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Interested in traversing a wormhole, the ultimate cheat code through space and time? Maybe you would like to jump from star system to star system across the universe without breaking a sweat? But first, you’d better make sure your wormhole is passable.
“Any traveler trying to go through a wormhole that doesn’t meet this will be crushed inside when the tunnel collapses,” João Rosa, a physicist at the University of Aveiro in Portugal, told Live Science.
Rosa attempts to practically “construct” a stable and traversable wormhole, which can be safely traversed without the theoretical passage collapsing or jamming its occupant. And he recently discovered that it is indeed possible, but only if we adjust our understanding of gravity.
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The problem of crossability
Wormholes are deceptively easy to construct – on paper. You start with a theory of gravity. In Einstein’s general theory of relativity, gravity defines the relationship between matter and energy, and space and time. The trick to building a wormhole is to find a configuration of matter and energy that allows you to form a tunnel – usually called a “throat” in wormhole research – connecting two distant points in space. .
In principle, this groove can be as long or short as you want, but the most interesting wormholes occur when the groove is much shorter than the normal distance between two points, making the wormhole a convenient shortcut. Oh, and wormholes can also act like time machines, sending you into the future or the past, depending on how they’re built.
The idea of such a whimsical shortcut has captured the imaginations of scientists and science fiction writers for decades.
“The ability to visit other stars (or even other galaxies), possibly find extraterrestrial civilizations, and the ability to revisit the past or not have to wait for the future are part of the imagination and the long human fancy, and wormholes provide a (relatively) simple and unified solution to both of these problems, ”Rosa told Live Science in an email.
But wormholes constructed on the basis of the criteria stated by general relativity suffer from a major problem: they are not really traversable. The entrances to general relativity wormholes are hidden behind event horizons, which are one-way barriers in space. This means that if you were to get into the wormhole, you would never be able to get out, which would defeat the purpose.
The other problem is that they are ridiculously unstable. The moment even a single photon, or light particle, enters the throat, the entire wormhole catastrophically collapses before that bundle of light can escape.
Pity.
A new gravity
In order to solve these general relativity issues and stabilize a wormhole, a cosmic traveler must fashion the wormhole from an incredibly exotic ingredient, a form of matter that has negative energy or mass. Negative mass (also known as exotic matter) is exactly what it sounds like: if something weighs less than 10 pounds, it would have negative mass. Scientists haven’t observed negative mass anywhere in the universe. Negative energy is slightly more accessible, which is just a condition where the energy in a particular location is negative in relation to its surroundings, but which can only be achieved on microscopic and quantum scales.
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“What is happening is that these gravitational effects necessary to ensure the traversability of the wormhole occur naturally if you change gravity.”
João Rosa
“The presence of this material is essential because it prevents the vortex throat from collapsing on a traveler, but it is also problematic,” Rosa explained. “It exhibits a negative average energy density, an extremely rare characteristic of matter in the universe that is only observed in very specific situations at the quantum level.”
Since such material is so rare, building an entire wormhole from exotic material would seem impossible in our universe.
But all this wormhole talk is grounded in general relativity. And although this theory of gravity has survived all the tests of observation and experimentation put to it over the past century, we know that general relativity is not the last word on gravity. Relativity is unable to describe the centers of black holes, the first moments of the universe and the link between itself and quantum physics.
So maybe a new improved theory of gravity would allow wormholes to exist.
Make the trip
This is exactly what Rosa investigated in a new article published online July 29 in the preprint journal. arXivwhich means the study has yet to be peer reviewed in the field.
Rosa used a modified form of gravity called hybrid metric-palatine generalized gravity. This theory of gravity is built on general relativity, but allows more flexibility in the relationships between matter and energy, and space and time.
Previous research had shown that traversable wormholes might be possible in this modified theory of gravity, but they still required negative energy outside of the wormhole throat. Rosa discovered that by superimposing wormhole entrances with thin double shells of regular material, the wormhole becomes traversable without any negative energy.
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“What is happening is that these gravitational effects necessary to ensure the traversability of the wormhole occur naturally if we change gravity and exotic matter. [matter with negative mass] is no longer necessary to achieve this goal, ”explained Rosa.
And after? Rosa wants to test this particular theory of modified gravity. “This is only a very small step towards the final goal: we must now use data and experimental observations (for example gravitational waves and the trajectories of stars near the center of the Milky Way) to test and (hopefully) confirm the validity of these theories, ”Rosa wrote.
While general relativity has so far explained all measurements of gravity (including gravitational waves and the neighborhood of black holes), the story is not over. Future observations might find a loophole in this venerable theory, and if generalized metric-palatal hybrid gravity better explains cosmic sightings, then travel-created wormholes might be possible.
But the questions would not end there. Wormholes can also act as time machines, so a viable wormhole solution would mean that time travel into the past is possible; this, of course, raises all kinds of difficult issues (like the so-called “grandfather’s paradox” and questions about causation). Knowing for sure that traversable wormholes might exist wouldn’t just make our sci-fi dreams come true, it would totally shake up our understanding of physics.
Originally posted on Live Science.
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