Hello, friends! The most amazing thing about our universe is, perhaps, its size. How unimaginably big this universe is! But, perhaps, this is the most disappointing aspect as well. Think about it, if today we use our powerful telescopes to find another planet like Earth in a galaxy, which is suitable for humans to live on, it will take centuries for us to reach it. In fact, for all individuals leaving this galaxy is impossible. Now, everyone knows that the Earth is in the Milky Way Galaxy. And the closest galaxy to the Milky Way is the Andromeda Galaxy. Approximately 2.5 million light years away from the Earth. So, if we use a spacecraft to reach there. With the usual speed of 28,000 km per hour it will take 94.5 Billion years to reach it.

Not only that, if we can somehow make the technology travel at the speed of light, it will still take 2.5 million years to reach there. This is truly disappointing. What is the point of finding all these planets when we will never be able to travel there? But if there were a shortcut to travel outside the galaxy, a shortcut through which we can travel across million light-years in a few months, then these things become interesting. These shortcuts, my friends, are Wormholes.

The 2014 film, Interstellar, my favourite space film, I would like to mention again. In this film, it is shown that when Cooper and his team leave Earth in search of other habitable planets, in search of other planets like Earth, they travel to another galaxy. From their galaxy to another galaxy, they travel through a wormhole in a matter of minutes. This is the scene in the film when Cooper’s team passes through the wormhole. According to the film, this wormhole was discovered near the orbit of Saturn by NASA. It is mentioned in the film many times because it plays an important role in the plot. But the most interesting thing is that this concept of wormholes is not science fiction. In fact, it is based on real science. What are wormholes exactly? And how can we use them? Before understanding all this, we have to come back to Einstein’s Theory of Relativity. I talked about it in the video on Black Holes too and explained the basic concept in that video.

Now let’s go a little deeper into it. When Albert Einstein wrote his Theory of Relativity, he wrote it in a set of equations. The set of equations is called Einstein’s Field Equations. It was first revealed publicly on 25th November 1915, when Einstein submitted his paper to the Prussian Academy of Sciences in Berlin, Germany. In total, these field equations are made up of 10 different equations. 10 non-linear partial differential equations. But in short, they can be represented by only 1 equation. And that equation looks something like this. Don’t worry, we won’t go into the mathematical details in this video. Because this one equation has a lot of complexity. If you expand this one equation, you can see these steps. Even if you love maths, you will get dizzy after seeing this. Broadly speaking, these equations tell us how matter and energy influence the curvature of space-time. Albert Einstein said that to visualize this, we need to imagine a big mesh. When you place objects on this mesh, it bends down due to the weight.

The space-time mesh also bends in the same way, it curves with the weight of big planets and stars. The more the gravitational force of a planetary object, the more the space-time mesh will curve around them. Now the interesting thing is that Albert Einstein himself was not able to solve his field equations completely. He had just found an approximate solution to his equation in a specific case. The first person who solved these field equations was Karl Schwarzschild in the year 1916. He calculated exactly how much the curve of space-time bends and to what degree in case of a single ball of mass. It was the solution by Karl Schwarzschild which helped scientists understand the concept of Singularity. What would happen if this mass becomes infinitely dense? The curvature of space-time would wrap around it so tightly that this region would pinch off from the rest of the universe. With this, the scientists were able to theoretically prove the concept of Black Holes. This was proven about 100 years ago.

Actually, decades later, for the first time in 2019, scientists were able to take a photo of a black hole. So, basically, what I want to say is that one of the solutions to these field equations was black holes. Theoretically, we already knew about the existence of black holes about 100 years before they were discovered. And the thing is, friends, that another solution to these field equations is Wormholes. You might be thinking how can we solve one equation and get two solutions. Well, you would remember studying quadratic equations in school. This simple equation also has two solutions, x=2 and x=3. Both are correct. So, if you see Einstein’s field equations, they are much more complicated. Actually, there can be numerous solutions to these. Wormhole is one suck solution and its scientific name of the Wormhole solution is the Einstein-Rosen Bridge.

This name is derived from Albert Einstein and his assistant Nathan Rosen who worked together and came up with this solution in 1935. So it is very easy to understand wormholes. It is basically a shortcut which connects two points of space-time. First, I will explain things in two dimensions so that it is easy for you to understand. Look at this paper. There are two points, A and B, on this paper. If you want to go from point A to point B using the shortest route, which route can it be? The straight line that connects A and B.

There can be no shorter route in two dimensions except the straight line connecting both points. But if this two-dimensional mesh is bent into three dimensions, you will see new paths emerge. I have bent A and B in such a way that if you want to choose the shortest path to go from A to B, then this distance of millimetres between A and B can be used directly. If I make a path here between these two, literally, by inserting a pen, then, literally, a shortcut has been found to go from A to B, which is much, much shorter, as compared to this path. Wormholes are also doing the same thing.

