0.3125rem;content:'//';display:inline;}

3 New Super-Earths Just Dropped

Can We Detect the Grav Waves of Alien Warp Drives?

Scientist Just Spotted a Black Hole 'Waking Up'

Microwave-Emitting Object Is a New Space Mystery

Life May Have Kicked Off Earlier Than We Thought

A Missing Piece in the Big Bang Theory Has Arrived

The Physics of Wormholes Is Absolutely Metal

A Researcher Says There Could Be an Anti-Universe

Supermassive Forces Are Making Black Holes Collide

Are We Living in a ‘Hall of Mirrors’ Universe?

Have We Already Found Evidence of Dyson Spheres?

share this!

January 13, 2021

Wormholes may be lurking in the universe—and new studies are proposing ways of finding them

by Andreea Font, The Conversation

Albert Einstein's theory of general relativity profoundly changed our thinking about fundamental concepts in physics, such as space and time. But it also left us with some deep mysteries. One was black holes, which were only unequivocally detected over the past few years. Another was "wormholes"—bridges connecting different points in spacetime, in theory providing shortcuts for space travelers.

Wormholes are still in the realm of the imagination. But some scientists think we will soon be able to find them, too. Over the past few months, several new studies have suggested intriguing ways forward.

Black holes and wormholes are special types of solutions to Einstein's equations, arising when the structure of spacetime is strongly bent by gravity. For example, when matter is extremely dense, the fabric of spacetime can become so curved that not even light can escape. This is a black hole.

As the theory allows the fabric of spacetime to be stretched and bent, one can imagine all sorts of possible configurations. In 1935, Einstein and physicist Nathan Rosen described how two sheets of spacetime can be joined together, creating a bridge between two universes. This is one kind of wormhole – and since then many others have been imagined.

Some wormholes may be "traversable", meaning humans may be able to travel through them. For that though, they would need to be sufficiently large and kept open against the force of gravity, which tries to close them. To push spacetime outward in this way would require huge amounts of "negative energy".

Sounds like sci-fi? We know that negative energy exists, small amounts have already been produced in the lab . We also know that negative energy is behind the universe's accelerated expansion. So nature may have found a way to make wormholes.

Spotting wormholes in the sky

How can we ever prove that wormholes exist? In a new paper, published in the Monthly Notices of the Royal Society , Russian astronomers suggest they may exist at the center of some very bright galaxies, and propose some observations to find them. This is based on what would happen if matter coming out of one side of the wormhole collided with matter that was falling in. The calculations show that the crash would result in a spectacular display of gamma rays that we could try to observe with telescopes.

This radiation could be the key to differentiating between a wormhole and a black hole, previously assumed to be indistinguishable from the outside. But black holes should produce fewer gamma rays and eject them in a jet, while radiation produced via a wormhole would be confined to a giant sphere. Although the kind of wormhole considered in this study is traversable, it would not make for a pleasant trip. Because it would be so close to the center of an active galaxy, the high temperatures would burn everything to a crisp. But this wouldn't be the case for all wormholes, such as those further from the galactic center.

The idea that galaxies can harbor wormholes at their centers is not new. Take the case of the supermassive black hole at the heart of the Milky Way. This was discovered by painstakingly tracking of the orbits of the stars near the black hole, a major achievement which was awarded the Nobel Prize in Physics in 2020. But one recent paper has suggested this gravitational pull may instead be caused by a wormhole .

Unlike a black hole, a wormhole may "leak" some gravity from the objects located on the other side. This spooky gravitational action would add a tiny kick to the motions of stars near the galactic center. According to this study, the specific effect should be measurable in observations in the near future, once the sensitivity of our instruments gets a little bit more advanced.

Coincidentally, yet another recent study has reported the discovery of some "odd radio circles" in the sky. These circles are strange because they are enormous and yet not associated with any visible object. For now, they defy any conventional explanation, so wormholes have been advanced as a possible cause.

A can of worms

Wormholes hold a strong grip on our collective imagination. In a way, they are a delightful form of escapism. Unlike black holes which are a bit frightening as they trap everything that ventures in, wormholes may allow us to travel to faraway places faster than the speed of light. They may in fact even be time machines, providing a way to travel backwards—as suggested by the late Stephen Hawking in his final book.

Wormholes also crop up in quantum physics, which rules the world of atoms and particles. According to quantum mechanics , particles can pop out of empty space, only to disappear a moment later. This has been seen in countless experiments. And if particles can be created, why not wormholes? Physicists believe wormholes may have formed in the early universe from a foam of quantum particles popping in and out of existence. Some of these "primordial wormholes" may still be around today.

Recent experiments on "quantum teleportation"—a "disembodied" transfer of quantum information from one location to another—have turned out to work in an eerily similar way to two black holes connected through a wormhole . These experiments appear to solve the "quantum information paradox", which suggests physical information could permanently disappear in a black hole. But they also reveal a deep connection between the notoriously incompatible theories of quantum physics and gravity—with wormholes being relevant to both—which may be instrumental in the construction of a "theory of everything".

The fact that wormholes play a role in these fascinating developments is unlikely to go unnoticed. We may not have seen them, but they could certainly be out there. They may even help us understand some of the deepest cosmic mysteries, such as whether our universe is the only one.

Provided by The Conversation

Explore further

Feedback to editors

Two new species of Psilocybe mushrooms discovered in southern Africa

3 hours ago

UV radiation damage leads to ribosome roadblocks, causing early skin cell death

4 hours ago

Dual-laser approach could lower cost of high-resolution 3D printing

Novel method enhances size-controlled production of luminescent quantum dots

Cosmic simulation reveals how black holes grow and evolve

5 hours ago

How climate change is affecting where species live

6 hours ago

Human presence shifts balance between leopards and hyenas in East Africa

Physicists' laser experiment excites atom's nucleus, may enable new type of atomic clock

Treatment with a mixture of antimicrobial peptides found to impede antibiotic resistance

Study reveals fireworks' impact on air quality

7 hours ago

Relevant PhysicsForums posts

Early universe massive black holes question.

12 hours ago

Questions about dark matter/energy

Jun 30, 2024

Galaxies as systems extended from the solar system

Jun 28, 2024

Interstellar navigation to Proxima B with an unmanned probe

Jun 25, 2024

Some photos of Antares and Sigma Sagittarii (Nunki)

Jun 23, 2024

Why is the CNO Cycle considered catalytic in stellar nucleosynthesis?

More from Astronomy and Astrophysics

Related Stories

How to see what's on the other side of a wormhole without actually traveling through it

Oct 13, 2020

Travel through wormholes is possible, but slow

Apr 15, 2019

How to spot a wormhole (if they exist)

Oct 23, 2019

One theory beyond the standard model could allow wormholes that you could actually fly through

Aug 27, 2020

Pair of researchers suggest black holes at center of galaxies might instead be wormholes

May 30, 2014

Video: Can wormholes act like time machines?

Apr 30, 2020

Recommended for you

German scientists investigate supernova remnant SNR G309.8+00.0 at high energies

NASA's Webb captures celestial fireworks around forming star

8 hours ago

Infrared glow high in Jupiter's atmosphere may be dark matter particles colliding

11 hours ago

Astronomers discover a peculiar radio galaxy

Jul 1, 2024

Research intern helps discover a new pulsar buried in a mountain of data

Let us know if there is a problem with our content.

Use this form if you have come across a typo, inaccuracy or would like to send an edit request for the content on this page. For general inquiries, please use our contact form . For general feedback, use the public comments section below (please adhere to guidelines ).

Please select the most appropriate category to facilitate processing of your request

Thank you for taking time to provide your feedback to the editors.

Your feedback is important to us. However, we do not guarantee individual replies due to the high volume of messages.

E-mail the story

Your email address is used only to let the recipient know who sent the email. Neither your address nor the recipient's address will be used for any other purpose. The information you enter will appear in your e-mail message and is not retained by Phys.org in any form.

Newsletter sign up

Get weekly and/or daily updates delivered to your inbox. You can unsubscribe at any time and we'll never share your details to third parties.

More information Privacy policy

Donate and enjoy an ad-free experience

We keep our content available to everyone. Consider supporting Science X's mission by getting a premium account.

E-mail newsletter

Wormhole Is Best Bet for Time Machine, Astrophysicist Says

The concept of a time machine typically conjures up images of an implausible plot device used in a few too many science-fiction storylines. But according to Albert Einstein's general theory of relativity, which explains how gravity operates in the universe, real-life time travel isn't just a vague fantasy.

Traveling forward in time is an uncontroversial possibility, according to Einstein's theory. In fact, physicists have been able to send tiny particles called muons , which are similar to electrons, forward in time by manipulating the gravity around them. That's not to say the technology for sending humans 100 years into the future will be available anytime soon, though.

Time travel to the past, however, is even less understood. Still, astrophysicist Eric W. Davis, of the EarthTech International Institute for Advanced Studies at Austin, argues that it's possible. All you need, he says, is a wormhole , which is a theoretical passageway through space-time that is predicted by relativity. [ Wacky Physics: The Coolest Little Particles in Nature ]

"You can go into the future or into the past using traversable wormholes," Davis told LiveScience.

