The Black Hole Mystery

Hello World !

Black hole is a term that we all have heard in our life but never completely understood. So lets understand it now and work our brains together to solve its mystery by thinking what will be inside a black hole, what will happen if we fall in a black hole, can a black hole consume the whole universe (or multiverse) and much more.

Black hole is a region of space and time (spacetime) where gravity is so strong that nothing can escape it including electromagnetic radiations like light. People call it "The Point of no Return". Description of black hole in two words would be that its a 'spacetime singularity'.

Scientific Model of a Black Hole

Parts of a black hole

1. Singularity: It is present at the very centre of a black hole where matter has collapsed into a region of infinite density called singularity. All the matter and energy that fall into black hole ends up here. The laws of quantum mechanics are not valid after this point. 
2. Event Horizon: This is the radius around a singularity where matter and energy cannot escape the black hole's gravity. This is the 'point of no return'. This is the "black" part of the "black hole".
3. Relativistic Jets: When a black hole feeds on star, gas or dust, the meal produces jets of particles and radiation, blasting out from black hole at near the speed of light. They can go to thousands of light years into space. 
4. Accretion Disc: The disc of superheated gas and and dust whirls around a black hole at immense speeds, producing electromagnetic radiations (X-rays, visible, infrared and radio) and reveal the black hole's location. Some of the material is doomed to cross the event horizon while the others may be forced out to create relativistic jets. The inner edge of an accretion disc is the last place that material can orbit safely without the risk of falling past the point of no return, this inner edge is called 'Innermost Stable Orbit'
5. Photon Sphere: Although the black hole itself is dark, photons are emitted from nearby hot plasma in jets or an accretion disc. In the absence of gravity, these photons would travel in straight lines, but just outside the event horizon, gravity is strong enough to bend their paths so that we see a bright ring surrounding a roughly circular dark "shadow". 

Types of Black Holes

1. Stellar Black Hole
• They are most common. 
• They form from stars 10-20 times more massive than our Sun. 
• Weigh between a few and 100 times the mass of the Sun. 
• In Milky Way there are 10 million to 1 billion stellar mass black holes.
• These black holes are also called collapsars.
2. Intermediate Black Hole
• Estimated to have a mass between 100 and 1000 solar masses.
• They are rare. 
• As the name implies, intermediate-mass black holes fall between stellar-mass black holes and supermassive black holes. This type of black hole is not too small, nor too big.
• Exist in centre of most galaxies including our Milky Way. 
• Intermediate black holes are those which have a mass somewhere between stellar and supermassive black holes — in fact, astronomers theorize they are an evolutionary in-between phase for these cosmic behemoths.
3. Supermassive Black Hole
• Largest and strongest type of Black Hole.
• Mass is a million or billion times that of Sun. 
• Exist in centre of most galaxies including our Milky Way. 
• Few have size same as that of the Sun. 
• Nor common nor rare to find. 
4. Quantum Mechanical Black Holes
• Also called as mini/micro black holes.
• Even smaller than Stellar Black Holes.
• Hypothetical concept introduced by Stephen Hawking in 1971.
5. Primordial Black Hole
• Formed after a mere fraction of second after the Big Bang.
• Primordial black holes could have masses as low as 10^-7ounces (10-5 grams), or 100,000 times less than a paperclip, up to about 100,000 times greater than the Sun.
• Few scientist consider that Planet 9 may be a Primordial Black Hole.
• It was an old idea of Stephen Hawking’s unseen “primordial” black holes might be the hidden dark matter. It fell out of favor for decades, but a new series of studies has shown how the theory can work.
  
  

Formation of Black Holes

Each type of black hole forms differently, let's see see each one by one.

1. Stellar Black Hole: When a star burns through the last of its fuel there is a possibility that it may collapse (fall into itself). For smaller stars (those up to about three times the sun's mass), the new core will become a 'Neutron Star' or a 'White Dwarf'. But when a larger star collapses, it continues to compress and creates a stellar black hole. Black holes formed by the collapse of individual stars are relatively small, but incredibly dense. This leads to a crazy amount of gravitational force. Stellar black holes then consume the dust and gas from their surrounding galaxies, which keeps them growing in size. 
2. Intermediate Black Hole: Formed by a chain reaction of collisions of stars in compact star clusters that results in the buildup of extremely massive stars, which then collapse to form intermediate-mass black holes. Another theory states that when many stellar black holes fuse together an Intermediate Black hole is formed.  
3. Supermassive Black Hole: One possible mechanism for the formation of supermassive black holes involves the star clusters to sink to the center of the galaxy, where many intermediate-mass black holes and stellar black holes merge together to form a supermassive black hole.
4. Mini /Micro/Quantum Black Hole: When two sub atomic particles collide at close range, their energy is concentrated into a tiny region of space. So one might guess that, once in a while, the colliding particles will get close enough to form a black hole. 
5. Primordial Black Hole: These black holes were formed at the time of the Big Bang. Scientists think that certain parts of the universe were unbelievably rich in energy at that time due uneven distribution of energy. It’s these tiny, insanely energetic points in space that could have theoretically collapsed directly into primordial black holes.

