The black hole that is in it. Black hole. What's inside a black hole? What is the information paradox

The boundless Universe is full of secrets, riddles and paradoxes. Despite the fact that modern science has made a huge leap forward in space exploration, much in this vast world remains incomprehensible to the human worldview. We know a lot about stars, nebulae, clusters and planets. However, in the vastness of the Universe there are such objects, the existence of which we can only guess. For example, we know very little about black holes. Basic information and knowledge about the nature of black holes is based on assumptions and conjectures. Astrophysicists and atomic scientists have been struggling with this issue for more than a dozen years. What is a black hole in space? What is the nature of such objects?

Talking about black holes in simple terms

To imagine what a black hole looks like, it is enough to see the tail of a train leaving the tunnel. The signal lights on the last car as the train deepens into the tunnel will decrease in size until they completely disappear from view. In other words, these are objects where, due to the monstrous attraction, even light disappears. Elementary particles, electrons, protons and photons are not able to overcome the invisible barrier, they fall into the black abyss of non-existence, that is why such a hole in space is called black. There is not the slightest bright spot inside it, solid blackness and infinity. What lies on the other side of a black hole is unknown.

This space vacuum cleaner has a colossal force of attraction and is able to absorb an entire galaxy with all clusters and superclusters of stars, with nebulae and dark matter to boot. How is this possible? It remains only to guess. The laws of physics known to us in this case are cracking at the seams and do not provide an explanation for the ongoing processes. The essence of the paradox lies in the fact that in a given section of the Universe, the gravitational interaction of bodies is determined by their mass. The process of absorption by one object of another is not affected by their qualitative and quantitative composition. Particles, having reached a critical amount in a certain area, enter another level of interaction, where gravitational forces become forces of attraction. The body, object, substance or matter under the influence of gravity begins to shrink, reaching a colossal density.

Approximately such processes occur during the formation of a neutron star, where stellar matter is compressed in volume under the influence of internal gravity. Free electrons combine with protons to form electrically neutral particles called neutrons. The density of this substance is enormous. A particle of matter the size of a piece of refined sugar has a weight of billions of tons. Here it would be appropriate to recall the general theory of relativity, where space and time are continuous quantities. Therefore, the compression process cannot be stopped halfway and therefore has no limit.

Potentially, a black hole looks like a hole in which there may be a transition from one part of space to another. At the same time, the properties of space and time itself change, twisting into a space-time funnel. Reaching the bottom of this funnel, any matter decays into quanta. What is on the other side of the black hole, this giant hole? Perhaps there is another other space where other laws operate and time flows in the opposite direction.

In the context of the theory of relativity, the theory of a black hole is as follows. The point in space, where gravitational forces have compressed any matter to microscopic dimensions, has a colossal force of attraction, the magnitude of which increases to infinity. A wrinkle of time appears, and space is curved, closing in one point. Objects swallowed by the black hole are unable to resist the force of retraction of this monstrous vacuum cleaner on their own. Even the speed of light possessed by quanta does not allow elementary particles to overcome the force of attraction. Any body that gets to such a point ceases to be a material object, merging with the space-time bubble.

Black holes in terms of science

If you ask yourself, how do black holes form? There will be no single answer. There are a lot of paradoxes and contradictions in the Universe that cannot be explained from the point of view of science. Einstein's theory of relativity allows only a theoretical explanation of the nature of such objects, but quantum mechanics and physics are silent in this case.

Trying to explain the ongoing processes by the laws of physics, the picture will look like this. An object formed as a result of colossal gravitational compression of a massive or supermassive cosmic body. This process has a scientific name - gravitational collapse. The term "black hole" first appeared in the scientific community in 1968, when the American astronomer and physicist John Wheeler tried to explain the state of stellar collapse. According to his theory, in place of a massive star that has undergone gravitational collapse, a spatial and temporal gap appears, in which an ever-growing compression acts. Everything that the star consisted of goes inside itself.

Such an explanation allows us to conclude that the nature of black holes is in no way related to the processes occurring in the Universe. Everything that happens inside this object does not affect the surrounding space in any way with one "BUT". The gravitational force of a black hole is so strong that it bends space, causing galaxies to rotate around black holes. Accordingly, the reason why galaxies take the form of spirals becomes clear. How long it will take for the huge Milky Way galaxy to disappear into the abyss of a supermassive black hole is unknown. A curious fact is that black holes can appear at any point in outer space, where ideal conditions are created for this. Such a wrinkle of time and space levels out the huge speeds with which the stars rotate and move in the space of the galaxy. Time in a black hole flows in another dimension. Within this region, no laws of gravity can be interpreted from the point of view of physics. This state is called a black hole singularity.

Black holes do not show any external identification signs, their existence can be judged by the behavior of other space objects that are affected by gravitational fields. The whole picture of the struggle for life and death takes place on the border of a black hole, which is covered by a membrane. This imaginary surface of the funnel is called the "event horizon". Everything that we see up to this limit is tangible and material.

Scenarios for the formation of black holes

Developing the theory of John Wheeler, we can conclude that the mystery of black holes is not in the process of its formation. The formation of a black hole occurs as a result of the collapse of a neutron star. Moreover, the mass of such an object should exceed the mass of the Sun by three or more times. The neutron star shrinks until its own light is no longer able to escape from the tight grip of gravity. There is a limit to the size to which a star can shrink to give birth to a black hole. This radius is called the gravitational radius. Massive stars at the final stage of their development should have a gravitational radius of several kilometers.

Today, scientists have obtained circumstantial evidence for the presence of black holes in a dozen x-ray binary stars. An X-ray star, pulsar or burster does not have a solid surface. In addition, their mass is greater than the mass of three Suns. The current state of outer space in the constellation Cygnus, the X-ray star Cygnus X-1, makes it possible to trace the formation of these curious objects.

Based on research and theoretical assumptions, there are four scenarios for the formation of black stars in science today:

• gravitational collapse of a massive star at the final stage of its evolution;
• collapse of the central region of the galaxy;
• the formation of black holes during the Big Bang;
• the formation of quantum black holes.

The first scenario is the most realistic, but the number of black stars with which we are familiar today exceeds the number of known neutron stars. And the age of the Universe is not so great that such a number of massive stars could go through the full process of evolution.

The second scenario has the right to life, and there is a vivid example of this - the supermassive black hole Sagittarius A *, sheltered in the center of our galaxy. The mass of this object is 3.7 solar masses. The mechanism of this scenario is similar to the scenario of gravitational collapse, with the only difference being that it is not the star that undergoes the collapse, but the interstellar gas. Under the influence of gravitational forces, the gas is compressed to a critical mass and density. At a critical moment, matter breaks up into quanta, forming a black hole. However, this theory is questionable, since astronomers at Columbia University recently identified satellites of the Sagittarius A* black hole. They turned out to be a lot of small black holes, which probably formed in a different way.

The third scenario is more theoretical and is related to the existence of the Big Bang theory. At the time of the formation of the Universe, part of the matter and gravitational fields fluctuated. In other words, the processes took a different path, not related to the known processes of quantum mechanics and nuclear physics.

The last scenario is focused on the physics of a nuclear explosion. In clumps of matter, in the process of nuclear reactions, under the influence of gravitational forces, an explosion occurs, in the place of which a black hole is formed. Matter explodes inward, absorbing all particles.

Existence and evolution of black holes

Having a rough idea of ​​the nature of such strange space objects, something else is interesting. What are the true sizes of black holes, how fast do they grow? The dimensions of black holes are determined by their gravitational radius. For black holes, the radius of the black hole is determined by its mass and is called the Schwarzschild radius. For example, if an object has a mass equal to the mass of our planet, then the Schwarzschild radius in this case is 9 mm. Our main luminary has a radius of 3 km. The average density of a black hole formed in the place of a star with a mass of 10⁸ solar masses will be close to the density of water. The radius of such formation will be 300 million kilometers.

