Physicists are accustomed to working with particles: the theory has been worked out, experiments converge. Nuclear reactors and atomic bombs are calculated using particles. With one caveat - gravity is not taken into account in all calculations.
Gravity is the attraction of bodies. When we talk about gravity, we imagine gravity. The phone falls from your hands onto the asphalt under the influence of gravity. In space, the Moon is attracted to the Earth, the Earth to the Sun. Everything in the world is attracted to each other, but to feel this, you need very heavy objects. We feel the gravity of the Earth, which is 7.5 × 10 22 times heavier than a person, and we do not notice the gravity of a skyscraper, which is 4 × 10 6 times heavier.
7.5×10 22 = 75,000,000,000,000,000,000,000
4×10 6 = 4,000,000
Gravity is described by Einstein's general theory of relativity. In theory, massive objects bend space. To understand, go to a children's park and place a heavy stone on the trampoline. A crater will appear on the rubber of the trampoline. If you put a small ball on the trampoline, it will roll down the funnel towards the stone. This is roughly how the planets form a funnel in space, and we, like balls, fall onto them.
Planets so massive they bend space
In order to describe everything at the level of elementary particles, gravity is not needed. Compared to other forces, gravity is so small that it was simply thrown out of quantum calculations. The force of earth's gravity is 10 38 times less than the force holding the particles of the atomic nucleus. This is true for almost the entire universe.
10 38 = 100 000 000 000 000 000 000 000 000 000 000 000 000
The only place where gravity is as strong as other forces is inside a black hole. This is a giant funnel in which gravity folds space itself and draws in everything nearby. Even light flies into a black hole and never comes back.
To work with gravity as with other particles, physicists came up with a quantum of gravity - the graviton. We carried out calculations, but they didn’t add up. Calculations showed that the graviton energy grows to infinity. But this shouldn’t happen.
Physicists first invent, then search. The Higgs boson was invented 50 years before its discovery.
Problems with divergences in calculations disappeared when the graviton was considered not as a particle, but as a string. Strings have a finite length and energy, so the graviton's energy can only grow up to a certain limit. So scientists have a working tool with which they study black holes.
Advances in the study of black holes help us understand how the universe came to be. According to the Big Bang theory, the world grew from a microscopic point. In the first moments of life, the universe was very dense - all modern stars and planets gathered in a small volume. Gravity was as powerful as other forces, so knowing the effects of gravity is important to understanding the early universe.
Success in describing quantum gravity is a step towards creating a theory that will describe everything in the world. Such a theory will explain how the universe was born, what is happening in it now, and what its end will be.
String theory is a thin thread connecting the theory of relativity (or General Theory of Relativity - GTR) and quantum physics. Both of these fields have appeared quite recently on a scientific scale, so there is not yet too much scientific literature on these fields. And, if the theory of relativity still has some kind of time-tested basis, then the quantum branch of physics is still very young in this regard. Let's first understand these two industries.
Surely many of you have heard about the theory of relativity, and are even a little familiar with some of its postulates, but the question is: why can’t it be connected with quantum physics, which works at the micro level?
They separate the General and Special Theories of Relativity (abbreviated as GTR and SRT; henceforth they will be used as abbreviations). In short, GTR postulates about outer space and its curvature, and STR about the relativity of space-time from the human side. When we talk about string theory, we are talking specifically about general relativity. The General Theory of Relativity says that in space, under the influence of massive objects, space bends around it (and with it time, because space and time are completely inseparable concepts). An example from the lives of scientists will help you understand how this happens. A similar case was recently recorded, so everything told can be considered “based on real events.” A scientist looks through a telescope and sees two stars: one in front of her and the other behind her. How were we able to understand this? It’s very simple, because the star whose center we don’t see, but only its edges are visible, is the larger of these two, and the other star, which is visible in its full form, is the smaller one. However, thanks to general relativity, it may be that the star in front is larger than the one behind. But is this possible?
It turns out yes. If the front star turns out to be a supermassive object that will very strongly bend the space around it, then the image of the star that is behind will simply go around the supermassive star in curvature and we will see the picture that was mentioned at the very beginning. You can see what was said in more detail in Fig. 1.
