Black Hole | Decoding the Mysteries of black hole | Weirdest thing of the Universe | Everything in it

There are many things in this universe about which we have not yet known much. Black holes are also one of them.

If you do not already know about black holes, then let me tell you that there are some places in space where the stretch of gravity is so much that it swallows up everything that comes near it. Even the light does not return from there. For this reason we do not see it. We call such places black holes. We know about them, how they are made, what happens outside them and how to detect them. But even today we are not able to know what happens inside them. In practical, it is almost impossible to know because even if we send a Prop inside a black hole, it will never be able to get out from the effect of the gravity of the black hole and will not be able to send any signal to us.

So it is better for us now that we consider black holes theorotically. In today's episode, we will learn how black holes are made. How does their size increase. What is the reason for the light shining near them and what is going on inside them. So let's start today's episode.

You know that there are such places in the space where the effect of gravity is so much that even light itself cannot come back from there. These places are called Black Holes. So we don't even see it. But do you know how it is made? You must have often heard that black holes are formed when the matter of huge stars is compressed into a small space. This often occurs after Supernova explosion when a giant star is on the verge of extinction. But what if I tell you that black hole can be created from everything present in this universe. Even to you. Yes, you heard right, we know that every object has its own mass. If we compress this mass inside its sphere made of Schwarzschild radius, then that object will become a black hole. Now the next question that arises is, what is this Schwarzschild radius? So let's know what it is? You might know that the distance from the center of the sphares or the circle to its boundary is the same which we know as radius. Schwarzschild radius is one such radius, but the difference between the ordinary radius and the Schwarzschild radius is that if we compress the mass of an object in the sphere it creates, that object will become a black hole.

Each object has a different Schwarzschild radius, which you can extract from this formula.

Here G is the gravitational constant, M is the mass of the object and C is the speed of light. As you can see in this chart, the Schwarzschild radius of our Sun is about 3 kilometers.

This means that if we pressurize the Sun and confine it inside a sphere whose radius is only 3 kilometers, it will become a black hole. Similarly, to make the Earth a black hole, we have to limit it to a sphere with radius of about 9 millimeters. But we have no way that we can do this. But the larger stars which are many times larger than our Sun, their Schwarzschild radius is also much larger. When the fuel of such stars is exhausted, they are unable to keep themselves warm as before and remain confined in a very small space. We know this small space as Singularity.

Its density becomes infinite. Due to this, its gravitational pull becomes so high that no object can come out of it. There is not even light. Usually this singularity is represented to us as a small point or particle. But in reality it is not a physical but an infinitesimally small mathematical point. I hope by now you will have understood how black holes are made. Let us now know how big they are. 

Although black holes are of different sizes, but according to size and mass, they are divided into three parts. The smallest size black holes are called primordial black holes. Scientists believe that such black holes must have been formed soon after the Big Bang. The size of these black holes is only the size of an atom. But their mass is equal to the mass of a huge mountain. The most detectable black holes are of medium size and are called stellar black holes. The mass of such black holes is up to 20 times the mass of our Sun. But this mass is reduced to only a small sphere by compressing, whose diameter is only equal to 10 miles. Some black holes are quite large in appearance. Such black holes are called supermassive black holes.

The mass of such black holes is as much as the mass of more than one million stars of the size of our Sun by joining them. But it is compressed and is reduced to only such a large sphere whose diameter is almost equal to the size of our solar system. Scientific evidence tells us that one such black hole is definitely present in the center of all the major galaxies. Many people asked us what is the bright light that we see in our Galaxy?

The answer is that all the pictures you see of the Milky Way Galaxy are not real. In most cases, it is only an artistic impression. The truth is that due to galactic dust we cannot see at the center of our galaxy. We can see this better in the infrared wavelength.

After studying the infrared rays coming from the center of the Milky Way Galaxy by Hubbell, we came to know that our galactic center has a lot of stars and dust. Perhaps this is because the artists depict a bright light in the center of the Milky Way. 

Quasar can also be another reason for showing bright light in our galactic center.

There is also a supermassive black hole in the center of our Milky Way Galaxy, named Sagittarius A, its mass equal to about 40 sun masses. While this mass is limited only in such a large sphere whose diameter is equal to that of the Sun. Due to the existence of this black hole, there is Quasar present, which we see shining. But now its brightness has become quite blurred. Therefore, it would be wrong to depict a bright light in our Galactic Center at the base of Quasar. Now you must be wondering what is this Quasar and if it exists near a black hole then how it can shine.

Because we all know that the attraction of gravity in black holes is so much that even light itself does not come back. Let's understand Quasar and know the answers to these questions. Quasar is the short name of the Quasi Stellar Object. As I already mentioned, a very large black hole exists in the center of every major galaxy. Whatever comes near these black holes swallows it. But it is not the case that any object is pulled directly into its center. In fact, any object that moves close to these black holes first orbits a black hole in the shape of a disk and only then enters the black hole. This disk is called accretion disk.

