Black holes –The Invisible Monsters
The recent photo of a black hole taken by the Event Horizon Telescope has created excitement and amazement around the world (see fig.3). This was the first instance when a black hole was seen in real, rather than the reel. Black holes were earlier restricted to science fiction movies and novels but not anymore (In the movie Interstellar, a black hole named Gargantua was shown (fig 1). This was the closest man ever came to picturing a black hole).
Fig.1: Gargantua in the movie Interstellar
What are Black holes?
A black hole is a region of space-time which is so twisted that even light cannot escape its gravity. These monsters can be understood using Einstein’s General Theory of Relativity. Einstein imaged the space-time as a fabric which could be bent and even twisted by heavy objects(see fig 2).
Fig.2(bending of spacetime fabric)
Now imagine an object which is a billion times heavier than Sun; this object can bend spacetime around itself to such an extent that even light cannot escape it.
The black dot at the centre of a black hole is called a singularity, where the laws of physics breakdown.
Fig.3: Image of a black hole taken by event horizon telescope
Evolution of the concept of black holes:
The concept of black holes was first proposed by John Michell and Pierre-Simon Laplace independently.
The idea was not taken seriously until Einstein entered the picture in 1915 with his General Theory of Relativity.
Einstein did not take the possibility of black holes seriously, however, a German named Schwarzschild calculated that if the mass of the object was too large then it would shrink to a tiny point called Singularity.
The boundary of such an object is called Event Horizon and the radius below which even light cannot escape is called the Schwarzchild radius.
An India born Physicist named Chandrasekhar showed that not all objects would collapse into black holes. He introduced a limit called the Chandrasekhar limit.
John Wheeler coined the term Blackhole.
Later, Roger Penrose and Hawking did fundamental work in the field of black holes. Hawking merged General Relativity and Quantum Mechanics and showed that black holes also lose energy and would one day die, albeit a slow death.
Hawking also predicted that the primordial black holes(which were formed in the early stages of the universe) contained dark matter. However, recent studies show that this is not true.
Conclusion: The picture of a black hole is a symbol of human ingenuity, endurance, and perseverance. It shows the power of imagination of individuals like Einstein and Hawking. A black hole may be a monster but not invisible anymore. It will surely inspire the next generation of physicists and astronomers to look deep into the secrets of the universe.