It is likely that such giant black holes are located in the center of galaxies. To date, 50 galaxies are known, in the center of which there are huge time and space wells. The mass of such giants is billions of the mass of the Sun. One can only imagine what a colossal and monstrous force of attraction such a hole possesses.

As for small holes, these are mini-objects, the radius of which reaches negligible values, only 10¯¹² cm. The mass of such a crumb is 10¹⁴g. Such formations arose at the time of the Big Bang, but over time they increased in size and today they flaunt in outer space as monsters. The conditions under which the formation of small black holes took place, scientists today are trying to recreate in terrestrial conditions. For these purposes, experiments are carried out in electron colliders, through which elementary particles are accelerated to the speed of light. The first experiments made it possible to obtain quark-gluon plasma in laboratory conditions - matter that existed at the dawn of the formation of the Universe. Such experiments allow us to hope that a black hole on Earth is a matter of time. Another thing is whether such an achievement of human science will turn into a catastrophe for us and for our planet. By artificially creating a black hole, we can open Pandora's box.

Recent observations of other galaxies have allowed scientists to discover black holes whose dimensions exceed all conceivable expectations and assumptions. The evolution that occurs with such objects makes it possible to better understand why the mass of black holes grows, what is its real limit. Scientists have come to the conclusion that all known black holes have grown to their real size within 13-14 billion years. The difference in size is due to the density of the surrounding space. If a black hole has enough food within reach of the forces of gravity, it grows by leaps and bounds, reaching a mass of hundreds and thousands of solar masses. Hence the gigantic size of such objects located in the center of galaxies. A massive cluster of stars, huge masses of interstellar gas are abundant food for growth. When galaxies merge, black holes can merge together, forming a new supermassive object.

Judging by the analysis of evolutionary processes, it is customary to distinguish two classes of black holes:

• objects with a mass 10 times the solar mass;
• massive objects, the mass of which is hundreds of thousands, billions of solar masses.

There are black holes with an average intermediate mass equal to 100-10 thousand solar masses, but their nature is still unknown. There is approximately one such object per galaxy. The study of X-ray stars made it possible to find two average black holes at a distance of 12 million light years in the M82 galaxy. The mass of one object varies in the range of 200-800 solar masses. Another object is much larger and has a mass of 10-40 thousand solar masses. The fate of such objects is interesting. They are located near star clusters, gradually being attracted to a supermassive black hole located in the central part of the galaxy.

Our planet and black holes

Despite the search for clues about the nature of black holes, the scientific world is concerned about the place and role of a black hole in the fate of the Milky Way galaxy and, in particular, in the fate of planet Earth. The fold of time and space that exists at the center of the Milky Way gradually engulfs all existing objects around. Millions of stars and trillions of tons of interstellar gas have already been absorbed into the black hole. Over time, the turn will reach the arms of Cygnus and Sagittarius, in which the solar system is located, having traveled a distance of 27 thousand light years.

The other nearest supermassive black hole is in the central part of the Andromeda galaxy. This is about 2.5 million light years from us. Probably, before the time when our object Sagittarius A * absorbs its own galaxy, we should expect a merger of two neighboring galaxies. Accordingly, there will be a merger of two supermassive black holes into one, terrible and monstrous in size.

A completely different matter is small black holes. To absorb the planet Earth, a black hole with a radius of a couple of centimeters is enough. The problem is that, by nature, a black hole is a completely faceless object. No radiation or radiation comes from her womb, so it is quite difficult to notice such a mysterious object. Only from a close distance can one detect the curvature of the background light, which indicates that there is a hole in space in this region of the Universe.

To date, scientists have determined that the closest black hole to Earth is V616 Monocerotis. The monster is located 3000 light years from our system. In terms of size, this is a large formation, its mass is 9-13 solar masses. Another nearby object that threatens our world is the black hole Gygnus X-1. With this monster we are separated by a distance of 6000 light years. The black holes revealed in our neighborhood are part of a binary system, i.e. exist in close proximity to a star that feeds an insatiable object.

Conclusion

The existence in space of such mysterious and mysterious objects as black holes, of course, makes us be on our guard. However, everything that happens to black holes happens quite rarely, given the age of the universe and huge distances. For 4.5 billion years, the solar system has been at rest, existing according to the laws known to us. During this time, nothing of the kind, neither the distortion of space, nor the fold of time, appeared near the solar system. Probably, there are no suitable conditions for this. That part of the Milky Way, in which the Sun star system resides, is a calm and stable section of space.

Scientists admit the idea that the appearance of black holes is not accidental. Such objects play the role of orderlies in the Universe, destroying the excess of cosmic bodies. As for the fate of the monsters themselves, their evolution has not yet been fully studied. There is a version that black holes are not eternal and at a certain stage may cease to exist. It is no longer a secret to anyone that such objects are the most powerful sources of energy. What kind of energy it is and how it is measured is another matter.

Through the efforts of Stephen Hawking, science was presented with the theory that a black hole still radiates energy, losing its mass. In his assumptions, the scientist was guided by the theory of relativity, where all processes are interconnected with each other. Nothing just disappears without appearing somewhere else. Any matter can be transformed into another substance, while one type of energy goes to another energy level. This may be the case with black holes, which are a transitional portal from one state to another.

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Predicts that a black hole has a singularity, a place where tidal forces become infinitely large, and once you cross the event horizon, you can't go anywhere else but into a singularity. Accordingly, it is better not to use GR in these places - it simply does not work. To tell what happens inside a black hole, we need a theory of quantum gravity. It is generally accepted that this theory will replace the singularity with something else.

How are black holes formed?

We currently know of four different ways that black holes form. Best understood associated with stellar collapse. A sufficiently large star forms a black hole after its nuclear fusion stops, because everything that could already be synthesized has been synthesized. When the pressure created by the fusion stops, the matter begins to fall towards its own center of gravity, becoming more and more dense. In the end, it is so compacted that nothing can overcome the gravitational effect on the surface of the star: this is how a black hole is born. These black holes are called "solar-mass black holes" and are the most common.

The next common type of black hole is the "supermassive black hole" found at the center of many galaxies, which has masses about a billion times greater than solar-mass black holes. It is not yet known exactly how they are formed. It is believed that they once began as solar-mass black holes that, in densely populated galactic centers, swallowed many other stars and grew. However, they seem to absorb matter faster than this simple idea suggests, and how exactly they do so is still a matter of research.

A more controversial idea has been primordial black holes, which could have been formed by almost any mass in large density fluctuations in the early universe. While it's possible, it's hard enough to find a model that makes them without making too many of them.

Finally, there is the very speculative idea that tiny black holes with masses close to that of the Higgs boson can form at the Large Hadron Collider. This only works if our universe has extra dimensions. So far, there has been no evidence to support this theory.

How do we know that black holes exist?

We have a lot of observational evidence for compact objects with large masses that do not emit light. These objects give themselves away by gravitational attraction, such as the movement of other stars or gas clouds around them. They also create gravitational lensing. We know that these objects do not have a solid surface. This follows from observations, because matter, falling on an object with a surface, should cause the emission of a larger number of particles than matter falling through the horizon.

Why did Hawking say last year that black holes don't exist?

He meant that black holes do not have an eternal event horizon, but only a temporary apparent horizon (see point one). In a strict sense, only the event horizon is considered a black hole.

How do black holes emit radiation?

Black holes emit radiation due to quantum effects. It is important to note that these are quantum effects of matter, not quantum effects of gravity. The dynamic space-time of a collapsing black hole changes the very definition of a particle. Like the passage of time, which is distorted near a black hole, the concept of particles is too dependent on the observer. In particular, when an observer falling into a black hole thinks that he is falling into a vacuum, an observer far from the black hole thinks that this is not a vacuum, but a space full of particles. It is the stretching of space-time that causes this effect.

