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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 .

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

Professor of Physics, University at Buffalo

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Dejan Stojkovic works for the State University of New York, University at Buffalo. He receives funding from the National Science Foundation.

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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.

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What Are Wormholes, and Could They Be the Answer to Time Travel?

Wormholes, cosmic tunnels also known as einstein-rosen bridges, are a staple of science fiction. could they allow real-world humans to travel back in time.

The sci-fi landscape is littered with wormholes. From Douglas Adam's Hitchhiker's Guide to the Galaxy and Rick and Morty to the Marvel Cinematic Universe, these theoretical constructs allow characters to zip between distant points in the universe as easy as stepping through a doorway.

An Einstein-Rosen bridge is the simplest kind of wormhole. And while it can, in theory, allow you to meet a new friend from a distant part of the universe, there are some important reasons why it won’t let you travel back in time.

Black Holes, White Holes and Wormholes

Let’s start with everybody’s favorite astronomical mystery: a black hole . Despite their fearsome reputation, they’re actually rather simple creature. They have a point of infinite density, known as the singularity, in their centers. They are surrounded by a boundary called the event horizon.

The event horizon doesn’t exist in the same way that the surface of a planet exists. Instead it’s just a mathematical line in the sand that tells you one thing: if you cross within that special distance, you’re trapped forever, because you’ll have to travel faster than the speed of light to escape.

Read More: 'Fuzzballs' Might Be the Answer to a Decades-Old Paradox About Black Holes

And that’s it. That’s a black hole. A singularity and an event horizon. All things that cross the event horizon will never escape back into the universe – things go in and never come out.

Mathematically we can also define the polar opposite of a black hole, which is conveniently called a white hole. White holes also have a singularity, but their event horizons act differently. Anything already on the outside of a white hole (like, the entire universe) can never, ever cross within it, no matter how hard it tries. And anything already inside the white hole will find itself ejected from it faster than the speed of light.

Now when we take a black hole and a white hole and connect their singularities together, we get an entirely new kind of object: an Einstein-Rosen bridge , better known as a wormhole.

Read More: Astronomers Found a Baffling Black Hole That Existed 13 Billion Years Ago

What Is a Wormhole?

Wormholes are essentially hollow tubes through space and time that can connect very distant regions of the universe. A star may be thousands of light-years away, but a wormhole can connect that star to us with a tunnel only a few steps long.

Wormholes also have the somewhat mystical ability to allow backwards time travel. If you take one end of the wormhole and accelerate it to a speed close to that of light, it will experience time dilation — its internal “clock” will run slower than the rest of the universe.

That will cause the two ends of the wormhole to no longer be synchronized in time. Then you could walk in one end and end up in your own past. Voilà: time travel.

Read More: Is There a Particle That Can Travel Back in Time?

Can Humans Travel Through Wormholes?

There's just one, tiny, teensy problem with this setup: Einstein-Rosen bridges are indeed wormholes, but the entrance to the wormhole sits behind the black hole event horizon. And the number one rule of black hole event horizons is that once you cross them, you’re never allowed to escape. Ever.

Once you pass through a black hole event horizon, you are forced towards the singularity, where you are guaranteed to meet your gruesome end. In other words, once you enter an Einstein-Rosen bridge, you will never escape.

So, the unfortunate truth with Einstein-Rosen bridges is that while they appear to be magical doorways to distant reaches of the universe, they are just as deadly as black holes. When you enter you can meet other travelers who have fallen in from the other side, and you could even carry on a conversation…briefly, before you both struck the singularity.

There have been attempts to stabilize Einstein-Rosen bridges and make them traversable by somehow getting their entrances to sit outside the event horizon. So far the only way we know how to do this is with exotic matter. If you threaded the wormhole tunnel with matter that had negative mass, then in principle you could have a not-deadly-at-all wormhole.

Alas, negative matter does not appear to exist in the universe, and so our wormhole — and time travel — dreams will have to remain as mere mathematical fantasies.

Read More: What Did Einstein's Theories Say About the Illusion of Time?

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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!”

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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.

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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.

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What is a Wormhole and Will Wormhole Travel Ever be Possible?

Science fiction's favorite method for exploring the universe, most recently in the movie Interstellar , won't be easy.

By Loren Grush | Published Oct 26, 2014 6:00 PM EDT

As a curious species, humans have long dreamed of traveling to the farthest depths of space. That’s the major theme of the upcoming science fiction epic Interstellar , which will take Matthew McConaughey and Anne Hathaway to the places we hope to one day reach ourselves. Except for that tiny hiccup called deep space travel .

The universe is big. And along with its enormous size, it’s also incredibly spread-out; any neighboring planets, stars, and galaxies are depressingly distant. Proxima Centauri, the closest star to Earth , for example, is 4.22 light years away. If the fast-moving Voyager spacecraft attempted to reach Proxima Centauri, it would take the tiny probe more than 80,000 years to get there.

So how are we supposed to explore the universe in a way that won’t take us thousands of generations? Among the many concepts researchers have devised, one technique has remained particularly popular, especially in the realm of science fiction: shortcuts, or theoretical tunnels known as wormholes.

Wormholes are thought to be highly unstable, and the insertion of foreign matter might cause them to collapse completely.

In theory, wormholes are tunnel-like connections made out of spacetime, offering a shorter distance between two vastly separated areas of the universe. The idea is that space travelers can use these tunnels to make space commutes much shorter than thousands of years. Numerous books, TV shows, and films have utilized the wormhole concept for deep space travel—from Dr. Arroway’s mysterious alien-filled journey in Contact to the Bajoran Wormhole, which allows access to the unexplored Gamma Quadrent in Star Trek: Deep Space Nine.

This plot device will be utilized yet again in Interstellar . In the film, a band of astronauts travel through a newly discovered wormhole connecting widely separated areas of space-time, in order to find a new world to call home . It sounds incredible, as if all our space travel fantasies can come true. But is it possible? Could humans one day use a wormhole to travel to another galaxy or beyond?

The science says it’s highly unlikely, yet possible. However, to make a traversable wormhole, we’re going to need a lot of specific conditions and an understanding of where these amazing secret passages come from.

What is a wormhole?

Up until the early 1900s, Newton’s theory of gravity held supreme. It was the idea that all objects in the Universe—including you and me—have an innate force within us that attracts other objects. The larger an object, the greater this intrinsic gravitational pull. This explains why we “stick” to the Earth instead of flying off into space.

