Soliton Technologies: At the end of the 20th century, 1 TB of data was sent using solitons in France in 1998.
These ‘solitons’ are everywhere around us.
These ‘solitons’ are everywhere around us.
In the early 19th century, a young engineer named John Scott Russell was experimenting with a design for a canal boat. Inside the narrow canal he roped two horses to the boat to propel the boat. On the way, suddenly the rope broke and the boat stopped. At the same time, a funny thing happened. Russell noticed a strange wave moving forward from the water in front of the boat at high speed. This is not the kind of waves we are usually familiar with, i.e. water rising and falling when a rock hits a pond and so on. There is no rise and fall of water here. Some of the water is rising and moving forward at a speed of about 10 km per hour! Young Russell chased the wave of fun on horseback and discovered a wonderful thing, which is one of the most important centers of non-linear science research today – the ‘soliton’. We will know how this naming happened a little later, before we try to understand what kind of wave it is?
When a wave or wave begins to propagate, its amplitude (which we can also think of as intensity in Goda Bengali) gradually decreases. This is the spreading of the wave, in science its cloth name is ‘dispersion’ or ‘dispersion’. But in this case the wave of water which Russell observed as a result of the cutting of the horse-rope, had no sign of dispersion. Its strength or intensity did not decrease, but continued with the initial intensity. Strange!
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Astounded Russell rode his horse for a couple of miles along the canal following this amazing wave. Finding no edge, the young engineer returned home and tried to repeat the same incident. The origin and spread of science is like that. Remembering in this context, it took Robert Hooke thirty years to give the timeless elasticity one-line formula that is now a high school textbook for all science students. Anyway, Russell returned home and built a 30-foot-long chowder. This strange wave was seen there again. He named it ‘Solitary Wave’ or ‘Solitary Wave’. Very strange name? He presented the results of his experiments so far in September 1844 at the 14th meeting of the British Association for the Advancement of Science. Until now, researchers have not given special attention to this work. This often happens in scientific circles. Although later two famous mathematicians George Airy and Stokes tried to explain its theory, but did not succeed. Russell is not famous for ‘lonely wave’ or ‘solitary wave’!
From then on, for the rest of the nineteenth century, and even into the mid-twentieth century, no one gave much thought to this ‘lonely wave’ in science. In the 1960s, researchers found the ‘solitary wave’ again when working with the flow of waves in non-linear media with the help of slightly advanced computers. And named it ‘Soliton’. Not only that, they saw that these ‘solitons’ are spread everywhere around us. Optics, fluid-dynamics, plasma-physics, shock waves, tornadoes, all over the place. From the sensitivity of matter to particles to proteins, natural disasters like tsunamis, even Jupiter’s red spot, there is, in short, no nonlinear natural realm in which scientific discussion can be conducted without the context of solitons. And interestingly, most of the events in the world around us are non-linear. The ‘soliton’ is one of the areas of research in modern non-linear kinetic science.
To understand the motion of the soliton we need to solve some non-linear lateral discretization equations, keeping in mind various adjoint conditions. In science it has a cheeky name, the KDV equation, after two mathematicians, Karatog and Debris. We are not going into those hard numbers now. We try to understand the subject rather from the natural knowledge of wave-science. We know that light is a type of wave. When the sun’s light is passed through a prism, it breaks into seven colors – violet, blue, sky, green, yellow, orange, red – which we all know as BeniAshakala. If the sun shines after the rains during the rainy season, then we see such a play of colors in the sky, which is called a rainbow. What actually happens? Immediately after rain, there are water droplets in the atmosphere, from which sunlight is reflected and broken into seven colors like a prism.
This is ‘Beni Asahkala’ with seven different colours, each with a unique characteristic, each with a different wavelength. This means that the red light and the green light will travel different distances during the time it takes for one full-cycle to occur. Simply put, different wavelengths mean different light! And how fast light will travel through a medium depends on a particular property of the medium, called ‘refraction’. This refractive index again depends on the wavelength, so how much light bends as it passes through a medium depends on its wavelength number. That’s why the rainbow looks curved. For the same reason, when a pencil is immersed in a glass filled with clear water, the part of the pencil that is inside the water, gets bent. The German scientist Snell discovered the law of how much light bends when passing through another medium. As children we read Snell’s formula involving trigonometry in the chapter on light. But why does the light bend? A few years later, Fermat, a French gentleman, gave a simple and beautiful explanation. The dress code of which is ‘Farmer’s principle’. Of course, that can be discussed later.
Let us now see instead, what happens if light is directed straight ahead through a medium? Even though the medium is the same, because each color of light has the same refractive index inside it, we can see that each light moves at a different speed. At first, all the colors are together, but later they start to separate. The light wave signal that was initially narrower gradually spread out. This is the nature of waves and is common to all waves. Scientists have not seen this behavior again in the case of solitary waves or solitons, it is like an unknown wave!
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We already know that refractive index depends on wavelength. Again it depends on the wave propagation. Although his influence has not been seen so far during the known wave. But this religion has important implications for solitary waves. After some thought, the scientists came to the conclusion that if the wave is too strong, it can also change the refraction. Most interestingly, wavelength changes the refractive index on the one hand, wave propagation on the other hand changes the refraction, and the whole thing happens in such a way that one change cancels out the other. As a result, our eyes do not detect any changes. Because the wave that was supposed to break up at some distance, the wave continues indefinitely with unabated propagation. Scientists encountered this condition through simulations on state-of-the-art computers, conceived by the young engineer Russell, more than a century ago.
Russell’s understanding was dismissed by the scientific community at that time, but now the situation has turned 180 degrees. Not only the latest research on solitons, researchers are trying to explain various incomprehensible phenomena of non-linear motion science with solitons. Although solitons are like waves, they also exist among particles. A soliton can collide with another soliton, even a soliton can pass through another soliton completely intact! A peculiarity of this is that the greater the spread of the soliton, the greater its velocity. So if two solitons are moving in the same direction, the one with the larger spread can quickly overtake the other. If their positions are the same in this case, then the wave intensity should be greater according to the constructive interference calculation, but this is not the case for solitons. Rather, combined waves are either of low intensity or spread. Intensity is usually measured in terms of propagation in wave science.
Not only in computer simulation, but its use in fiber optics is widespread. Digital signals are sent over long distances through optical fibers as solitons. Scientists at Bell Laboratories first envisioned such an application of solitons in the 1970s. At the end of the 20th century, 1 TB of data was sent using solitons in France in 1998. A few years after that, true telecommunication systems using solitons began in Europe. Solitary waves, or solitons, have been studied so much over the past two decades that any five researchers in the nonlinear sciences will find at least two or three who work with solitons. What could be a bigger achievement for Russell?
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