First discovered by Stephen Hawking, the radiation emitted by a black hole is called "Hawking radiation". This radiation has a temperature that is inversely proportional to the mass of the black hole: the smaller the black hole, the higher the temperature. The stellar and supermassive black holes that we know of have temperatures well below that of the microwave background and are therefore not observed.

What is an information paradox?

The information loss paradox is due to Hawking radiation. This radiation is purely thermal, that is, random and of certain properties it has only temperature. The radiation itself does not contain any information about how the black hole formed. But when a black hole emits radiation, it loses mass and shrinks. All this is completely independent of the matter that became part of the black hole or from which it was formed. It turns out that knowing only the final state of evaporation, it is impossible to say from what the black hole was formed. This process is "irreversible" - and the catch is that there is no such process in quantum mechanics.

It turns out that the evaporation of a black hole is incompatible with quantum theory as we know it, and something needs to be done about it. Fix the inconsistency somehow. Most physicists believe that the solution is that Hawking radiation must contain information in some way.

What does Hawking propose to solve the black hole information paradox?

The idea is that black holes must have a way to store information, which has not yet been accepted. The information is stored at the black hole's horizon and can cause tiny displacements of particles in the Hawking radiation. In these tiny displacements there may be information about the matter that got inside. The exact details of this process are not currently determined. The scientists are awaiting a more detailed technical paper from Stephen Hawking, Malcolm Perry and Andrew Strominger. They say it will appear at the end of September.

At the moment, we are sure that black holes exist, we know where they are, how they are formed and what they will become in the end. But the details of where the information goes into them is still one of the biggest mysteries in the universe.

Due to the relatively recent rise in interest in making popular science films about space exploration, the modern viewer has heard a lot about such phenomena as the singularity, or black hole. However, films obviously do not reveal the full nature of these phenomena, and sometimes even distort the constructed scientific theories for greater effect. For this reason, the idea of ​​many modern people about these phenomena is either completely superficial or completely erroneous. One of the solutions to the problem that has arisen is this article, in which we will try to understand the existing research results and answer the question - what is a black hole?

In 1784, the English priest and naturalist John Michell first mentioned in a letter to the Royal Society a hypothetical massive body that has such a strong gravitational attraction that the second cosmic velocity for it would exceed the speed of light. The second cosmic velocity is the speed that a relatively small object will need to overcome the gravitational attraction of a celestial body and go beyond a closed orbit around this body. According to his calculations, a body with the density of the Sun and with a radius of 500 solar radii will have on its surface a second cosmic velocity equal to the speed of light. In this case, even the light will not leave the surface of such a body, and therefore this body will only absorb the incoming light and remain invisible to the observer - a kind of black spot against the background of dark space.

However, the concept of a supermassive body proposed by Michell did not attract much interest until the work of Einstein. Recall that the latter defined the speed of light as the limiting speed of information transfer. In addition, Einstein expanded the theory of gravity for speeds close to the speed of light (). As a result, it was no longer relevant to apply the Newtonian theory to black holes.

Einstein's equation

As a result of applying general relativity to black holes and solving Einstein's equations, the main parameters of a black hole were revealed, of which there are only three: mass, electric charge, and angular momentum. It should be noted the significant contribution of the Indian astrophysicist Subramanyan Chandrasekhar, who created a fundamental monograph: "The Mathematical Theory of Black Holes".

Thus, the solution of the Einstein equations is represented by four options for four possible types of black holes:

• A black hole without rotation and without a charge is the Schwarzschild solution. One of the first descriptions of a black hole (1916) using Einstein's equations, but without taking into account two of the three parameters of the body. The solution of the German physicist Karl Schwarzschild allows you to calculate the external gravitational field of a spherical massive body. A feature of the German scientist's concept of black holes is the presence of an event horizon and the one behind it. Schwarzschild also first calculated the gravitational radius, which received his name, which determines the radius of the sphere on which the event horizon would be located for a body with a given mass.
• A black hole without rotation with a charge is the Reisner-Nordström solution. A solution put forward in 1916-1918, taking into account the possible electric charge of a black hole. This charge cannot be arbitrarily large and is limited due to the resulting electrical repulsion. The latter must be compensated by gravitational attraction.
• A black hole with rotation and no charge - Kerr's solution (1963). A rotating Kerr black hole differs from a static one by the presence of the so-called ergosphere (read more about this and other components of a black hole).
• BH with rotation and charge - Kerr-Newman solution. This solution was calculated in 1965 and is currently the most complete, since it takes into account all three BH parameters. However, it is still assumed that black holes in nature have an insignificant charge.

The formation of a black hole

There are several theories about how a black hole is formed and appears, the most famous of which is the emergence of a star with sufficient mass as a result of gravitational collapse. Such compression can end the evolution of stars with a mass of more than three solar masses. Upon completion of thermonuclear reactions inside such stars, they begin to rapidly shrink into a superdense one. If the pressure of the gas of a neutron star cannot compensate for the gravitational forces, that is, the mass of the star overcomes the so-called. Oppenheimer-Volkov limit, then the collapse continues, causing matter to shrink into a black hole.

The second scenario describing the birth of a black hole is the compression of protogalactic gas, that is, interstellar gas that is at the stage of transformation into a galaxy or some kind of cluster. In the case of insufficient internal pressure to compensate for the same gravitational forces, a black hole can arise.

Two other scenarios remain hypothetical:

• The occurrence of a black hole as a result - the so-called. primordial black holes.
• Occurrence as a result of nuclear reactions at high energies. An example of such reactions is experiments on colliders.

Structure and physics of black holes

The structure of a black hole according to Schwarzschild includes only two elements that were mentioned earlier: the singularity and the event horizon of a black hole. Briefly speaking about the singularity, it can be noted that it is impossible to draw a straight line through it, and also that most of the existing physical theories do not work inside it. Thus, the physics of the singularity remains a mystery to scientists today. of a black hole is a certain boundary, crossing which, a physical object loses the ability to return back beyond its limits and unambiguously “falls” into the singularity of a black hole.

The structure of a black hole becomes somewhat more complicated in the case of the Kerr solution, namely, in the presence of BH rotation. Kerr's solution implies that the hole has an ergosphere. Ergosphere - a certain area located outside the event horizon, inside which all bodies move in the direction of rotation of the black hole. This area is not yet exciting and it is possible to leave it, unlike the event horizon. The ergosphere is probably a kind of analogue of an accretion disk, which represents a rotating substance around massive bodies. If a static Schwarzschild black hole is represented as a black sphere, then the Kerry black hole, due to the presence of an ergosphere, has the shape of an oblate ellipsoid, in the form of which we often saw black holes in drawings, in old movies or video games.

