What are black holes?
Black holes are massive cosmic objects. It is almost impossible to see them because
Black holes are not black balls as we are used to seeing them. They are transparent but leave a black shadow. This is not even a hole, but a spherical absorber of everything that falls under the influence of its gravity.
How do black holes appear?
Stars that exceed the mass and size of our Sunmany times, at the end of their life, they explode and form either a neutron star, or begin to shrink strongly, as if "falling" inward, rapidly decreasing their size at a constant mass. The density of matter at a compressible point becomes very high, respectively, gravity increases greatly. When the size of a star becomes so small and the density is so high in one place, it "falls" inward, resulting in a black hole.
A black hole, for example, with a mass of one Sun will be smaller in size than our star.
However, small stars like our Sunwill not turn into a black hole at the end of their life cycle - their mass is insufficient even for an explosion and the formation of a supernova. There will be an explosion, of course, but at the final stage small stars turn into white dwarfs - very small and hot stars, which will also soon fade out.
We currently know of four different ways black holes form.
- The best studied is the one associated with the stellarcollapse. A large enough 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 fusion ceases, matter begins to fall towards its own gravitational center, becoming more and more dense. In the end, it becomes so dense 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 holeare "supermassive black holes" that can be found at the centers of many galaxies and which have masses about a billion times greater than the 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 consumed many other stars in densely populated galactic centers and grew. However, they seem to absorb matter faster than this simple idea suggests, and how exactly they do it is still a subject of research.
- A more controversial idea was primordial black holes,which could have been formed by virtually any mass in large density fluctuations in the early universe. While it is possible, it is difficult to find a model that produces them without over-creating them.
- Finally, there is the idea that the Large Hadronthe collider can form tiny black holes with masses close to the mass of the Higgs boson. This only works if our universe has extra dimensions. So far, there has been no confirmation in favor of this theory.
How big are black holes?
You can imagine the horizon of a black hole as a sphere, and its diameter will be directly proportional to the mass of the black hole. Therefore, the more mass that falls into a black hole, the larger the black hole becomes.
Compared to stellar objects, black holestiny because the mass is compressed into very small volumes under the influence of irresistible gravitational pressure. The radius of a black hole with a mass of planet Earth, for example, is only a few millimeters. This is 10,000,000,000 times less than the present radius of the Earth.
The radius of a black hole is called the Schwarzschild radius after Karl Schwarzschild, who first deduced black holes as a solution to Einstein's general theory of relativity.
Where are the black holes?
They are most often located in the center of galaxies. They have a great force of gravity, thanks to which they manage to keep star systems at a very large distance, forming the galaxies we know today.
At the center of our Milky Way there is alsoa supermassive black hole called Sagittarius A *. It is 4.02 million times heavier than the Sun, and its radius is ≈ 45 astronomical units (one astronomical unit = one distance from the Earth to the Sun).
In addition to supermassive black holes in the centers of the galaxy, there are also “local” ones that form after the death of massive stars.
What's inside a black hole?
Nobody knows for sure. General relativity predicts that in a black hole there is a singularity, a place where tidal forces become infinitely large, and once you get past the event horizon, you can't go anywhere else but the singularity. Accordingly, it is better not to use the general theory of relativity 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.
Why could there be universes inside a black hole?
There are many hypothetical black holes -with or without electric charge, rotating or stationary, surrounded by matter or floating in empty space. Some of these hypothetical black holes probably exist in our universe. For example, a rotating black hole surrounded by falling matter is a fairly common type of these objects.
But some other types of black holes arepurely theoretical. Their behavior and properties can be described relying only on mathematical methods. One such object is an electrically charged black hole surrounded by anti-de Sitter space. This kind of space has a constant negative geometric curvature and is similar in shape to a saddle.
There is no such space in our Universeexists, but its existence in theory opens up many interesting effects that can be investigated. One of the reasons this is worth investigating is that charged black holes have a lot in common with the rotating black holes that exist in our universe.
The authors of the new study foundthat when such black holes become relatively cold, they create a “fog” of quantum fields around their surface. On the surface of the object, this fog is supported by the gravity of the black hole, but is pushed outward by the electric field. As a result, a superconducting medium is formed in such a fog. In addition to the usual event horizon, such black holes also have an internal horizon. Thanks to this, charged black holes can be penetrated without being torn into atoms.
Scientists have shown that on the other side of the chargedblack hole you can expect mysterious effects. The researchers found that the innermost regions of a superconducting black hole could represent an expanding universe - a place where space can stretch and deform at different rates in different directions.
Moreover, dependingFrom the temperature of the black hole in some of these regions of space can cause a new round of oscillations, which will then create another section of expanding space, which will cause a new round of oscillations, which will then create a new section of expanding space, and so on on infinity. This will be a fractal mini-Universe, endlessly repeating itself with a decrease in size.
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