Where's my wormhole?

Wormholes have never been proven to exist, and if they are ever found, they are likely to be so tiny that a person couldn't fit inside, never mind a spaceship.

Even so, Davis' paper, published in July in the American Institute of Aeronautics and Astronautics' journal, addresses time machines and the possibility that a wormhole could become, or be used as, a means for traveling backward in time.

Sign up for the Live Science daily newsletter now

Get the world’s most fascinating discoveries delivered straight to your inbox.

Both general-relativity theory and quantum theory appear to offer several possibilities for traveling along what physicists call a "closed, timelike curve," or a path that cuts through time and space — essentially, a time machine.

In fact, Davis said, scientists' current understanding of the laws of physics "are infested with time machines whereby there are numerous space-time geometry solutions that exhibit time travel and/or have the properties of time machines."

A wormhole would allow a ship, for instance, to travel from one point to another faster than the speed of light — sort of. That's because the ship would arrive at its destination sooner than a beam of light would, by taking a shortcut through space-time via the wormhole. That way, the vehicle doesn't actually break the rule of the so-called universal speed limit — the speed of light — because the ship never actually travels at a speed faster than light. [ Warped Physics: 10 Effects of Traveling Faster Than Light ]

Theoretically, a wormhole could be used to cut not just through space, but through time as well. 

" Time machines are unavoidable in our physical dimensional space-time," David wrote in his paper. "Traversable wormholes imply time machines, and [the prediction of wormholes] spawned a number of follow-on research efforts on time machines."

However, Davis added, turning a wormhole into a time machine won't be easy. "It would take a Herculean effort to turn a wormhole into a time machine. It's going to be tough enough to pull off a wormhole," he told LiveScience.

That's because once a wormhole is created, one or both ends of it would need to be accelerated through time to the desired position, according to general relativity theory.

Challenges ahead

There are several theories for how the laws of physics might work to prevent time travel through wormholes .

"Not only do we assume [time travel into the past] will not be possible in our lifetime, but we assume that the laws of physics, when fully understood, will rule it out entirely," said Robert Owen, an astrophysicist at Oberlin College in Ohio who specializes in black holes and gravitation theory.

According to scientists' current understanding, keeping a wormhole stable enough to traverse requires large amounts of exotic matter, a substance that is still very poorly understood.  

General relativity can't account for exotic matter — according to general relativity, exotic matter can't exist. But exotic matter does exist . That's where quantum theory comes in. Like general relativity, quantum theory is a system for explaining the universe, kind of like a lens through which scientists observe the universe. [ Video – How to Time Travel ]

However, exotic matter has only been observed in very small amounts — not nearly enough to hold open a wormhole. Physicists would have to find a way to generate and harness large amounts of exotic matter if they hope to achieve this quasi-faster-than-light travel and, by extension, time travel.

Furthermore, other physicists have used quantum mechanics to posit that trying to travel through a wormhole would create something called a quantum back reaction.

In a quantum back reaction, the act of turning a wormhole into a time machine would cause a massive buildup of energy, ultimately destroying the wormhole just before it could be used as a time machine.

However, the mathematical model used to calculate quantum back reaction only takes into account one dimension of space-time.

"I am confident that, since [general relativity] theory has not failed yet, that its predictions for time machines, warp drives and wormholes remain valid and testable, regardless of what quantum theory has to say about those subjects," Davis added.

This illustrates one of the key problems in theories of time travel: physicists have to ground their arguments in either general relativity or quantum theory, both of which are incomplete and unable to encompass the entirety of our complex, mysterious universe.

Before they can figure out time travel, physicists need to find a way to reconcile general relativity and quantum theory into a quantum theory of gravity. That theory will then serve as the basis for further study of time travel.

Therefore, Owen argues that it's impossible to be certain of whether time travel is possible yet. "The wormhole-based time-machine idea takes into account general relativity, but it leaves out quantum mechanics," Owen added. "But including quantum mechanics in the calculations seems to show us that the time machine couldn't actually work the way we hope."

Davis, however, believes scientists have discovered all they can about time machines from theory alone, and calls on physicists to focus first on faster-than-light travel. 

"Until someone makes a wormhole or a warp drive , there's no use getting hyped up about a time machine," Davis told LiveScience.

Accomplishing this will require a universally accepted quantum gravity theory — an immense challenge — so don't go booking those time-travel plans just yet.

Email  [email protected] or follow her @JillScharr . Follow LiveScience @livescience , Facebook  & Google+ . Original article on  LiveScience .

'Holy grail' of solar technology set to consign 'unsustainable silicon' to history

DARPA's military-grade 'quantum laser' will use entangled photons to outshine conventional laser beams

Earth from space: Green River winds through radioactive 'labyrinth of shadows'

Most Popular

• 2 Milky Way's black hole 'exhaust vent' discovered in eerie X-ray observations
• 3 James Webb Space Telescope spies strange shapes above Jupiter's Great Red Spot
• 4 What defines a species? Inside the fierce debate that's rocking biology to its core
• 5 Newly discovered asteroid larger than the Great Pyramid of Giza will zoom between Earth and the moon on Saturday
• 2 Self-healing 'living skin' can make robots more humanlike — and it looks just as creepy as you'd expect
• 3 What causes you to get a 'stitch in your side'?
• 4 This robot could leap higher than the Statue of Liberty — if we ever build it properly
• 5 Zany polar bears and a '3-headed' giraffe star in Nikon Comedy Wildlife Awards

A Smithsonian magazine special report

Would Astronauts Survive an Interstellar Trip Through a Wormhole?

Well, it depends on your definition of “wormhole” …

Victoria Jaggard

In the space opera Interstellar , astronauts seeking to save humanity have found a lifeline: a wormhole that has mysteriously appeared next to Saturn. The tunnel through spacetime leads to a distant galaxy and the chance to find habitable planets that humans can colonize. The movie's wormhole is based on real physics from retired CalTech professor Kip Thorne , an astrophysics pioneer who also helped Carl Sagan design his wormhole for the novel Contact . The visualizations are stunning and are being hailed as some of the most accurate simulations of wormholes and black holes in film. But there is one aspect of plunging into an interstellar express that the film doesn't address: How do you survive the trip?

Although they didn't call it such, the original wormhole was the brainchild of Albert Einstein and his assistant Nathan Rosen. They were trying to solve Einstein's equations for general relativity in a way that would ultimately lead to a purely mathematical model of the entire universe, including gravity and the particles that make up matter. Their attempt involved describing space as two geometric sheets connected by "bridges," which we perceive as particles.

Another physicist, Ludwig Flamm, had  independently discovered such bridges  in 1916 in his solution to Einstein's equations. Unfortunately for all of them, this "theory of everything" didn't work out, because the theoretical bridges did not ultimately behave like real particles. But Einstein and Rosen's  1935 paper  popularized the concept of a tunnel through the fabric of spacetime and got other physicists thinking seriously about the implications.

Princeton physicist John Wheeler coined the term "wormhole" in the 1960s when he was exploring the models of Einstein-Rosen bridges. He noted that the bridges are akin to the holes that worms bore through apples. An ant crawling from one side of the apple to another can either plod all the way around its curved surface, or take a shortcut through the worm's tunnel. Now imagine our three-dimensional spacetime is the skin of an apple that curves around a higher dimension called "the bulk." An Einstein-Rosen bridge is a tunnel through the bulk that lets travelers take a fast lane between two points in space. It sounds strange, but it is a legit mathematical solution to general relativity.

Wheeler realized that the mouths of Einstein-Rosen bridges handily match descriptions of what's known as a Schwarzschild black hole , a simple sphere of matter so dense that not even light can escape its gravitational pull. Ah-ha! Astronomers believe that black holes exist and are formed when the cores of exceedingly massive stars collapse in on themselves. So could black holes also be wormholes and thus gateways to interstellar travel? Mathematically speaking, maybe—but no one would survive the trip.

In the Schwarzschild model, the dark heart of a black hole is a singularity, a neutral, unmoving sphere with infinite density. Wheeler calculated what would happen if a wormhole is born when two singularities in far-flung parts of the universe merge in the bulk, creating a tunnel between Schwarzschild black holes. He found that such a wormhole is inherently unstable: the tunnel forms, but then it contracts and pinches off, leaving you once more with just two singularities. This process of growth and contraction happens so fast that not even light makes it through the tunnel, and an astronaut trying to pass through would encounter a singularity. That's sudden death, as the immense gravitational forces would rip the traveler apart.

"Anything or anyone that attempts the trip will get destroyed in the pinch-off!" Thorne writes in his companion book to the movie, The Science of Interstellar . 

The Science of Interstellar

Amazon.com: The Science of Interstellar (9780393351378): Kip Thorne, Christopher Nolan: Books

There is an alternative: a rotating Kerr black hole, which is another possibility in general relativity. The singularity inside a Kerr black hole is a ring as opposed to a sphere, and some models suggest that a person could survive the trip if they pass neatly through the center of this ring like a basketball through a hoop. Thorne, however, has a number of objections to this notion. In a 1987 paper about travel via wormhole , he notes that the throat of a Kerr wormhole contains a region called a Cauchy horizon that is very unstable. The math says that as soon as anything, even light, tries to pass this horizon, the tunnel collapses. Even if the wormhole could somehow be stabilized, quantum theory tells us that the inside should be flooded with high-energy particles. Set foot in a Kerr wormhole, and you will be fried to a crisp.

