in this article we will know, how black hole works, where black hole is located, where black hole is found, why black hole has high gravity, why black hole exist, will black hole consume milky way, will black hole consume earth, who found black hole,
Hello, friends! If you remember, in 2014, a blockbuster film by director Christopher Nolan, Interstellar, came out. The space-related concepts in this film, wormholes, black holes, alien planets, were shown in a scientifically accurate manner. But perhaps the most terrifying scene was at the end of the film. At the climax, when the main character, Cooper, falls into a black hole. The name of this black hole is known as Gargantua. they fall into the black hole with their spacecraft. In the beginning, everything around them is black. Complete darkness. But as they fall further in, they see some grain-like particles. These particles hit their spacecraft, and start to burst. Some light flashes come out. Some sparks are lit, and their spacecraft starts to burn. They are forced to eject from their spacecraft.
And they keep falling into the black hole. But then, all of a sudden, they find themselves in a 5-dimensional space. A 5-dimensional desert. It's a mind-blowing thing. A place where they can communicate with their past, using gravity. You must have a big question in your mind after seeing all this. Is all this possible? Does something like this really happen in a black hole? If we actually fall into a black hole, what will we see? Let's try to understand all these questions in today's article.
- Let's start with the story,
friends. The history of black holes is not too old. 100 years ago, no one knew about black holes. It was Einstein's theory of relativity that led to the discovery of black holes. There are two parts to this theory, friends. The Special Theory of Relativity and the General Theory of Relativity. The Special Theory of Relativity, published by Einstein in 1905, tells us how speed influences time. If you are sitting in a spaceship that is flying very fast, and its speed is very high, then time will run slowly for you. Relative to those people who are not sitting in the spaceship and are on Earth.
The word relative is very important because when you are sitting in a spaceship, you won't feel that time is running very slowly. Time for you will be running at the same speed as it normally does. If you go back to Earth, you will find out how different the time was. This is called Kinematic Time Dilation. Time can be dilated not only by speed but also by gravity. Einstein explained this in his General Theory of Relativity. He developed this in the year 1915. The more you experience the gravitational force, the slower the time will be for you. It is known as Gravitational Time Dilation. And it was beautifully shown in the Interstellar film.
When Cooper and his companions land on an aqua planet, one hour on that planet is equivalent to 7 years on Earth. This happens on this planet because this planet is close to a black hole. So the gravitational force coming from the black hole impacts on it. Einstein had said to visualise this, to imagine a space-time fabric. To imagine a kind of mesh. where all the planetary objects are placed. The more their mass is, the more they are bending the mesh of space-time. And when the mesh is bending, not only are the physical objects attracted to it, but the time is also being dilated by it. And the other forms of energy, like sound, heat, and light, are also affected by gravity. You heard it right, friends.
This was another conclusion that Einstein came up with. almost everything is affected by gravity. Not only are physical objects attracted by the force of gravity, but heat, sound, and light are also attracted by it. This means that there can be objects in the Universe, where the gravitational force is so intense, that they can completely absorb the light. And if there are such objects, it means that they will be completely black. They won't be visible to us. Because the light won't be able to come out of them. These are exactly the black holes. But when Einstein told his theory of general relativity, at that time, the concept of black holes was only theoretical. Einstein knew that gravity influences light, and theoretically, there can be objects that can absorb light.
But Einstein didn't know that there are actually black holes. In fact, as long as Einstein was alive, he found the concept of black holes very strange. He knew that theoretically, such things can happen, but He thought that theoretically, things like infinity could exist. But realistically, practically, he didn't believe that such things exist in reality. So, actually, until he realized it, he hadn't even invented the word black holes. Here's an interesting fun fact. In Einstein's theory, a key point was that the speed of light limits the influence of gravity. It's not that we instantly feel the force of gravity everywhere. The speed of its upper limit is the speed of light. To explain it with practical examples, it means that suppose the Sun suddenly disappears.
You all must know that we will only know after 8 minutes that the Sun has disappeared. Because the light takes 8 minutes to reach the Earth. But according to Einstein, the gravitational impact of the Sun disappearing on the Earth, we will also feel it after 8 minutes. Isn't it a very interesting thing? After Einstein, the theory of general relativity, was worked by many other scientists. Like Karl Schwarzschild, Johannes Droste, Subrahmanyam Chandrashekhar. There were many equations. They solved them and tried to find solutions. And by finding solutions to these equations, it was theoretically proved that black holes exist. By the 1960s, researchers and scientists finally realised that not only theoretically, but maybe one day, realistically, we will be able to see black holes. Because these things actually exist in space.