• How much does a black hole weigh? – The largest theoretical material on the appearance of a black hole is available for the scenario of its appearance as a result of the collapse of a star. In this case, the maximum mass of a neutron star and the minimum mass of a black hole are determined by the Oppenheimer - Volkov limit, according to which the lower limit of the BH mass is 2.5 - 3 solar masses. The heaviest black hole ever discovered (in the galaxy NGC 4889) has a mass of 21 billion solar masses. However, one should not forget about black holes, hypothetically resulting from nuclear reactions at high energies, such as those at colliders. The mass of such quantum black holes, in other words "Planck black holes" is of the order of , namely 2 10 −5 g.
• Black hole size. The minimum BH radius can be calculated from the minimum mass (2.5 – 3 solar masses). If the gravitational radius of the Sun, that is, the area where the event horizon would be, is about 2.95 km, then the minimum radius of a BH of 3 solar masses will be about nine kilometers. Such relatively small sizes do not fit in the head when it comes to massive objects that attract everything around. However, for quantum black holes, the radius is -10 −35 m.
• The average density of a black hole depends on two parameters: mass and radius. The density of a black hole with a mass of about three solar masses is about 6 10 26 kg/m³, while the density of water is 1000 kg/m³. However, such small black holes have not been found by scientists. Most of the detected BHs have masses greater than 105 solar masses. There is an interesting pattern according to which the more massive the black hole, the lower its density. In this case, a change in mass by 11 orders of magnitude entails a change in density by 22 orders of magnitude. Thus, a black hole with a mass of 1 ·10 9 solar masses has a density of 18.5 kg/m³, which is one less than the density of gold. And black holes with a mass of more than 10 10 solar masses can have an average density less than the density of air. Based on these calculations, it is logical to assume that the formation of a black hole occurs not due to the compression of matter, but as a result of the accumulation of a large amount of matter in a certain volume. In the case of quantum black holes, their density can be about 10 94 kg/m³.
• The temperature of a black hole is also inversely proportional to its mass. This temperature is directly related to . The spectrum of this radiation coincides with the spectrum of a completely black body, that is, a body that absorbs all incident radiation. The radiation spectrum of a black body depends only on its temperature, then the temperature of a black hole can be determined from the Hawking radiation spectrum. As mentioned above, this radiation is the more powerful, the smaller the black hole. At the same time, Hawking radiation remains hypothetical, since it has not yet been observed by astronomers. It follows from this that if Hawking radiation exists, then the temperature of the observed BHs is so low that it does not allow one to detect the indicated radiation. According to calculations, even the temperature of a hole with a mass of the order of the mass of the Sun is negligibly small (1 10 -7 K or -272°C). The temperature of quantum black holes can reach about 10 12 K, and with their rapid evaporation (about 1.5 min.), such black holes can emit energy of the order of ten million atomic bombs. But, fortunately, the creation of such hypothetical objects will require energy 10 14 times greater than that achieved today at the Large Hadron Collider. In addition, such phenomena have never been observed by astronomers.

What is a CHD made of?

Another question worries both scientists and those who are simply fond of astrophysics - what does a black hole consist of? There is no single answer to this question, since it is not possible to look beyond the event horizon surrounding any black hole. In addition, as mentioned earlier, the theoretical models of a black hole provide for only 3 of its components: the ergosphere, the event horizon, and the singularity. It is logical to assume that in the ergosphere there are only those objects that were attracted by the black hole, and which now revolve around it - various kinds of cosmic bodies and cosmic gas. The event horizon is just a thin implicit border, once beyond which, the same cosmic bodies are irrevocably attracted towards the last main component of the black hole - the singularity. The nature of the singularity has not been studied today, and it is too early to talk about its composition.

According to some assumptions, a black hole may consist of neutrons. If we follow the scenario of the occurrence of a black hole as a result of the compression of a star to a neutron star with its subsequent compression, then, probably, the main part of the black hole consists of neutrons, of which the neutron star itself consists. In simple words: when a star collapses, its atoms are compressed in such a way that electrons combine with protons, thereby forming neutrons. Such a reaction does indeed take place in nature, with the formation of a neutron, neutrino emission occurs. However, these are just guesses.

What happens if you fall into a black hole?

Falling into an astrophysical black hole leads to stretching of the body. Consider a hypothetical suicide astronaut heading into a black hole wearing nothing but a space suit, feet first. Crossing the event horizon, the astronaut will not notice any changes, despite the fact that he no longer has the opportunity to get back. At some point, the astronaut will reach a point (slightly behind the event horizon) where the deformation of his body will begin to occur. Since the gravitational field of a black hole is non-uniform and is represented by a force gradient increasing towards the center, the astronaut's legs will be subjected to a noticeably greater gravitational effect than, for example, the head. Then, due to gravity, or rather, tidal forces, the legs will “fall” faster. Thus, the body begins to gradually stretch in length. To describe this phenomenon, astrophysicists have come up with a rather creative term - spaghettification. Further stretching of the body will probably decompose it into atoms, which, sooner or later, will reach a singularity. One can only guess how a person will feel in this situation. It is worth noting that the effect of stretching the body is inversely proportional to the mass of the black hole. That is, if a BH with the mass of three Suns instantly stretches/breaks the body, then the supermassive black hole will have lower tidal forces and, there are suggestions that some physical materials could “tolerate” such a deformation without losing their structure.

As you know, near massive objects, time flows more slowly, which means that time for a suicide astronaut will flow much more slowly than for earthlings. In that case, perhaps he will outlive not only his friends, but the Earth itself. Calculations will be required to determine how much time will slow down for an astronaut, but from the above it can be assumed that the astronaut will fall into the black hole very slowly and may simply not live to see the moment when his body begins to deform.

It is noteworthy that for an observer outside, all bodies that have flown up to the event horizon will remain at the edge of this horizon until their image disappears. The reason for this phenomenon is the gravitational redshift. Simplifying somewhat, we can say that the light falling on the body of a suicide astronaut "frozen" at the event horizon will change its frequency due to its slowed down time. As time passes more slowly, the frequency of light will decrease and the wavelength will increase. As a result of this phenomenon, at the output, that is, for an external observer, the light will gradually shift towards the low-frequency - red. A shift of light along the spectrum will take place, as the suicide astronaut moves further and further away from the observer, albeit almost imperceptibly, and his time flows more and more slowly. Thus, the light reflected by his body will soon go beyond the visible spectrum (the image will disappear), and in the future the astronaut's body can only be detected in the infrared region, later in the radio frequency region, and as a result, the radiation will be completely elusive.

Despite what has been written above, it is assumed that in very large supermassive black holes, tidal forces do not change so much with distance and act almost uniformly on the falling body. In such a case, the falling spacecraft would retain its structure. A reasonable question arises - where does the black hole lead? This question can be answered by the work of some scientists, linking two such phenomena as wormholes and black holes.

Back in 1935, Albert Einstein and Nathan Rosen, taking into account, put forward a hypothesis about the existence of so-called wormholes, connecting two points of space-time by way in places of significant curvature of the latter - the Einstein-Rosen bridge or wormhole. For such a powerful curvature of space, bodies with a gigantic mass will be required, with the role of which black holes would perfectly cope.

The Einstein-Rosen Bridge is considered an impenetrable wormhole, as it is small and unstable.

A traversable wormhole is possible within the theory of black and white holes. Where the white hole is the output of information that fell into the black hole. The white hole is described in the framework of general relativity, but today it remains hypothetical and has not been discovered. Another model of a wormhole was proposed by American scientists Kip Thorne and his graduate student Mike Morris, which can be passable. However, as in the case of the Morris-Thorn wormhole, as well as in the case of black and white holes, the possibility of travel requires the existence of so-called exotic matter, which has negative energy and also remains hypothetical.

Black holes in the universe

The existence of black holes was confirmed relatively recently (September 2015), but before that time there was already a lot of theoretical material on the nature of black holes, as well as many candidate objects for the role of a black hole. First of all, one should take into account the dimensions of the black hole, since the very nature of the phenomenon depends on them:

• stellar mass black hole. Such objects are formed as a result of the collapse of a star. As mentioned earlier, the minimum mass of a body capable of forming such a black hole is 2.5 - 3 solar masses.
• Intermediate mass black holes. A conditional intermediate type of black holes that have increased due to the absorption of nearby objects, such as gas accumulations, a neighboring star (in systems of two stars) and other cosmic bodies.
• Supermassive black hole. Compact objects with 10 5 -10 10 solar masses. Distinctive properties of such BHs are paradoxically low density, as well as weak tidal forces, which were discussed earlier. It is this supermassive black hole at the center of our Milky Way galaxy (Sagittarius A*, Sgr A*), as well as most other galaxies.

