We are used to the fact that in Hollywood science fiction films, characters travel interstellar distances in a few seconds. At the same time, we know that in reality this is impossible, because even the light travels to the nearest stars for more than four years. Are there ways to overcome the barriers set by nature and make fiction a reality?
BRANA IN THE BULK
In his general theory of relativity, Albert Einstein showed that massive bodies not only change the flow of time, but also bend space. Both theoretical positions were almost immediately proved by observing Mercury and stars, the light of which is deflected in the gravitational field of the Sun. But for a long time, the accuracy of existing instruments did not allow us to measure the dimensions of the deformation of the space created by our luminary.
In 1976-1977, American physicists Robert Riesenberg and Irwin Shapiro conducted an experiment in which the modules of the Viking-1 and Viking-2 spacecraft, which were in orbits near Mars, were used. They sent radio signals towards the vehicles when the red planet was near the Sun, as viewed from Earth. The Vikings intercepted the signals, amplified them and sent them back. Measuring the real speed of the radio signal with the calculated one, the Americans have established: the delay is hundreds of microseconds, which in recalculation gives an increase in the signal transmission distance by 50 km. Such an "addition" to the distance would not be possible if the space was as flat as a sheet of paper. Hence, it is curved near the surface of the Sun.
Scientists have established theoretically and experimentally that space bends. But where? They hypothesized that it sags into a multidimensional hyperspace called the "bulk". Our space, in this interpretation, appears as a brane, that is, a three-dimensional membrane. The proven existence of higher dimensions gives hope that someday a way will be found to literally pierce space, instantly overcoming the colossal distances separating us from other worlds.
BRIDGE OVER THE WORLD
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In 1916, that is, just a year after Einstein published his main articles on general relativity, the Austrian physicist Ludwig Flamm found a solution to his equations, describing such a curvature of space in which a "short" transition from one point of the Universe to another becomes possible, and as far as you like, through special "bridges".
Flamm's exotic conclusion was ignored at the time. Much more resonance was caused by the so-called "space-time bridge", which was described in 1935 by Albert Einstein himself and his assistant Nathan Rosen. Unlike their predecessor, they thought about the significance of the proposed model for the real world, but came to the conclusion that the "bridge" cannot exist on our brane as a material object accessible to observation. Nevertheless, almost immediately the idea was used by science fiction writers as a hypothetical means of transportation, which contributed to its popularization.
In 1957, American physicist John Wheeler proposed his own version of the "bridge". Describing it, he resorted to an analogy with an ant on an apple, which can take a very long time to get to the opposite part of the fruit, or can use the tunnel gnawed by worms for speed. Based on this analogy, Wheeler called the spatial tunnels "wormholes"; among Soviet physicists, the term "wormholes" later became entrenched. In addition to introducing new words, the American, together with his student Robert Fuller, developed a model of the birth, expansion and collapse of "wormholes" through the bulk, and although it seemed to show the inevitability of the almost instantaneous "death" of these formations, the theoretical justification of their existence provided the basis for further research.
THORN'S HYPOTHESIS
The next step was taken by Kip Thorne, Wheeler's student. He turned to the problem of wormholes after the famous popularizer Carl Sagan sent him a manuscript of his science fiction novel Contact for review in May 1985. In the original text, the characters of the novel, scientists, were sent to a meeting with representatives of the ancient supercivilization through a "black hole". Thorne knew that it was impossible to travel in the Universe in this way, since any material object inside the "black holes" would be destroyed, so he suggested that Sagan replace them with Wheeler's "wormholes". This required substantiating under what conditions a tunnel through the bulk would be possible.
Thorne was able to prove mathematically that a "wormhole" can exist in our world for an arbitrarily long time if inside it there is "exotic matter", that is, a substance with negative mass and negative energy. Although at first glance such a thought seems to be nonsense, the presence of "exotic matter" does not contradict the laws of physics we know.
In 1988, Kip Thorne, co-authored with his students, Mark Morris and Ulvi Yartsever, published a paper calling on the scientific community to discuss the creation and stabilization of wormholes. For four decades, as Thorne himself admits, a satisfactory answer has not been received, which did not prevent the physicist from taking part in consulting the fantastic film "Interstellar", where the appearance of an artificial "wormhole" in the vicinity of Saturn became one of the plot-forming assumptions.
However, there are still some achievements. For example, it has been shown that the natural occurrence of "wormholes" is extremely unlikely. Unlike “black holes”, the process of birth of which from massive stars has been described and calculated, there are no objects in the Universe that could be “linked” with “wormholes”. The hypothesis was considered that "wormholes" can appear at the subatomic level in the form of the so-called "quantum foam", but this option is also subject to serious criticism.
It turns out that if "wormholes" ever appear, they will be a product of supercivilization technology, as shown in Carl Sagan's novel Contact and Christopher Nolan's Interstellar. Kip Thorne even proposed a scheme for how such a civilization could build them: “You just take and push part of our brane (Universe) down into the bulk and get a dent, then bend the brane in the bulk, poke a hole in it, as if under a dent, poke another hole at the bottom of the dent and finally stitching the edges of the holes. Delov something!"
FIND A "WORM"
Not all scientists agreed with the pessimistic conclusions of Kip Thorne. For example, the Russian astrophysicist Nikolai Semenovich Kardashev, known for his classification of hypothetical extraterrestrial civilizations, develops the theory of the Multiverse as a set of an infinite set of worlds with different physical constants and, accordingly, deployed on other branes.
According to the calculations of the Kardashev group, "wormholes" are formed along with numerous universes and persist, connecting them as they grow. Of course, "wormholes" evolve, but they can be found by their characteristic features: in particular, they can look like "black holes" with anomalous properties. Among the objects that fell under suspicion, Kardashev calls the quasar Q0957 + 561.
At present, the Radioastron orbiter (Spektr-R) is engaged in the search for "wormholes"; in 2025, the Millimetron (Spectrum-M) orbital observatory is to join it. Russian physicists believe in success. If they manage to confirm their theoretical calculations, then the opening of a tunnel into the neighboring universe will surpass even Einstein's theory in its significance. And there, you see, using the example of a natural "wormhole" they will learn to create artificial ones.
Anton Pervushin