The word black hole was first used by a magazine in 1964. But it became popular after 1967, when a physicist, John Wheeler, popularised it. Although the word black hole sounds sensational, it is a slightly misleading word. Black hole. After hearing it, you might think that there is actually a hole there. But that's not the case. There is no hole in space. Black holes are formed by stars. So there is some material in the centre of them. What happens in stars, friends? Just like the Sun is one of our stars, there are nuclear fusion reactions between them. Due to these reactions, heat and light are produced. The heat that is being produced, puts a force on the outside. And the force on the inside of the stars is due to the gravitation, due to which the stars are united and alive.
In a way, every star maintains an equilibrium in its life. The forces going outward are due to the reaction and the forces going inward are due to the gravitation. But this reaction is due to a fuel. Hydrogen or helium. This fuel will not last forever. This fuel will end at some point. And when this fuel ends, the force going outward will not last. The force of gravity on the inside, there will be no force to counter it. Then this star will collapse on top of itself, in its own gravity. It will take a long time to happen. The life of our own Sun is around 10 billion years. But what happens next depends on the mass of that star. Let's look at a chart of the life cycle of a star.
If the mass of a star is small, an average-sized star, it turns into a red giant. After that, it can become a planetary nebula or a white dwarf. But if it's a big star, a very heavy star, When its fuel runs out, it cools down and becomes a red supergiant. And then that supergiant explodes and becomes a supernova. After that, a very small core is left. If the core is too small, it is called a neutron star. And if it is too big, it is called a black hole. Basically, the mass of a star, when it is compressed due to its gravitational force, when it is small and condensed, it can become a black hole. Specifically, the volume at which the material compresses.
If a star is as big as our Sun, and a black hole is formed, the diameter of that black hole will be only 50 km. The volume reduces this much, you can imagine. But the interesting thing here is that our son will never become a black hole when he grows up. This was proved by an Indian-American astrophysicist, Subramanian Chandrashekhar, who came up with the Chandrashekhar limit value. He said that a white dwarf can have a maximum mass of 1.4 times the mass of our Sun. It won't be able to stay stable above it. Then it will become a neutron star or a black hole. But because our Sun is below this limit, it will become a white dwarf, not a black hole. Now that you know why a black hole exists, let's understand how a black hole exists.
There are mainly 3-4 types of black holes. The first is the stellar black hole, which is the most common type of black hole. Those black holes are formed by stars. Scientists estimate that there are at least 10 million to 1 billion such black holes in our galaxy. Apart from this, there are primordial black holes. These black holes are as small as an atom. But their mass is as big as a mountain. So even this is an assumption that their size is as small as an atom. These black holes are only theoretical, hypothetical. We don't know much about them. The third type of black holes is supermassive black holes. These are very large black holes. So large that their mass is more than 1 million suns combined.
And they will fit in such a large ball, that the diameter of that ball is as large as our solar system. Scientists believe that there is a supermassive black hole in every large galaxy. The supermassive black hole in our Milky Way galaxy is called Sagittarius A. And the black hole shown in the Interstellar film, which they named Gargantua, which is also a supermassive black hole. Other than this, scientists believe that there could be a fourth type of black hole. Maybe. It can't be for sure. The fourth type of black hole would be the Intermediate Black Hole. Which is somewhere between the Stellar Black Hole and the Supermassive Black Hole. Although, no proof of it has been discovered yet. One thing that you must have seen in the film Interstellar, and the photos that you must have seen, after seeing them,
that a black hole is not a big black ball, that sucks everything in. Black holes look something like this. I'm showing you a movie black hole on the screen, because it's more HD and three-dimensional, compared to the photo taken by humans a few years ago. The first thing you'll notice in this photo, is an orange ring that is forming around this black hole. It is called an accretion disk. And it is a very important feature of black holes. As you know, black holes have a lot of gravitational force. Because of the gravitational force, a lot of gaseous matter and debris is attracted to the black hole. And it keeps floating around it. Just like the planets around the Sun, because of the gravitational force of the Sun.
The difference here is that the gravitational force has increased so much that the things that are revolving around it, they are revolving at a very high speed, they have heated up so much that everything has become a flowing, fluid matter. They have become like the particles of fire, which are hotter than a million degrees Celsius. The closer they get to the black hole, the faster these particles will revolve around it. These particles revolve so fast, they rub against each other, there is compression, that they start glowing. Electromagnetic radiation starts coming out of them. Which are mainly X-rays. This accretion disc has been shown very accurately in the movie. But one thing is wrong. It is not orange in colour. Humans' eyes cannot actually see X-rays.
