Black Hole

                                                                                                        Abid Hussain Bhutto 

What does it mean? According to the Webster’s Dictionary, “Black hole is a hypothetical object, perhaps the invisible remains of a collapsed star, with an intense gravitational field from which neither matter nor light can escape”. That is why it looks like a black hole. But black hole manifests more than mere hypothetical existence. Modern hi-tech science recognizes the presence of such mysterious being.     

                 The name Black hole was given by an American Relativist (follower of The Einstein’s Theory of Relativity) John Wheeler in 1969. 

How we knew the Black Holes? In the early 1960’s, astronomers already knew that any star which contains more than about three times as much matter as our sun (Solar mass), eventually ends its life by collapsing inward to form a black hole. Scientists made these calculations by using Einstein’s Theory of General Relativity (presented in 1915) and deducted that such an object would bend even Space-Time completely round upon itself, cutting the central mass off from the rest of the universe. 

                 Before the concept of Black hole, the White Dwarves were considered as most dense and heavy objects in the universe. Each cubic centimeter of a white dwarf weighs almost one thousand kilograms. White Dwarf is also known as Collapsar and is formed when an ordinary star loses energy by going through stellar evolutionary cycle, is collapsed under its own gravity and becomes dense like pressed cotton bale. Thus it is converted in to a collapsed star (Collapsar). But it is not the extreme of density and thickness and still more compact objects are present in the universe. 

How are Black Holes formed? Before going to discuss the formation of a black hole, it would be beneficial to recollect the structure of an atom - the smallest unit of matter, which is composed of two regions: a Nucleus (composed of protons and neutrons); and a cloud of Electrons orbiting around the nucleus. If we consider our whole body composed of purely atoms, the contribution of mass of electronic shells would not be more than mass of our eye lashes while remaining whole body weight would be the contribution of nuclei. More over, if we consider a nucleus the size of a cricket ball placed on middle of cricket ground, the nearest orbiting electron would be at least one kilometer away and second one would be farther. It shows that almost whole of the atomic space is occupied by cloudy shells made of extremely light revolving electrons while almost whole of the atomic mass is occupied by extremely small yet heavy nucleus. Now, what will happen if we fill just a common match box with such tiny nuclei? Probably, it would not be lighter than Mount Everest. This very specialty of an atom plays a vital role in the formation of a black hole. 

                 Please recall the formation of Collapsar, formed under intense gravitational field. Due to further increase in gravity, process leads to more collapsing inward and resulting in all of the atoms of collapsar become buckled and abort their respective electronic shells. Not only electrons but Protons are also lost in this way and only remain a chunk of Neutrons. By this process, star loses almost whole of space and half of the mass and collapsar is converted in to a Neutron Planet. 

                 As a matter of fact, if density of mass increases, gravity also increases, pulls every object which comes in to its field. To measure this gravitational pull, we simply use term “escape velocity” which means the minimum velocity required by a missile or rocket to escape from the gravitational pull of any planet or star. Our Earth has escape velocity of 11 kilometers a second. There fore our rockets must be faster than this velocity to get rid of the gravity and to go in to the space. The escape velocity of sun is 600 km, white dwarf 6000 km, and a neutron planet is 150000 km a second. Due to such intense gravity, neutron planet collapses more inward and due to absence of any more space left to accommodate more neutrons, finally planet loses its material physics and becomes a Black hole with escape velocity of more than velocity of light (300000 km a second.)

How the Black hole physics work? Black holes are so dense and compact that there is neither any mass to occupy nor any space to be occupied. The gravity achieves such an immense magnitude, that every thing is confined not to go out of black hole, even light is super imposed to be bent back ward. That is why black hole looks like a black hole. The boundaries of a black hole are called “event horizon”, discovered by Schwarzschild, thus also called Schwartzschild’s radius. Out side the event horizon, lies a full colored and live universe but inside it, a world of great chaos and death.  Neither any type of matter nor any common physical law survives within the black hole. There remains only the realm of infinite gravity which pulls each and every thing that comes near event horizon even it bends space and time and cuts the world of black hole off from the rest of the universe. It shows that there is no any space and time present in the black hole. Thus black hole is devoid of any past, present and future. There lurks only “Infinity” and dwells merely nothingness. Entry for material physics and conventional kinematics is prohibited there. There is one- way traffic- every thing enters only in to it, but, with out exit.

How the Black hole was observed? Recently, astronomers have observed a star which behaves like one of the members of Binary star system (two stars orbiting each other) and become surprised when they found that the other partner is invisible. They also observed that the surface mass of visible star is protruding towards its presumed invisible partner. Scientists took no time to guess that invisible star is nothing but a black hole which attracts and ultimately engulfs the surface mass of its partner constantly, and in future, the day will come, when whole of the mass of unfortunate prey star would be part of the infinities of the black hole- once an innocent partner of the prey star.

 Should we be afraid of Black holes? The impact of black holes on our life is not merely a sci-fi (science fiction), and can affect our existence if any of black holes comes near by our earth. But it looks like almost impossible, because if the black hole, nearest to the earth, travels with even velocity of light, will take millions of years to reach our planet or even the sun. So for our own solar system and near by stars are concerned, there is no any star which can compose about three solar masses to qualify the basic requirement to become a black hole. There fore we should not be afraid of or worried about any black hole.

            Black holes are open challenge to physicists and a free feast to philosophers and religious-men to think about and to journey in to the world of infernal regions which have been the part of curiosity of religions, mythology, metaphysics and obviously the science it self. So for the research is concerned, not only the black holes, but things like dark matter and antimatter are also mysterious questions for human intellect.