The trick is that physics has yet to marry the classical rules of gravity with the quantum world, an elusive bit of mathematics that many researchers are trying to pin down. In one twist on the picture, Juan Maldacena at Princeton and Leonard Susskind at Stanford proposed that wormholes may be like the physical manifestations of entanglement, when quantum objects are linked no matter how far apart they are.

Einstein famously described entanglement as "spooky action at a distance" and resisted the notion. But plenty of experiments tell us that entanglement is real—it's already being used commercially to protect online communications, such as bank transactions. According to Maldacena and Susskind, large amounts on entanglement change the geometry of spacetime and can give rise to wormholes in the form of entangled black holes . But their version is no interstellar gateway.

"They are wormholes which do not allow you to travel faster than light," says Maldacena. "However, they can allow you to meet somebody inside, with the small caveat that they would both then die at a gravitational singularity."

OK, so black holes are a problem. What, then, can a wormhole possibly be?  Avi Loeb at the Harvard-Smithsonian Center for Astrophysics says our options are wide open: "Since we do not yet have a theory that reliably unifies general relativity with quantum mechanics, we do not know of the entire zoo of possible spacetime structures that could accommodate wormholes."

There's still a hitch. Thorne found in his 1987 work that any type of wormhole that is consistent with general relativity will collapse unless it is propped open by what he calls "exotic matter" with negative energy. He argues that we have evidence of exotic matter thanks to experiments showing how quantum fluctuations in a vacuum seem to create negative pressure between two mirrors placed very close together. And Loeb thinks our observations of dark energy are further hints that exotic matter may exist.

"We observe that over recent cosmic history, galaxies have been running away from us at a speed that increases with time, as if they were acted upon by repulsive gravity," says Loeb. "This accelerated expansion of the universe can be explained if the universe is filled with a substance that has a negative pressure … just like the material needed to create a wormhole." Both physicists agree, though, that you'd need too much exotic matter for a wormhole to ever form naturally, and only a highly advanced civilization could ever hope to gather enough of the stuff to stabilize a wormhole.

But other physicists are not convinced. "I think that a stable, traversable wormhole would be very confusing and seems inconsistent with the laws of physics that we know," says Maldacena. Sabine Hossenfelder  at the Nordic Institute for Theoretical Physics in Sweden is even more skeptical: "We have absolutely zero indication that this exists. Indeed it is widely believed that it cannot exist, for if it did the vacuum would be unstable." Even if exotic matter was available, traveling through it may not be pretty. The exact effects would depend on the curvature of spacetime around the wormhole and the density of the energy inside, she says. "It is pretty much as with black holes: too much tidal forces and you get ripped apart."

Despite his ties to the film, Thorne is also pessimistic that a traversable wormhole is even possible, much less survivable. "If they can exist, I doubt very much that they can form naturally in the astrophysical universe," he writes in the book. But Thorne appreciates that Christopher and Jonah Nolan, who wrote Interstellar , were so keen to tell a story that is grounded in science.

“The story is now essentially all Chris and Jonah's,” Thorne told Wired in an exclusive interview. “But the spirit of it, the goal of having a movie in which science is embedded in the fabric from the beginning—and it's great science—that was preserved.”

Get the latest Science stories in your inbox.

Victoria Jaggard | | READ MORE

Victoria Jaggard is the science editor for Smithsonian.com. Her writing has appeared in Chemical & Engineering News , National Geographic , New Scientist and elsewhere.

Wormholes: What Are They and Can We Use Them?

• Stars, Planets, and Galaxies
• An Introduction to Astronomy
• Important Astronomers
• Solar System
• Space Exploration
• Weather & Climate
• Ph.D., Physics and Astronomy, Purdue University
• B.S., Physics, Purdue University

Space travel through wormholes sounds like quite an interesting idea. Who wouldn't like to have the technology to hop in a ship, find the nearest wormhole and travel to distant places in a short time? It would make space travel so easy!  Of course, the idea pops up in science-fiction movies and books all the time. These "tunnels in space-time" supposedly allow characters to move through space and time in a heartbeat, and the characters don't have to worry about physics.

Are wormholes real?  Or are they only literary devices to keep science-fiction plots moving along. If they do exist, what's the scientific explanation behind them? The answer could be a little of each. However, they are a direct consequence of general relativity , the theory first developed by Albert Einstein early in the 20th century. However, that doesn't necessarily mean that they exist or that people can travel through them in spaceships. To understand why they're even an idea for space travel, it's important to know a little about the science that might explain them.

What are Wormholes?

A wormhole is supposed to be a way to transit through space-time that connects two distant points in space. Some examples from popular fiction and movies include the movie Interstellar , where the characters used wormholes as portals to distant parts of the galaxy. However, there is no observational evidence that they exist and there's no empirical proof that they aren't out there somewhere.  The trick is to find them and then figure out how they work. 

One way for a stable wormhole to exist is for it to be created and supported by some kind of exotic material. Easily said, but what's exotic material? What special property does it need to have to make wormholes? Theoretically speaking, such "wormhole stuff"  has to have "negative" mass. That's just what it sounds like: matter that has a negative value, rather than regular matter, which has a positive value. It's also something scientists have never seen.

Now, it is possible for wormholes to spontaneously pop into existence using this exotic matter. But, there's another problem. There would be nothing to support them, so they would instantaneously collapse back in on themselves. Not so great for any ship that happens to be passing through at the time. 

Black Holes and Wormholes

So, if spontaneous wormholes aren't workable, is there another way to create them? Theoretically yes, and we have black holes to thank for that. They are involved in a phenomenon known as an Einstein-Rosen bridge. It's essentially a wormhole created due to the immense warping of space-time by the effects of a black hole . Specifically, it has to be a Schwarzschild black hole, one that has a static (unchanging) amount of mass, doesn't rotate, and has no electrical charge.

So, how would that work? Essentially as light falls into the black hole, it would pass through a wormhole and escape out the other side, through an object known as a white hole. A white hole is similar to a black hole but instead of sucking material in, it repels material away. Light would be accelerated away from a white hole's  "exit portal" at, well, the  speed of light , making it a bright object, hence the term "white hole." 

Of course, reality bites here: it would be impractical to even attempt to pass through the wormhole to begin with. That's because the passage would require falling into a black hole, which is a remarkably lethal experience. Anything passing the event horizon would be stretched and crushed, which includes living beings. To put it simply, there is no way to survive such a trip.

The Kerr Singularity and Traversable Wormholes

There is yet another situation in which a wormhole might arise, from something called a Kerr black hole. It would look quite different than a normal "point singularity" that is what astronomers think make up black holes. A Kerr black hole would orient itself in a ring formation, effectively balancing the immense gravitational force with the rotational inertia of the singularity.

Since the black hole is "empty" in the middle it could be possible to pass through that point. The warping of space-time in the middle of the ring could act as a wormhole, allowing travelers to pass through to another point in space. Perhaps on the far side of the universe, or in a different universe all together. Kerr singularities have a distinct advantage over other proposed wormholes as they don't require the existence and use of exotic "negative mass" in order to keep them stable. However, they haven't yet been observed, only theorized. 

Could We Someday Use Wormholes?

Putting aside the technical aspects of wormhole mechanics, there are also some hard physical truths about these objects. Even if they do exist, it is difficult to say if people could ever learn to manipulate them. Plus, humanity really doesn't even have starships yet, so figuring out ways to use wormholes to travel is really putting the cart before the horse. 

There is also the obvious question of safety. At this point, no one knows exactly what to expect inside a wormhole. Nor do we know exactly WHERE a wormhole could send a ship. It could be in our own galaxy, or perhaps somewhere else in the very distant universe. Also, here's something to chew on.  If a wormhole took a ship from our galaxy to another one billions of light-years away, there's a whole question of time to consider. Does the wormhole transport instantaneously? If so, WHEN do we arrive in the distant shore? Does the trip ignore the expansion of space-time? 

So while it may certainly be possible for wormholes to exist and function as portals across the universe, it is considerably less likely that people will ever be able to find a way to use them. The physics just don't work out. Yet. 

Edited and updated by Carolyn Collins Petersen

• Is Time Travel Possible?
• Can We Travel Through Time to the Past?
• The Science of Star Trek
• Is Warp Drive From 'Star Trek' Possible?
• Time Travel: Dream or Possible Reality?
• Learn About the True Speed of Light and How It's Used
• An Introduction to Black Holes
• An Introduction to Gravitational Lensing
• Amazing Astronomy Facts
• Sub-light Speed in Star Trek: Can It Be Done?
• The Top Space Questions
• What Lies Between Galaxies?
• Cosmic Rays
• What is Matter?
• How Did the Universe Get Started?
• Cold Dark Matter

• Subscribe to BBC Science Focus Magazine
• Previous Issues
• Future tech
• Everyday science
• Planet Earth
• Newsletters

Wormholes: Could we travel through a black hole into another galaxy?