Quantum physics is much more difficult for the average person than TO. If we generalize all its provisions, we get the following: micro-objects exist only when we look at them. In addition, quantum physics also says that if a microparticle is broken into two parts, then these two parts will continue to rotate along their axis in the same direction. And any impacts on the first particle will undoubtedly be transmitted to the second, instantly and completely regardless of the distance of these particles. 
So what is the difficulty in combining the concepts of these two theories? The fact is that GTR considers objects in the macroworld, and when we talk about the distortion/curvature of space, we mean ideally smooth space, which is completely inconsistent with the provisions of the microworld. According to the theory of quantum physics, the microworld is completely uneven and has omnipresent roughness. This is speaking in everyday language. And mathematicians and physicists translated their theories into formulas. And so, when they tried to combine the formulas of quantum physics and general relativity, the answer turned out to be infinity. Infinity in physics is tantamount to saying that the equation is constructed incorrectly. The resulting equality was rechecked many times, but the answer was still infinity.
String theory has brought fundamental changes to the everyday world of science. It represents a decree that all microparticles are not spherical in shape, but in the form of elongated strings that permeate our entire universe. Such quantities as mass, particle speed, etc. are established by the vibrations of these strings. Each such string is theoretically located in a Calabi-Yau manifold. These manifolds represent very curved space. According to the theory of diversity, they are not connected by anything in space and are found separately in small balls. String theory literally erases the clear boundaries of the process of connecting two microparticles. When microparticles are represented by balls, then we can clearly trace the boundary in space-time when they connect. However, if two strings are connected, then the place where they “glue” can be viewed from different angles. And at different angles we will get completely different results of the boundary of their connection, that is, there is simply no exact concept of such a boundary!
At the first stage of study, string theory, told even in simple words, seems mysterious, strange and even simply fictitious, but it is not unfounded words that speak for it, but research that, using many equations and parameters, confirms the probability of the existence of string particles.
And finally, another video explaining string theory in simple language from the Internet magazine QWRT.
Various versions of string theory are now considered to be the leading contenders for the title of a comprehensive, universal theory that explains the nature of everything. And this is a kind of Holy Grail of theoretical physicists involved in the theory of elementary particles and cosmology. The universal theory (also the theory of everything that exists) contains only a few equations that combine the entire body of human knowledge about the nature of interactions and the properties of the fundamental elements of matter from which the Universe is built.
Today, string theory has been combined with the concept of supersymmetry, resulting in the birth of superstring theory, and today this is the maximum that has been achieved in terms of unifying the theory of all four basic interactions (forces acting in nature). The theory of supersymmetry itself is already built on the basis of an a priori modern concept, according to which any remote (field) interaction is due to the exchange of interaction carrier particles of the corresponding kind between interacting particles (see Standard Model). For clarity, interacting particles can be considered the “bricks” of the universe, and carrier particles can be considered cement.
String theory is a branch of mathematical physics that studies the dynamics not of point particles, like most branches of physics, but of one-dimensional extended objects, i.e. strings
Within the standard model, quarks act as building blocks, and gauge bosons, which these quarks exchange with each other, act as interaction carriers. The theory of supersymmetry goes even further and states that quarks and leptons themselves are not fundamental: they all consist of even heavier and not experimentally discovered structures (building blocks) of matter, held together by an even stronger “cement” of super-energy particles-carriers of interactions than quarks composed of hadrons and bosons.
Naturally, none of the predictions of the theory of supersymmetry have yet been tested in laboratory conditions, however, the hypothetical hidden components of the material world already have names - for example, the electron (the supersymmetric partner of the electron), squark, etc. The existence of these particles, however, is theorized kind is predicted unambiguously.
