Black hole is a place in space where large mass is concentrated in a small place and so there is a relentlessly strong gravitational pull which drags everything towards itself and not even light can escape from it. Many observations based on experiments have discovered interesting facts about black holes but yet much more is unknown. As a black hole absorbs everything including light, black holes cannot be seen but special telescopes and radio receivers can detect their presence.
Black Holes exist in varying sizes and small ones can be as small as an atom in size. But such tiny black holes have enormous amount of mass squeezed in it. It is known as the central singularity. Another type of black holes is evident known as the stellar. Such black holes are approx. 20 times larger than that of the sun. So it’s hard to imagine the mass compressed in it. It’s the combined mass of 4 million suns. The term Black Hole was coined by John Archibald Wheeler in 1967. Black holes are formed when stars die. When big stars collapse, supernova occurs. Black holes are formed from such phenomena. From the advanced studies made till date, it is expected that the sun is not large enough to form a black hole. The behavior of stars which are in close proximity to a black hole shows divert from their natural properties and these observations confirm existence of a black hole nearby. Moreover high energy light is produced when stars are close to a black hole and exceptionally strong space satellites can detect it.
There are uncountable black holes in the universe of varying sizes. The black hole closest to the earth is quite a few light years away, i.e. too far to cause any harm to the earth. What will happen if two black holes collide? This phenomenon is not likely to happen but if they do, they will attract each other towards them with their gigantic gravitational pull and will merge to become a larger black hole. Prodigious energy will be produced and the process will be a violent one and will emit massive ripples of gravitational pull. Till now no such merging event has occurred.
Now the question arises does Black Hole obey the laws of gravitation? The answer is “Yes”. Among the millions of forces acting upon each and every object of the universe, gravity is one of the weakest forces known. Gravitational force of an object tends to drag everything towards itself and it is proportional to the product of the masses of the two objects and inversely proportional to the square of the intervening distance. These laws were put forward by Sir Isaac Newton. Sir Albert Einstein took it forward to give a generalized form by blending these laws with his special theory of relativity. According to him, the 4-dimensional space-time frame of reference must be in continuum. However objects having mass tend to distort this continuum. The distortion is known as gravity. In weak gravitational fields the theories of both Einstein and Newton are identical. But when the situation extends to objects like black holes where extraordinary strong gravitational pull is present, Einstein’s theory concludes some really fascinating observations.
If a black hole is so powerful to grasp everything, is it indestructible? The British physicist Stephen Hawking proved in 1974 that black holes evaporate slowly and gradually and eventually returns the energy to the universe. Sub atomic particles and light particles are continuously created and destroyed. The light thus created has a very small chance of escape before it is destroyed. This phenomenon appears to be an event horizon glowing. This energy of the glow diminishes the mass of the black hole and eventually vanishes.
What is inside the black hole cannot be determined as it does not even let light to escape. However studies have brought a conclusion that the mass of the black hole is concentrated at a single point. The concept of this central singularity is under the study of Quantum Physics along Gravity but still major conclusions could not be drawn as the mystery has not yet been unlocked. Some mysterious derivation’s of the equations of Einstein’ theory of relativity has sown the seeds of many interesting concepts like the singularity might be a bridge to another Universe, or may become worm holes that are expected to time travel but we do not know whether they really exist in this Universe. If they do, a new door of mystery will be unlocked and we never know perhaps a new universe somewhere else will be traced.