Could we travel through a black hole to take a shortcut into another galaxy?

Robert Matthews

Ever since a trip througha wormhole was first portrayed in 2001: A Space Odyssey 50 years ago, the idea of them has captured the public imagination. And small wonder: they’re the ultimate form of cosmic travel: a way of zipping across galaxies in an instant.

But while wormholes have become a staple of science fiction, among scientists they’ve been a source of endless frustration. Not because the idea is ridiculous, but because it isn’t. The astonishing fact is that wormholes are a natural consequence of current theories of gravity, and were investigated by Einstein himself over 80 years ago. Ever since, researchers have been trying to find out if such a bizarre theoretical possibility could be a reality.

And now they have made a major breakthrough – one which exploits deep connections between the nature of space and time and the laws of the subatomic world. The result is a new understanding of exactly what’s required to make a real-life wormhole.

• The hunt for the oldest galaxies in the Universe
• Black holes: how did we discover these 'dark stars'?

Einstein first investigated the properties of wormholes with his colleague Nathan Rosen in 1935, using his theory of gravity known as General Relativity. They found that what we now call a black hole could be connected to another via a tube-like ‘throat’. Now called the Einstein-Rosen bridge, this seemed to open the way to taking shortcuts through space and time, entering a black hole in one part of the Universe and emerging from another perhaps millions of light-years away, but without taking millions of years to do so – thus effectively travelling faster than the speed of light.

It was a stunning idea, but in the early 1960s it was dealt a severe blow by John Wheeler, the brilliant US physicist who first coined the terms ‘black hole’ and ‘wormhole’. Together with fellow theorist Robert Fuller, he showed that the Einstein-Rosen bridge would collapse almost as soon as it formed. As Dr Daniel Jafferis, associate professor of physics at Harvard University explains: “We could jump in from opposite sides and meet in the connected interior, but then we would both be doomed.”

Jafferis is one of an elite group of theorists around the world searching for ways to dodge this problem. For years, the most promising idea has been to support the bridge using a type of ‘exotic matter’ withnegative energy. As its name suggests, this is pretty weird stuff – so weird it’s capable of bending the normal rules of gravity. While ordinary matter always generates a gravitational pull, the negative energy produced by this exotic matter generates an antigravitational repulsion. Amazingly, such energy is known to exist. In the 1990s, astronomers discovered that the whole Universe is expanding under the antigravitational effect of so-called ‘dark energy’. There’s just one problem - the exact origins of dark energy are as yet unknown. The same goes for the exotic matter – no one has any idea how to create the stuff, let alone use it keep a wormhole open long enough to fly through.

The worm has turned

But now the debate over such so-called traversable wormholes has taken a radical new turn. It follows the discovery of a new way of keeping the bridge intact based on a surprising link between wormholes and quantum theory (the laws of the subatomic world). It emerged during attempts to solve a problem that has obsessed some of the greatest theorists of our time, including the late Stephen Hawking: what happens to objects that fall into a black hole?

Everyone knows there’s no escaping a black hole once inside it: the pull of gravity is too strong even for light to evade its clutches. Yet Hawking famously showed that a black hole doesn’t last forever, but eventually explodes in a burst of intense radiation, leaving no trace of whatever fell into it.

The trouble is, this contradicts one of the key principles of quantum theory, which states that information can never be destroyed. Black holes, however, seem quite capable of utterly destroying information about what they’ve consumed. This is the notorious ‘black hole information paradox’, and it hints at a big gap in our understanding of how the Universe works.

For decades, Hawking and many others tried to resolve the paradox without success. But now there’s growing excitement that the answer has been found. And it lies in the ability of wormholes to provide a way out of black holes. Put simply, theorists think the supposedly inescapable boundary of a black hole – the so-called event horizon – is riddled with tiny wormholes that allow information to seep out, along with the radiation which Hawking showed destroys black holes. This, in turn, has led to new insights into the nature of wormholes, and whether they can be traversed.

Until now, the only known way to traverse a wormhole was to stop the Einstein-Rosen bridge collapsing using the negative energy of exotic matter. “Quantum effects allow some negative energy,” explains Jafferis. “But it was long suspected that what is required for a traversable wormhole is physically impossible.”

Now, Jafferis and his colleagues Dr Ping Gao and Dr Aron Wall think they’ve discovered another source. “What we found is that a direct interaction between the [black holes at the] two ends of a non-traversable wormhole can lead to negative energy,” says Jafferis. The resulting antigravitational effect then stops the Einstein-Rosen bridge from collapsing, therefore making the wormhole traversable.

When Jafferis and his colleagues say “direct interaction”, they mean that the two black holes forming the mouths of the wormhole are affecting each other across real, ordinary space. “Binary black hole systems consuming each other’s Hawking radiation is a good example,” says Jafferis. “The consuming of the radiation is the direct connection.”

In a tangle

So, the good news is that traversable wormholes really can exist. Better still, according to Jafferis there’s no problem sending a human through one of them, at least in principle. But, perhaps unsurprisingly, there are some major problems to overcome.

First, the black holes can’t just be the standard type formed from the collapsed remnants of huge stars; they have to be ‘maximally entangled’. This refers to a strange quantum connection that can exist between two objects, so that anything done to one affects the other instantly – no matter how far apart they are.

• Do black holes rotate?
• Do black holes collapse?

Like negative energy, the bizarre phenomenon of quantum entanglement really exists. It was first detected in lab experiments nearly 40 years ago, and it’s now being investigated by companies like Google for creating ultra-fast quantum computers. Yet while subatomic particles can be entangled relatively easily in the lab, no one has any idea how to do the same with black holes. “We can’t even make unentangled black holes, let alone precisely quantum entangled ones,” explains Jafferis.

Yet direct interaction between two black holes comes with a catch: it forbids any amazing time travel trickery. But could it still allow faster-than-light travel? That’s a tricky question, says Jafferis. Gravity, space and time are all intimately linked, and that messes with the very notion of speed. According to Jafferis, calculations based on the wormhole types studied so far suggest that using them would actually be slower than simply travelling directly through space. He admits, though, that the details have yet to be fully worked out. So, it seems that science fact is still running a little behind science fiction. The laws of nature seem to insist that wormholes can either perform amazing feats but collapse in an instant, or be traversable but useless.

Yet time and again, nature has sprung big surprises on theorists. The mere possibility of black holes was disputed for decades, and Einstein himself refused to believe in quantum entanglement. Could it be that somewhere in the Universe lie natural wormholes performing their miracles?

Science or sci-fi?

The possibility of observing a real-life wormhole is now the focus of research by theorists using a mix of mathematics and computer models. The challenge is spotting the difference between normal black holes and those that are the portals of wormholes. According to Rajibul Shaikh, a gravity theorist at the Tata Institute of Fundamental Research in Mumbai, India, the answer may lie in subtle differences in the way they affect their surroundings – and in particular the behaviour of light. “As predicted by Einstein’s General Relativity, photons undergo bending in a gravitational field,” he explains.

The intense gravity of black holes creates incredibly hot, bright accretion discs around them, formed of matter spiralling down to its doom. The otherwise invisible hosts of these discs then reveal their presence as a pitch-black shadow cast on them. It’s the shape of this shadow that could reveal when a black hole is actually something even more bizarre. According to Shaikh, the telltale signs of a wormhole come from the gravitational effect of its throat on the resulting shadow.

“What I found is that the shape of the shadow of a slowly rotating wormhole would be very similar to the almost perfectly disc-like shadow cast by a slowly rotating black hole,” he explains. “But a faster spinning wormhole would cast a shadow which is more distorted than that of a black hole with the same spin.”

He stresses that research is still in progress, and the results so far are based on specific types of black holes and wormholes. “There’s no guarantee the type of rotating wormholes I considered are the most common.”

But Shaikh points out that astronomers already have the means to detect the effects predicted to exist around wormholes. Known as the Event Horizon Telescope (EHT), it consists of a global network of radio antennas able to make studies of black holes and wormholes. “And it has already started taking data,” says Shaikh. It could just be that, half a century after it made its debut on movie screens, the space-time wormhole is about to become more than just science fiction.

• This article first appeared in issue 322 of BBC Focus Magazine

Share this article

• Terms & Conditions
• Privacy policy
• Cookies policy
• Code of conduct
• Magazine subscriptions
• Manage preferences

Advertisement

We are closer than ever to finally proving the multiverse exists

One hundred years ago, we discovered there were other galaxies beyond our own. Now, we might be on the verge of another discovery: that there are other universes

By Miriam Frankel

25 June 2024

Shutterstock/Dr. Norbert Lange

This story is part of our Cosmic Perspective series, in which we confront the staggering vastness of the cosmos and our place in it. Read the rest of the series  here .

We think our universe contains everything that exists, has ever existed and will exist in the future. But this might not be the case: there are many ways other universes could exist.