Candidates for CHD

The nearest black hole, or rather a candidate for the role of a black hole, is an object (V616 Unicorn), which is located at a distance of 3000 light years from the Sun (in our galaxy). It consists of two components: a star with a mass of half the solar mass, as well as an invisible small body, the mass of which is 3-5 solar masses. If this object turns out to be a small black hole of stellar mass, then by right it will be the nearest black hole.

Following this object, the second closest black hole is Cyg X-1 (Cyg X-1), which was the first candidate for the role of a black hole. The distance to it is approximately 6070 light years. Quite well studied: it has a mass of 14.8 solar masses and an event horizon radius of about 26 km.

According to some sources, another closest candidate for the role of a black hole may be a body in the star system V4641 Sagittarii (V4641 Sgr), which, according to estimates in 1999, was located at a distance of 1600 light years. However, subsequent studies increased this distance by at least 15 times.

How many black holes are in our galaxy?

There is no exact answer to this question, since it is rather difficult to observe them, and during the entire study of the sky, scientists managed to detect about a dozen black holes within the Milky Way. Without indulging in calculations, we note that in our galaxy there are about 100 - 400 billion stars, and about every thousandth star has enough mass to form a black hole. It is likely that millions of black holes could have formed during the existence of the Milky Way. Since it is easier to register huge black holes, it is logical to assume that most of the BHs in our galaxy are not supermassive. It is noteworthy that NASA research in 2005 suggests the presence of a whole swarm of black holes (10-20 thousand) orbiting the center of the galaxy. In addition, in 2016, Japanese astrophysicists discovered a massive satellite near the object * - a black hole, the core of the Milky Way. Due to the small radius (0.15 light years) of this body, as well as its huge mass (100,000 solar masses), scientists suggest that this object is also a supermassive black hole.

The core of our galaxy, the black hole of the Milky Way (Sagittarius A *, Sgr A * or Sagittarius A *) is supermassive and has a mass of 4.31 10 6 solar masses, and a radius of 0.00071 light years (6.25 light hours or 6.75 billion km). The temperature of Sagittarius A* together with the cluster around it is about 1 10 7 K.

The biggest black hole

The largest black hole in the universe that scientists have been able to detect is a supermassive black hole, the FSRQ blazar, at the center of the galaxy S5 0014+81, at a distance of 1.2·10 10 light-years from Earth. According to preliminary results of observation, using the Swift space observatory, the mass of the black hole was 40 billion (40 10 9) solar masses, and the Schwarzschild radius of such a hole was 118.35 billion kilometers (0.013 light years). In addition, according to calculations, it arose 12.1 billion years ago (1.6 billion years after the Big Bang). If this giant black hole does not absorb the matter surrounding it, then it will live to see the era of black holes - one of the eras in the development of the Universe, during which black holes will dominate in it. If the core of the galaxy S5 0014+81 continues to grow, then it will become one of the last black holes that will exist in the Universe.

The other two known black holes, although not named, are of the greatest importance for the study of black holes, as they confirmed their existence experimentally, and also gave important results for the study of gravity. We are talking about the event GW150914, which is called the collision of two black holes into one. This event allowed to register .

Detection of black holes

Before considering methods for detecting black holes, one should answer the question - why is a black hole black? - the answer to it does not require deep knowledge in astrophysics and cosmology. The fact is that a black hole absorbs all the radiation falling on it and does not radiate at all, if you do not take into account the hypothetical. If we consider this phenomenon in more detail, we can assume that there are no processes inside black holes that lead to the release of energy in the form of electromagnetic radiation. Then if the black hole radiates, then it is in the Hawking spectrum (which coincides with the spectrum of a heated, absolutely black body). However, as mentioned earlier, this radiation was not detected, which suggests a completely low temperature of black holes.

Another generally accepted theory says that electromagnetic radiation is not at all capable of leaving the event horizon. It is most likely that photons (particles of light) are not attracted by massive objects, since, according to the theory, they themselves have no mass. However, the black hole still "attracts" the photons of light through the distortion of space-time. If we imagine a black hole in space as a kind of depression on the smooth surface of space-time, then there is a certain distance from the center of the black hole, approaching which the light will no longer be able to move away from it. That is, roughly speaking, the light begins to "fall" into the "pit", which does not even have a "bottom".

In addition, if we take into account the effect of gravitational redshift, it is possible that light in a black hole loses its frequency, shifting along the spectrum to the region of low-frequency long-wave radiation, until it loses energy altogether.

So, a black hole is black and therefore difficult to detect in space.

Detection methods

Consider the methods that astronomers use to detect a black hole:

In addition to the methods mentioned above, scientists often associate objects such as black holes and. Quasars are some clusters of cosmic bodies and gas, which are among the brightest astronomical objects in the Universe. Since they have a high intensity of luminescence at relatively small sizes, there is reason to believe that the center of these objects is a supermassive black hole, which attracts the surrounding matter to itself. Due to such a powerful gravitational attraction, the attracted matter is so heated that it radiates intensely. The detection of such objects is usually compared with the detection of a black hole. Sometimes quasars can emit jets of heated plasma in two directions - relativistic jets. The reasons for the emergence of such jets (jet) are not completely clear, but they are probably caused by the interaction of the magnetic fields of the BH and the accretion disk, and are not emitted by a direct black hole.

A jet in the M87 galaxy hitting from the center of a black hole

Summing up the above, one can imagine, up close: it is a spherical black object, around which strongly heated matter rotates, forming a luminous accretion disk.

Merging and colliding black holes

One of the most interesting phenomena in astrophysics is the collision of black holes, which also makes it possible to detect such massive astronomical bodies. Such processes are of interest not only to astrophysicists, since they result in phenomena poorly studied by physicists. The clearest example is the previously mentioned event called GW150914, when two black holes approached so much that, as a result of mutual gravitational attraction, they merged into one. An important consequence of this collision was the emergence of gravitational waves.

According to the definition of gravitational waves, these are changes in the gravitational field that propagate in a wave-like manner from massive moving objects. When two such objects approach each other, they begin to rotate around a common center of gravity. As they approach each other, their rotation around their own axis increases. Such variable oscillations of the gravitational field at some point can form one powerful gravitational wave that can propagate in space for millions of light years. So, at a distance of 1.3 billion light years, a collision of two black holes occurred, which formed a powerful gravitational wave that reached the Earth on September 14, 2015 and was recorded by the LIGO and VIRGO detectors.

How do black holes die?

Obviously, for a black hole to cease to exist, it would need to lose all of its mass. However, according to her definition, nothing can leave the black hole if it has crossed its event horizon. It is known that for the first time the Soviet theoretical physicist Vladimir Gribov mentioned the possibility of emission of particles by a black hole in his discussion with another Soviet scientist Yakov Zeldovich. He argued that from the point of view of quantum mechanics, a black hole is capable of emitting particles through a tunnel effect. Later, with the help of quantum mechanics, he built his own, somewhat different theory, the English theoretical physicist Stephen Hawking. You can read more about this phenomenon. In short, there are so-called virtual particles in vacuum, which are constantly born in pairs and annihilate each other, while not interacting with the outside world. But if such pairs arise at the black hole's event horizon, then strong gravity is hypothetically able to separate them, with one particle falling into the black hole, and the other going away from the black hole. And since a particle that has flown away from a hole can be observed, and therefore has positive energy, a particle that has fallen into a hole must have negative energy. Thus, the black hole will lose its energy and there will be an effect called black hole evaporation.

According to the available models of a black hole, as mentioned earlier, as its mass decreases, its radiation becomes more intense. Then at the final stage of the existence of a black hole, when it will possibly decrease to the size of a quantum black hole, it will release a huge amount of energy in the form of radiation, which can be equivalent to thousands or even millions of atomic bombs. This event is somewhat reminiscent of the explosion of a black hole, like the same bomb. According to calculations, primordial black holes could have been born as a result of the Big Bang, and those of them, the mass of which is on the order of 10 12 kg, should have evaporated and exploded around our time. Be that as it may, such explosions have never been seen by astronomers.

