What Are Black Holes?
Black holes are the super-massive, dense regions of space-time where gravitational acceleration is so strong that nothing can pass through them, not even light can escape through them.
History Of Black Holes.
Black holes were first considered in the 18th century by John Michell and Pierre-Simon Laplace. Then, in 1916, Karl Schwarzschild found the first solution to the theory of general relativity that would describe black holes. He also discovered the concept of Schwarzschild radius, which describes how large a black hole can be based on its mass or density. But the concept that nothing can escape the pull of a black hole, which means that the gravitational black hole is enormous, was first proposed by David Finkelstein in 1958. But, more information about black holes was jotted down when the discovery of neutron stars took place by Jocelyn Bell Burnell in 1967, and from that day till now, every day we get to know more about black holes.
Pathway To Discovery:
- 1687- Sir Isaac Newton described the gravity in his publication, "Principia"
- 1783- John Michell suspected that there might be a massive object enough to escape velocity greater than the speed of light.
- 1796- Simon Pierre LaPlace assumed the existence of black holes." It is, therefore, possible that the largest luminous bodies in the universe may, through this cause, be invisible"- Le Systeme du monde ( The System of the World )
- 1915- Albert Einstein issued the Theory Of General Relativity, which surmised spacetime curvature.
- 1916- Karl Schwarzchild used the theory of relativity to explain the black hole. The explained gravitational radius of black holes, later named as Schwarzchild radius.
- 1926- Sir Arthur Eddington along with Einstein opposed black hole theory.
- 1935- Subrahmanyan Chandrashekhar discovered the theory of white dwarfs that led to an understanding of mass limits that decide whether a star will die as a dwarf, neutron star or black hole.
- 1964- John Wheeler coined the term, "black hole".
- 1964- Jocelyn Bell Burnell found neutron stars that, at the time, were the densest matter found through inspections.
- 1970- Sir Stephen Hawking described the modern theory of black holes, which explains the final fate of black holes.
- 1970- Cygnus X-1, the first good black hole candidate that astronauts found. It releases x-rays and has a partner smaller than Earth although with a mass greater than that of a neutron star.
- 1994- Hubble Space Telescope gave the best evidence to date pf supermassive black holes that lie low in the centre of some galaxies. The Space Telescope Imaging Spectrograph (STIS) disclosed largely orbiting velocities around the nucleus of these galaxies, proposing a huge mass inside a very small region.
What the laws say?
The laws of general relativity differ from the classical mechanical laws, and according to general relativity theory, a mass sufficiently compressed or compact can deform space-time to form a black hole. A black hole consists of a region around it from which no object can escape. As the pull of gravity is very great in the region, for an object to escape its pull, it needs to travel faster than the speed of light, which was impossible until now. There’s a point at the centre of the black hole which is a single-dimensional point where a huge amount of mass is concentrated in an infinitely small space. That point is known as the singularity of the black hole.
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So,
how are they really formed…?
Stars are an enormous mass of hydrogen atoms that collapse from enormous gas clouds under their own gravity. At its core, nuclear fusion crushes hydrogen atoms into helium, releasing an enormous amount of energy. This energy is extremely high. This energy is in the form of radiation, which maintains a balance between gravity and energy. Until there is fusion in the core, the star remains stable, but for stars having a mass far greater than the sun, the heat and pressure in the core allow them to fuse heavier elements until they reach iron. Unlike other elements formed earlier in the core, iron doesn't release any energy, and the balance between energy and gravity is disturbed, and the star implodes, moving at a quarter the speed of light and feeding more mass to the core. At this very movement, the star dies into a supernova or it entirely collapses into a black hole. According to quantum field theory, the event horizon emits Hawking radiation with the same spectrum as a black body of temperature, and it is inversely proportional to its mass.
How we can create them…?
Any object can collapse into a black hole if it is compressed to its Schwarzschild radius, which is 1.49 times 10–27 m/kg times its mass. This was the most important equation presented by Karl Schwarzschild. That means if we want to convert the sun into a black hole, we have to compress it to about 2.96 km. That is about 0.00000426 times the radius of the sun, and the mass must remain constant. We can also convert a particular object into another by adding mass to it, keeping the density the same. So, if we want to convert the earth into a black hole, then we have to add rock (of comparative density) from all sides equally till it reaches a distance close to the sun. If it reaches it, then the earth will collapse into the black hole.
Furthermore, if we study black holes deeply enough, there is much more to discover.
The topics are broad and deep until the end. far beyond the singularity.
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