What really is a black hole?

A black hole is a  celestial body, which has a very high gravitational pull, and nothing,  not even light can escape it. The escape velocity is so high that not  even light can achieve that speed. And as most of you will know, nothing  known can travel faster than light. So, indirectly, nothing can escape a black hole, once it crosses the Event Horizon. Black holes are quite dangerous for our existence. These celestial  bodies can swallow everything that comes into their path. The sizes of  the black holes may vary, depending on the size of the stars from which  they formed. Some theorists believe that there is a massive black hole at the  center of our galaxy, but these are just theories. Nobody knows for sure  what is there, at the very center. If a black hole nears the Earth, then nothing can stop us from our  fate. That’s just a matter of speech, but in the future, we can really  behold this situation. So, to study black holes, we will see how they are formed, in this article.

 How does a black hole comes into existence?

 

For a black hole to get  formed, certain requirements should be met. The main thing that matters  is the size of the parent star, from which the black hole is formed. As most of you may know that stars sustain themselves by nuclear  fusions inside their core, which requires hydrogen as a fuel. These  nuclear fusions produce heat and light energy, which balances the  pressure on the outside and inside. But, once the star consumes all of  the hydrogen, then it has nothing to burn. Hence, the pressure inside  the star lowers, and the star collapses under its own gravity to a  single point, with critical density. The gravitational pull is so high  that, as stated already, even light isn’t able to escape. To get a black hole, the mass of the star should be about 200 times  bigger than that of our Sun. If the star is smaller than that, the  electron balances the pressure, and the stars turn into a white dwarf  (our sun would be one of them, after billions of years). Once the bigger  star consumes the hydrogen, it starts collapsing, and the outer layer  erupts to form a supernova. If the core remaining is about 2.5 times the mass of the sun, then  there is nothing that can stop the star from becoming a black hole. The  star collapses continuously, under its own gravity, and the core  collapses too. The collapsing continues, and a point is reach when the volume of the  star is mathematically zero, and it has a critical density. The mass  contracts into an infinitely small point, which is called a singularity. Due to the massive density, the gravitational pull reaches such a  point, that it is virtually impossible to reach the escape velocity,  which is the velocity required to escape a body’s sphere of influence. I know that you will now ask; if nothing can come back out of a black  hole, then why does it radiate X-rays and gamma rays. The answer is  that, before reaching the Event Horizon, the matter orbits the black  hole in an accretion disk, which is a belt of hot gas. If the matter is  dust or gas, it experiences friction, and the orbital energy of the gas  is converted into heat energy. The closer is the matter to the black  hole, the more it will heat up. This can continue until it heats up to  thousands and billions of degrees, thus producing X-rays and gamma rays. The black holes sometimes emit high-speed jets of matter too.  Scientists have known that these jets contain electrons, but they  recently figured out that iron and nickel is also present in these jets.  These jets are caused due to very heavy atoms. And to prove this  theory, they found that an iron atom is very massive, as compared to the  formerly hyped positrons, which were antimatter brothers of  positively charged atoms. The accretion disk is found to be responsible  for providing the matter for these high-speed jets. From where does  these jets from? Well, the answer to this question has not been found  out till now, but the chances are that they will, by the end of the  decade. So, that was the journey, from a star to a black hole.

 Will entering a black hole be fun?

A question that has always screwed astronomers is; what will happen if we enter a black hole? Many theories, as an answer to this question, exist. Some say that if  you enter a black hole, you will be pulled deeper and deeper, until you  hit the singularity. And then, in a moment, you will vaporize into  nothing. Some other people say that if you enter a black hole, the  gravitational difference between your foot and your head will be so  high, that you will become human spaghetti. You will keep stretching  until you too reach an infinitely small point, and get vaporized. And one of the most continuously intriguing theories is that black  holes can be used for time travel. Some people refer it as a joke, but  some others take this seriously.

 Can black hole really help in time travel?

 

As most of you would  know, gravity affects everything, from light to time. Yes, gravity can  affect time also. An experiment conducted by Pound and Rebka shows that  if a clock is put near to a very strong gravitational field, it will  tick more slowly. In the same way, black holes can be ideal for the ‘very strong  gravitational field’. If you start nearing a clock towards the Event  Horizon, you will see that one second of the clock would start  increasing to days, months and years. But, for the clock, it will still  be ticking at one second interval! This happens because the gravity is  affecting the time. Suppose you enter a black hole, you will surely be vaporized. But, if  it’s very, very massive one, then the force near the Event Horizon will  be very small. And if you are able to survive that force, and escape  just before reaching the Event Horizon, you will find yourself jumped up  some years, or even a century. This has not been proven yet, but the facts and figures are so  accurate that it cannot be wrong. If this method works, we would be able  to travel into the future only. There is no way you can go to the past;  the nature is against traveling to the past. The universe above our head is vast, and pretty confusing. There is  no way to know for sure what will happen next. But, thanks to the  super-intelligent folks working down here to make sure that every  mystery is solved. This article is dedicated to all of them. 

Thanks for reading!!