The picture of the Universe offered by these theories, however, is quite easy to visualize. On a scale of about 10E–35 m, that is, 20 orders of magnitude smaller than the diameter of the same proton, which includes three bound quarks, the structure of matter differs from what we are used to even at the level of elementary particles. At such small distances (and at such high energies of interactions that it is unimaginable) matter turns into a series of field standing waves, similar to those excited in the strings of musical instruments. Like a guitar string, in such a string, in addition to the fundamental tone, many overtones or harmonics can be excited. Each harmonic has its own energy state. According to the principle of relativity (see Theory of Relativity), energy and mass are equivalent, which means that the higher the frequency of the harmonic wave vibration of the string, the higher its energy, and the higher the mass of the observed particle.
However, if it is quite easy to visualize a standing wave in a guitar string, the standing waves proposed by superstring theory are difficult to visualize - the fact is that the vibrations of superstrings occur in a space that has 11 dimensions. We are accustomed to four-dimensional space, which contains three spatial and one temporal dimensions (left-right, up-down, forward-backward, past-future). In superstring space, things are much more complicated (see box). Theoretical physicists get around the slippery problem of “extra” spatial dimensions by arguing that they are “hidden” (or, in scientific terms, “compactified”) and therefore are not observed at ordinary energies.
More recently, string theory has been further developed in the form of the theory of multidimensional membranes - essentially, these are the same strings, but flat. As one of its authors casually joked, membranes differ from strings in about the same way that noodles differ from vermicelli.
This, perhaps, is all that can be briefly told about one of the theories that, not without reason, today claim to be the universal theory of the Great Unification of all force interactions. Alas, this theory is not without sin. First of all, it has not yet been brought to a strict mathematical form due to the insufficiency of the mathematical apparatus to bring it into strict internal correspondence. 20 years have passed since this theory was born, and no one has been able to consistently harmonize some of its aspects and versions with others. What’s even more unpleasant is that none of the theorists proposing string theory (and especially superstrings) have yet proposed a single experiment in which these theories could be tested in the laboratory. Alas, I am afraid that until they do this, all their work will remain a bizarre game of fantasy and exercises in comprehending esoteric knowledge outside the mainstream of natural science.
Studying the properties of black holes
In 1996, string theorists Andrew Strominger and Kumrun Vafa built on earlier results by Susskind and Sen to publish “The Microscopic Nature of Bekenstein and Hawking Entropy.” In this work, Strominger and Vafa were able to use string theory to find the microscopic components of a certain class of black holes, and to accurately calculate the entropy contributions of these components. The work was based on a new method that went partly beyond the perturbation theory used in the 1980s and early 1990s. The result of the work exactly coincided with the predictions of Bekenstein and Hawking, made more than twenty years earlier.
Strominger and Vafa opposed the real processes of black hole formation with a constructive approach. They changed the view of black hole formation, showing that they can be constructed by painstakingly assembling into one mechanism the exact set of branes discovered during the second superstring revolution.
With all the controls on a black hole's microscopic structure in hand, Strominger and Vafa were able to calculate the number of permutations of a black hole's microscopic components that would leave the overall observable characteristics, such as mass and charge, unchanged. They then compared the resulting number with the area of the black hole's event horizon - the entropy predicted by Bekenstein and Hawking - and found perfect agreement. At least for the class of extreme black holes, Strominger and Vafa were able to find an application of string theory to analyze microscopic components and accurately calculate the corresponding entropy. The problem that had confronted physicists for a quarter of a century had been solved.
For many theorists, this discovery was an important and convincing argument in support of string theory. The development of string theory is still too crude for direct and precise comparison with experimental results, for example, with measurements of the mass of a quark or electron. String theory, however, provides the first fundamental explanation for a long-discovered property of black holes, the impossibility of explaining which has stalled the research of physicists working with traditional theories for many years. Even Sheldon Glashow, a Nobel laureate in physics and a staunch opponent of string theory in the 1980s, admitted in an interview in 1997 that “when string theorists talk about black holes, they are talking almost about observable phenomena, and that’s impressive.” "
String cosmology
There are three main ways in which string theory modifies the standard cosmological model. First, in the spirit of modern research, which is increasingly clarifying the situation, it follows from string theory that the Universe must have a minimum acceptable size. This conclusion changes the understanding of the structure of the Universe immediately at the moment of the Big Bang, for which the standard model yields a zero size of the Universe. Secondly, the concept of T-duality, that is, the duality of small and large radii (in its close connection with the existence of a minimum size) in string theory, is also important in cosmology. Thirdly, the number of space-time dimensions in string theory is more than four, so cosmology must describe the evolution of all these dimensions.
