— Your scientific group has presented theoretical evidence of the traversability of “wormholes” for light in Friedman’s model of the expanding universe without the presence of so-called exotic matter in them. Previously this was considered impossible. What are “wormholes” and exotic matter from the point of view of modern science?
— As you know, Einstein’s general theory of relativity (GTR), as well as its numerous generalizations, identify the gravitational field with the curvature of space-time. Under normal conditions this curvature is very small. But widely known examples of objects with very strong curvature are black holes and wormholes. A “wormhole” is a curvature of space that can be imagined as a tunnel connecting some slightly curved areas. These areas may belong to the same universe, or they may belong to different ones.
In a certain sense, wormholes are simpler than black holes: they do not have event horizons from which even light cannot escape. But for a stable wormhole to exist, it requires so-called exotic matter - a very strange substance with negative density. Its density increases when stretched - in contrast to ordinary matter. Such matter has not yet been found either on Earth or in space, and wormholes remain only a very interesting, but hypothetical possibility.
— What main conclusions did you come to?
— The main conclusion is the possibility of the existence of “wormholes” in the expanding Universe with the most ordinary dust-like matter, consisting of non-interacting particles, or rather interacting only through a gravitational field. The role of such particles can be, for example, stars or even galaxies. However, the neck of such a “wormhole,” that is, the narrowest part of the tunnel, cannot exist for a particularly long time and collapses in a time short compared to the lifetime of the Universe. Nevertheless, it lives long enough for photons—that is, light or radio emission—or fast enough moving particles to pass through it.
Curvature of space-time
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© MARK GARLICK/SPL
If you do not require the constant, stable existence of a “wormhole,” then the need for exotic matter disappears, and dusty matter completely retains its usual properties and does not play any role unusual for it. The effect of the possible temporary appearance of a “wormhole” under these conditions depends, one might say, on the initial conditions: a certain type of distribution of the density of dusty matter at the initial moment is required, as well as a certain type of distribution of initial particle velocities. In other words, in order to launch the desired process, it is necessary to provide suitable initial conditions for this - similar to many other processes.
— Is it true that a prerequisite for the emergence of “wormholes” in the space-time continuum is a strong gravitational influence that distorts space and time?
- Indeed, being an example of a strong curvature of space-time, the “wormhole” contains very strong gravitational fields of the tidal type, compressing or stretching any body of finite size. Calculations show that in “wormholes”, in which the size of the neck is comparable to the size of the human body or some kind of vehicle - say, several tens of meters - enormous overloads arise that are incompatible with life. To ensure that the forces arising in the neck area do not exceed the normal force of gravity too much, it is necessary that the dimensions of such a neck be at least of the order of the size of the globe.
— Are there any empirical observations that confirm the possibility of the existence of “wormholes” in the Universe?
— There are theoretical estimates made based on the results of observations of the most powerful processes in the Universe. In principle, they allow interpretation involving wormholes. However, so far there is no clear indication of the existence of such tunnels.
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© Dawam Syah / 500px
- There is a hypothesis that, in addition to black holes, there are also white holes in the Universe - if matter cannot leave black holes, then matter cannot get into white ones...
— The hypothesis exists for a very simple reason: the equations of general relativity (as well as most theories) are symmetric with respect to the replacement of time by minus time. A white hole is a black hole facing the past instead of the future. But if it is quite clear how a black hole can form - due to the catastrophic compression of a large piece of matter, then for white holes a similar mechanism is unknown, and therefore it is not surprising that they are not observed.
— The “wormhole” connects different points not only in space, but also in time, since the entire space-time continuum is bent. Is time travel theoretically possible? Does the idea of creating a time machine contradict the basic tenets of physics?
— Yes, it contradicts the principle of causality: the cause must precede the effect in time. Although it is possible to write the corresponding solutions to the equations, you need to understand that not every solution to even the correct equation describes phenomena in the real world.
— For final answers to all questions about “wormholes” in space-time, science must first find answers to questions about the quantum nature of gravity? What is known about it today, are there any particles that are candidates for the role of carriers of gravitational interaction?
“There are many hopes placed on the future quantum theory of gravity with hypothetical gravitons—carriers of gravitational interaction.” But perhaps no theory will ever answer all questions. “Wormholes” are not necessarily quantum objects, and new information about them can also be expected from classical theories of gravity in combination with astrophysics.
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© Randy Faris
— They say that “wormholes” hardly exist in nature, although they are possible from the point of view of physics, and such tunnels must be created by man himself. Is it so? What technologies are needed for this?
“If humanity learns to control the curvature of space-time without resorting to the use of huge masses such as planetary or stellar, then, among other still unimaginable achievements, we can expect the creation of “wormholes.”