What is a black hole?
A black hole is the death bed of a supermassive star. It is a place in space with such a great gravitational pull that even light cannot get out of this space. Since light cannot get out of this hole, we cannot see it, and hence it is called the black hole.
The black hole is made up of two main parts: the event horizon and singularity.
If we compare the black hole to watermelon, the outer green covering would be the event horizon, while the center or the inner red half would be the singularity.
The event horizon is also known as the point of no return. Nothing, including light, returns after passing this line. This is one line that should have the “Do not step beyond this line” warning on it. If you pass this line, then your body will most probably end up distorted. This is because the extremely strong gravitational pull will rip apart the atoms constituting your body.
If you were a professional runner, the singularity would be the one finish point you would not want to reach. Once you reach the singularity, it will definitely mean the end of you.
What happens if you cross the event horizon of the black hole?
The events that take place when a person passes the event horizon of a black hole can be seen from two perspectives: the person who is passing through the event horizon (let’s call him Chad) and the person who is observing Chad pass through the event horizon (let’s call her Brooke).
Brooke is standing, and the closer Chad gets to the event horizon, the more distorted he gets. It appears to Brooke as if she is looking at Chad through a magnifying glass. The second thing that Brooke observes is that the closer Chad gets to the event horizon, the slower he seems to travel.
When Chad finally reaches the event horizon, it appears to her that Chad has stopped moving. He is completely stuck at one point, stretched out against the event horizon. Suddenly Brooke will be reduced to tears because the next thing that happens is gruesome. Chad gets eaten away by flames. These flames are, in fact, radiations, which are known as Hawking’s radiations. The radiations, which are named after Stephen Hawking, are streams of hot particles emitted into the universe. After a certain amount of time, the black hole will completely disappear due to continuous radiations that are given out by it.
While Brooke’s perspective is interesting in itself, Chad’s perspective will shock you.
According to Chad, absolutely nothing has changed! He does not feel himself being stretched or burnt and converted into radiation. He moves past the event horizon without a single scratch on his body. As long as the black hole is big enough and he does not encounter the center (singularity), he will be just fine. If he does make it towards the singularity, then it’ll be time to say goodbye to our dear friend Chad.
On the other hand, if the black hole isn’t big enough, gravity’s force would be stronger on the feet and less at the head. This would stretch poor Chad out like spaghetti! If you’re desperate enough to increase your height, going and visiting a black hole would probably be a great idea!
What is the black hole information paradox?
Now the question obviously arises, how can there be two different versions of the same event. Is Brooke sadistic that she’s imagining Chad burning to a crisp, or is Chad trying to sugarcoat what he’s actually going through? The answer is none of the above. In reality, Chad has two selves now, which are also known as clones. Hence both of the observations are correct.
From Brooke’s point of view, Chad has been reduced to ashes. The law of physics, in fact, demands that Chad remains outside the event horizon so that information is not lost.
However, these same laws also demand that he not encounter any heated particles or anything extraordinary while passing the event horizon.
So at the same time, the law of physics is demanding two different things. In addition to this, there is also a law that states one cannot clone information. This is known as the black hole information paradox.
Understanding the black hole despite the information paradox…
Leonard Susskind realized that the paradox does not exist because neither Brooke nor Chad will see Chad’s other copy (the one which gets burnt or is unharmed, respectively). Brooke will only see Chad’s copy, which gets burnt, while Chad will only see that copy of himself that remains unharmed. These two observers will never interact with each other. At the same time, there is no third party who can see both inside and outside the black hole at the same time.
What black holes have taught scientists is that there is nothing certain about them. Like in life, there are different versions of the same story; black holes also have different realities. Hence the reality depends upon whom you ask. Brooke and Chad’s reality will differ in this case, and you cannot call either of them a liar. They could also maintain that this very complicated black hole theory has confused them, as I am sure it has confused you.