One is that we could be a single part of a branch of infinite universes known collectively as the multiverse . These universes might have appeared shortly after the big bang, they might be hiding in extra dimensions or they could pop into existence whenever a quantum property goes from a cloud of possible states to a single reality.

Quantum time travel: The experiment to 'send a particle into the past'

Multiverse ideas gained scientific weight in the 1980s with the invention of inflation , a period when the early universe suddenly expanded. Inflation explains why the cosmos is so flat and smooth, but it also predicts the creation of a multitude of independent bubble universes.

Cyclic universes

Yet inflation is just one route to a multiverse, and it has its critics. In recent years, many cosmologists have turned to alternatives like cyclic universe theories, which say the universe is on an unending cycle between ballooning and compressing. These theories still invoke multiple universes, but at different times.

“What I didn’t like about inflation was that there are very few genuine predictions – you don’t get out much more than you put in,” says Neil Turok , a physicist at the University of Edinburgh, UK, who…

Sign up to our weekly newsletter

Receive a weekly dose of discovery in your inbox! We'll also keep you up to date with New Scientist events and special offers.

To continue reading, subscribe today with our introductory offers

No commitment, cancel anytime*

Offer ends 2nd of July 2024.

*Cancel anytime within 14 days of payment to receive a refund on unserved issues.

Inclusive of applicable taxes (VAT)

Existing subscribers

More from New Scientist

Explore the latest news, articles and features

Why this is a golden age for life to thrive across the universe

Subscriber-only

Is it possible to fully understand the universe while living in it?

Why you should feel comforted, not scared, by the vastness of space

This mind-blowing map shows Earth’s position within the vast universe

Popular articles.

Trending New Scientist articles

• Weird But True
• Sex & Relationships
• Viral Trends
• Human Interest
• Fashion & Beauty
• Food & Drink

trending now in Lifestyle

Ex-McDonald's chef reveals what not to order at the Golden...

Men are 'raw dogging' it on flights  — here's what the weird...

Disturbing Gen Z sex trend exposed

These popular antidepressants cause the most weight gain: Harvard...

I was a CIA spy — here's how I kept my job secret while dating...

Gen Z 'sadfishing' trend on social media may be sign of serious...

Dear Abby: My boyfriend is addicted to watching porn

I flew to Turkey for an $810 full-body health scan that would...

Breaking news, study hints that we can see traces of alien travel from ‘warp drives’ in space.

• View Author Archive
• Follow on X
• Get author RSS feed

Thanks for contacting us. We've received your submission.

It’s the next generation — of science.

A new study appears to have legitimized the popular science fiction belief that “warp drives” — known by nerds as super-powered space engines from “Star Trek” — may actually exist and be a way to discover aliens .

The research team, plucked from prestigious institutions like Oxford and the Max Planck Institute, hones in on the legitimacy of “faster-than-light travel” and its ties to “application to the search for extraterrestrial life.”

In other words, traces of warp travel could be indicators of non-human travel throughout the universe.

And there is potential for plausibility of their existence, the team stated.

“Despite originating in science fiction, warp drives have a concrete description in general relativity,” they wrote in the paper’s abstract .

“Our work highlights the importance of exploring strange new spacetimes, to (boldly) simulate what no one has seen before.”

This enterprise of thinkers is building on a concept from theoretical physicist Miguel Alcubierre.

In the 1990s, the Mexico City-based expert conceptualized the potential for a spaceship to zoom past light speed thanks to warp abilities, along with the existence of wormholes in space.

“It is possible to modify a spacetime in a way that allows a spaceship to travel with an arbitrarily large speed,” Alcubierre wrote at the time .

Advertisement

Screen Rant

10 things movies always get wrong about time travel.

Your changes have been saved

Email Is sent

Please verify your email address.

You’ve reached your account maximum for followed topics.

One Of The Best Scenes Of Tom Hanks' Entire 44-Year Career Is In This Movie That Just Landed On Netflix

A quiet place: day one rotten tomatoes audience score breaks franchise record, i refuse to get my hopes up for pirates of the caribbean 6 despite recent positive updates.

• Time travel movies often ignore the relationship between time and space, failing to account for the inseparable variable of spacetime.
• Most movie time machines disregard the two theoretical methods of time travel: faster-than-light (FTL) travel and the use of wormholes or black holes.
• Time loops, although popular in movies, are more of a narrative twist than a scientifically plausible theory according to Stephen Hawking's chronology protection conjecture.

While it may be one of the most popular ideas in science fiction, there are so many things that movies get wrong about time travel. There's never been a real-world example of time travel — at least not one that's been unanimously confirmed to be genuine by the international physics community. As it stands, time travel, as in the act of traveling to the past or at an accelerated rate to the future, remains in the realm of speculation. At the same time, scientific theories about time travel do account for its possibility.

There are time travel movies that actually make sense from a scientific perspective, but they are far outnumbered by the ones that don't. This isn't to say that the latter are necessarily terrible movies — even when the time travel elements don't line up, it remains a powerful plot device that has given audiences some of the most compelling tales about the human condition. That being said, movies that get time travel right actually pave the way for audiences to better understand complex science. For audiences who want to understand the most popular trope in sci-fi a little better, it's worth looking at what movies always get wrong about time travel.

Related: 15 Awesome Time Travel Movies That Aren't Back To The Future

10 The Separation Of Space & Time

Time travel movies don't always account for the relationship between time and space. However, most scientists agree with Albert Einstein's special theory of relativity, one of the core principles of which is that spacetime exists as an inseparable variable. This is often ignored by time travel movies. For instance, as Doc Brown's time machine in Back to the Future only has coordinates for time, Marty wouldn't have been transported to the same location where the DeLorean first worked. Instead, Marty would've ended up in the vacuum of space, as the Earth would've been in an entirely different location in the galaxy decades in the past.

9 How Time Machines Can Potentially Work

Physicists generally only take two theoretical time travel methods seriously: faster-than-light (FTL) travel and using wormholes or black holes. However, this is often disregarded by most movie time machines , the inner workings of which are typically left to the viewers' imagination. This goes back to the 1895 H.G. Wells novel The Time Machine — credited with popularizing the idea of a machine that can allow a person to willingly go back or forward through time. As seen in the 2002 sci-fi movie of the same name, Wells's device accounts neither for FTL nor the use of wormholes, which can also be said of the countless unexplained time machines in sci-fi.

8 Wormholes/Black Holes As Portals To Different Dimensions

In Interstellar, Cooper goes through a black hole and reaches a strange place where time is represented by compartmentalized rooms. Meanwhile, Event Horizon imagines how going through a wormhole can not only lead to Hell but also cause random echoes of the past. Theoretically, however, if wormholes exist — and if spacetime travel is possible through black holes — they are likely to lead to another defined point in spacetime. That said, even if the way black holes and wormholes work is one of the things movies always get wrong about time travel, the fantasy element of different dimensions does make for great cinema.

Related: Interstellar Ending & Space Travel Explained

7 Time Loops Being Scientifically Plausible

Edge of Tomorrow , Looper , 12 Monkeys , Source Code , and Groundhog Day are just some of the movies that prominently feature time loops in their plots. The sheer popularity of time loops makes this one of the most common things movies get wrong about time travel. As Stephen Hawking explains in his chronology protection conjecture theory, " The laws of physics do not allow the appearance of closed timelike curves " (via Advancing Physics ). Still, the time loop trope is more of a narrative twist on classic time travel than an actual scientific theory. They may be more implausible than time travel itself, but time loops remain effective storytelling devices.

6 Hyperdrive Not Accounting For Time Dilation

Based on theoretical warp drives, hyperdrive in the Star Wars films explains why FTL travel is possible in the galaxy. However, none of the Star Wars movies have ever accounted for how this can lead to time travel or time dilation. On one hand, as the Star Wars movies don't involve time travel, it may have been proven impossible by FTL causing no time distortions. On the other hand, Star Wars Rebels' World Between Worlds canonically confirms that time travel is possible. Moreover, as physics in Star Wars seems to work the same way as in the real world, FTL should at least cause noticeable time dilations.

5 The Existence of Tachyons

The Star Trek movies almost always link time travel events to the existence of tachyons, which in the real world are theoretical particles that only exist at FTL speeds, and are therefore potentially capable of time travel. The movie Land of the Lost also involves a " tachyon amplifier " that transports the user to a seemingly different point in space and time. While it's fun to envision the existence of such particles, tachyons come solely from the imagination of physicist and popular science author Gerald Feinberg. There have also been no experiments that were able to prove the existence of tachyons in the real world.

Related: Star Trek Confirms the Jaw-Dropping True Nature of Subspace

4 Time Travel Not Existing Yet

Technically speaking, traveling through time at unusual speeds already happens. Astronauts and satellites in orbit are already traveling through time milliseconds slower than people on Earth because they're moving at much faster speeds. Another example is how looking at stars through telescopes is technically a way of looking back in time — a result of light taking its time to travel through the vast distances between celestial bodies. Even for sci-fi movies that get time travel right, it's very rare for such basic spacetime-related science facts to be addressed, even though they could significantly help viewers understand how time travel could be possible.