Brandenberg and Vafa model
At the end of the 1980s. Robert Brandenberger and Kumrun Vafa have taken the first important steps toward understanding how string theory will change the implications of the standard model of cosmology. They came to two important conclusions. First, as we move back to the Big Bang, the temperature continues to rise until the size of the Universe in all directions becomes equal to the Planck length. At this point the temperature will reach its maximum and begin to decrease. On an intuitive level, it is not difficult to understand the reason for this phenomenon. Let us assume for simplicity (following Brandenberger and Vafa) that all spatial dimensions of the Universe are cyclic. As we move backwards in time, the radius of each circle shrinks and the temperature of the universe increases. From string theory, we know that contracting the radii first to and then below the Planck length is physically equivalent to reducing the radii to the Planck length, followed by their subsequent increase. Since the temperature falls during the expansion of the Universe, unsuccessful attempts to compress the Universe to sizes smaller than the Planck length will lead to a cessation of temperature growth and its further decrease.
As a result, Brandenberger and Vafa arrived at the following cosmological picture: first, all spatial dimensions in string theory are tightly folded to a minimum size on the order of the Planck length. Temperature and energy are high, but not infinite: the paradoxes of the zero-size starting point in string theory are resolved. At the initial moment of the existence of the Universe, all spatial dimensions of string theory are completely equal and completely symmetrical: they are all curled up into a multidimensional lump of Planck dimensions. Further, according to Brandenberger and Vafa, the Universe goes through the first stage of symmetry reduction, when at the Planck moment of time three spatial dimensions are selected for subsequent expansion, and the rest retain their original Planck size. These three dimensions are then identified with the dimensions in the inflationary cosmology scenario and, through the process of evolution, take the form now observed.
Veneziano and Gasperini model
Since the work of Brandenberger and Vafa, physicists have been making continuous progress towards understanding string cosmology. Among those leading this research are Gabriele Veneziano and his colleague Maurizio Gasperini from the University of Turin. These scientists presented their own version of string cosmology, which in some places is similar to the scenario described above, but in other places is fundamentally different from it. Like Brandenberger and Vafa, to rule out the infinite temperature and energy density that arise in the standard and inflationary models, they relied on the existence of a minimum length in string theory. However, instead of concluding that, due to this property, the Universe is born from a lump of Planck dimensions, Gasperini and Veneziano suggested that there was a prehistoric universe that arose long before the moment called the zero point, and which gave birth to this cosmic “embryo” of Planck dimensions.
The initial state of the Universe in this scenario and in the Big Bang model are very different. According to Gasperini and Veneziano, the Universe was not a hot and tightly twisted ball of dimensions, but was cold and had an infinite extent. Then, as follows from the equations of string theory, instability invaded the Universe, and all its points began, as in the era of inflation according to Guth, to rapidly scatter to the sides.
Gasperini and Veneziano showed that because of this, space became increasingly curved and as a result there was a sharp jump in temperature and energy density. A little time passed, and the three-dimensional region of millimeter dimensions inside these endless expanses was transformed into a hot and dense spot, identical to the spot that is formed during inflationary expansion according to Guth. Then everything went according to the standard scenario of Big Bang cosmology, and the expanding spot turned into the observable Universe.
Since the pre-Big Bang era was undergoing its own inflationary expansion, Guth's solution to the horizon paradox is automatically built into this cosmological scenario. As Veneziano put it (in a 1998 interview), “string theory hands us a version of inflationary cosmology on a silver platter.”
The study of string cosmology is quickly becoming an area of active and productive research. For example, the scenario of evolution before the Big Bang has been the subject of heated debate more than once, and its place in the future cosmological formulation is far from obvious. However, there is no doubt that this cosmological formulation will be firmly based on physicists' understanding of the results discovered during the second superstring revolution. For example, the cosmological consequences of the existence of multidimensional membranes are still unclear. In other words, how will the idea of the first moments of the existence of the Universe change as a result of the analysis of the completed M-theory? This issue is being intensively researched.