X-rays are outside the spectrum of visible light. We just represent it by giving it an orange-yellowish colour so that to show that something is there. The real colour of this disc would be close to blue. In 2019, for the first time, a photo of a black hole was taken. And they used this yellowish-orange colour to represent this accretion disc. One thing that you can clearly notice in the real photo, that you don't notice in the movie, is that on one side, the particles look brighter than the other. There is a simple reason behind this. The particles that are spinning towards us, seem to be of a brighter colour. And the ones that are spinning away from us, seem to be dim. This is due to the Doppler beaming effect.
When you look at the real photo of this black hole, you can understand from this blurry photo, the direction in which these particles are rotating. The places that are brighter, are coming towards us. And the dim is going away from us. Coming back to the movie image, another interesting thing you'll notice is that the Accretion Disc gives an optical illusion due to gravity. It looks as if the disc has covered both the top and bottom of the black hole. We can see this because the gravity is bending the light. The part of the disc hidden behind the black hole, when we look at it from the front, the light that comes out of it, comes from the top and bends because of the gravity.
If we look at the black holes from the top view, they will look round, the disc will look normal. We see this illusion only when we look at the black holes from the side view. Apart from this, if you go inside the black holes, you will see a last circle of light. This is called a photon sphere. In this area, the gravity has become so strong that the light has started orbiting the black hole. Light is formed by photons. The photons have started orbiting the black holes. This means that if you reach this area of the black hole and survive, then it is theoretically possible that you will see the back of your head. Because the light is circling around the formation of this ring.
And after this point, comes the boundary of the black hole, which we call the event horizon. This boundary is considered because the gravity has become so strong after this point that even the light is not able to escape. Meaning that everything is black. If you are about to fall into a black hole, and you have crossed the event horizon, then theoretically, there is no chance of you escaping. Because even light cannot escape. How can a human escape? In the Interstellar film, it is shown that Cooper's spacecraft keeps going into the black hole. It keeps going. It crosses the event horizon. And then suddenly, it is in a 5-dimensional space. This part of the movie is purely imagination, speculation. Because we don't know what will happen in the event horizon.
The producers of the Interstellar movie hired a Nobel Prize-winning physicist to keep everything scientifically accurate. But obviously, the things that science doesn't even know yet, the things that we don't even know, the movie has used imagination for those things. What will happen in the centre of a black hole? This is what Einstein's General Theory of Relativity tries to describe. This theory has called the center of the black hole as singularity. Singularity is a region of the black hole, the center where the curvature of space-time becomes infinite. Do you remember the mesh I told you about in the beginning of the article? The heavier an object is, the more it bends the mesh of space-time. In the case of the black hole, the bending is so intense that it becomes an infinite bending.
And because we know from the theory of relativity, that time affects everything related to the energy of gravity, If the gravitational force is so high, then time also becomes infinitely slow. But what does it mean to be infinitely slow in time? Does it mean that if you go into a black hole, and ever get out of it, then the universe would be over for the outer world? We don't know all this actually. Only theories can be made. What do you think? You can tell us in the comments below. There are some interesting theories that are suggested here. For example, we can't see from outside in the black hole, because light is being absorbed in it. But a theory says that in the event horizon, light is reflecting from many places and reaching the singularity.
So it is possible that in the event horizon, we can actually see things. What humans have seen about black holes for sure, is just this photo. This photo was taken by the Event Horizon Telescope on 10th April 2019. It showed the existence of black holes was practically proved. About 100 years ago, when it was theoretically proved. One thing is certain here, if you fall into a black hole, the chances are that you will break into pieces, due to the gravitational force. You will die within milliseconds. But still, friends, there is no need to be so scared of black holes. Many people had this misconception that black holes, suck up all matter and keep growing, and eventually destroy the entire Universe. But that is not the case.
As I said, there is a supermassive black hole in the centre of every galaxy. The rest of the planetary bodies and stars, that are in the range of the black hole's gravitation, revolve around it. Just like the planets revolve around the Sun in our solar system. This happens in the middle of the galaxy in a more powerful way. So as a conclusion, if you maintain a good distance from the black hole, maintain social distancing, will be safe and secure. The concept of five dimensions in the Interstellar film, is also an interesting concept. We'll talk about it in a future article. That's it for now.
