Black Holes Explained | They are not what you think they are

If you recall, in 2014, Christopher Nolan's blockbuster movie was Interstellar. Space related concepts like wormholes, black holes, alien planets were depicted in this movie in a scientifically accurate manner. But perhaps the most shocking scene was at the end of the film. 

At the climax, the film's main character, Cooper, falls into a black hole. In the movie, the black hole was called Gargantua. Cooper falls with his spaceship into a black hole. At first everything around him was black, complete darkness. But as he descends deeper, he notices some grain-like particles. These particles hit his spaceship and cause scratches on it. There were some flashes of light, some sparks, and his spaceship caught fire. He was forced to eject from his spaceship and kept falling into the black hole. And suddenly he found himself in a five-dimensional space. The five-dimensional tesseract. It was an overwhelming experience. A place where he could communicate with his past self using gravity. Looking at these scenes, you might have wondered if this is actually possible. Does this exist in a black hole? If we fall into a black hole, what will we see? Come, let's try to understand these aspects in today's article." Black holes remained largely unknown until the 20th century. 

A black hole is a region in space where the gravitational force is so strong that not even light can escape from it." you can't tell what's inside a black hole from the outside.” “Black holes haunt our universe. Dark centroids. They will swallow everything in their path." Let's start at the beginning of this story, friends. The history of black holes is not very long. 100 years ago, no one knew about black holes. Because of Einstein's theory of relativity, black holes were later discovered. Friends, the theory has two parts . Special Theory of Relativity and General Theory of Relativity. Special Theory of Relativity published by Einstein in 1905 tells us how speed affects time. If you are in a spaceship that is moving very fast, if the speed is too fast, time will slow down. in relation to people who are not in the spaceship, back on Earth. The word relative is very important because when you are in a spaceship, you don't experience time slowing down. You would think that time passes at the same rate as it normally does. But when you return to Earth , you will find that there was a difference in the flow of time. This is called kinematic time dilation. And if you saw my article on Time Traveler, I explained in detail how it works there. Not only speed, but also gravity ace cca n also leads to time dilation, as shown by Einstein in his General Theory of Relativity. 

He developed this in 1915. The more gravitational force you experience, the more time slows down for you. This is known as gravitational time dilation. And that was wonderfully depicted in Interstellar. When Cooper and his team land on Aqua Planet, one hour on that planet is equal to 7 years on Earth. This is happening on the planet because the planet was very close to the Gargantua black hole. So the gravitational force of the Black Hole affected time. To visualize this, Einstein wanted us to visualize the space-time fabric. Sort of like a grid on which all the planetary objects are placed. The space-time fabric bends due to the weight of objects And when the web bends, not only does it pull more on physical objects, but it also causes time dilation, and other forms of energy like sound, heat, or light are also affected by gravity. , It is true. This was another conclusion of Einstein. Gravity affects almost everything. Not only are physical objects attracted by gravitational force, heat, sound and light are also attracted. Friends, this means that there can be such objects in space that have such a high gravitational force that they can completely absorb light. 

If such objects are there, it means that they would be completely black. We won't see them. Because not even light can escape from them. Friends, these are exactly what black holes are. Einstein presented his Theory of General Relativity, the concept of black holes was only theoretical at the time. Einstein knew that gravity affects light. And objects that can absorb light were theoretically possible. But Einstein didn't know that real black holes existed. When Einstein was alive, the concept of black holes seemed strange to him. He knew that such things could be, in theory, but then the existence of infinity was also theoretically possible. he basically didn't believe such things actually existed. At the time he died, the term Black Hole had not even been invented. Here's an interesting fun fact, a key point in Einstein's theory was that the speed of light limits the effect of gravity. Not feeling the force of gravity instantly, everywhere, its upper limit is the speed of light To use a practical example, suppose the sun suddenly disappeared, as you know, we will know about that disappearance on earth 8 minutes later, because sunlight takes 8 minutes to reach the earth . 