3 A Time Paradox Would Destroy The Universe

From The Flash and Back to the Future to Avengers: Endgame , scientists from movies that break their own time travel rules have warned would-be time travelers of the infinite dangers of changing the spacetime continuum — at the peak of which is destroying the universe itself. Much like time loops or any other paradox involving temporal distortion, there is no real theory, even in quantum physics, that points to paradoxes causing such apocalyptic effects. Time paradoxes and their devastating effects are more creative thought experiments, not concepts supported by science.

2 FTL Travel Involving A Different Physical Plane Of Reality

Most versions of FTL travel involve a realm where time is a bit wonky — like hyperspace in Star Wars , the mycelial network in Star Trek , or the Quantum Realm in the MCU. They turn the "road" of time travel into a different physical plane of existence. However, this suggests that time travel is possible only in a different dimension with different physical rules, even though these movies seemingly have similar physics as the real world. While FTL travel can theoretically transport someone backward through spacetime, there are no theories that support how traveling FTL can somehow lead to a different reality outside the known universe.

Related: How Hyperspace Works In Star Wars

1 People Inexplicably Surviving FTL Speeds

Even critically acclaimed movies like Interstellar and Contact fail to explain how people traveling FTL — over 670,000,000 miles per hour — survive the acceleration. While time travel through FTL is theoretically possible, what's impossible is humans inexplicably surviving the g-forces caused by accelerating to FTL speeds in seconds. Modern jet planes that accelerate to over 4,000 mph in less than a minute subject fighter pilots to around 6 to 9 g-forces, and they're able to remain conscious only with the help of specialized training and suits. Scientifically, the g-forces of accelerating to FTL speeds wouldn't just cause travelers to faint or have strokes but would completely destroy their machines.

'ZDNET Recommends': What exactly does it mean?

ZDNET's recommendations are based on many hours of testing, research, and comparison shopping. We gather data from the best available sources, including vendor and retailer listings as well as other relevant and independent reviews sites. And we pore over customer reviews to find out what matters to real people who already own and use the products and services we’re assessing.

When you click through from our site to a retailer and buy a product or service, we may earn affiliate commissions. This helps support our work, but does not affect what we cover or how, and it does not affect the price you pay. Neither ZDNET nor the author are compensated for these independent reviews. Indeed, we follow strict guidelines that ensure our editorial content is never influenced by advertisers.

ZDNET's editorial team writes on behalf of you, our reader. Our goal is to deliver the most accurate information and the most knowledgeable advice possible in order to help you make smarter buying decisions on tech gear and a wide array of products and services. Our editors thoroughly review and fact-check every article to ensure that our content meets the highest standards. If we have made an error or published misleading information, we will correct or clarify the article. If you see inaccuracies in our content, please report the mistake via this form .

Don't forget these 5 gadgets when you travel this week

As a tech journalist, I often travel across the US -- and sometimes out of it -- to attend product launch events, trade shows, and other briefings for news that readers care about. It certainly helps to be based in New York City, where most of the gadgetry madness tends to occur, but when I am out and about (for work or play), there's a bag full of tech that I always have with me.

My treasure trove of electronics has evolved over recent years, transitioning to newer GaN chargers and more capable yet still portable camera systems . The five picks below are among my current arsenal of travel tech, and if you're traveling this week for the Fourth of July holiday, I highly encourage packing a few of these items into your carry-on. 

I'll make this a little more exciting for you by stating the obvious: My phone and a reliable Bluetooth tracker are always with me, so I've opted not to put them on this list. Instead, you'll find products I've personally tested that are useful enough for you to consider for your next adventure.

Also: The best travel gadgets of 2024  

DJI Osmo Pocket 3

While smartphone cameras have become very capable at capturing life's moments, I still prefer the enhanced stabilization and portability of a dedicated pocket camera, especially when I'm recording smooth-panning videos of product demos and scenery. The camera I've most recently settled on is the DJI Osmo Pocket 3, famous for its ability to record up to 4K resolution through a one-inch CMOS sensor. The output I've gotten has been reliable and impressive, both for vertical and horizontal footage, which can be set by physically swiveling the touchscreen viewfinder.

Does carrying an additional camera feel unnecessary? Not when the quality is noticeably better and it greatly reduces the battery consumption you'd otherwise put on your phone when recording videos. Reddit users who have used the Osmo Pocket 3 seem to agree, with the added benefits being better audio recording, improved video stabilization, and a larger sensor for more dramatic shots.

Also:  The best vlogging cameras of 2024

Lenovo Go Wireless Power Bank 10,000mAh

Lenovo's power bank may look unassuming, but trust me when I say there's more to it than what meets the eye. Besides having a 10,000mAh capacity, meaning there's enough juice to power a phone (and other accessories like earbuds) two to three times, a fairly long USB-C cable is built into the battery pack, saving you the hassle of carrying a separate one. 

Here's the second trick: the Lenovo Go can wirelessly charge Qi-supported devices when you place them on top of the accessory, allowing you to charge two devices at once (via wired and wireless) if you're feeling adventurous.

While the charge output is capped at 30W, many customers on Lenovo's website have found the power bank adequate for powering phones, tablets, and earbuds, and have been particularly satisfied with the built-in charging cable.

Also: The best power banks of 2024: Expert tested

Ayaneo Flip

I don't consider myself a hardcore gamer, but I've found traveling, especially when on long flights, to be the perfect opportunity to get my NBA 2K and Rocket League fix. Lately, my vehicle of choice for gaming has been the Ayaneo Flip, a Windows-powered handheld with Nintendo DS written all over it, from the dual touchscreen displays to the ergonomic shoulder triggers. Thanks to the OS and a capable AMD Ryzen 7 processor, I've been able to play Steam and Epic Games titles right on the device at medium to high graphic settings.

The big question mark with the Ayaneo Flip is its price point and availability, according to several interested Reddit users. With a starting price of $699, the Flip can best be justified by those who want a competent, on-the-go gaming handheld that can also be used for standard PC tasks like web browsing, streaming videos, and emailing. One of the Flip's most underrated features is the ability to output to a monitor or TV screen for a gaming experience more similar to standard consoles.

Also: Everything you need to create the ultimate gaming setup

Meta Ray-Ban Smart Glasses

While the Meta Ray-Ban smart glasses are fantastic for recording hands-free videos, I've found them more practical as a wearable tour guide. Thanks to recent Meta AI updates , the glasses can pull context from what's in front of you, whether it's a monument, statue, or restaurant storefront, and answer your most burning questions. I've used the smart glasses to identify unfamiliar landmarks, tell me the most popular food items at a local restaurant, play music from artists from the city that I've traveled to, and more.

The general sentiment toward the Meta Ray-Bans has been mostly positive, with Reddit users favoring the ease of use, comfort, and various capabilities. The price point of the glasses, starting at $299, is fairly competitive as well. 

Review: Meta Ray-Ban Smart Glasses: The best AI-powered AR glasses to buy right now

Nomad 65W Slim Power Adapter

Besides carrying a portable battery pack, I also travel with Nomad's 65 Slim Power Adapter, which fields two USB-C ports to charge tablets, phones, earbuds, and even laptops, like my MacBook Air. To help with portability, the prongs are collapsible, the charger is very slim, and it lies flush when plugged into the outlet. Carrying the accessory around is like carrying a pack of mints.

Customers, including ZDNET's Adrian Kingsley-Hughes, have expressed satisfaction with Nomad's 65W Slim Power Adapter, appreciating the speedy power delivery and support for two USB-C inputs. I especially recommend this charging adapter for users with ultraportable devices like lightweight and smaller laptops and iPads.

Also: Nomad's 130W charger has one unique feature that's game-changing for me

Why should you trust me?

When I'm not writing about technology, I'm probably working overtime as my family's IT support guy. And when I'm not working at all, I'm likely watching, reading, or consuming some form of content about technology. So when I make product recommendations, I suggest gadgets I've personally tested and have proven to deliver the value (if not more value) that manufacturers promise.

My main expertise is mobile, from phones to wearables to accessories, which plays hand-in-hand with the topic of this story. I also travel about 10 times throughout the year, including from New York to California, so I've developed an understanding of which gadgets are essential and which are optional.

How do you pack electronics for traveling?

When traveling, storing any devices with lithium-ion batteries, such as laptops, tablets, and power banks, in your carry-on baggage is best. If my gadgets aren't already stored in a tech pouch or cushioned bag, I'll surround them with clothing to prevent any damage during travel.

Other travel-friendly tech we think you'd love 

Zdnet recommends, i never go to the beach without these 4 gadgets, my 2 favorite iphone accessories let you see around corners or into pipes - and detect heat, everything you need for a 4th of july get-together.

Can AI find you the cheapest plane tickets? How Google and Skyscanner compared.

• Skyscanner’s Savvy Search and Google’s Gemini are AI-powered tools that can help you plan your trip.
• Both tools can also find you cheap flights, but Gemini was able to find the lowest price.
• Skyscanner’s tool is a good starting place if you don’t have a destination in mind.

Get more news like this delivered to your inbox by signing up for our Travel newsletter here . 

