The Black Hole

                     The Void into Being

In the previous section entitled ‘The Free Space’ we had discussed about many different theories about the markings of the universe (Space-Time variations) and ended by the idea of Roger Penrose and Stephen Hawking about the black holes and in this section too we will discuss everything that deals further on its relativities.

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After Roger Penrose and Hawking started the approach of Black Holes in 1965, this term again coined in 1969 by an American Scientist John Wheeler, he gave a graphic description of the idea that goes back around 200 years ago. At that time, there were two theories about light- One was that it is composed of particles, the other was that it is made of waves; we know that both the theories are correct. In the context of the first theory that it is made up of waves, we don’t know how it will respond to gravity but if we talk about the second one that light is composed of particles then it will be expected to behave in the same way with gravity as that of the rockets, planets, and everything does.

On this assumption in 1783, John Michell wrote a paper and pointed out that a star that was sufficiently massive and compact would have such a strong gravitational field that light could not escape and too suggested that there’s not only one but many stars like this. Although we couldn’t see them as their light would not reach us but would still feel their gravitational attraction. Such objects are what we now called Black Holes because they are-black voids in space.

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Process of emerging a star to form a Black Hole-

To understand how the black hole might be formed, we first need an understanding of the life-cycle of a star. A star is formed when a large amount of gas; mostly hydrogen starts to collapse in on itself due to its gravitational attraction. As it contracts, the atoms of the gas collide with each other, and more frequently and at greater and greater speeds- the gas heats up. Eventually, the gas will be so hot that when the hydrogen atoms collide, they no longer bounce off each other but instead merge with each other to form helium atoms. The heat released in this reaction, which is like a controlled hydrogen bomb, is what makes the stars shine. This additional heat also increases the pressure of gas until it is sufficient to balance the gravitational attraction, and the gas stops contracting. It is a bit like a balloon where there’s a balance between the pressure of air inside, which is trying to make the balloon expand, and the tension in the rubber which is trying to make the balloon smaller. The stars will remain stable like this for a long time, with the heat from nuclear reactions balancing the gravitational attraction. Eventually, however, the star will run out of hydrogen and other nuclear fuels. And paradoxically, the more fuel a star starts off with, the sooner it runs out. This is because the massive the star is, the hotter it needs to balance its gravitational attraction and the hotter it is, the faster it will use up its fuel. Eventually, when a star shrunk to a certain critical radius, the gravitational field at the surface becomes so strong that the light cones are bent inward so much that the light can no longer escape. According to the theory of relativity, nothing can travel faster than light. Thus, if the light cannot escape, then nothing else would. A region of space-time from which it is not possible to escape to reach a distant observer. This region is what is now called is Black Hole.

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Suppose, an astronomer on the surface of a collapsing star sent a signal every second, according to his watch, to his spaceship orbiting about the star. At some time on his watch, say, for example, 11’o clock, the star would shrink below the critical radius at which the gravitational field would become so strong that the signals would no longer reach the spaceship. His companions watching from the spaceship would find the intervals from the astronaut getting longer and longer as 11’o clock approached. However, the effect would be very small before 10:59:59. They have to wait only very slightly more than a second between the astronaut’s 10:59:58 signal and one with that he sent when his watch read 10:59:59, they would have to wait forever for the 11’o clock signal. The lightwave emitted from the surface of the star between 10:59:59 and 11’o clock, by the astronomer’s watch, would be spread out over an infinite period of time, as seen from the spaceship. The time interval in arriving at the different waves would become longer and longer. Eventually, the star would become so dim that it would no longer be seen from the spaceship. All that would be left would be a black hole in space. The star would, however, continue to exert the same gravitational force on the spaceship. And thus, the spaceship would continue to orbit the black hole.                                                                              

Any observer who remained outside the black hole would not be affected by the failure of this predictability, because neither light nor any other signal can reach them from the singularity.

But it does nothing at all for the poor unfortunate astronaut who falls into the black hole. Shouldn’t God protect his modesty as well? Who knows!!

There are some solutions to general relativity in which it is possible for our astronaut to see that singularity – He may be able to avoid hitting the singularity and instead fall through a “worm hole” and come out in another region of the universe. This would offer great possibilities for travel in space-time variations, but unfortunately, it seems that the solutions may all be highly unstable.  Such as the presence of the astronaut, may change them so that the astronaut cannot see the singularity until he hits it and his time came to an end. In other words, the singularity always lies in his future and never in his past.

According to Einstein’s theory of general relativity, there’s no absolute time, each observer has his own measure of time. Then comes the strong version of the cosmic censorship hypothesis states that in a realistic solution, the singularities always lie either entirely in the future, like the singularities of gravitational collapse, or entirely in the past, like the big bang. Although many dilutions too added in this cosmic hypothesis that one can see the singularities and though travel in the past like travelling into the past and kill your grandfather before your father was born, etc but such are now called ‘the paradoxes’ that are only best suited in science fiction till it will gain as much to be relied upon.   

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I repeat- “The universe shall diverge

                  Or the time may emerge,

                  To think of covert will throb;

                  Lest the mindedness to Jacob.”

                                                   

Any type of related query is most welcomed--