But according to Einstein, the gravitational impact of the Sun's disappearance will also be felt 8 minutes later. Isn't it very interesting? After Einstein's theory of general relativity was worked out, many scientists, such as several equations, solved these equations and tried to derive solutions, and by arriving at the solution of these equations, it was theoretically proven that things like black holes really exist. In the 1960s, archers and scientists finally agreed that we would be able to see black holes not only in theory, maybe one day, but also in reality. Because they exist in space. The term black hole was first used by a magazine in 1964. It wasn't until 1967 that the term gained popularity when physicist John Wheeler popularized it. Although the term black hole sounds quite sensational, it is a misleading name. Black hole. It might sound like there is an actual hole. But that's not the case. There is no hole in the universe. Black holes are made of stars. So there is some material in the middle of them. 

But in stars, even our Sun is a star, there is a continuous reaction of nuclear fusion going on at their center. These reactions produce heat and light. The heat produced sends a force outward, and there is a gravitational force at the center of the star that helps the star stay intact and alive. This is how stars maintain their balance throughout their lives, forces pushing outwards due to reaction and pulling forces inward due to gravity. But these reactions take place when there is fuel. Either hydrogen or helium. The fuel wouldn't always be there. At some point it would burn. And when the fuel runs out, it won't be there. there must be no forces pushing out. would not be resisted by the same force, so the star itself collapses due to its own gravity. This will take a long time by the way. The life expectancy of our Sun is around 10 billion years. But what happens next depends on the star's mass. Let's look at the life cycle graph of a star. If the mass of the star is not high, i.e. if it would be a small or medium-sized star, it will turn into a Red Giant. It can then become a planetary nebula or a White Dwarf. But if it were a massive star, the star will have a lot of mass when it runs out of fuel, cools down and turns into a Red Supergiant. Super Giant bursts and turns into Super Nova. After that, a small core remains. If the core is small, it is called a neutron star, but anything larger than this, we call it a Black Hole. Basically, the mass of a star can turn into a black hole after it collapses, shrinks and condenses due to its gravitational pull. How small, specifically, is the volume of a compressed star? For a star the size of our Sun, if it becomes a black hole, the diameter of the black hole will be only 50 km. Can you imagine the volume being that small? But the interesting thing is that our "son" will not grow into a black hole. 

Indian-American astrophysicist Subrahmanyan Chandrasekhar proved this. He developed the value of the Chandrasekhar limit. He said the maximum mass of a White Dwarf could be 1.4 times the mass of our Sun. Above that, it cannot be stable and would turn into either a neutron star or a black hole. But because our son, the Sun, is below this limit, it becomes a white dwarf instead of a black hole. Friends, I'm going to take a little ad to tell you about the savings black hole. Correctly. Now that you understand why a black hole exists, let's now understand how black holes are. There are mainly 3-4 types of black holes, my friends.

The first is a stellar black hole. This is the most common type of black hole. Black holes that were created by stars. Scientists estimate that there are somewhere between 10 million and 1 billion such black holes in our Milky Way Galaxy. primordial black holes exist. These black holes are as small as an atom. But their weight is like a mountain. They are believed to be as small as an atom. Friends, these black holes are only theoretical, hypothetical, we don't know much about them. The third type of black hole is the supermassive black hole. These black holes are huge. So big that their mass is greater than the mass of 1 million Suns combined. And it fits into a sphere the diameter of which is as big as our Solar System. Scientists believe that at the center of every large galaxy is a supermassive black hole. This supermassive black hole at the center of our Milky Way Galaxy is called Sagittarius A. The black hole in the movie Interstellar, which was named Gargantua, was said to be a supermassive black hole. In addition, scientists believe that there may be a fourth type of black hole. 

Although it cannot be said for sure, the fourth type of black hole will be an intermediate black hole, which lies somewhere between the sizes of Stellar and supermassive black holes. Although no evidence of this has yet been discovered. One thing you've seen in the movie Interstellar and in the photos you've seen so far, and your interpretation is, a black hole is I don't like a big black ball sucking up everything around it. Black holes look something like this. This is the black hole as shown in the movie because it is in HD and is more 3-dimensional than the photo we captured some time ago. The first thing you would notice in this photo is the orange ring that forms around the black hole. It is known as an accretion disk. It is an important feature of black holes. As you know, the gravitational force in black holes is very high, so due to gravity, a large amount of gaseous matter and debris is attracted to the black hole and remains floating around it. Much like the planets orbit the sun due to the sun's gravitational pull. The difference is that the gravitational pull of a black hole is so strong that things spinning around them spin at very high speeds and heat up so much that they turn into a flowing fluid-like mass. They literally become fire-like particles hotter than a million degrees. Celsius. The closer they get to the black hole, the faster they spin around it. 

