holes in the Universe
Rajibul Sheikh from the Tata Institute of Basic Research in India has proposed a way to distinguish the mouths of wormholes from black holes. A preprint of a scientific article with theoretical calculations of the physicist is published on the website arXiv.org .
A wormhole (also known as a wormhole and wormhole) is a hypothetical object that at any given time represents a "straight tunnel" between certain areas of space. Imagine a crumpled piece of paper. You can travel without leaving its surface. Then, in order to get from point A to point B, you will have to conscientiously overcome all its bends. Or you can "pierce" the surface and get to the right point on the other side straight. This is the opportunity that the wormhole provides (though not to spaceships, but at best to photons).
Wormholes have long excited the imagination of physicists, because it is a way to look into areas of space that are inaccessible to direct observation due to the very small speed of light on the scale of space. In addition, according to some theories, wormholes connect different universes in the Multiverse. This means that it is potentially possible to look into another universe.
The presence of wormholes does not contradict Einstein's general theory of relativity, the most profound and best–tested theory of space-time to date. However, to maintain the mole, exotic forms of matter are needed, the existence of which physicists are not yet sure.
Where theorists lack knowledge, observation can help. The difficulty is that for an astronomer, the "entrance" to a wormhole (the neck, as experts say) should look almost the same as a black hole.
As you know, black holes are not directly observed, that's why they are black. They are detected due to the glow of matter falling on them, the parameters of the orbits of satellite bodies, and more recently, gravitational waves. However, until now, astronomers have not known a way to distinguish a black hole from a wormhole.
The Sheikh suggests this method. It is based on a special structure that is formed due to the effect of the gravity of a black hole on the photons surrounding it. This is a characteristic dark area on a bright background, the so-called shadow. The source of the "illumination" necessary to create a shadow can be either a disk of matter falling into a black hole (an accretion disk, as experts say), or other celestial bodies.
The physicist considered a certain class of wormholes, the so-called Theo wormholes. He theoretically studied the dependence of the shape of the neck shadow on the speed of its rotation around its axis. The author then compared the results with the behavior of the most popular model of a rotating black hole, known as the Kerr black hole.
As ScienceAlert clarifies, it turned out that with slow rotation, the neck of a wormhole cannot be distinguished from a black hole. However, if the object is spinning faster, the shape of the shadow allows us to tell whether there is a black hole in front of us or the neck of a wormhole. It is important that such speeds are not prohibitively high and may well be observed in reality.
"The results obtained here show that the wormholes that are considered in this paper and have a reasonable rotation speed around their axis, thanks to observations of their shadows, can be distinguished from black holes," Sheikh writes in the annotation to his article.
The difficulty lies in the fact that to date, shadows from neither black holes nor wormhole necks have never been observed. The reason is that it requires a very high resolution (the ability to distinguish small details). However, the EHT radio telescope system, designed to directly "see" the event horizon of a black hole, presumably has the necessary parameters and has already made the first observations.
Johns Hopkins University scientists have proposed a hypothesis about the existence of a special type of space objects that are invisible and bend light like black holes, but do not have a classical event horizon. The discovery is reported in an article published in the journal Physical Review D.
The researchers used string theory to conduct a theoretical search for objects that could reproduce the same gravitational effects as black holes. They found that topological solitons correspond to this condition, which represent an unusual type of deformation of space and time involving additional compact dimensions.
Computer simulations have shown that topological solitons, unlike ordinary black holes, emit weak light rays that otherwise would not be able to escape the gravity of a real black hole. Photons move along numerous curved trajectories, as a result of which the shadow of a false black hole looks blurred. For an ordinary black hole, such a shadow defines the boundaries of the event horizon, an area from which light cannot escape.
Topological solitons are the result of a modification of Einstein's general theory of relativity in 2021 using some conclusions from string theory. They are an example of exotic objects within the framework of quantum gravity, which tries to reconcile quantum mechanics and the effects of relativity theory. However, even without the use of string theory, there may be other hypothetical objects that are alternatives to black holes, such as bosonic stars and gravastars.
From the book by Tikhomirov A.E. Structural levels and systematic organization of matter. LitRes, Moscow, 2023, P. 1 (translated from English): "Theoretical physicists from Radboud University in Nijmegen conducted a study verifying the correctness of Stephen Hawking's theory of black holes. The results obtained partially confirmed it, and also allowed us to suggest that everything in the universe is gradually evaporating. The new theoretical study was conducted by physicists Michael Vondrak, Walter van Suilek and Heino Falke. They tested the theory of the famous theoretical physicist Stephen Hawking about black holes and found out that he was right in many ways, but not in everything. At one time, Hawking, using a combination of quantum physics and Einstein's theory of gravity, argued that the spontaneous generation and annihilation of pairs of particles should occur near the event horizon. This is called the "point of no return", that is, an invisible line beyond which there is no escape from the gravitational force of a black hole for any objects, even the smallest ones.
A particle and its antiparticle are born from a quantum field for a very short time, after which they immediately annihilate. But sometimes it still happens that one particle falls into a black hole, and the other flies out of it. This phenomenon is called Hawking radiation. According to Hawking himself, such a process should eventually lead to the evaporation of a black hole.
In a new study, theoretical confirmation has been obtained that black holes will eventually evaporate due to Hawking radiation. But calculations at the same time showed that the event horizon is not as important as it was thought until now. Gravity and the curvature of spacetime also cause Hawking radiation. This means that all large objects in the universe, including the remnants of stars, will eventually evaporate.
The study showed that new particles can be created far beyond the event horizon. If it was previously believed that no radiation was possible without an event horizon, then a new study shows that there is no urgent need for this horizon. This means that objects without an event horizon, such as the remnants of dead stars and other large objects in the universe, also have this kind of radiation. The universe is evaporating, as are black holes. This changes not only our understanding of Hawking radiation, but also our view of the universe and its future."
From the book by Tikhomirov A.E. The origin of words and signs. The Science of Superstition, Ridero, Yekaterinburg, 2017, pp. 80-81: "A time machine – Any human thought (no matter how fantastic it may be) does not arise just like that, for no reason. There is always a rational grain in it. The problem of time travel also has its own nature. In real nature, it exists, and we can observe it every day. We see stars in the sky, some of them no longer exist, but we still observe them, that is, we see the past. This is due to the fact that billions of years pass before the light from these stars reaches the Earth, during which time many stars cease to exist. The possibility of time travel was also written by the English writer G. Wells in the novel "The Time Machine" (1895). In 1935, scientists Einstein and Rosen proposed the idea of "wormholes"