Despite the mechanism proposed by Hawking for the destruction of black holes, the properties of Hawking radiation cause a paradox in the framework of quantum mechanics. If a black hole absorbs some body, and then loses the mass resulting from the absorption of this body, then regardless of the nature of the body, the black hole will not differ from what it was before the absorption of the body. In this case, information about the body is forever lost. From the point of view of theoretical calculations, the transformation of the initial pure state into the resulting mixed (“thermal”) state does not correspond to the current theory of quantum mechanics. This paradox is sometimes called the disappearance of information in a black hole. A real solution to this paradox has never been found. Known options for solving the paradox:

• Inconsistency of Hawking's theory. This entails the impossibility of destroying the black hole and its constant growth.
• The presence of white holes. In this case, the absorbed information does not disappear, but is simply thrown out into another Universe.
• Inconsistency of the generally accepted theory of quantum mechanics.

Unsolved problem of black hole physics

Judging by everything that was described earlier, black holes, although they have been studied for a relatively long time, still have many features, the mechanisms of which are still not known to scientists.

• In 1970, an English scientist formulated the so-called. "principle of cosmic censorship" - "Nature abhors the bare singularity." This means that the singularity is formed only in places hidden from view, like the center of a black hole. However, this principle has not yet been proven. There are also theoretical calculations according to which a "naked" singularity can occur.
• The “no-hair theorem”, according to which black holes have only three parameters, has not been proven either.
• A complete theory of the black hole magnetosphere has not been developed.
• The nature and physics of the gravitational singularity has not been studied.
• It is not known for certain what happens at the final stage of the existence of a black hole, and what remains after its quantum decay.

Interesting facts about black holes

Summing up the above, we can highlight several interesting and unusual features of the nature of black holes:

• Black holes have only three parameters: mass, electric charge and angular momentum. As a result of such a small number of characteristics of this body, the theorem stating this is called the "no-hair theorem". This is also where the phrase “a black hole has no hair” came from, which means that two black holes are absolutely identical, their three parameters mentioned are the same.
• The density of black holes can be less than the density of air, and the temperature is close to absolute zero. From this we can assume that the formation of a black hole occurs not due to the compression of matter, but as a result of the accumulation of a large amount of matter in a certain volume.
• Time for bodies absorbed by black holes goes much slower than for an external observer. In addition, the absorbed bodies are significantly stretched inside the black hole, which has been called spaghettification by scientists.
• There may be about a million black holes in our galaxy.
• There is probably a supermassive black hole at the center of every galaxy.
• In the future, according to the theoretical model, the Universe will reach the so-called era of black holes, when black holes will become the dominant bodies in the Universe.

Black holes, dark matter, dark matter... These are undoubtedly the strangest and most mysterious objects in space. Their bizarre properties can defy the laws of physics in the universe and even the nature of existing reality. To understand what black holes are, scientists offer to “change landmarks”, learn to think outside the box and apply a little imagination. Black holes are formed from the cores of super massive stars, which can be described as a region of space where a huge mass is concentrated in the void, and nothing, not even light, can escape the gravitational attraction there. This is the area where the second space velocity exceeds the speed of light: And the more massive the object of motion, the faster it must move in order to get rid of its gravity. This is known as the second escape velocity.

The Collier Encyclopedia calls a black hole a region in space that has arisen as a result of a complete gravitational collapse of matter, in which the gravitational attraction is so strong that neither matter, nor light, nor other information carriers can leave it. Therefore, the interior of a black hole is causally unrelated to the rest of the universe; physical processes occurring inside a black hole cannot affect processes outside it. A black hole is surrounded by a surface with the property of a unidirectional membrane: matter and radiation freely fall through it into the black hole, but nothing can escape from it. This surface is called the "event horizon".

Discovery history

Black holes, predicted by the general theory of relativity (the theory of gravity proposed by Einstein in 1915) and other more modern theories of gravity, were mathematically substantiated by R. Oppenheimer and H. Snyder in 1939. But the properties of space and time in the vicinity of these objects turned out to be so unusual, that astronomers and physicists did not take them seriously for 25 years. However, astronomical discoveries in the mid-1960s forced us to look at black holes as a possible physical reality. New discoveries and studies can fundamentally change our understanding of space and time, shedding light on billions of cosmic mysteries.

Formation of black holes

While thermonuclear reactions take place in the interior of the star, they maintain high temperature and pressure, preventing the star from collapsing under the influence of its own gravity. However, over time, the nuclear fuel is depleted, and the star begins to shrink. Calculations show that if the mass of a star does not exceed three solar masses, then it will win the “battle with gravity”: its gravitational collapse will be stopped by the pressure of “degenerate” matter, and the star will forever turn into a white dwarf or neutron star. But if the mass of a star is more than three solar, then nothing can stop its catastrophic collapse and it will quickly go under the event horizon, becoming a black hole.

Is a black hole a donut hole?

Anything that doesn't emit light is hard to see. One way to search for a black hole is to look for areas in outer space that have a lot of mass and are in dark space. When searching for these types of objects, astronomers have found them in two main areas: at the centers of galaxies and in binary star systems in our galaxy. In total, as scientists suggest, there are tens of millions of such objects.

At present, the only reliable way to distinguish a black hole from another type of object is to measure the mass and size of the object and compare its radius with

Consider the mysterious and invisible black holes in the Universe: interesting facts, Einstein's research, supermassive and intermediate types, theory, structure.

- one of the most interesting and mysterious objects in outer space. They have a high density, and the gravitational force is so powerful that even light cannot escape beyond it.

For the first time, Albert Einstein spoke about black holes in 1916, when he created the general theory of relativity. The term itself originated in 1967 thanks to John Wheeler. And the first black hole was "noted" in 1971.

The classification of black holes includes three types: stellar mass black holes, supermassive and intermediate mass black holes. Be sure to watch the video about black holes to learn a lot of interesting facts and get to know these mysterious cosmic formations better.

Interesting facts about black holes

• If you are inside a black hole, then gravity will stretch you. But there is no need to be afraid, because you will die before you even reach the singularity. A 2012 study suggested that quantum effects turn the event horizon into a wall of fire that turns you into a pile of ash.
• Black holes don't "suck in". This process is caused by vacuum, which is not present in this formation. So the material just falls.
• The first black hole was Cygnus X-1, found by rockets with Geiger counters. In 1971, scientists received a radio signal from Cygnus X-1. This object became the subject of a dispute between Kip Thorne and Stephen Hawking. The latter believed that this is not a black hole. In 1990, he admitted defeat.
• Tiny black holes could have appeared right after the Big Bang. Rapidly rotating space squeezed some areas into dense holes, with less massiveness than the Sun.
• If the star gets too close, it can break.
• According to general estimates, there are up to about a billion stellar black holes with a mass three times that of the sun.
• If we compare string theory and classical mechanics, then the former generates more varieties of massive giants.

The danger of black holes

When a star runs out of fuel, it can start the process of self-destruction. If its mass was three times that of the sun, then the remaining core would become a neutron star or a white dwarf. But the larger star transforms into a black hole.

Such objects are small, but have incredible density. Imagine that in front of you is an object the size of a city, but its mass is three times that of the sun. This creates an incredibly huge gravitational force that attracts dust and gas, increasing its size. You will be surprised, but several hundred million stellar black holes can be located in it.

Supermassive black holes

Of course, nothing in the universe compares to the terrifying supermassive black holes. They are billions of times the mass of the sun. It is believed that such objects exist in almost every galaxy. Scientists do not yet know all the intricacies of the formation process. Most likely, they grow due to the accumulation of mass from the surrounding dust and gas.