Science is an immense field and a huge amount of research and discoveries is carried out every day, and it is worth noting that some theories seem to be interesting, but at the same time they do not have real confirmation and seem to “hang in the air.”
What is string theory?
The physical theory that represents particles in the form of vibration is called string theory. These waves have only one parameter - longitude, and no height or width. In figuring out what string theory is, we need to look at the main hypotheses it describes.
- It is assumed that everything around us consists of threads that vibrate and membranes of energy.
- Tries to combine general relativity and quantum physics.
- String theory offers a chance to unify all the fundamental forces of the Universe.
- Predicts symmetric coupling between different types of particles: bosons and fermions.
- Provides a chance to describe and imagine dimensions of the Universe that have not previously been observed.
String theory - who discovered it?
- Quantum string theory was first created in 1960 to explain phenomena in hadronic physics. At this time it was developed by: G. Veneziano, L. Susskind, T. Goto and others.
- The scientist D. Schwartz, J. Scherk and T. Enet told what string theory is, since they were developing the bosonic string hypothesis, and this happened 10 years later.
- In 1980, two scientists: M. Green and D. Schwartz identified the theory of superstrings, which had unique symmetries.
- Research on the proposed hypothesis is still ongoing, but it has not yet been proven.
String theory - philosophy
There is a philosophical direction that has a connection with string theory, and it is called the monad. It involves the use of symbols in order to compact any amount of information. The monad and string theory make use of opposites and dualities in philosophy. The most popular simple monad symbol is Yin-Yang. Experts have proposed depicting string theory on a volumetric, and not on a flat, monad, and then strings will be a reality, although their length will be miniscule.
If a volumetric monad is used, then the line dividing Yin-Yang will be a plane, and when using a multidimensional monad, a volume curled into a spiral is obtained. There is no work yet on philosophy relating to multidimensional monads - this is an area for future study. Philosophers believe that cognition is an endless process and when trying to create a unified model of the universe, a person will be surprised more than once and change his basic concepts.
Disadvantages of String Theory
Since the hypothesis proposed by a number of scientists is unconfirmed, it is quite understandable that there are a number of problems indicating the need for its refinement.
- The string theory has errors, for example, during calculations a new type of particle was discovered - tachyons, but they cannot exist in nature, since the square of their mass is less than zero, and the speed of movement is greater than the speed of light.
- String theory can only exist in ten-dimensional space, but then the relevant question is: why doesn’t a person perceive other dimensions?
String theory - proof
The two main physical conventions on which scientific evidence is based are actually opposed to each other, since they represent the structure of the universe at the micro level differently. To try them on, the theory of cosmic strings was proposed. In many respects, it looks reliable, not only in words, but also in mathematical calculations, but today a person does not have the opportunity to practically prove it. If strings exist, they are at a microscopic level, and there is no technical capability yet to recognize them.
String theory and God
The famous theoretical physicist M. Kaku proposed a theory in which he uses the string hypothesis to prove the existence of God. He came to the conclusion that everything in the world operates according to certain laws and rules established by a single Mind. According to Kaku, string theory and the hidden dimensions of the Universe will help create an equation that unifies all the forces of nature and allows us to understand the mind of God. He focuses his hypothesis on tachyon particles, which move faster than light. Einstein also said that if such parts were discovered, it would be possible to move time back.
After conducting a series of experiments, Kaku concluded that human life is governed by stable laws and does not react to cosmic accidents. The string theory of life exists and it is associated with an unknown force that controls life and makes it whole. In his opinion, this is what it is. Kaku is sure that the Universe is vibrating strings that emanate from the mind of the Almighty.
Of course, the strings of the universe are hardly similar to those we imagine. In string theory, they are incredibly small vibrating threads of energy. These threads are more like tiny “rubber bands” that can wriggle, stretch and compress in all sorts of ways. All this, however, does not mean that it is impossible to “play” the symphony of the Universe on them, because, according to string theorists, everything that exists consists of these “threads.”
