inyildi – A white hole.
The existence of black and white holes was a consequence of Einstein’s theory of gravity. The proof of the existence of these astrophysical objects is a test of the truth of our understanding of the properties of space and time in extreme gravitational fields.
Theoretical studies of black and white holes have been particularly active since the early 70s.
At present, there is a relatively complete understanding of the properties of holes, their possible astrophysical manifestations and features of the flow of various physical processes in them.
The connection of the theory of black and white holes with thermodynamics, information theory, and quantum theory was revealed.
A black hole.
A black hole is considered a space-time region that has such a strong gravitational field that even waves of light are not able to leave it and go to infinity.
A black hole occurs when a body with a mass of $M$ is compressed, so that its size becomes less than the value equal to:
where $G$ is the gravitational constant; $c$ is the speed of light. The parameter $r_g$ is called the gravitational radius.
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The second cosmic velocity of a body that could fly away from the boundary of a black hole should be equal to the speed of light. Taking into account the fact that the speed of light in a vacuum is the maximum speed of propagation of signals in physics, it is easy to understand that a signal cannot escape from the inside of a black hole.
In Einstein’s theory of gravity, this conclusion is absolute, since the gravitational interaction is considered universal. The role of the gravitational charge is played by the mass, the value of which is proportional to the total energy of the system. Therefore, all objects endowed with energy take part in the gravitational interaction.
Einstein’s general theory of relativity (GR) is used to describe black holes.
The surface of a black hole can be considered a kind of membrane, since signals cannot leave the interior of this hole, while physical bodies and radiation can fall inside it. The boundary of a black hole (it is a light surface) in space and time is called the event horizon.
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The name “black hole” appeared in 1968 and is associated with the name of Wheeler. However, the question of the existence of objects with similar properties was discussed already in the XVIII century. In the framework of GRT, this problem was encountered after Schwarzschild (1916) obtained the first exact solution of the Einstein equation in the void.
This solution, in addition to the singularity at the center of symmetry (at $r=0$), had an additional property at $r=r_g$. It took more than thirty years for the analysis of the features of the Schwarzschild solution to gain an understanding of the structure of space – time in a strong gravitational field. Oppenheimer and Snyder first described the gravitational collapse of a large-mass star, which would lead to the appearance of a black hole, in 1939.
The assumption about the existence of black holes can be obtained from understanding the evolution of a star. When stars with a large mass die, they shrink (collapse), there is an” explosion ” inwards, a region with a large gravity arises.
It was found that a black hole:
has a mass; can have a charge; the moment of the amount of motion.
The structure of a black hole is very complex. For a complete and visual representation of the geometry of the black hole space – time, the Kruskal – Szekeresch and Penous diagrams were created.
For the Schwarzschild black hole, this diagram is shown in Figure 1. It indicates that all the matter in the universe falls through the event horizon into the black hole, collides with the singularity, and collapses.
Figure 1. Black hole. Author24-online exchange of student papers.
A white hole is an expanding space-time region that cannot be reached by any signal or particle from spatial infinity (from a region with a distance greater than $r_g$).
It is believed that white holes can not occur in the Universe and be the collapse of an object. However, they can exist in the expanding Universe from the moment of its origin (the beginning of expansion).
Let’s assume that there was already matter and radiation near the singularity in the past. In this case, over time, this matter and radiation will leave the event horizon and pass into the Universe. This effect indicates the presence of a white hole (Figure 2).
Figure 2. A white hole. Author24-online exchange of student papers.
Most scientists now believe that our universe was created as a result of the big bang of a primordial state that had infinite density. We can assume that some parts of space did not experience expansion during the explosion of the Universe, that is, as a result of some reason, a small particle of the singularity managed to survive and did not expand for a long time. At the moment when a given object of the primary singularity has begun the expansion process, it will exhibit the properties of a white hole. This element is a singularity of the past, from this past, matter and radiation came to us in the universe. The idea that the tiny fates of the singularity of the past could be preserved for a long time led the Russian scientist D. I. Novikov to the idea of the existence of Schwarzschild white holes.
The problem of white holes was studied by Eardley (USA) in 1970. The scientist suggested that the singularities of the past should surround the event horizon in the past.
In a black hole, the event horizon corresponds to a time stop for an outside observer. For this observer, the light wave coming from the vicinity of the event horizon undergoes a strong redshift (the wave spends a lot of energy overcoming the strong field of gravity). Whereas light falling inside a black hole experiences a strong violet shift.
At the Big Bang, the universe had a very high temperature. If there are “sleeping” singularities left from the Big Bang, then a huge amount of very powerful radiation should accumulate around them. In this case, the light gathers near the event horizon of the past, forming a purple layer. After a short period of time, so much light energy accumulates in this violet layer that the energy itself strongly bends space-time.
According to Eardley’s calculations, the light that accumulates near the dormant singularities bends space-time so much that a black hole appears around a potential white hole. This creates a future event horizon and a singularity.
Scientists believe that white holes can occur when the matter of a black hole, which is located in the opposite direction of the arrow of time, comes out of the event horizon.
The aggregate space-time map has both a black hole and a white hole. A separate black hole and a separate white hole do not exist in principle.
Currently, no white holes have been detected and there are no methods to find them.
The Schwarzschild solution contains black and white holes, but it is believed that there are no Schwarzschild white holes.
The complete Kerr solution also shows the presence of both types of holes. At the same time, it is believed that if a black hole appears in one Universe, then a white hole appears in another.
Some scientists believe that white holes break up immediately after they occur. There are theories according to which black holes become white over time.
In 2006, Israeli scientists A. Retter and S. Heller discovered an anomalous $ \ gamma$ – burst $GRB 06014$, suggesting that it was a white hole.
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