But in 1915, Albert Einstein completely tore that idea apart. He theorized that gravity is actually the result of a warping in spacetime (a combination of space and time into one continuum). Essentially, an object’s very existence deforms space and time around itself, creating an imprint on the universe.

And it’s this deformation of space-time that gives rise to gravity’s effects. “Suppose that there’s you and another mass. You deform the spacetime around you and the mass deforms the space-time around it, and you’re both falling into each other’s wells,” says Richard Holman , a physics professor at Carnegie Mellon University.

Now here’s the part where this all ties into wormholes. According to Einstein and his colleague Nathan Rosen, a wormhole is actually deformed space that has warped in such a way to connect two different points in space-time. The result is a tunnel-like structure that could be straight or curved, linking two areas of the Universe that are incredibly far apart.

Einsteinian mathematical models predict that wormholes exist, but none have ever been found. Fumio Abe, an astrophysicist at Nagoya University, has proposed a way to search for large wormholes (big enough for a spaceship) by looking at a star’s brightness when it moves in front of the tunnel. An effect called gravitational lensing would cause the brightness to fluctuate in a unique way.

However, chances are that we’re not going to find big wormholes any time soon.

Enter If You Dare

The problem with wormholes

So far, physicists haven’t determined a way in which wormholes would form naturally in the Universe. However, theoretical physicist John Wheeler said it’s possible that wormholes may spontaneously appear and disappear, according to his quantum foam hypothesis (the idea that virtual particles are, quite weirdly, popping in and out of existence at all times).

Unfortunately, Wheeler theorized that these impromptu wormholes would be super small, appearing at the Planck scale . That’s about 10-33 centimeters long. In other words, the wormhole would be so small that it’d be almost impossible to detect.

Let’s suppose, however, that we could find tiny wormholes as they pop into existence: We might be able to make them bigger. And to do that, you’d need a funky material called exotic matter.

“The rule of ordinary matter in the universe is that it has positive energy density and positive pressure,” says Eric Davis, a senior research physicist at the Institute for Advanced Studies at Austin. “Exotic matter is a little bit different. It’s matter that has negative energy density and/or negative pressure. You can have a clump of matter with negative energy and positive pressure or visa versa.”

Negative properties of exotic matter might push the sides of a wormhole outward, making it large enough—and stable enough—for a person or a spaceship to fit through it. Except exotic matter isn’t exactly easy to come by; it exists only in theory, we don’t know what it looks like, and we have yet to know where to find it.

But say we surmount even that in our hypothetical. We’ve found a tiny wormhole, we somehow have obtained some exotic matter, and we’ve expanded and stabilized the tunnel to be big enough to fit a spaceship. Holman explains that it’s possible inserting anything that isn’t exotic matter would destabilize the wormhole completely. In other words: Entering a wormhole could immediately kill you.

Wormholes come with a lot of caveats, but here’s an even bigger one. Wormholes could very well connect two completely different space-times; i.e. the entry point might exist in a completely different era. That means traversing via wormhole comes with the risk of winding up in a different time in the universe’s history. Some have even theorized that wormholes could connect completely different universes altogether. Wrap your head around that one for a second.

When it comes to the prospect of using wormholes for space travel, Davis is a bit more optimistic than Holman, explaining that harnessing exotic matter is all you need to create your own functional wormhole from scratch. (He’s currently working on a way to create exotic matter in a lab in Toronto.) Holman takes a more realistic approach.

“If you really could do it, with all the exoplanets and stars out there, you’d figure someone ‘else’ would already have done this,” Holman explains. “And as far as we could tell, from looking at a decent fraction of the universe, we’re not seeing any evidence of that. That starts telling you that you may just have to travel the hard way.”

To find out more about the science of Interstellar, click here.

Correction (10/30/2014, 12:24 pm ET): The original story said that Davis is working on a way to create exotic matter in his lab at Icarus Interstellar. He is actually working at a lab in Toronto at Hathaway Consulting Services. We’ve fixed the mistake, and we regret the error.

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How to time travel with wormholes

Brian Greene ,   professor of physics and mathematics at Columbia University and co-founder of the World Science Festival , explains what we know about time travel so far. Following is a transcript of the video.

Brian Greene: I’m Brian Greene, professor of physics and mathematics at Columbia University and co-founder of the World Science Festival.

It's critical that you realize that there are two types of time travel , and they are radically different. Time travel to the future? Definitely possible.

We know how to do it because Einstein showed us the way over a hundred years ago. It’s surprising how few people actually really know about this in their bones. He showed that if you go out into space and travel near the speed of light, and you turn around, and you come back, your clock will be ticking off time more slowly. So, when you step off it's going to be the future on planet Earth. You will have time traveled into the future.

He also showed that if you hang out near a nice strong source of gravity — a neutron star, a black hole — and you kind of get right near the edge of that object, time also for you would slow down real slow relative to everybody else. And therefore, when you come back to Earth, for instance, it'll again be far into the future.

This is not controversial stuff. Any physicist who knows what they're talking about agrees with this. But the other kind of time travel — to the past is where the arguments start to happen because many of us don't think that time travel to the past is possible.

The main proposal that people at least consider worthy of attention for traveling to the past does make use of a weird concept called wormholes . A wormhole is something that really … Albert Einstein again discovered. The guy has like got his name written over everything in this field.

It's a bridge, if you will, from one location space to another. It's kind of a tunnel that gives you a shortcut to go from here to here. Now he discovered this in 1935 but it was subsequently realized that if you manipulate the openings of a wormhole — put one near a black hole or take one on a high-speed journey — then time of the two openings of this wormhole tunnel will not take off at the same rate, so that you will no longer just go from one location in space to another, if you go through this tunnel — through this wormhole — you'll go from one moment in time to a different moment in time. Go one way, you'll travel to the past, the other way, travel to the future.

Now again, we don't know if wormholes are real. We don't know if they are real whether you'll be able to go through them. So, there are all sorts of uncertainties here. Most of us think that you're not going to actually go on a whirlwind journey through a wormhole to the past. But it's still not ruled out.

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Scientists Have Determined How to Travel Back in Time With a Ring Wormhole

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• A recent study claims to have calculated a potential method of time travel.
• It involves a highly theoretical object called a “ring wormhole,” which is a type of wormhole that connects two regions of space, like a portal.
• Ring wormholes had previously been theorized to be portals to other universes, and researchers now propose they could act as time machines as well.

But that hasn’t stopped scientists from trying to figure out how we maybe could, someday, jump around out of order in the time stream. And recently, a team of theoretical physicists published a paper on exactly what laws of physics could be stretched just far enough to make it happen.