Perhaps they owe their scale to the merger of thousands of small black holes. Or an entire star cluster could collapse.

Black holes at the centers of galaxies

Astrophysicist Olga Silchenko on the discovery of a supermassive black hole in the Andromeda Nebula, research by John Kormendy and dark gravitating bodies:

Nature of cosmic radio sources

Astrophysicist Anatoly Zasov about synchrotron radiation, black holes in the nuclei of distant galaxies and neutral gas:

intermediate black holes

Not so long ago, scientists have found a new type - black holes of medium mass (intermediate). They can form when stars in a cluster collide in a chain reaction. As a result, they fall to the center and form a supermassive black hole.

In 2014, astronomers discovered an intermediate type in the arm of a spiral galaxy. They are very difficult to find because they can be located in unpredictable places.

micro black holes

Physicist Eduard Boos on the safety of the LHC, the birth of a microblack hole and the concept of a membrane:

Theory of black holes

Black holes are extremely massive objects, but cover a relatively modest amount of space. In addition, they have a huge gravity, not allowing objects (and even light) to leave their territory. However, they cannot be seen directly. Researchers have to turn to the radiation that comes out when a black hole is fed.

Interestingly, it happens that matter heading for a black hole bounces off the event horizon and is thrown out. In this case, bright jets of material are formed, moving at relativistic speeds. These emissions can be fixed at long distances.

- amazing objects in which the force of gravity is so huge that it can bend light, warp space and distort time.

Black holes can be divided into three layers: the outer and inner event horizons and the singularity.

The event horizon of a black hole is the boundary where light has no chance of escaping. As soon as a particle crosses this boundary, it will not be able to leave. The inner region where the black hole's mass is located is called the singularity.

If we speak from the standpoint of classical mechanics, then nothing can leave a black hole. But quantum makes its own correction. The point is that every particle has an antiparticle. They have the same masses but different charges. If they intersect, they can annihilate each other.

When such a pair occurs outside the event horizon, then one of them can be drawn in, and the second will be repelled. Because of this, the horizon can shrink, and the black hole can collapse. Scientists are still trying to study this mechanism.

accretion

Astrophysicist Sergei Popov on supermassive black holes, planet formation and matter accretion in the early Universe:

The most famous black holes

Frequently Asked Questions About Black Holes

If more capaciously, then a black hole is a certain area in space in which such a huge amount of mass is concentrated that not a single object can escape the gravitational influence. When it comes to gravity, we rely on the general theory of relativity proposed by Albert Einstein. To understand the details of the object under study, we will move step by step.

Let's imagine that you are on the surface of the planet and throw up a rock. If you don't have the power of the Hulk, you won't be able to apply enough force. Then the stone will rise to a certain height, but under the pressure of gravity it will collapse back. If you have the hidden potential of the green strongman, then you are able to give the object sufficient acceleration, due to which it completely leaves the zone of gravitational influence. This is called "runaway speed".

If broken down into a formula, then this speed depends on the planetary mass. The larger it is, the more powerful the gravitational grip. The departure speed will depend on exactly where you are: the closer to the center, the easier it is to get out. The departure speed of our planet is 11.2 km/s, but it is 2.4 km/s.

We are approaching the most interesting. Let's say you have an object with an incredible concentration of mass gathered in a tiny place. In this case, the escape velocity exceeds the speed of light. And we know that nothing moves faster than this indicator, which means that no one can overcome such a force and escape. Not even a beam of light can do it!

Back in the 18th century, Laplace reflected on the extreme concentration of mass. Following general relativity, Karl Schwarzschild was able to find a mathematical solution to the theory's equation to describe a similar object. Further contributions were made by Oppenheimer, Wolkoff, and Snyder (1930s). From that moment on, people began to discuss this topic in earnest. It became clear that when a massive star runs out of fuel, it is unable to withstand the force of gravity and must collapse into a black hole.

In Einstein's theory, gravity is a manifestation of curvature in space and time. The fact is that the usual geometric rules do not work here and massive objects distort space-time. A black hole has bizarre properties, so its distortion is most clearly visible. For example, an object has an "event horizon". This is the surface of the sphere, marking the feature of the hole. That is, if you step over this limit, then there is no turning back.

Literally, this is the place where the speed of escape is equal to the speed of light. Outside this point, the escape velocity is less than the speed of light. But if your rocket is capable of accelerating, then there will be enough energy to escape.

The horizon itself is rather strange in terms of geometry. If you are far away, you will feel like you are looking at a static surface. But if you get closer, then you realize that it is moving outward at the speed of light! Now I understand why it is easy to enter, but so difficult to escape. Yes, this is very confusing, because in fact the horizon is standing still, but at the same time it is rushing at the speed of light. It's like in the situation with Alice, who had to run as fast as possible just to stay in place.

When hitting the horizon, space and time experience such a strong distortion that the coordinates begin to describe the roles of radial distance and switching time. That is, "r", which marks the distance from the center, becomes temporary, and "t" is now responsible for "spatiality". As a result, you will not be able to stop moving with a smaller r, just as you will not be able to get into the future in normal time. You will come to a singularity, where r = 0. You can throw rockets, run the engine to the maximum, but you cannot escape.

The term "black hole" was coined by John Archibald Wheeler. Prior to that, they were called "cooled stars."

Physicist Emil Akhmedov on the study of black holes, Karl Schwarzschild and giant black holes:

There are two ways to calculate how big something is. You can name the mass or what size the area occupies. If we take the first criterion, then there is no specific limit to the massiveness of a black hole. You can use any amount as long as you can compress it to the right density.

Most of these formations appeared after the death of massive stars, so we can expect that their weight should be equivalent. The typical mass for such a hole should be 10 times greater than the sun's - 10 31 kg. In addition, each galaxy must have a central supermassive black hole, whose mass exceeds the solar one by a million times - 10 36 kg.

The more massive the object, the more mass it encompasses. The horizon radius and mass are directly proportional, that is, if a black hole weighs 10 times more than another, then its radius is 10 times larger. The radius of a hole with solar massiveness is 3 km, and if it is a million times larger, then 3 million km. It seems that these are incredibly massive things. But let's not forget that for astronomy these are standard concepts. The solar radius reaches 700,000 km, while a black hole has 4 times more.

Let's say you're out of luck and your ship is heading inexorably towards a supermassive black hole. There is no point in fighting. You just turned off the engines and go towards the inevitable. What to expect?

Let's start with weightlessness. You are in free fall, so the crew, the ship and all the details are weightless. The closer you get to the center of the hole, the stronger the tidal gravitational forces are felt. For example, your legs are closer to the center than your head. Then you begin to feel like you are being stretched. In the end, you will just be torn to pieces.

These forces are inconspicuous until you come within 600,000 km of the center. It's already beyond the horizon. But we are talking about a huge object. If you fall into a solar-mass hole, the tidal forces would engulf you 6,000 km from the center and tear you apart before you got to the horizon (which is why we send you into a big one so you can die inside the hole, not on the way) .

What is inside? I don't want to disappoint, but nothing remarkable. Some objects may be distorted in appearance and nothing else out of the ordinary. Even after crossing the horizon, you will see things around you as they move with you.

How long will all this take? Everything depends on your distance. For example, you started from a point of rest, where the singularity is 10 times the radius of the hole. It will take only 8 minutes to approach the horizon, and then another 7 seconds to enter the singularity. If you fall into a small black hole, then everything will happen faster.

As soon as you step over the horizon, you can shoot rockets, scream and cry. You have 7 seconds for all this, until you get into the singularity. But nothing will save. So just enjoy the ride.

Let's say you are doomed and fall into a hole, and your friend / girlfriend is watching from afar. Well, he will see things differently. He will notice that closer to the horizon you will slow down. But even if a person sits for a hundred years, he will not wait until you reach the horizon.