In our three-dimensional world, we think that the shortest way to go from Milky Way Galaxy to Andromeda Galaxy is 2.5 million light-years long. But if our 3-dimensional space is curved or bent into the 4th dimension, then it’s possible that we can find a shorter, better shortcut. Now, it is very difficult for us to imagine the 4th dimension because we all live in 3 dimensions. But to some extent, you can understand it better if you compare 2 dimensions and 3 dimensions. I’ll give you another example. This is the world map. If you want to go from Delhi to New York by flight, what would be the shortest route of the flight? You’d say, a straight line connecting Delhi to New York with the flight flying over Africa.

But in reality, this would not be the shortest route. Because you’re thinking in two dimensions. The shortest route would be to travel over Finland, Sweden, passing by Iceland and Greenland to reach New York. Which on 2-dimensions looks like a longer route unnecessarily flying to the North. But if you look at it in 3D, it looks obvious that it is the shortest route. In 1957, scientist John Wheeler published a paper on Einstein’s Rosen bridges. He compared it with a similar analogy. He gave an example of an apple and an insect is eating that apple, a worm. It reaches from one side of the apple to the other while eating it or travelling through the middle. Instead of travelling on the surface of the apple like our aeroplanes travel around the surface of the earth, Earth’s circumference. By doing this, the worm will travel a shorter distance. In a way, it has taken a shortcut in space-time. And this term was named by Wheeler as a Wormhole. And this is where the word Wormhole originated. When you search the word wormhole on the internet, you get to see many such diagrams. Basically, the same thing I did with the paper, two points were connected through a hole. Here, it is imagined that we have a space-time mesh, on which there is an object with an extremely strong gravitational force. So strong that the curvature of space-time has bent so much that it has pierced through the other side. The space-time mesh has folded on itself.

Just like I folded that paper. And this wormhole has become a shortcut to travel from one galaxy to another. But in all these visualizations, the problem is with the dimensions. We try to represent a wormhole in two dimensions. But as I said, the wormhole works in 3D to 4D. So in reality, if a wormhole exists, it will look like a spherical ball. There is a very interesting website where you can visualize what wormholes will actually look like if their existence is proved indeed. A ball-like figure, where, as you go inside, everything that you see around you is curved. And if you turn around and look, the earth is moving away from you. And everything will look in a circular shape. That’s why the wormhole shown in the Interstellar film is depicted in a very realistic way. Here, it is important to mention that the concept of wormholes for now, as of 2023, is just a theoretical concept. It has been theoretically derived as a solution to Einstein’s field equations. In movies, scientists have tried to visualize it. Many theories have been formed about it, but practically no one has seen a wormhole yet. Scientists don’t know whether wormholes really exist or not. But if wormholes exist, they will work as a time machine too. Just imagine that you will be able to travel millions of light-years in a few minutes. This means that you can reach there even before light. If the light didn’t reach there, then basically you have jumped from one place in time to another. Now it’s a different thing that if wormholes do exist, if wormholes are to be considered real. The first question is how will the opening of the wormhole be formed? We will need an extremely heavy gravitational force here.

Where can we find this gravitational force? If you have seen my old space-related videos, you can guess what the answer to this question is. A black hole. Einstein and his assistant Rosen theorized that only black holes can have such a gravitational force that they can open up these tunnels of wormholes. Everything is attracted to black holes. Everything will be attracted to it and will flow through this wormhole through this tunnel. But the next question is what will be on the other side of this tunnel? If there is a black hole on the other side then there will be no way to get out of this tunnel. You will be trapped inside this tunnel. Basically, in that case, this wormhole will not be a tunnel to go from one place to another but rather it will be a trap. There should be something on the other side which is the opposite of a black hole in every sense. Something which is as powerful as black holes but works in the exact opposite way. Something that instead of attracting things towards itself, sends things away from itself. So that an exit point can be created. And here, enters our story, the white holes. Once again, White Holes is a concept that has been proved theoretically by Einstein’s Field Equations. Apart from black holes and wormholes, white holes are another solution to these field equations. What are these white holes? Like white is the opposite of black, a white hole is the opposite of a black hole in every sense. Like in a black hole, no light can escape once it is trapped inside. On the other hand, in a white hole, no light can enter. It can only be emitted by it.