The key to the whole idea is wormholes —specifically, a type of wormhole called a ring wormhole. Now, wormholes are already entirely theoretical, so this discussion is going to get weird. And ring wormholes get even weirder than “normal” wormholes.

Your average, run-of-the-mill wormholes, as we tend to think of them, are basically holes punched in the fabric of spacetime by the immense gravity of black holes. The gravity well at the center of these objects is so intense that scientists have often theorized they could act as tunnels to another universe , or another time.

But ring wormholes aren’t black-hole dependent. Instead, the (again, highly theoretical) objects are caused by circles of mass that have negative energy, something only made possible by the strange effects of the quantum realm . This circle of negative energy would basically create a portal to another universe without the need to go through a black hole tunnel.

“You could go through and not even notice that you went to another universe,” Andrei Zelnikov, one of the authors on the recent paper, told New Scientist .

The paper —published in the journal Physical Review D by Zelnikov and his team—puts forth calculations that claim a ring wormhole could not only act as a universe-to-universe teleport, but as a time machine .

According to the heavy-duty number-crunching, the ring wormholes could generate something called a “closed timelike curve” if one “mouth” of the wormhole near a bunch of mass and the other “mouth” was far away from any significant amount of mass . If the conditions are right around the mouths of the wormhole, the closed timelike curves generated are then able to turn a portal into a time machine.

“The time machine is a natural consequence of the wormhole existing,” Toby Wiseman, a professor of theoretical physics at the Imperial College London who was not a part of the study, told New Scientist . “Apart from the crazy matter that makes up the wormhole, there’s nothing too wild being postulated here, and then the consequence is something even more crazy.”

You can decide for yourself if proposing a method for time travel is “too wild.” But wild or not, scientists remain dedicated to truly understanding all of the laws of time and space —and exactly how we can bend them to make the coolest things possible.

Jackie is a writer and editor from Pennsylvania. She's especially fond of writing about space and physics, and loves sharing the weird wonders of the universe with anyone who wants to listen. She is supervised in her home office by her two cats.

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Wormholes: What Are They and Can We Use Them?

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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

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Understanding Wormholes: A Path To Time Travel?

Have you ever dreamed of traveling through time? It may seem like an impossible feat, but scientists have been exploring the concept of time travel for decades. One theory that has gained momentum in recent years is the idea of using wormholes as a path to time travel.

Wormholes are tunnels in space-time that connect two distant points in the universe. They were first proposed by physicist Albert Einstein's theory of general relativity, and although they have yet to be discovered, they continue to capture our imagination. In this article, we'll explore the science behind wormholes, how they could potentially be used for time travel, and what implications this might have on our understanding of the universe. So buckle up and get ready for a journey through space-time!

The Science Behind Wormholes

Wormholes as shortcuts in space, could wormholes be used for time travel, the implications of time travel, the future of wormhole research, frequently asked questions, what is the history of the concept of wormholes in science fiction, how would the discovery of a stable wormhole affect global politics and economics, what ethical considerations should be taken into account when considering the use of time travel, could wormholes be used for intergalactic travel, what technological advancements would be necessary for practical use of wormholes.

You're about to discover the mind-bending science that could revolutionize our understanding of the universe. To begin with, let's talk about wormhole mechanics. A wormhole is a theoretical concept in physics that suggests the existence of a shortcut between two points in space-time. According to Einstein's theory of relativity, space and time are intertwined, and any massive object warps spacetime around it. Therefore, a wormhole would be formed by connecting two points in spacetime through a tunnel-like structure.

Theoretical physicists have been studying the possibility of wormholes for decades, but it wasn't until recently that they started to understand how they could work. The key lies in the idea of negative energy, which is required to keep a wormhole stable enough for travel. This negative energy would create an anti-gravitational force that could counterbalance the gravitational pull of matter and prevent the collapse of the wormhole. With this knowledge in hand, we can begin to explore how wormholes might serve as shortcuts in space without having to bend or warp time itself.

Imagine taking a cosmic detour that cuts through the fabric of space and shaves off light-years from your journey - wormholes essentially act as galactic bypasses. These shortcuts in space are fascinating phenomena that have intrigued scientists and science fiction enthusiasts alike. As we delve deeper into understanding the science behind wormholes, one important aspect to consider is their stability. While theoretical physicists have proposed the existence of these tunnels connecting two points in space-time, it is still unclear whether they could actually exist or if they would collapse before anything could pass through.

Despite the unknowns surrounding wormhole stability, there are potential practical applications for these cosmic shortcuts. For instance, a stable wormhole could be used to transport cargo or people across vast distances without expending too much energy or time. The concept of using wormholes as portals has also been explored in popular culture, where characters travel between different worlds by hopping through a hole in space-time. However, until we can confirm the existence and stability of wormholes, their use remains purely speculative.

As we explore further into the possibilities that come with understanding wormholes, one question arises: Could these tunnels be used for time travel?

If you're a fan of science fiction, the idea of using shortcuts in space to journey through time may seem like an exciting possibility. But is it really possible? According to some theories in physics, wormholes could be used for time travel. However, this concept raises many questions about paradoxes and limitations.

One major concern with the use of wormholes for time travel is the potential for paradoxes. For example, if someone were to go back in time and prevent their own birth from occurring, how would they have been able to travel back in time in the first place? This creates a loop that seems impossible to resolve. Additionally, there are limitations on the use of wormholes for time travel due to their instability and high energy requirements. It's unclear whether we will ever be able to create or sustain a stable wormhole long enough for human transportation.

These philosophical implications raise important questions about our understanding of time and its relationship with space. What does it mean to truly “travel” through time? Is it possible or simply a fantasy? The implications of time travel extend far beyond scientific theory – they challenge our very perception of reality itself.

The consequences of potentially traveling through temporal dimensions pose a significant challenge to our comprehension of the nature of existence. The concept of time travel is not only fascinating, but it also raises ethical concerns and societal impacts that must be considered. If time travel were possible, one could potentially change the course of history, leading to unforeseen consequences in the present day. This could have severe implications for society as a whole, altering the trajectory of human development and progress.

Moreover, there are also philosophical implications to consider. If we could go back in time or travel to the future, then what does that say about free will? Are we really making choices if we can go back and change them? These are complex questions that require careful consideration before any exploration into time travel is made. Nevertheless, understanding the possibilities offered by wormholes allows us to better comprehend our place in space-time and how it shapes our reality.

