Traversable wormholes are possible under certain gravity conditions

Are you interested in exploring a wormhole? This is the ultimate cheat-code to time and space. Maybe you want to travel the entire universe, from one star system to another without getting sweaty? First, make sure that your wormhole can be traversed.
Joo Rosa, a Portuguese physicist from Aveiro University, said that any traveler who attempts to cross a tunnel through a wormhole without satisfying this requirement will be crushed as the tunnel collapses." Live Science was also informed by Joo Rosa.

Rosa is trying to "build" a safe, navigable wormhole that can be traversed without it collapsing or trapping its owner. He has discovered that it is possible. However, this requires that we modify our perception of gravity.

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The problem with traversability

Wormholes can be deceptively simple to create on paper. The theory of gravity is the first step. Einstein's theory general relativity states that gravity is the relationship between matter, energy, space, and time. To build a wormhole, you need to find the right combination of matter and energy to create a tunnel. This is what wormhole researchers call a "throat". It connects two distant points in space.

The throat can be as long as it wants, but the most interesting wormholes occur when the throat is much shorter than the distance between two points. This makes the wormhole an easy shortcut. Wormholes can also be used as time machines to send you into the past or future, depending on their construction.

Scientists and scientists have been fascinated by the idea of a whimsical shortcut for decades.

Rosa explained to Live Science that the possibility of visiting other stars or galaxies, possibly finding alien civilisations, and the possibility of revisiting the past or not having the future to wait have all been part of human imagination and fantasy. "Wormholes offer a (relatively simple and unifying solution to both of these problems," Rosa said in an email.

However, wormholes that are constructed using the general relativity criteria have a serious problem. They can't be traversed. General relativity wormholes' entrances are concealed behind event horizons. These are barriers that block space from moving. This means that even if you entered the wormhole, it would be impossible to leave.

They are also extremely unstable. Once even one photon or light particle enters the throat, the entire wormhole collapses before it can escape.


A new gravity

To solve the problems of general relativity and stabilize the wormhole, a cosmic explorer must create the wormhole from an extremely exotic ingredient. This is a form or matter with negative energy or mass. Exotic matter, also known as negative mass, is exactly what it sounds. If something weighs less than 10 pounds it would have negative weight. Negative mass has never been observed anywhere in the universe by scientists. Although negative energy is more possible, it is a condition in which the energy in a specific location is less than its surroundings. This can only be done at microscopic quantum scales.

Related: 8 ways to see Einstein's theory on relativity in action

"What happens is that the gravitational effects necessary to ensure the traversability through the wormhole occur naturally if one modifies the gravity." Joo Rosa

Rosa explained that "the presence of this matter is crucial as it prevents wormhole throats from collapsing upon a traveling party, but it is also problematic." It has a negative energy density, which is a rare property of matter in the universe. This can only be observed in very limited situations at the quantum level.

Because such rare matter is hard to find, it would be difficult to create a wormhole from this exotic matter in our universe.

All this talk about wormholes hinges on general relativity. Although general relativity has survived all the experimental and observational tests it has been subject to over the past century, we now know that it is not the final word on gravity. Relativity cannot describe the centers of black hole, the earliest moments in the universe and the link between it and quantum physics.

Perhaps a new theory of gravity could allow for wormholes.

The trip is worth it

Rosa examined exactly this in her new paper, published online in arXiv's preprint journal arXiv on July 29th. However, peers have yet to review the study.

Rosa used a modified form of gravity, called generalized hybrid-Palatini gravity. This theory of gravity, which is based on general relativity allows for more flexibility in the relationships between matter, energy, space, and time.

Previous research had shown that traversable wormholes may be possible under this modified theory. However, they still require negative energy to exit the wormhole throat. Rosa discovered that the wormhole can be made traversable by layering its entrances with thin shells of regular material.

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Rosa explained that the gravitational effects necessary to ensure the passageability of the wormhole occur naturally if one modifies the gravity. Exotic matter [matter having negative mass] no longer serves this purpose.

What's next? Rosa would like to test this theory of modified gravity. "This is only a small step towards the ultimate goal. One must now use experimental and observation data (e.g. Rosa wrote that gravitational waves, trajectories and orbits of stars close to the center of Milky Way are used to verify and (hopefully) validate these theories.

Although general relativity has been able to explain all known measurements of gravity, including gravitational waves and the proximity of black holes, it is not the end of the story. Future observations may uncover a crack in this venerable theory. If generalized hybrid metric -Palatini gravity is able to better explain cosmic observations, then wormholes that allow for travel might be possible.

The questions don't stop there. Also, wormholes can act as time machines. A viable wormhole solution could allow time travel to the past. However, this raises many difficult questions (such as the "grandfather paradox" or questions about causality). It would not only make sci-fi dreams become a reality, but it would also revolutionize our understanding of physics.

Original publication on Live Science