Now before going to the imagination part few more terminologies should be known 

• White hole: It is a hypothetical region of spacetime singularity which is just opposite of a black hole. Nothing can enter a white hole though the objects inside a white hole can leave and interact with the outside world. Its event horizon is a "point of no admission". 
• The Information Paradox: This has raised from general relativity and quantum mechanics. Calculations suggest that physical information could permanently disappear in a black hole, allowing many physical states to devolve into the same state and this violates the rules of modern physics.
• Supernova: It is the biggest explosion that humans have ever seen. Each blast is the extremely bright, super-powerful explosion of a star. 

That's enough of  scientific/facts part. Now lets go to the imagination part!

What will happen if something (or someone) falls in a Black Hole ?

There can be different answers for this particular question. 

(i) If you are falling vertically into a stellar black hole then your legs will feel a stronger gravitational pull than your upper body which will cause your body to stretch vertically and will get squeezed horizontally, which will unfortunately tear your body apart and you'll die. This is what scientist call 'spaghettification'. 

(ii) If you are smart enough and choose to fall in a supermassive black hole then your body wont tear apart as the gravity there is extremely strong so your upper body and legs will feel almost same gravitational pull. Now there are multiple possibilities that can happen

• First, you may end up somewhere else in space at same time, which means it may act as a teleportation device 
• Second, you may end up in a parallel world, which means it may act as a portal to a parallel world
• Third, you might enter another dimension, which means it may act as a door to other dimensions
• Fourth, you might reach to same place but at a different time, which means it may show some time travelling mechanisms.
• Fifth, you are most likely to die
• Sixth, if we think black hole as a sphere instead of a circle then a person landing towards centre of the black hole will have a tending to zero magnification as closer the person will be from centre more will be the difference of gravity be comparing his head and legs. As the difference will be huge so spaghettification will take place and he'll be as thin as a line which means his existence will be erased because his size would become negligible.

Here black hole is the point of entry so for first, second, third and fourth point you can think white hole as a point of exit.

Can Black Hole consume the whole universe? If it does what will happen next ?

I think yes it can. Imagine a black hole in the vast space. That black hole feeds on anything that reaches near its event horizon. The more things it consume the bigger it gets. Now after a certain time it has grown big enough that it starts to feed on supermassive black holes also. Now it gets even more bigger. Again time passes and it becomes so huge that it starts consuming galaxies and soon the universe. Now after consuming the universe it has reached its critical point i.e. it can no longer consume anything. At this point it will be converted into a white hole. The white hole will release the matter present in it. As the matter gets released it spreads. And this phenomenon can be thought as The Big Bang.

Black hole vs white hole, who is going to win?

My thoughts are similar to this -

Key Words

• Multiverse: A hypothetical space or realm consisting of a number of universes, of which our own universe is only one.
• Light Year: A unit of astronomical distance equivalent to the distance that light travels in one year, which is 9.4607 × 10¹² km (nearly 6 million million miles).
• Plasma: It is superheated matter – so hot that the electrons are ripped away from the atoms forming an ionized gas.
• Solar Mass: A solar mass is the mass of the sun. Or, more precisely, it's 1.989 x 10^30 kilograms, about 333,000 Earths.
• Dark Matter: It is a hypothetical, invisible and unknown mass that make up the most of the universe. Universe is made up of nearly 80-85% dark matter.
• Neutron Star: A neutron star is the collapsed core of a massive supergiant star, which had a total mass of between 10 and 25 solar masses, possibly more if the star was especially metal-rich.
• White Dwarf: A white dwarf, also called a degenerate dwarf, is a stellar core remnant composed mostly of electron-degenerate matter. A white dwarf is very dense: Its mass is comparable to that of the Sun, while its volume is comparable to that of Earth. A white dwarf's faint luminosity comes from the emission of stored thermal energy; no fusion takes place in a white dwarf. 
• Hawking Radiation: Thermal radiation that is theorized to be released outside a black hole's event horizon because of relativistic quantum effects.
• Relativistic Quantum Effects: Combination of relativity and quantum physics.

Facts

• There is a supermassive black hole at the centre of our galaxy called Sagittarius A
• After you cross the event horizon space and time reverse their roles. So a person looking at you from far away would see you as stationary but for you, you would keep moving towards the singularity. 
• The only thing that can escape a black hole is Hawking Radiation
• Albert Einstein rejected the idea that black holes might exist
• The closest known black hole, called 1A 0620-00, is 3,000 light years away. For comparison, our nearest stellar neighbor is 4.2 light-years away 

Famous Quote on Black Hole 

"Black holes are where God divided by zero."

                                                                                                                            -Albert Einstein 

Question of the Week

What you think are the smallest particles that makes everything? 

References

• space.com
• Nasa
• Space and Beyond Box 
• eso.org
• Wikipedia
• Lectures by Stephen Hawking 
• Scientific American
• astronomy.com
• inverse.com
• Britannica