As we continue to explore these fascinating scientific concepts, it's important to think critically about their potential impacts on society. The future of wormhole research promises exciting advancements in physics and technology, but it's crucial that we approach these developments with caution and foresight. We must remain mindful of not just what is scientifically possible but also what is ethically responsible.

Scientists are delving deeper into the mysteries of space-time, unlocking new possibilities for interstellar travel and exploration. The future of wormhole research is promising as interdisciplinary collaborations between physicists, mathematicians, and engineers continue to push the boundaries of our understanding. With technological advancements in fields such as quantum mechanics and astrophysics, we may soon be able to harness the power of wormholes for practical applications.

One potential application is time travel. While still a theoretical concept, wormholes could potentially allow us to travel through time by creating a shortcut through space-time. However, there are many challenges that must be overcome before this becomes a reality. For example, we would need to find stable wormholes that can remain open long enough for us to pass through them safely. Nonetheless, with continued research and development in this field, it's exciting to think about what the future holds for interstellar travel and exploration using wormholes.

When it comes to the exploration of wormholes in popular culture, science fiction has played a significant role. The concept of wormholes as shortcuts through space and time has been used in various forms of media, from books to movies. However, the scientific accuracy of wormholes in fiction is often debated. While some authors and filmmakers strive to depict them as realistically as possible based on current theories, others take artistic liberties for the sake of storytelling. Regardless, the idea of traversing through a wormhole remains an intriguing one that continues to capture our imaginations.

As the possibility of discovering a stable wormhole becomes more feasible, the impact on society cannot be understated. The geopolitical implications alone are staggering. With the potential to transport people and goods across vast distances in an instant, entire industries could be disrupted, governments could rise or fall based on access to this technology, and global power dynamics could shift overnight. As the adage goes, "with great power comes great responsibility," and it will be up to those who control this technology to ensure that its benefits are shared equitably among all nations and peoples. The discovery of a stable wormhole would undoubtedly change the course of human history forever, for better or for worse.

When we consider the use of time travel, there are a multitude of moral implications and societal consequences that must be taken into account. The ability to travel through time would undoubtedly have an enormous impact on our world as we know it, both in terms of how we view the past, present, and future but also how we interact with each other. It's important to consider questions such as: Who gets access to this technology? What happens if someone alters the timeline? How do we ensure that people don't use time travel for personal gain or harm others? These are complex ethical considerations that require careful thought and planning before any sort of time travel technology is developed or implemented.

Interstellar transportation is an exciting prospect that could revolutionize the way we explore the universe. While it may seem like science fiction, recent advancements in technology have made intergalactic travel a scientific feasibility. One proposed method for achieving this type of transportation is through the use of wormholes, which are tunnels through space-time that connect distant points in the universe. Although still largely theoretical, scientists believe that harnessing this phenomenon could allow us to travel vast distances and explore new worlds beyond our solar system. However, there are many challenges and risks associated with such a venture, including the potential dangers of navigating unknown territories and ensuring the safety of astronauts over long periods of time. Despite these challenges, interstellar transportation remains an exciting area of research with the potential to unlock some of the greatest mysteries of our universe.

To fully harness the power of wormholes for intergalactic travel, we would need to make significant advancements in quantum mechanics and our understanding of black holes. The ability to manipulate quantum particles and understand their behavior is crucial in creating a stable wormhole that can withstand the immense gravitational forces present near black holes. Furthermore, we must have a deeper understanding of how black holes function and interact with space-time. Only then can we hope to create a practical method of utilizing these cosmic shortcuts for efficient space travel. These technological advancements are not just important for intergalactic travel but also have implications for our fundamental understanding of the universe around us.

So, can wormholes really be a path to time travel? While the science behind wormholes is fascinating and holds promise for space exploration, the idea of using them for time travel remains purely theoretical. The implications of such technology are mind-boggling, but also raise important ethical questions about altering the course of history or creating paradoxes.

Despite these uncertainties, the research into wormholes continues to push the boundaries of our understanding of space-time. Like a diver exploring uncharted depths, scientists are diving deeper into this mysterious phenomenon in hopes of uncovering more secrets and unlocking new possibilities. Wormholes may not lead us to time travel just yet, but they have opened up a whole new realm of possibility that is sure to captivate both scientists and science fiction enthusiasts alike. As we continue to unravel the mysteries of our universe, who knows what other hidden treasures await us?

We can build a real, traversable wormhole … if the universe has extra dimensions

Paul M. Sutter  is an astrophysicist at SUNY Stony Brook and the Flatiron Institute, host of " Ask a Spaceman " and " Space Radio ," and author of " How to Die in Space ." Sutter contributed this article to Space.com's Expert Voices: Op-Ed & Insights .

It may be possible to build a real, traversable wormhole, but only if our universe has extra dimensions, a team of physicists has found.

To make a wormhole , you need to glue together different parts of the universe, connecting them by a bridge or a tunnel, usually called a "throat." This throat can be as big or as long as you want, but typically, you want it to be shorter than the normal distance to your destination. In Einstein's theory of general relativity , making a wormhole is pretty straightforward: You just build a black hole and connect it to a white hole (which is the exact opposite of a black hole), and boom, there you have it: a tunnel through space-time.

Unfortunately, the biggest problem with wormholes is that they are fantastically unstable. As soon as they form, their enormous gravitational strengths (they are literally made of black holes, after all) rip them apart faster than the speed of light, which makes them rather useless as actual shortcuts through the universe.

Related : Was Einstein wrong? The case against space-time theory

The only known way to stabilize a wormhole is to use some form of exotic matter. Exotic matter can take the form of matter with negative mass, which doesn't appear to exist in the universe, or some other scenario that violates what are known as the energy conditions of general relativity. The energy conditions simply state that everybody should experience positive energy, on average, pretty much everywhere they go. To stabilize a wormhole, however, a traveler would have to experience a region of negative energy. This negative energy would balance out the positive energy of the mass of the traveler, keeping the wormhole open as they passed through it.

There are some physical scenarios that lead to violations of some of the energy conditions some of the time. However, physicists do not know of a single instance in which all of the energy conditions are violated, on average, over long periods of time — which is exactly what you need to do to build a wormhole.

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Your "brane" on physics

Gravity is extremely weak; it's billions upon billions of times weaker than any other force of nature. This fact troubles many physicists, because when something is so strikingly different from the rest of the universe, there's usually some interesting physical explanation behind it.

But we have no physical explanation for why gravity is so weak. One idea among theoretical physicists is that there's more to the universe than meets the eye. Inspired by string theory 's concept of many extra spatial dimensions all wrapped up on themselves and compressed to submicroscopic scales, some theories propose that there are additional spatial dimensions to reality, besides the usual three.