When booking a flight, chances are you want to score the best deal. (This is especially true now that flights from U.S. airports are more expensive than a few years ago.)

There are already a few tools out there to help you find affordable airfare , such as flight price trackers and low-fare calendars, but what about those new AI tools? Travel search engines like Booking.com, Expedia and Skyscanner have recently launched AI-powered features to help customers plan their vacations.

These AI trip planners – which act like chatbots – assist travelers in planning aspects of their trip, like finding accommodations and destinations, even building an itinerary for them. But some of them may even be able to help you find cheap flights. 

Launched in May, Skyscanner’s Savvy Search tool is powered by OpenAI’s ChatGPT and “accesses a vast database of over 18 million flight routes and 80 billion daily price searches to offer the best travel recommendations,” Laura Lindsay, Global Travel Trends Expert at Skyscanner, told USA TODAY.

Learn more: Best travel insurance

Make travel easy: We tested ChatGPT itineraries in 5 US tourist spots

Google’s own AI tool, Gemini, is a “creative and productivity tool” that can also assist travelers with trip planning, according to a Google spokesperson. Gemini can also connect to and access “relevant information from the Google tools you use every day,” from Google Flights, Google Hotels, Google Maps and Docs, according to a Google spokesperson. So you can check out flights, hotels and driving directions all in one conversation with Gemini. 

I tested Skyscanner’s AI Trip Planner and Google’s Gemini to see if they could find me the most affordable round-trip flights for a trip from Honolulu to New York for the week of August 18-25. For reference, a search on Google Flights on Thursday afternoon revealed the cheapest flight was a $761 round-trip ticket on United Airlines in its basic economy cabin. Here’s what I found.

What is it like using Skyscanner’s Savvy Search?

After making an account with Skyscanner, I easily found the Savvy Search on the mobile app's home screen. I had to input my departure city and answer the question, “What kind of trip is on your mind?” Getting straight to the point, I typed in, “What are the cheapest flights from Honolulu to New York for the week of August 18-25?” 

Savvy Search offered “three recommended places,” including New York, Los Angeles and San Francisco. Not really what I asked, but I suppose the answer was technically there. I clicked to see flights for New York and was taken to a list of flights to compare. I could sort by “best,” “cheapest,” “fastest” and “direct,” as well as choose my cabin class and add other travelers. 

The cheapest flight that came up cost $645 round-trip, and although inexpensive, it wasn’t looking easy. Both my departing and return flights would be self-transfers, requiring me to re-check any bags and go through security again, and also include an 11-hour layover on my return journey. 

I went ahead to book, and since Skyscanner is a flight comparison tool, the AI took me to an outside travel platform called DoHop , an Iceland-founded travel search engine that creates “unique connecting flights,” according to its website. I’ve never used DoHop before, and when I continued with my booking, I discovered I was also being charged a $32.64 DoHop booking fee and $12.50 if I wanted to bring a carry-on. (Only a personal item is free.)

The total was $664.83, around $97 cheaper than what Google Flights found. 

I also tested whether Savvy Search could find me cheap flights without a destination in mind (only my budget). It offered Los Angeles, San Francisco, and Tokyo. The cheapest option to Los Angeles was two direct flights on Alaska Airlines for $341. Once again, it sent me to book externally, but this time through Kiwi.com. 

Booking through third-party vendors like Kiwi or DoHop can be tricky for travelers, especially if things don’t go as planned, because airlines and hotels won’t typically claim responsibility if you didn’t book directly with them. Often, third-party support isn’t always reliable. 

Are Tuesdays still the best day to book? Here's what major travel platforms found about purchasing airfare.

What is it like to use Google’s Gemini to find cheap flights?

I accessed Gemini through its website – which required a Google account sign-in – and asked the same question I posed to Skyscanner's Trip Planner. Gemini warned me that it “doesn’t always get it right. Be sure to check the following flight details.” 

Gemini provided five flight options, with the lowest price one being a $615 round-trip flight on United Airlines –  $49 less than what Skyscanner told me and $146 cheaper than my own Google Flights search. 

Gemini told me how long the entire journey would take with each flight option, plus layovers. I clicked the flight I wanted and was taken right to Google Flights, where I could book through the airline or adjust my flights. 

I tested out other prompts, such as finding the cheapest flight from Honolulu for the same dates. (The answer was a flight to Maui for $160 round-trip.) Since that answer was a bit obvious, I tried again, asking for flights not within Hawaii. (That would be San Francisco starting at $354 round-trip.) I also asked if it was a cheap time to fly from Honolulu to New York in August. (No, because summer break is peak travel season.)  

The verdict

As far as finding the cheapest flight, Gemini takes the cake. I liked how seamless it was to move between Gemini and Google Flights. Although I wouldn’t want to book Skyscanner’s cheapest flight, I think it’s a helpful tool to compare prices and see the range of options. (Maybe you don’t mind a self-transfer.) 

I mainly like how Skyscanner’s tool recommended a variety of destinations when I asked for affordable flights from Honolulu, so it’s a good starting place if you don’t have a destination in mind. In fact, this is what half of Skyscanner’s users do, according to Lindsay. You can also ask Skyscanner for affordable destination alternatives and look for flights from there. 

Overall, both AI tools can fit into any passenger’s repertoire when searching for the best flight deals.

Kathleen Wong is a travel reporter for USA TODAY based in Hawaii. You can reach her at [email protected] .

The Key Points at the top of this article were created with the assistance of Artificial Intelligence (AI) and reviewed by a journalist before publication. No other parts of the article were generated using AI. Learn more .

• More to Explore
• Series & Movies

Published Jul 1, 2024

All Episodes of Star Trek: Prodigy Season 2 Now Available

Old friends, new worlds, even time travel.

StarTrek.com

Ready for a brand-new classified mission? All episodes of Season 2 of Star Trek: Prodigy are now streaming!

In Season 2, these six young outcasts who make up the Prodigy crew are assigned a new mission aboard the U.S.S. Voyager -A to rescue Captain Chakotay and bring peace to Gwyn's home world. However, when their plan goes astray, it creates a time paradox that jeopardizes both their future and past.

Season 2 Episode Titles and Synopses:

201 – "Into the Breach, Part I" 

The Prodigy crew is reunited and assigned a new mission aboard the U.S.S. Voyager -A, only to discover Admiral Janeway has other plans.

202 – "Into the Breach, Part II"

After Gwyn's plan to save Solum is sabotaged, she must turn to an unlikely ally. On Voyager , Janeway's secret mission is interrupted by the arrival of a mysterious entity — and the Prodigy crew is accidentally sent through a rift.

203 – "Who Saves the Saviors"

The Prodigy crew crash lands in future Solum where they try to rescue Captain Chakotay, but when their plan goes astray, it creates a time paradox putting Gwyn in danger.

204 – "Temporal Mechanics 101"

In a race to save Gwyn, the Prodigy crew use their scientific know how to escape the dark future they are stranded in and travel back to the present, with some mysterious help from an unknown entity.

205 – "Observer's Paradox"

After saving Gwyn during a botched rescue mission, the Prodigy crew faces new scrutiny aboard Voyager . But hope is not lost if they can find the Protostar and repair the time paradox — and decode a cryptic message from Murf.

206 – "Imposter Syndrome"

Ready to embark on their quest to find the Protostar , the Prodigy crew creates holograms of themselves to leave Voyager undetected — but their holo-doubles jeopardize everything in a case of mistaken identity.

207 – "The Fast and the Curious"

As our crew travels to the spiral nebula in search of the lost Protostar , they take a shortcut through an old transwarp conduit— but are detoured by a Kazon warlord who enters them into a literal race for their lives. 

208 – "Is There in Beauty No Truth?"

With Zero's suit damaged beyond repair, the Prodigy crew visits a colony of non-corporeal beings who may be able to help Zero — by granting the Medusan a physical body.

209 – "The Devourer of All Things, Part I"

Upon arriving at the coordinates given to Gwyn by the mysterious entity, the Prodigy crew find themselves on a strange hidden planet where someone is waiting for them… and it's someone unexpected.

210 – "The Devourer of All Things, Part II"

After meeting the entity who's been helping our crew find the Protostar and fix the timeline, their plans are interrupted by an attack from the Loom and the arrival of Voyager .

211 – "Last Flight of the Protostar , Part I"

After a brush with the Loom, the Prodigy crew find the lost Protostar on a deserted ocean planet, but their only hope to fix the timeline is in jeopardy when its captain refuses to leave.

212 – "Last Flight of the Protostar , Part II"

After convincing Chakotay to help repair the Protostar , the Prodigy crew now need fuel for it to fly — which means converting it into a literal ship and sailing across the planet's gaseous ocean in an epic tale of survival.

213 – "A Tribble Called Quest"

The Protostar crew lands on a strange new world in search of the exotic matter they need to proto-warp back to Voyager … only to discover the planet is infested with an unusually large species of Tribbles. 

214 – "Cracked Mirror"

When a proto-warp gone wrong fractures Voyager into different realities, the Prodigy crew must venture through dangerous alternate dimensions to reunite with Admiral Janeway.