This means that the white hole will be extremely bright and white in colour. Russian theoretical physicist and cosmologist Igor Novikov was the first person to use the term White Hole in 1964. According to scientists, a white hole is basically a time reversal of a black hole. Like the event horizon of a black hole is a point of no return. Once it is crossed, nothing can escape from it. Similarly, the event horizon of a white hole is a boundary of no admission. Nothing can go beyond that point. The objects inside the white hole can go outside and interact with the outside world but they cannot go back inside. Even though this is a solution to Einstein’s Relativity Theory, no one actually knows how white holes will form in reality. I explained the formation of black holes in the video about black holes when a star collapses on itself. But what can be the opposite of this? So, can a white hole exist or not? This is the topic of discussion among scientists to date. Some scientists believe that when Big Bang happened and the universe was formed, at that moment of creation, everything must have emerged from a gigantic white hole. Another theory is based on the idea by Stephen Hawking. Stephen Hawking said that a black hole will eventually evaporate when radiation keeps leaking from it. “Black holes are not eternal. They evaporate away at an increasing rate until they vanish in a gigantic explosion.” But when a black hole evaporates and dies, what will happen to the information and matter inside it? Quantum theory has a fundamental law which states that no information can be lost. It is called the No Hiding Theorem.

According to the No Hiding Theorem, even if any information disappears from a system, it would still exist somewhere or the other in the universe. Theoretically, if all this matter and information is being sucked into a black hole, it will be spitted out after the death of the black hole. And this is likely happening through a white hole. Based on this argument, many scientists say that a white hole forms when a black hole dies. But till now, we do not have any substantial information about how a black hole dies. On the other hand, some scientists argue that it is theoretically impossible for a white hole to exist because it violates the Second Law of Thermodynamics. As you must have studied in school, the second law of thermodynamics states that entropy in any system cannot be reduced. Take this paper as an example. If I tear this paper, after the paper is torn, the entropy is simply increasing. Now, it is not possible to join it again in the same way. The way a paper shredding machine shreds the paper which increases the entropy in the same way, black holes shred everything in the universe. Black holes swallow the entire planets and stars and only radiation is left behind. This increases the entropy in the universe. But if you try to imagine that it is happening in reverse, with the entropy decreasing, this is not possible. And if white holes do exist, then essentially this is what they will aim to do. So, as per this logic, perhaps they cannot exist. But despite this, some scientists believe that not only do white holes exist, but that in 2006, scientists saw a white hole. On 14th June 2006, a space satellite named Neil-Gehrels Swift Observatory captured an astronomical event. Scientists saw an explosion of a white light which suddenly disappeared.

This event was named GRB 060614. It was a gamma-ray burst. Gamma-ray bursts are basically are highly energetic explosions observed in distant galaxies. Usually, these events occur when a black hole swallows a big star. You can see very bright explosions of light. But in this case, no evidence of a star was found. So, it was hypothesized that this was an observation of a white hole. Since then, we have not seen such an event again. And that’s why till now, white holes is only a theoretical concept. But the thing to note here is that black holes were also theoretical at one time. But then, one day, they were practically proven. So, it’s possible that in the future the same will happen with white holes. The same thing can be said about wormholes, friends. It’s possible that they can be proven in the future. But even if their existence is proven, scientists still doubt whether humans will be able to travel through them or not. The most interesting news about wormholes’ existence is from 2015 when scientists created a magnetic wormhole in a laboratory. So, till now, we were talking about wormholes in the sense of gravitational force. But if we talk about magnetic force, scientists have already been successful in creating wormholes. What does this mean? There are two ends of a magnet, a North Pole and a South Pole. We know that the two ends always stay together. Even if you break a magnet into two pieces, both the pieces will still have both poles. Scientists used some special materials and achieved something by separating the two poles of the magnets and put an invisible gap between the two. Basically, the magnetic field of one magnet went inside one end of the wormhole and came out from the other end.

You can see its visualization here. The left image shows a device which was created by the scientists which separated the two poles of the magnet. So, this device is basically working as a wormhole for the magnetic field. We can see this device with our eyes but if you look at the magnetic fields in the right picture, you will see that on one side, there is a pole of the magnet and on the other side, the other pole is separated and at a distance. Like in space, a wormhole works by bending the space-time curvature, here, this wormhole, bent the magnetic field. To make this magnetic wormhole a high-temperature superconducting material was used known as the Yttrium Barium Copper Oxide and it was kept in a liquid nitrogen bath to conduct this experiment. Finally, friends, I would like to say that even if the existence of wormholes is not proven in the future it does not mean that we cannot find other ways to travel faster than light. Theoretically, several other solutions are proposed. One is Alcubierre Drive. It was proposed in 1994 by theoretical physicist Miguel Alcubierre. The idea here is that there will be a spacecraft which will be able to travel at a speed faster than light. But how will it be able to do that? By contracting the space-time curvature in front and expanding the space-time curvature in the back. Theoretically, another solution to Einstein’s Field Equation is presented by Alcubierre Drive. It will be very interesting to see the other solutions proposed for these field equations and what practical things can be derived from them. Thank you very much!