In these theories, our three dimensions are just a "brane," a relatively thin membrane that exists within a higher-dimensional "bulk." Those extra dimensions aren't necessarily huge; if they were, we would've noticed particles or planets appearing and disappearing from the extra dimension. But the extra dimensions might be larger than the minuscule dimensions of string theory — perhaps as big as a millimeter.

In this scenario, all the forces and particles of nature are then confined to the three-dimensional brane, while gravity alone has the privilege of traveling through the bulk. Thus, gravity could be just as strong as every other force, but it's so heavily diluted among all the extra dimensions that it appears weak to our three-dimensional experience.

Through the wormhole 

Because these brane-based ideas are attempts to understand gravity, they open up new opportunities to explore the nature of wormholes. Our knowledge of wormholes is governed by general relativity, but perhaps the presence of extra dimensions changes how general relativity operates, thus making wormholes possible, an Indian research team proposes in a new paper posted to the preprint database arXiv .

In the paper, the physicists explored whether it would be possible to build a wormhole in the "braneworld" model first proposed by physicists Lisa Randall and Raman Sundrum in 1999.

The authors of the new paper found that they could indeed build a stable, traversable wormhole in this brane-based model of gravity. Even better, they didn't need any exotic matter to do it.

Although the team did find that this situation still violated the energy conditions of general relativity, they argued that this violation was a feature, not a bug. Instead of requiring some weird and exotic (and probably impossible) ingredient to build a wormhole, the nature of gravity in the extra spatial dimensions naturally gave rise to a violation of the energy conditions. Once those conditions were broken, wormholes became a natural consequence, they said.

The researchers even went so far as to suggest that if we were to ever directly observe or create a wormhole, this might indicate that the universe has more spatial dimensions than the usual three.

— Wormholes may be lurking in the universe, and new studies are proposing ways of finding them — Einstein's theory of general relativity passes one of its toughest tests yet — Here's how we could detect a wormhole  

As with all theoretical work on the subject of wormholes, this is not the final word. Nobody knows if the Randall-Sundrum theory, or any other theory based on branes and extra dimensions, is correct. And nobody has a quantum theory of gravity — a theory of strong gravity at small scales — which would almost certainly change the calculations, perhaps to the point of once again eliminating the possibility of wormholes.

But this result is still interesting, as it joins a number of efforts to explore the edges of our understanding of gravity, taking general relativity to the absolute limits. Wormholes may or may not exist, but attempting to understand them will definitely increase our knowledge of the universe.

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Paul M. Sutter is an astrophysicist at SUNY Stony Brook and the Flatiron Institute in New York City. Paul received his PhD in Physics from the University of Illinois at Urbana-Champaign in 2011, and spent three years at the Paris Institute of Astrophysics, followed by a research fellowship in Trieste, Italy, His research focuses on many diverse topics, from the emptiest regions of the universe to the earliest moments of the Big Bang to the hunt for the first stars. As an "Agent to the Stars," Paul has passionately engaged the public in science outreach for several years. He is the host of the popular "Ask a Spaceman!" podcast, author of "Your Place in the Universe" and "How to Die in Space" and he frequently appears on TV — including on The Weather Channel, for which he serves as Official Space Specialist.

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Physicists Just Released Step-by-Step Instructions for Building a Wormhole

All you need are a couple of black holes and some cosmic strings. No biggie.

Everybody wants a wormhole. I mean, who wants to bother traveling the long-and-slow routes throughout the universe, taking tens of thousands of years just to reach yet another boring star? Not when you can pop into the nearest wormhole opening, take a short stroll, and end up in some exotic far-flung corner of the universe. 

There's a small technical difficulty, though: Wormholes , which are bends in space-time so extreme that a shortcut tunnel forms, are catastrophically unstable. As in, as soon as you send a single photon down the hole, it collapses faster than the speed of light.

But a recent paper, published to the preprint journal arXiv on July 29, has found a way to build an almost-steady wormhole, one that does collapse but slowly enough to send messages — and potentially even things — down it before it tears itself apart. All you need are a couple of black holes and a few infinitely long cosmic strings. 

Easy-peasy.

The wormhole problem

In principle, building a wormhole is pretty straightforward. According to Einstein's Theory of General Relativity , mass and energy warp the fabric of space-time. And a certain special configuration of matter and energy allows the formation of a tunnel, a shortcut between two otherwise distant portions of the universe.

Related: 8 Ways You Can See Einstein’s Theory of Relativity in Real Life

Unfortunately, even on paper, those wormholes are fantastically unstable. Even a single photon passing through the wormhole triggers a catastrophic cascade that rips the wormhole apart. However, a healthy dose of negative mass — yes, that's matter but with an opposite weight — can counteract the destabilizing effects of regular matter trying to pass through the wormhole, making it traversable.

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OK, matter with negative mass doesn't exist, so we need a new plan.

Let's start with the wormhole itself. We need an entrance and an exit. It's theoretically possible to connect a black hole (a region of space where nothing can escape) to a white hole (a theoretical region of space where nothing can enter). When these two odd creatures join together, they form a brand-new thing: a wormhole. So you can jump into either end of this tunnel and instead of getting crushed into oblivion you just harmlessly waltz out the other side.

Oh, but white holes don't exist, either. Man, this is getting tricky.

Charge it up

Since white holes don't exist, we need a new plan. Thankfully, some clever math reveals a possible answer: a charged black hole. Black holes can carry an electric charge (it's not common because of the way they're formed naturally, but we'll take what we can get). The inside of a charged black hole is a strange place, with the normal point-like singularity of a black hole stretched and distorted, allowing it to form a bridge to another oppositely charged black hole.

Voila: a wormhole, using only things that might actually exist.

But this wormhole-via-charged-black-holes has two issues. One, it's still unstable, and if something or someone actually tries to use it, it falls apart. The other is that the two oppositely charged black holes will be attracted to each other — both through gravitational and electric forces — and if they fall together you just get a single, big, neutrally charged and altogether useless black hole.

Put a cosmic bow on it

So to make this all work we need to make sure the two charged black holes stay safely far away from each other, and make sure the tunnel of the wormhole can hold itself open. A potential solution: cosmic strings .

Cosmic strings are theoretical defects, similar to the cracks that form when ice freezes, in the fabric of space-time. These cosmic leftovers formed in the early, heady days of the first fractions of a second after the Big Bang . They are truly exotic objects, no wider than a proton but with a single inch of their length outweighing Mount Everest . You never want to encounter one yourself, since they would slice you clean in half like a cosmic lightsaber, but you don't have to worry much since we're not even sure they exist, and we've never seen one out there in the universe.