When many objects are orbiting a black hole at high speed in this accretion disk, friction and gravitational force cause a lot of hits between them. Just as hot objects emit light and radiation, similarly the objects present in the accretion disk also emit light and radiation as they become quite hot. This is the bright light that we see. So do not think that this light comes from a black hole. It is impossible for light to come out from a black hole. The more materials there are to swallow near the black hole, the more bright this light will be. It is not that all such supermassive black holes always have such light coming out. As I already mentioned, such light is visible to us only when the black hole is swallowing the material. If a block hole has no material to swallow. So we do not see any such light with them. Generally, only those galaxies have a quasar formed in it that is either so young that they have a high amount of material to feed the black hole in the center of it, or when the two galaxies collide. Because when this happens, black holes have a lot of materials to eat. Which supermassive black holes consume a mass equal to the mass of the sun every year, they continue to eject large amounts of energy in the North and South Pole. Astronomer called it cosmic jet. While we know little about the Galaxias Formation, some astronomers about the quasar also believe that it represents the early stage of formation of the Galaxy. Most of us think that the black hole's gravity is so strong that it pulls the object from far away. But actually it is not so. Black holes cannot pull them until an object moves close to them. This is why we often see Planet and Stars circling it. A similar Planet was shown in the film Interstellar.

It is just like if for some reason our Sun turns into a black hole, then it will not happen that all the planets will come under the influence of its gravity and will immediately get inside it. It will happen that darkness will befall the entire planets due to the absence of the Sun, but all the planets still keep circling the black hole in the middle as before. Many people here will say that the sun can never become a black hole. Yes, rightly you said, this is just an example. If we talk about reality, then the mass of the Sun is not so much that it can become a black hole. After million years, when the Sun is taking its last breath, it will become a Red Giant Star and when its fuel is completely exhausted it will turn into a Planetary nebula. In the end our sun will become a cool white draf star. 

The biggest mystery about black holes is that we do not know exactly what happens inside it. The current theories propose that all the matter swallowed by a black hole go to its center and squeeze into a mathematically infinitesimall point, which we know as singularity. But we have not yet understood how this singularity works. Because the mass of singularity is very high, but to understand its behavior, the size is very small, we need to combine the Theory of Gravity with Quantum Physics. This Unified Theory is already in the works and has been named Quantum Gravity. At the moment we do not have any working quantum gravity theory yet.

Wormholes are mysterious solutions to the Einstein field equation.

If you do not know about them, then tell us in the comments, we will make separate articles on them. In short, it connects two parts of space-time through shortcuts, which if used, we can reach a distant planet in the universe far before light.

But Wormholes still only exist in theory. Actually no type of Wormhole has been seen yet. But if we talk about a black hole, we know that it definitely also exists and maybe it can also act like a wormhole.

Einstein's General Theory of Relativity tells us that every kind of mass warps space. The higher the mass, the more space will be warped.

Now if we look at the mass of a black hole, it is much higher. This means that it will warps space-time so much that it will be like a bridge for us to go to another universe or any other time period. That is, a working wormhole. But at the moment without experimental data and observation, all these are just speculations. But If this happens in some way, then it is impossible for a survivor to survive beyond singularity. As you grow closer to singularity, your body will pull. The molecules of your body will also be stretched and a time will come when you will die. We do not know what will happen when we reach Singularity. Such stretching caused by the effect of powerful gravity is called Spaghettifucation.

The way we do not know what happens inside a black hole. We do not even know whether a black hole is always alive or destroyed when it has nothing to swallow. According to Stephen Hawking, the black hole is always emit a radiation, which we know today as Hawking Radiation.

We will learn more about this in other episodes. At the moment, you only know that black holes always carry radiation, which is also called black hole evapuration. Due to this, their mass and energy keeps decreasing gradually. Therefore, the black holes which have nothing to swallow, they are completely destroyed by emitting slowly the mass and energy inside them in the form of radiation. That is, according to this theory you can call black holes a Universe Recycling Machine. Stephen Hawking proved this theory in 1974 based on the laws of quantum mechanics.

A question about black holes may also come to your mind that if we do not see them, then how do we know that they are present and where it exists. It is absolutely true that due to powerful gravity, the light does not come back through the black hole. The reason we do not see this, based on the effect of their powerful gravity on the bodies around them, we can tell that there is a black hole there. For example, if a star is orbiting a particular point in space and there is no object visible to us, then there are many chances that the star is rotating to a black hole. If we talk about the other way, when a star rotates near a black hole, then there is high energy light production. With scientific instrument, we detect such special light, which shows that there is definitely a black hole there. Talking about the third way, many times the black hole's gravity is so high that it starts pulling the outer gases of the nearest star orbiting it in the form of a disk.

This disc we called Accretion disk. When these gases move from the accretion disk to the black hole, friction causes considerable heat production, leading to the emittance of x-rays all around. Our telescopes capture and study these x-rays. Black hole is a mystery that if we have solved it, then we will be able to understand this universe and gravity better.

So this is all for today guys, I just hope that you liked this episode. If so, do not forget to share. If you are new to this website then do subscribe & bookmark to it. See you in the next episode till then Namaste.