The Emergence Of A Black Hole Essays Examples
According to Einstein's theory, as soon as the radius of a celestial body is equal to its gravitational radius, the light cannot escape from the surface of the body to the distant observer, that is, it becomes invisible. But the reader will have noticed that it is extremely unusual property is not the only one of those "miracles" that need to happen to the body, the size of which equals the gravitational radius. According to the discussion in the previous section, the force of gravity on the surface of a star with a radius equal to the gravitational should become infinitely large, as well as the infinite must be the acceleration of gravity. What does it lead to? To answer this question, let us recall, first, why ordinary stars and planets are not compressed to the center under the influence of gravity, and represent the equilibrium of the body. Compression force to prevent the center of the internal pressure of the material. In stars the pressure of gas at very high temperature, which tends to expand the star. In the earthly planets is the tension force, elasticity, pressure, and prevent compression. Equality of gravitational forces and these opposing forces just balance and provide a celestial body.
The opposing forces of gravitation depend "on the state of matter from its pressure and temperature. When it is compressed, they are increasing. However, if you compress the substance to some finite (not infinitely large) density, they will also end. It is different with the force of gravity. As we approach the size of a celestial body to the gravitational radius tends gravity, as we know, to infinity. Now it cannot be balanced by the opposing force of the final pressure, and body must shrink irresistibly to the center under its influence.
Thus, the most important conclusion of Einstein's theory states that a spherical body whose radius is equal to the gravitational radius and smaller, can not be at rest, must be compressed to the center. "But let me - the reader will ask, - if the gravitational radius of the force of gravity is infinite, what it will be, once the body is reduced to a size smaller than the gravitational radius?"
The answer is quite obvious. So far we have talked about the force of gravity on the surface of a static, non-compressed body at a given time. But it depends on the state of motion. As we mentioned above, the free fall brings a state of weightlessness - a freely falling body in general is not affected by the gravitational force. Therefore, on the surface of freely contracting body feels no force of gravity (and outside the Schwarzschild sphere, and within it). He is fond of gravity substance cannot stay on the Schwarzschild sphere (it would have experienced the infinite force of gravity). Still less can it stay inside the Schwarzschild sphere. Any particle, such as a rocket, with arbitrarily powerful engine, staying away from gravitating center at a distance smaller than the gravitational radius, must fall uncontrollably to this center. Hence, we have the answer to the question of what is an infinite increase in gravitational force with the approach of the body to the Schwarzschild sphere: catastrophic, irrepressible its compression. Physicists call this phenomenon relativistic collapse. Thus, it is sufficient to compress the body to the size of the gravitational radius, and then it itself will shrink uncontrollably. So there is an object that later became known as the black hole.
We have described the process of relativistic gravitational collapse was first rigorously calculated using the equations of general relativity American physicists Robert Oppenheimer and Volkov in 1939. Their paper is a model of brevity and clarity. Fully and rigorously describing the essence of the phenomenon, it takes only a few pages. R. Oppenheimer name is well known not only to physicists, but also the general public. He participated in the creation of the US atomic bomb; in 1943-1945 he headed the famous Los Alamos Scientific Laboratory. But later realized the danger to humanity is the creation of the hydrogen bomb and the arms race, called for the use of atomic energies of only for peaceful purposes and in 1953 was removed from all his posts as unreliable American. The work of R. Oppenheimer and Volkov should be considered strict prediction possibility of black holes. The name "black hole" appeared much later - in the late 60s. It came up with American physicist D. Wheeler. Before that, they were known by different names. For example, we called them "collapsar-mi", but it turned out that this word does not sound very sweetly in English. However, with the name "black hole" in spite of its accuracy and imagery, too, there were incidents.
Black hole can be made artificially. For this purpose it is necessary to compress any weight to the size of the gravitational radius, she will continue to shrink, experiencing gravitational collapse. However, in this way are enormous technical difficulties. Less weight than we want to turn into a black hole, the smaller it to be compressed because the gravitational radius is directly proportional to the mass. So, we know that the gravitational radius of the Earth is about one centimeter. And to turn into a black hole, for example, the size of a mountain billion tons, it would have to be compressed to the size of the atomic nucleus!
Gallo, Elena; Marolf, Donald (2009). "Resource Letter BH-2: Black Holes". American Journal of Physics 77 (4): 294. arXiv:0806.2316. Bibcode:2009AmJPh..77..294G. doi:10.1119/1.3056569.
Wald, Robert M. (1992). Space, Time, and Gravity: The Theory of the Big Bang and Black Holes. University of Chicago Press. ISBN 0-226-87029-4.
Frolov, Valeri P.; Zelnikov, Andrei (2011). Introduction to Black Hole Physics. Oxford: Oxford University Press. ISBN 978-0-19-969229-3. Zbl 1234.83001.