215 – "Ascension, Part I"

The Prodigy crew and Chakotay reunite with Voyager , bringing the timelost Protostar with them. But the past catches up to them when Ilthuran delivers a dire warning — Asencia is coming.

216 – "Ascension, Part II"

When Asencia's mysterious time weapon strikes Voyager and threatens all aboard, it's up to the crews of the Protostar , Voyager , and Nova Squadron to survive the attack.

217 – "Brink"

To prevent a war with Solum, Gwyn leads the Protostar crew on a mission to rescue Ilthuran. But surprising discoveries force Gwyn to make hard choices which have dire consequences for everyone.

218 – "Touch of Grey"

Admiral Janeway and her senior officers feel their age as they find themselves thrown back in danger on an old school away mission to rescue the Protostar crew. 

219 – "Ouroboros, Part I"

Determined to save both Starfleet and Solum, the Prodigy crew must stop an invasion and open the wormhole that will send the Protostar back to Tars Lamora.

220 – "Ouroboros, Part II"

To save the present and fix the past, our crew must face the Loom and pilot the Protostar through the temporal wormhole back to Tars Lamora. Even if they succeed, what will the future hold?

Get Updates By Email

Star Trek: Prodigy will stream on Netflix globally (excluding Canada, Nordics, CEE, Netherlands, Spain, Portugal, Poland, Russia, Belarus and Mainland China) and Season 1 is currently available on SkyShowtime in the Nordics, the Netherlands, Spain, Portugal and Central and Eastern Europe with Season 2 coming soon. Season two has launched in France on France Televisions channels and Okoo.

Riot-stricken New Caledonia is empty of travellers. Businesses hope it can regain its place as a Pacific tourism jewel

Nestled between banana trees and palms on the outskirts of New Caledonia's capital, Anne Fonua's guesthouse and two tour buses sit empty.

Before civil unrest erupted in the French Pacific territory last month, her diary was filled with bookings from cruise ship passengers and other visitors arriving soon in Nouméa.

"Everything was cancelled," Ms Fonua said.

Blessed with pristine beaches, lagoons and coral reefs, New Caledonia was a jewel in Pacific tourism hoping to grow its share of Australian tourists.

Travel to the archipelago came to a startling halt in May, when violent turmoil broke out over French plans to add thousands of voters who have been in the territory for 10 years to electoral rolls.

It's a reform many fear will dilute the Indigenous Kanak vote in future referendums on independence.

Tourism operators wait in limbo — and in hope of a peaceful solution.

"We need to stay positive," said Gateaway Shore Tours guide Alfred Nauka, whose weeks are usually filled showing Australians and other tourists around New Caledonia.

"However, being here and actually seeing and facing and living through all that's going on since May, definitely doesn't help me in keeping a positive mindset."

His business was recovering after COVID border closures, before the deadly unrest began on May 13.

"We have lost the totality of our income since then," Mr Nauka said.

Frederic Ballo of Nouméa Turtle Tour, usually busy with tourists, has seen none for about 50 days.

"We hope and we do everything we can to continue. We're adapting day-by-day," he said.

New Caledonia's business and tourism groups say 41,000 bookings have been cancelled, and the halt has cost several billion francs in turnover.

Pro-independence protesters continue to erect road blockades, and unrest last week spread beyond the capital.

"Obviously we can't transport our clients in such conditions," Mr Nauka said.

He believes it will take years to rebuild New Caledonia, once peace returns.

"I don't see how our business can survive this."

'We need peace'

Four decades of peace opened New Caledonia as a destination for Australians seeking a tropical getaway.

It had been on Andrea Bold's bucket list for 30 years when she booked a family holiday there.

She was planning visits to the Isle of Pines and Nouméa in June, before she saw the territory's civil disorder unfold in the news.

Nine people, including two police officers, were killed as violence erupted over France's attempt to push through the electoral reforms.

More than 3,000 international visitors stranded in the tumult , including Australians, were evacuated from New Caledonia.

"We watched it for about a week, and it was very clear that things weren't going to get better quickly, so we made the decision to cancel the trip," Ms Bold said.

Qantas gave her a credit for the family's cancelled flights between Australia and Nouméa.

She hasn't been able to reach anyone in New Caledonia about refunding her domestic flights.

After waiting several weeks, her travel insurer agreed to pay her claim for money lost on cancelled bookings.

Ms Bold was saddened to see how cancellations had affected tourism businesses.

"They've lost their livelihoods in the space of a couple of weeks," she said.

New Caledonia will stay firmly on her bucket list, but she expects a long wait.

"I can't imagine when we would go. And from what I've heard, there's a lot of rebuilding to happen in Nouméa. There's a lot of burnt buildings."

Before the turmoil, New Caledonia's tourism was recovering from COVID border closures, receiving more than 125,000 international tourists and 340,000 cruise ship passengers in 2023.

Most of its recovery was driven by increases in Australian, New Zealand and French tourists compared to 2019.

But there was room to grow, and tourism was viewed as an important industry as New Caledonia looked to develop its economy outside nickel mining.

The territory drew 24,000 Australian tourists last year, half the number compared to neighbouring Vanuatu (51,000), and a fraction of the number visiting Fiji (390,000).

Mimsy Daly, president of business group Mouvement des Entreprises de Nouvelle-Calédonie, said businesses were ready to invest in the industry before recent events crashed the economy.

There were plans to open a new five-star hotel in the Loyalty Islands, east of New Caledonia's main island.

"All of this has been put to an end by the unrest."

P&O Cruises Australia and Carnival Cruise Line have cancelled 10 visits to Nouméa between June and August, re-routing to Vanuatu.

Air New Zealand has paused flights to Nouméa until September, while Qantas and Fiji Airways have not announced when they'll resume services to New Caledonia.

New Caledonia's international airport partially reopened earlier this month, and the territory's international carrier, Air Calin, is operating a limited schedule of flights.

Tourism businesses, industry leaders and the government say New Caledonia is many months away from being able to host tourists.

In a recent survey, about 50 per cent of tourism operators said they believed they could resume business within three months if the unrest subsided.

A fresh surge in violence last week, after French authorities sent seven pro-independence activists to France for detention, may have dashed any hopes of a quicker return for tourism.

"For now, we don't feel safe. Mostly, it's complicated in New Caledonia to go from one place to another," Ms Daly said.

"We need peace. We need a political solution that is long lasting, that can guarantee that peace will be lasting as well."

Surviving, and hoping

In a bid to quell the unrest, France sent 3,000 troops and police to New Caledonia in May. Some hotels in Nouméa were requisitioned to accommodate the forces.

Other businesses are still looking for relief from the halt in tourism, and are concerned for their finances.

Debt repayments for a new bus weigh on Ms Fonua, who hopes her bank can give her some reprieve.

Erin Mattei, who operates La Belle Verte Canopy Tours, a zipline in Nouméa, believes she can continue her business if local people are able to visit.

"We survived the COVID crisis. I am going to do everything I can to keep our business open," she said.

Further north on New Caledonia's main island, Kiara Mediara, who operates Chez Élise guesthouse, is cooking with wood fires due to gas shortages.

"We're keeping our heads up and we're moving forward. I remain positive for the future of Kanaky," she said.

"I hope that things will calm down and that tourism will get back to what it was, because we like to share our knowledge and our culture with everyone."

But Ms Daly said the business community was concerned about the future of tourism operators outside Nouméa.

"We are pretty worried that for a long time, there will be no activity. And we are working closely with the French government to see if we can find ways to [keep] these companies living for the time being."

Tourism is only one of the industries devastated in New Caledonia's turmoil.

Ms Daly said the territory's unemployment was at 20 per cent, up from about 5 per cent before the violence erupted.

"We have lost most of our commercial distribution capacity in the Nouméa area," she said.

"Forty per cent of the food stores have been destroyed. Other commercial areas have been totally destroyed as well, the automobile sector, the industry sector in some areas.

"It's happened all of a sudden. And we need to figure out how we can manage the country now, in this new situation."

The electoral reforms have been suspended because of France's parliamentary elections, which begin today, and many in New Caledonia hope talks about a political solution to the unrest can start soon.

The territory's main tourism body, Nouvelle-Calédonie Tourisme, aims to have international visitors returning in the last quarter of 2024.

When it comes time to rebuild New Caledonia, Ms Daly said tourists will play a major part.

"We will be very happy to welcome tourism again," she said.

Ms Fonua said messages of support from her former customers have lifted her spirits during a dark chapter.

Her message for people overseas is to think positively about New Caledonia.

"Once things open up, I'm sure that a lot of tourists will come back in, because a lot of areas for tourism are not spoiled."

• X (formerly Twitter)

Related Stories

New wave of violence in new caledonia as activists sent 17,000km away to detention in france.

'Too many': Ninth person dies in New Caledonia riots as French president suspends controversial voting reform

'What a mess this place is': Australians stranded in New Caledonia desperate to get home

France lifts TikTok ban in New Caledonia as calm returns

• Foreign Affairs
• New Caledonia
• New Zealand
• Referendums
• Tourism and Leisure Industry
• Travel Health and Safety
• World Politics