Physics contradiction
In the second half of the 19th century, it seemed to physicists that nothing serious could be discovered in their science anymore. Classical physics believed that there were no serious problems left in it, and the entire structure of the world looked like a perfectly regulated and predictable machine. The trouble, as usual, happened because of nonsense - one of the small “clouds” that still remained in the clear, understandable sky of science. Namely, when calculating the radiation energy of an absolutely black body (a hypothetical body that, at any temperature, completely absorbs the radiation incident on it, regardless of the wavelength - NS).
Calculations showed that the total radiation energy of any absolutely black body should be infinitely large. To get away from such obvious absurdity, the German scientist Max Planck in 1900 proposed that visible light, X-rays and other electromagnetic waves can only be emitted by certain discrete portions of energy, which he called quanta. With their help, it was possible to solve the particular problem of an absolutely black body. However, the consequences of the quantum hypothesis for determinism were not yet realized. Until, in 1926, another German scientist, Werner Heisenberg, formulated the famous uncertainty principle.
Its essence boils down to the fact that, contrary to all previously dominant statements, nature limits our ability to predict the future on the basis of physical laws. We are, of course, talking about the future and present of subatomic particles. It turned out that they behave completely differently from the way any things do in the macrocosm around us. At the subatomic level, the fabric of space becomes uneven and chaotic. The world of tiny particles is so turbulent and incomprehensible that it defies common sense. Space and time are so twisted and intertwined in it that there are no ordinary concepts of left and right, up and down, or even before and after.
There is no way to say for sure at what point in space a particular particle is currently located, and what is its angular momentum. There is only a certain probability of finding a particle in many regions of space-time. Particles at the subatomic level seem to be “smeared” throughout space. Not only that, but the “status” of the particles itself is not defined: in some cases they behave like waves, in others they exhibit the properties of particles. This is what physicists call the wave-particle duality of quantum mechanics.
Levels of the structure of the world: 1. Macroscopic level - matter 2. Molecular level 3. Atomic level - protons, neutrons and electrons 4. Subatomic level - electron 5. Subatomic level - quarks 6. String level /©Bruno P. Ramos
In the General Theory of Relativity, as if in a state with opposite laws, the situation is fundamentally different. Space appears to be like a trampoline - a smooth fabric that can be bent and stretched by objects with mass. They create warps in space-time—what we experience as gravity. Needless to say, the harmonious, correct and predictable General Theory of Relativity is in an insoluble conflict with the “eccentric hooligan” – quantum mechanics, and, as a result, the macroworld cannot “make peace” with the microworld. This is where string theory comes to the rescue.
2D Universe. Polyhedron graph E8 /©John Stembridge/Atlas of Lie Groups Project
Theory of Everything
String theory embodies the dream of all physicists to unify the two fundamentally contradictory general relativity and quantum mechanics, a dream that haunted the greatest “gypsy and tramp” Albert Einstein until the end of his days.
Many scientists believe that everything from the exquisite dance of galaxies to the crazy dance of subatomic particles can ultimately be explained by just one fundamental physical principle. Maybe even a single law that unites all types of energy, particles and interactions in some elegant formula.
General relativity describes one of the most famous forces of the Universe - gravity. Quantum mechanics describes three other forces: the strong nuclear force, which glues protons and neutrons together in atoms, electromagnetism, and the weak force, which is involved in radioactive decay. Any event in the universe, from the ionization of an atom to the birth of a star, is described by the interactions of matter through these four forces.
With the help of the most complex mathematics, it was possible to show that electromagnetic and weak interactions have a common nature, combining them into a single electroweak interaction. Subsequently, strong nuclear interaction was added to them - but gravity does not join them in any way. String theory is one of the most serious candidates for connecting all four forces, and, therefore, embracing all phenomena in the Universe - it is not for nothing that it is also called the “Theory of Everything”.
In the beginning there was a myth
Until now, not all physicists are delighted with string theory. And at the dawn of its appearance, it seemed infinitely far from reality. Her very birth is a legend.