Let's try to explain. A black hole could have come from a collapsing star. Since the material is being destroyed, Cyril (let him be your friend) sees its decrease, but he will never notice the approach to the horizon. That is why they were called "frozen stars", because they seem to freeze with a certain radius.

What's the matter? Let's call it an optical illusion. To form a hole, infinity is not needed, as well as to cross the horizon. As you approach, the light takes longer to reach Cyril. To be more precise, the real-time radiation from your transition will be fixed at the horizon forever. You have already stepped over the line for a long time, and Kirill is still watching the light signal.

Or you can approach from the other side. Time stretches longer near the horizon. For example, you have a super-powerful ship. You managed to approach the horizon, stay there for a couple of minutes and get out alive to Kirill. Who will you see? Old man! For you, time passed much more slowly.

What then is true? Illusion or game of time? It all depends on the coordinate system used to describe the black hole. If we rely on the Schwarzschild coordinates, then when crossing the horizon, the time coordinate (t) is equated to infinity. But the indicators of this system provide a blurry view of what is happening near the object itself. At the horizon line, all coordinates are distorted (singularity). But you can use both coordinate systems, so two answers are valid.

In reality, you will simply become invisible, and Cyril will stop seeing you even before a lot of time has passed. Don't forget about redshift. You emit observable light at a certain wavelength, but Cyril will see it at a longer wavelength. Waves lengthen as they approach the horizon. In addition, do not forget that radiation occurs in certain photons.

For example, at the moment of transition, you will send the last photon. It will reach Cyril at a certain finite time (about an hour for a supermassive black hole).

Of course not. Don't forget about the existence of the event horizon. Only from this area you cannot get out. It is enough just not to approach her and feel calm. Moreover, from a safe distance, this object will seem the most ordinary to you.

Hawking's Information Paradox

Physicist Emil Akhmedov on the effect of gravity on electromagnetic waves, the informational paradox of black holes and the principle of predictability in science:

Don't panic, as the Sun will never transform into such an object because it simply doesn't have enough mass. Moreover, it will retain its current appearance for another 5 billion years. Then it will move to the stage of the red giant, absorbing Mercury, Venus and frying our planet well, and then it will become an ordinary white dwarf.

But let's indulge in fantasy. So the sun became a black hole. To begin with, darkness and cold will immediately envelop us. Earth and other planets will not be sucked into the hole. They will continue to revolve around the new object in normal orbits. Why? Because the horizon will reach only 3 km, and gravity will not be able to do anything with us.

Yes. Naturally, we cannot rely on visible observation, since the light fails to escape. But there is circumstantial evidence. For example, you see an area where there could be a black hole. How to check it? Start by measuring your weight. If you can see that there is too much of it in one area or it seems to be invisible, then you are on the right track. There are two search points: the galactic center and X-ray binary systems.

Thus, massive central objects were found in 8 galaxies, whose mass of nuclei ranges from a million to a billion solar. The mass is calculated by observing the speed of rotation of stars and gas around the center. The faster, the more mass must be to keep them in orbit.

These massive objects are considered black holes for two reasons. Well, there are simply no other options. There is nothing more massive, darker and more compact. In addition, there is a theory that all active and large galaxies have such a monster hiding in the center. However, this is not 100% proof.

But two recent findings speak in favor of the theory. Near the nearest active galaxy, a "water maser" system (a powerful source of microwave radiation) was noticed near the nucleus. Using an interferometer, scientists displayed the distribution of gas velocities. That is, they measured the speed within half a light year at the galactic center. This helped them understand that there is a massive object inside, whose radius reaches half a light year.

The second find is even more convincing. Using X-rays, researchers stumbled upon the spectral line of the galactic nucleus, indicating the presence of nearby atoms, the speed of which is incredibly high (1/3 of the speed of light). In addition, the radiation corresponded to the redshift, which corresponds to the horizon of the black hole.

Another class can be found in the Milky Way. These are stellar black holes that form after a supernova explosion. If they existed separately, then even close we would hardly notice it. But we are lucky, because most exist in binary systems. They are easy to find, since the black hole will pull the mass of its neighbor and influence it with gravity. The “torn out” material forms an accretion disk, in which everything heats up, which means it creates strong radiation.

Suppose you managed to find a binary system. How to understand that a compact object is a black hole? Again we turn to the masses. To do this, measure the orbital velocity of a neighboring star. If the mass is incredibly huge for such a small size, then there are no more options.

This is a complex mechanism. Stephen Hawking raised a similar topic back in the 1970s. He said that black holes are not exactly "black". There are quantum mechanical effects that cause it to create radiation. Gradually, the hole begins to shrink. The rate of radiation increases with decreasing mass, so the hole radiates more and accelerates the process of contraction until it dissolves.

However, this is only a theoretical scheme, because no one can say exactly what happens at the last stage. Some think that a small but stable footprint remains. Modern theories have not yet come up with anything better. But the process itself is incredible and complex. It is necessary to calculate the parameters in a curved space-time, and the results themselves cannot be verified under the usual conditions.

Here you can use the Law of Conservation of Energy, but only for short durations. The universe can create energy and mass from scratch, but they must quickly disappear. One of the manifestations is vacuum fluctuations. Pairs of particles and antiparticles grow out of nowhere, exist for a certain short period of time and perish in mutual annihilation. When they appear, the energy balance is disturbed, but everything is restored after the disappearance. It seems fantastic, but this mechanism has been confirmed experimentally.

Let's say one of the vacuum fluctuations acts near the horizon of a black hole. Perhaps one of the particles falls inward, while the second one escapes. The escapee takes with her part of the energy of the hole and can fall into the eyes of the observer. It will seem to him that the dark object simply released a particle. But the process repeats itself, and we see a continuous stream of radiation from the black hole.

We have already said that it seems to Cyril that you need infinity to step over the horizon line. In addition, it was mentioned that black holes evaporate after a finite time interval. So when you reach the horizon, the hole will disappear?

No. When we described Kirill's observations, we did not talk about the evaporation process. But, if this process is present, then everything changes. Your friend will see you fly over the horizon just at the moment of evaporation. Why?

Cyril is dominated by an optical illusion. Emitted light in the event horizon takes a long time to get to a friend. If the hole lasts forever, then the light can travel indefinitely, and Kirill will not wait for the transition. But, if the hole has evaporated, then nothing will stop the light, and it will get to the guy at the moment of the explosion of radiation. But you don't care anymore, because you died long ago in the singularity.

There is an interesting feature in the formulas of the general theory of relativity - symmetry in time. For example, in any equation, you can imagine that time flows backwards and get a different, but still correct, solution. If we apply this principle to black holes, then a white hole is born.

A black hole is a certain area from which nothing can escape. But the second option is a white hole into which nothing can fall. In fact, it repels everything. Although, from a mathematical point of view, everything looks smooth, but this does not prove their existence in nature. Most likely, they are not, as well as a way to find out.

Up to this point, we've been talking about the black hole classic. They do not rotate and are devoid of electrical charge. But in the opposite version, the most interesting begins. For example, you can get inside but avoid the singularity. Moreover, its "inside" is able to contact the white hole. That is, you will find yourself in a kind of tunnel, where the black hole is the entrance, and the white hole is the exit. Such a combination is called a wormhole.

Interestingly, a white hole can be anywhere, even in another universe. If we can manage such wormholes, then we will provide fast transportation to any area of ​​\u200b\u200bspace. And even cooler - the possibility of time travel.

But don't pack your backpack until you know a few things. Unfortunately, there is a high probability that there are no such formations. We have already said that white holes are a conclusion from mathematical formulas, and not a real and confirmed object. And all the observed black holes create the fall of matter and do not form wormholes. And the final stop is the singularity.