Still, there's no reason they can't exist, so they're fair game.

They have another very useful property when it comes to wormholes: enormous tension. In other words, they really don't like being pushed around. If you thread the wormhole with a cosmic string, and allow the string to pass along the outside edges of the black holes and stretch out of either end all the way to infinity, then the tension in the string prevents the charged black holes from being attracted to each other, holding the two ends of the wormhole far away from each other. Essentially, the distant ends of the cosmic string act like two opposing tug-of-war teams, holding back the black holes.

Calming the tremors

One cosmic string solves one of the problems (holding the ends open), but it doesn't prevent the wormhole itself from collapsing if you were to actually use it. So, let's toss in another cosmic string, also threading the wormhole, but also looping it through normal space between the two black holes. 

When cosmic strings are closed in a loop, they wiggle — a lot. These vibrations churn the very fabric of space-time around them, and when tuned just right the vibrations can cause the energy of space in their vicinity to go negative, effectively acting like negative mass within the wormhole, potentially stabilizing it.

It seems a little complex, but in the recent paper, a team of theoretical physicists gave step-by-step instructions for constructing just such a wormhole. It's not a perfect solution: Eventually the inherent vibrations in the cosmic strings — the same ones that might keep the wormhole open — pull energy, and therefore mass, away from the string, making it smaller and smaller. Essentially, over time the cosmic strings wiggle themselves into oblivion, with complete collapse of the wormhole not far behind. But the kludged-together wormhole may stay stable long enough to allow messages or even objects to travel down the tunnel and actually not die, which is nice. 

But first we need to find some cosmic strings.

Paul M. Sutter  is an astrophysicist at The Ohio State University , host of Ask a Spaceman and Space Radio , and author of Your Place in the Universe .

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Originally published on Live Science .

Paul M. Sutter is a research professor in astrophysics at  SUNY Stony Brook University and the Flatiron Institute in New York City. He regularly appears on TV and podcasts, including  "Ask a Spaceman." He is the author of two books, "Your Place in the Universe" and "How to Die in Space," and is a regular contributor to Space.com, Live Science, and more. Paul received his PhD in Physics from the University of Illinois at Urbana-Champaign in 2011, and spent three years at the Paris Institute of Astrophysics, followed by a research fellowship in Trieste, Italy. 

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The best time travel movie ever isn't 'Back to the Future,' based on data. Find out the top 25.

Posted: April 27, 2024 | Last updated: April 27, 2024

Best time travel movies

Many films come with an escapism element, the ability to separate ourselves from our current timeline and reality to imagine an alternate time or place. It is a common feature in entertainment, which can serve as an outlet to explore our fears, dreams, and hopes for the future. Many movies take their characters on a journey to the past or future in hopes of teaching profound lessons, offering new perspectives, or simply presenting a challenge or a solution to a problem that they are facing in their current timeline. They expand the reach of what we think is possible in our current lives.

To celebrate these innovative and time-twisting tales, Stacker compiled data on the top time travel movies to come up with a Stacker score—a weighted index split evenly between IMDb and Metacritic scores. To qualify, the film had to involve some sort of time travel (be it literal, like "Back to the Future," or metaphysical, like "Donnie Darko"), have a Metascore, and have at least 5,000 votes. Ties were broken by Metascore and further ties were broken by IMDb votes. These films are some of the most memorable and culturally significant time-travel adventures in American cinema.

#25. Star Trek IV: The Voyage Home (1986)

- Director: Leonard Nimoy - Stacker score: 82.3 - Metascore: 71 - IMDb user rating: 7.3 - Runtime: 119 minutes

The famous space travel franchise's fourth film takes well-known USS Enterprise crew members Captain Kirk (William Shatner), Spock (Leonard Nimoy), and others into an interesting mission. The crew, living in 2286, must travel back in time to 1986 to find humpback whales. The extinct animals are the only species that can understand messages from a foreign probe threatening Earth.

#24. Predestination (2014)

- Directors: Michael Spierig, Peter Spierig - Stacker score: 82.3 - Metascore: 69 - IMDb user rating: 7.5 - Runtime: 97 minutes

Ethan Hawke plays a time traveler who races against time to keep a foe from killing innocent people. The film spans through several points in the 1960s and 1970s, taking its protagonist on a twisty trip that brings up surprises until the last minutes. "Predestination" is based on "All You Zombies," a science-fiction short story by Robert A. Heinlein, about paradoxes that happen due to time traveling.

#23. Pleasantville (1998)

- Director: Gary Ross - Stacker score: 83.4 - Metascore: 71 - IMDb user rating: 7.5 - Runtime: 124 minutes

This comedic film takes brother and sister duo David (Tobey Maguire) and Jennifer (Reese Witherspoon) on a strange trip. David's love for 1950s television leads to him meeting a man who is able to put him and his sister inside an ongoing program. Jennifer stirs up drama among the cookie-cutter people to the chagrin of David.

#22. Source Code (2011)

- Director: Duncan Jones - Stacker score: 85.1 - Metascore: 74 - IMDb user rating: 7.5 - Runtime: 93 minutes

A military pilot (Jake Gyllenhaal) sees the last minutes of a man's life during a mission that takes him back to that point in time. He's supposed to deduce who the responsible party is in the train accident to bring him to justice. But, the pilot takes things to the next level, going against the clock to attempt to prevent things from going awry in the first place.

#21. Time Bandits (1981)

- Director: Terry Gilliam - Stacker score: 85.1 - Metascore: 79 - IMDb user rating: 7.0 - Runtime: 110 minutes

Kevin (Craig Warnock) is a preteen history lover who meets dwarves in his room. The tiny beings work for a Supreme Being and are slipping through holes in time to take treasures. Kevin goes with them as they hop around and meet famous historical people while trying to stay two steps ahead of the Supreme Being.

#20. Edge of Tomorrow (2014)

- Director: Doug Liman - Stacker score: 85.7 - Metascore: 71 - IMDb user rating: 7.9 - Runtime: 113 minutes

Tom Cruise stars as William Cage, a military officer who dies and ends up in a time loop. He continues to relive his terrible (and deadly) final moments until he levels up his knowledge and skills. Cage slowly moves towards the initial mission to fight aliens threatening Earth. Emily Blunt stars opposite Cruise as a sergeant who understands what he is experiencing and works with him.