In the late 1960s, a young Italian theoretical physicist, Gabriele Veneziano, was searching for equations that could explain the strong nuclear force—the extremely powerful “glue” that holds the nuclei of atoms together, binding protons and neutrons together. According to legend, one day he accidentally stumbled upon a dusty book on the history of mathematics, in which he found a two-hundred-year-old function first written down by the Swiss mathematician Leonhard Euler. Imagine Veneziano's surprise when he discovered that the Euler function, long considered nothing more than a mathematical curiosity, described this strong interaction.
What was it really like? The formula was probably the result of Veneziano's many years of work, and chance only helped take the first step towards the discovery of string theory. Euler's function, which miraculously explained the strong force, has found new life.
Eventually, it caught the eye of the young American theoretical physicist Leonard Susskind, who saw that, first of all, the formula described particles that had no internal structure and could vibrate. These particles behaved in such a way that they could not be just point particles. Susskind understood - the formula describes a thread that is like an elastic band. She could not only stretch and contract, but also oscillate and squirm. After describing his discovery, Susskind introduced the revolutionary idea of strings.
Unfortunately, the overwhelming majority of his colleagues greeted the theory very coolly.
Standard model
At the time, conventional science represented particles as points rather than as strings. For years, physicists have studied the behavior of subatomic particles by colliding them at high speeds and studying the consequences of these collisions. It turned out that the Universe is much richer than one could imagine. It was a real “population explosion” of elementary particles. Physics graduate students ran through the corridors shouting that they had discovered a new particle - there weren’t even enough letters to designate them. But, alas, in the “maternity hospital” of new particles, scientists were never able to find the answer to the question - why are there so many of them and where do they come from?
This prompted physicists to make an unusual and startling prediction - they realized that the forces at work in nature could also be explained in terms of particles. That is, there are particles of matter, and there are particles that carry interactions. For example, a photon is a particle of light. The more of these carrier particles - the same photons that matter particles exchange - the brighter the light. Scientists predicted that this particular exchange of carrier particles is nothing more than what we perceive as force. This was confirmed by experiments. This is how physicists managed to get closer to Einstein’s dream of uniting forces.
Interactions between various particles in the Standard Model /
Scientists believe that if we fast forward to just after the Big Bang, when the Universe was trillions of degrees hotter, the particles that carry electromagnetism and the weak force will become indistinguishable and combine into a single force called the electroweak force. And if we go back even further in time, the electroweak interaction would combine with the strong one into one total “superforce.”
Even though all this is still waiting to be proven, quantum mechanics suddenly explained how three of the four forces interact at the subatomic level. And she explained it beautifully and consistently. This coherent picture of interactions ultimately became known as the Standard Model. But, alas, this perfect theory had one big problem - it did not include the most famous macro-level force - gravity.
Graviton
For string theory, which had not yet had time to “bloom,” “autumn” has come; it contained too many problems from its very birth. For example, the theory's calculations predicted the existence of particles, which, as was soon established, do not exist. This is the so-called tachyon - a particle that moves in a vacuum faster than light. Among other things, it turned out that the theory requires as many as 10 dimensions. It's not surprising that this has been very confusing to physicists, since it's obviously bigger than what we see.
By 1973, only a few young physicists were still grappling with the mysteries of string theory. One of them was the American theoretical physicist John Schwartz. For four years, Schwartz tried to tame the unruly equations, but to no avail. Among other problems, one of these equations persisted in describing a mysterious particle that had no mass and had not been observed in nature.
The scientist had already decided to abandon his disastrous business, and then it dawned on him - maybe the equations of string theory also describe gravity? However, this implied a revision of the dimensions of the main “heroes” of the theory – strings. By assuming that strings are billions and billions of times smaller than an atom, the “stringers” turned the theory’s disadvantage into its advantage. The mysterious particle that John Schwartz had so persistently tried to get rid of now acted as a graviton - a particle that had long been sought and that would allow gravity to be transferred to the quantum level. This is how string theory completed the puzzle with gravity, which was missing in the Standard Model. But, alas, even to this discovery the scientific community did not react in any way. String theory remained on the brink of survival. But that didn't stop Schwartz. Only one scientist wanted to join his search, ready to risk his career for the sake of mysterious strings - Michael Green.