The particles spin so fast that they rub against each other and compress, causing them to glow. They emit electromagnetic radiation, which is mainly X-rays. the accretion disk was shown very accurately in the movie, the only thing they got wrong was that it's not really orange. Human eyes cannot see X-rays. X-rays lie outside the spectrum of visible light. We simply depict it in orange-yellow spol lours to illustrate this. The actual color of this disk would be closer to blue. In 2019, the first photograph of a black hole was taken. Again, a yellow-orange color was used to represent this accretion disk. One thing you can clearly notice in the real photo that you might not notice in the film is that the particles on one side are brighter than the other. There is a simple reason for this. Particles rotating towards us appear brighter and those rotating away from us appear fainter. This is due to the Doppler beam effect. When you see a real photo of this black hole, you can look at this blurry photo and interpret the direction of the spinning particles. The area that is brighter is coming closer to us and the dark area is moving away from us. Going back to the image from the movie, another interesting thing you would notice is that the accretion disk gives off an optical illusion due to gravity. A black hole appears to cover the top and bottom of the disk. It appears that way because gravity bends light. An area hidden behind the disk when viewed from the front, light coming from this area must travel through it because it is bent by gravity. If you look at a black hole from above, it will look like a normal round disk. We only get this illusion when looking at a black hole from the sides. In addition, when you enter the black hole, you will see the last circle of light. photon sphere. The gravity in this region is so strong that light begins to orbit the black hole. What is light made of? Photons. Photons begin to orbit the black hole. 

This means that if you get into this region of the black hole alive, it is theoretically possible to see the back of the head, because the light moves in a circle, in the form of a ring. Beyond this point is the boundary of the black hole. This is known as the event horizon. It is considered the limit because after this point gravity is so strong that even light cannot escape. Beyond this point, everything is black. If you're falling into a black hole and you've crossed the event horizon, theoretically, you have no chance of escaping. If even light can't escape it, how would a human do it? In the movie Interstellar, it is shown that Cooper's spaceship is still falling into the black hole, having crossed this Event Horizon, it suddenly reaches the fifth dimension. This part of the movie is purely imagination. It's speculation because we don't know what's inside the Event Horizon. The producers of Interstellar hired a Nobel Prize winning physicist to keep everything scientifically accurate. But apparently the things science has yet to discover, the things we know nothing about, for those parts the film turned towards the imagination. What will be at the center of a black hole? Einstein's General Theory of Relativity tries to describe it. In this theory, the center of the black hole is called the Singularity. A singularity is a region of a black hole, the center where the curvature of spacetime is infinite. Remember the network I talked about in the first half of the article? The heavier the object, the more the space-time web will bend. In the case of a black hole, it is so curved that it stretches infinitely. As we know from the theory of relativity, time, energy and everything else is affected by gravity. As the force of gravity increases, time slows down infinitely. But what does it mean that time slows down infinitely? Does this mean that if you enter a black hole and if we could ever get out of it, the universe outside would end for the rest of us? We don't know. We can only create theories. What do you think about it? Comment below and let me know. Some interesting theories are proposed. It's like we can't see inside a black hole from the outside because when light is absorbed into it, one theory says that inside the event horizon, the light is reflected at several points before reaching the Singularity. So it is possible that inside the Event Horizon things would actually be visible. Things we've seen for sure with black holes is this single photo. 

This photo taken by the Event Horizon telescope on April 10, 2019. This practically proved the existence of a black hole. About 100 years after they were theoretically proven. One thing is for sure, if you fall into a black hole, chances are you will be blown to pieces by the force of gravity. You will die in milliseconds. But even so, friends, there is no need to fear black holes. Before, many people had this misconception that black holes suck up all the matter, keep getting bigger and eventually it will end the whole universe. But it doesn't work that way. As I told you, at the center of every galaxy is a supermassive black hole. of other planetary bodies and a hundred In range of the black hole revolves around it. The same way that all the planets in our solar system revolve around the sun. The same thing happens in the center of the galaxy, although in a much stronger way. if you keep the right distance from the black hole, if you keep social distancing, you'll be safe. And the 5-Dimension concept mentioned in InterSettlar is another interesting concept.