#19. Evil Dead II (1987)

- Director: Sam Raimi - Stacker score: 85.7 - Metascore: 72 - IMDb user rating: 7.8 - Runtime: 84 minutes

Ash Williams (Bruce Campbell) continues his battle against demons as his girlfriend Linda (Denise Bixler) becomes possessed by an evil spirit. He realizes that he may be stuck in this remote cabin in the woods and must fight foes who arise from a mysterious audiotape. Towards the end of the film, Ash and his car travel through a portal and end up in 1300 A.D. for a bizarre ending that no one could predict.

#18. Groundhog Day (1993)

- Director: Harold Ramis - Stacker score: 86.9 - Metascore: 72 - IMDb user rating: 8.0 - Runtime: 101 minutes

What would you do if you had to live the same day over and over again? This is what happens to Phil Connors (Bill Murray), a TV weatherman covering Groundhog Day in Punxsutawney who ends up in a time loop. He begins to realize some things about himself, and others, while stuck in this seemingly endless day. The film's popularity led to the term "groundhog day" becoming synonymous with being stuck in a time loop.

#17. Run Lola Run (1998)

- Director: Tom Tykwer - Stacker score: 87.4 - Metascore: 77 - IMDb user rating: 7.6 - Runtime: 80 minutes

Manni (Moritz Bleibtreu), a Berlin criminal, brings stolen goods to his boss and loses money he owes him. The boss gives him 20 minutes to conjure the funds, leading Manni to enlist his girlfriend Lola (Franka Potente) to come up with the money in a race against the clock, which keeps running through that same period as she makes choices.

#16. Superman (1978)

- Director: Richard Donner - Stacker score: 87.4 - Metascore: 80 - IMDb user rating: 7.3 - Runtime: 143 minutes

Based on the iconic DC Comics character, this film follows Kal-El's (Christopher Reeve) journey from his home planet, Krypton, to becoming Superman, an all-American hero. He goes from being adopted by Midwestern farmers to discovering his powers and fighting an evil force while working undercover as a reporter. At one point, Superman flies around the world so quickly that the Earth spins another way, making time go back so he can undo events with tragic consequences. 

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#15. 12 Monkeys (1995)

- Director: Terry Gilliam - Stacker score: 88 - Metascore: 74 - IMDb user rating: 8.0 - Runtime: 129 minutes

Bruce Willis plays James Cole, an incarcerated man living in the 2030s. Humans live underground after an apocalyptic event nearly kills everyone. He's given a chance to travel back to the '90s and gather information about a plague that will have big future consequences. The goal is to find out more information about the Army of the Twelve Monkeys, who may have been responsible for this earth-shattering event. But things don't go as expected, a classic trope in time travel tales.

#14. X-Men: Days of Future Past (2014)

- Director: Bryan Singer - Stacker score: 88 - Metascore: 75 - IMDb user rating: 7.9 - Runtime: 132 minutes

Wolverine, played by Hugh Jackman, goes back in time to 1973 to gather past X-Men to change a moment in time to help save them from the Sentinels. The latter group is a killing collective eradicating anyone who possesses a mutant gene. The film gained an Oscar nomination for its visual effects.

#13. Palm Springs (2020)

- Director: Max Barbakow - Stacker score: 89.7 - Metascore: 83 - IMDb user rating: 7.4 - Runtime: 90 minutes

Two strangers meet at a wedding in Palm Springs and end up stuck in a time loop. They relive the same day over and over again with weird circumstances taking over while they eventually fall in love with each other. The pair have to find a way to get out of this wedding day circle so they can resume their lives once again.

#12. Midnight in Paris (2011)

- Director: Woody Allen - Stacker score: 90.3 - Metascore: 81 - IMDb user rating: 7.7 - Runtime: 94 minutes

Writer Gil Pender (Owen Wilson) is on vacation in Paris when he decides to traverse around the city. Gil runs into a strange collective who take him back in time every night at midnight. He meets iconic people from yesteryear and starts to reevaluate his life, and romance with his fiancée.

#11. Looper (2012)

- Director: Rian Johnson - Stacker score: 90.3 - Metascore: 84 - IMDb user rating: 7.4 - Runtime: 113 minutes

In this film, time travel is a commodity that only certain people can afford. People like Joe, played by Joseph Gordon-Levitt, capitalize on it by using their hitman skills to complete jobs for a crime group. Set in 2044, Joe goes back several times in the past before his employer aims to stop his loop by sending future Joe (Bruce Willis) to kill his younger self. "Looper" is written and directed by Rian Johnson of "Star Wars" and "Knives Out" fame.

#10. Planet of the Apes (1968)

- Director: Franklin J. Schaffner - Stacker score: 90.9 - Metascore: 79 - IMDb user rating: 8.0 - Runtime: 112 minutes

A group of astronauts crash onto a planet in the far future where apes have the upper hand over humans. The primates can walk, talk, and have a complex social system that includes enslaving humans. The group finds themselves having to switch roles and become the "lesser" species. "Planet of the Apes" sparked a film franchise years later and was inducted into the Library of Congress' Film Registry in 2001.

#9. Interstellar (2014)

- Director: Christopher Nolan - Stacker score: 91.4 - Metascore: 74 - IMDb user rating: 8.6 - Runtime: 169 minutes

Set in 2067, this film shows Earth on the brink of destruction from storms and farming woes. Professor Brand, played by Michael Caine, plans to save the planet by sending people into a wormhole to another place. A few researchers test this travel plan and end up in different places and times to see where people can possibly inhabit.

#8. Terminator 2: Judgment Day (1991)

- Director: James Cameron - Stacker score: 91.4 - Metascore: 75 - IMDb user rating: 8.5 - Runtime: 137 minutes

Linda Hamilton returns as Sarah Connor, who aims to protect her young son John (Edward Furlong) from yet another (and more dangerous) Terminator. The cyborg intends to kill John, thereby preventing him from his future role in a resistance movement. Sarah, John, and T-800 (Arnold Schwarzenegger) work together to keep John, and the future resistance, alive.

#7. Harry Potter and the Prisoner of Azkaban (2004)

- Director: Alfonso Cuarón - Stacker score: 92 - Metascore: 82 - IMDb user rating: 7.9 - Runtime: 142 minutes

Titular hero Harry Potter (Daniel Radcliffe) continues his studies at the magical Hogwarts School. He realizes Sirius Black, an escaped prisoner, wants to kill him. Harry and his friends Hermione (Emma Watson) and Ron (Rupert Grint) must work together to defend the school while Harry realizes his true connection to Black.

#6. Star Trek (2009)

- Director: J.J. Abrams - Stacker score: 92 - Metascore: 82 - IMDb user rating: 7.9 - Runtime: 127 minutes

A modern take on the classic space traveling series, this film goes back in time to show James T. Kirk, Spock, and Uhura's (Zoe Saldana) journeys in their younger days. Kirk, portrayed by Chris Pine, inadvertently makes his way onto the USS Enterprise and rises to power while they fight dangerous threats. Spock's (Zachary Quinto) future self makes an appearance to aid him in making a sage decision.

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#5. Avengers: Endgame (2019)

- Directors: Anthony Russo, Joe Russo - Stacker score: 92.6 - Metascore: 78 - IMDb user rating: 8.4 - Runtime: 181 minutes

Five years after Thanos eliminated half of the living beings across the universe, the remaining Avengers band together to bring everyone back. The film includes the Quantum Realm, where time does not pass as it does on Earth and time travel is possible. Things end with a battle royale between the purple genocidal titan and all the super beings on Earth. The film marked the penultimate offering from the Marvel Cinematic Universe's Phase Three of its release/storytelling schedule.

#4. The Terminator (1984)

- Director: James Cameron - Stacker score: 93.7 - Metascore: 84 - IMDb user rating: 8.0 - Runtime: 107 minutes

The current year is 2029. A killer cyborg known as a "Terminator" goes back to 1984 to hunt Sarah Connor (Linda Hamilton). The killing machine (Arnold Schwarzenegger) stays on Connor's tracks as she uncovers the truth about her role in affecting humanity's future. Sarah must protect her family and stay alive so her son can fulfill a specific role.

#3. Donnie Darko (2001)

- Director: Richard Kelly - Stacker score: 96 - Metascore: 88 - IMDb user rating: 8.0 - Runtime: 113 minutes

In 1988, the title character (Jake Gyllenhaal) is a teenager dealing with sleepwalking episodes. He goes outside one night to encounter a massive, scary rabbit who tells him that the world will end in 28 days. Donnie, unsure of what is real or not, starts to go into a dark direction as time seems to go into flux for him, taking him into a different timeline.

#2. Back to the Future (1985)

- Director: Robert Zemeckis - Stacker score: 98.3 - Metascore: 87 - IMDb user rating: 8.5 - Runtime: 116 minutes

Michael Fox stars as Marty McFly, a teenager in 1985 who is friends with a strange scientist (Christopher Lloyd) named Doc. The latter's latest experiment goes wrong, throwing him back into 1955. He must find a young Doc and try to help him figure out how to get back to his correct timeline. Meanwhile, Marty also encounters his parents as their younger selves. The film has become a sci-fi classic, spawning its own franchise.

#1. It's a Wonderful Life (1946)

- Director: Frank Capra - Stacker score: 100 - Metascore: 89 - IMDb user rating: 8.6 - Runtime: 130 minutes

George Bailey is a man who is in over his head with family and general life problems. He considers dying by suicide but his family's prayers reach the heavens. His life is shown in flashbacks and an angel comes down to show him how much he matters to those closest to him. The now-iconic Christmas film was shot during the summer—in a heat wave, no less.

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Screen Rant

Sisko transforms his relationship with the prophets by turning his greatest strength against them.

Captain Benjamin Sisko has permanently altered his relationship with the Bajoran Prophets, by playing to his single greatest strength.

• Captain Sisko turns his greatest strength against the Bajoran Prophets in Star Trek #19, by Jackson Lanzing, Collin Kelly and Megan Levens.
• The Prophets have forbidden Captain Sisko from traveling to the Pleroma, but he ignores their commands and goes anway.
• By bucking the Prophets, Sisko may have ensured the galaxy's safety.

Warning: contains spoilers for Star Trek #19!

Star Trek ’s Captain Sisko has had a testy relationship with the Bajoran Prophets, and now this relationship changes forever as Ben turns his greatest strength against them. In Star Trek #19, the Prophets forbid Sisko from traveling to the Pleroma, the recently discovered “realm of the gods.” With the fate of existence hanging in the balance, Sisko takes his greatest strength, and uses it against the Prophets.

Star Trek #19 is written by Jackson Lanzing and Collin Kelly and drawn by Megan Levens. After hearing T’Lir’s plea for help, Sisko communes with the Prophets. T’Lir wishes the crew of the Theseus to travel to the Pleroma, but the Prophets tell Sisko he is not allowed. However, Sisko decides to go anyway.

As he takes the Theseus to be refitted at Utopia Planitia, he reflects on a conversation he once had with General Martok on Deep Space Nine, in which the Klingon praised Sisko’s greatest strength, which is not being good at doing what he is told.

Sisko Is Going Back To Where It All Started For Him: Utopia Planitia

The god war has forced him to reevaluate his relationship with the prophets.

The issue ends with Sisko arriving at his pre- Deep Space Nine posting: Utopia Planitia, bringing his arc full circle. After his career nearly died at Planitia, Sisko was sent to Deep Space Nine. At the time, it was just another posting, but with the discovery of the Bajoran Wormhole, and the non-linear beings called the Prophets that resided in it, Sisko’s life changed drastically. The Prophets declare Sisko “the Emissary,” an important role in the spiritual life of Bajor. This position often put Captain Sisko at odds with his duties as a Starfleet officer.

In the Deep Space Nine series finale, “What We Leave Behind,” Sisko was taken by the Prophets to the wormhole, where he would learn more about a non-linear, non-corporeal existence. Sisko was gone for three years, and it put a massive strain on his personal relationships, particularly with his son Jake. The Prophets pulled Sisko to their realm with no regard for these relationships. When the threat of Kahless and the god-killer reared its head, the Prophets sent Sisko back to stop him, with the understanding that he would return when the task was finished.

Star Trek: Q Explains Why Benjamin Sisko Is Humanity's Ideal Messiah

Captain sisko's greatest strength might save the galaxy, sisko does not like being told what to do...by anyone.

Yet in Star Trek #19, Sisko uses his greatest strength, his stubbornness and dislike of authority, against them. The Prophets did not give him a reason why to avoid the Pleroma, only speaking in cryptic phrases. Sisko’s patience for the Prophets is wearing thin. If Sisko and the Theseus do not go there to fix the damage Kahless has wrought, then the entire multiverse may be at stake. Sisko has no use for the Prophets or their riddles. With a racing clock hanging over his head, Sisko has (for now) forsaken the Prophets.

Star Trek #19 is on sale now from IDW Publishing!