Subatomic nesting dolls
Despite everything, in the early 1980s, string theory still had insoluble contradictions, called anomalies in science. Schwartz and Green set about eliminating them. And their efforts were not in vain: scientists were able to eliminate some of the contradictions in the theory. Imagine the amazement of these two, already accustomed to the fact that their theory was ignored, when the reaction of the scientific community blew up the scientific world. In less than a year, the number of string theorists has jumped to hundreds of people. It was then that string theory was awarded the title of Theory of Everything. The new theory seemed capable of describing all the components of the universe. And these are the components.
Each atom, as we know, consists of even smaller particles - electrons, which swirl around a nucleus consisting of protons and neutrons. Protons and neutrons, in turn, consist of even smaller particles - quarks. But string theory says it doesn't end with quarks. Quarks are made of tiny, wriggling strands of energy that resemble strings. Each of these strings is unimaginably small.
So small that if an atom were enlarged to the size of the solar system, the string would be the size of a tree. Just as different vibrations of a cello string create what we hear, just as different musical notes, different ways (modes) of vibration of a string give particles their unique properties - mass, charge, etc. Do you know how, relatively speaking, the protons at the tip of your nail differ from the as yet undiscovered graviton? Only by the collection of tiny strings that make them up, and the way those strings vibrate.
Of course, all this is more than surprising. Since the times of Ancient Greece, physicists have become accustomed to the fact that everything in this world consists of something like balls, tiny particles. And so, not having had time to get used to the illogical behavior of these balls, which follows from quantum mechanics, they are asked to completely abandon the paradigm and operate with some kind of spaghetti scraps...
Fifth Dimension
Although many scientists call string theory a triumph of mathematics, some problems still remain with it - most notably, the lack of any possibility of testing it experimentally in the near future. Not a single instrument in the world, neither existing nor capable of appearing in the future, is capable of “seeing” the strings. Therefore, some scientists, by the way, even ask the question: is string theory a theory of physics or philosophy?.. True, seeing strings “with your own eyes” is not at all necessary. Proving string theory requires, rather, something else—what sounds like science fiction—confirmation of the existence of extra dimensions of space.
What is it about? We are all accustomed to three dimensions of space and one – time. But string theory predicts the presence of other—extra—dimensions. But let's start in order.
In fact, the idea of the existence of other dimensions arose almost a hundred years ago. It came to the mind of the then unknown German mathematician Theodor Kaluza in 1919. He suggested the possibility of another dimension in our Universe that we do not see. Albert Einstein learned about this idea, and at first he really liked it. Later, however, he doubted its correctness, and delayed the publication of Kaluza for two whole years. Ultimately, however, the article was published, and the additional dimension became a kind of hobby for the genius of physics.
As you know, Einstein showed that gravity is nothing more than a deformation of space-time dimensions. Kaluza suggested that electromagnetism could also be ripples. Why don't we see it? Kaluza found the answer to this question - the ripples of electromagnetism may exist in an additional, hidden dimension. But where is it?
The answer to this question was given by Swedish physicist Oskar Klein, who suggested that Kaluza's fifth dimension is folded billions of times stronger than the size of a single atom, which is why we cannot see it. The idea of this tiny dimension that is all around us is at the heart of string theory.
One of the proposed forms of additional twisted dimensions. Inside each of these forms, a string vibrates and moves - the main component of the Universe. Each form is six-dimensional - according to the number of six additional dimensions /
Ten dimensions
But in fact, the equations of string theory require not even one, but six additional dimensions (in total, with the four we know, there are exactly 10 of them). They all have a very twisted and curved complex shape. And everything is unimaginably small.
How can these tiny measurements influence our big world? According to string theory, it's decisive: for it, shape determines everything. When you press different keys on a saxophone, you get different sounds. This happens because when you press a particular key or combination of keys, you change the shape of the space in the musical instrument where the air circulates. Thanks to this, different sounds are born.
String theory suggests that additional curved and twisted dimensions of space manifest themselves in a similar way. The shapes of these extra dimensions are complex and varied, and each causes the string located within such dimensions to vibrate differently precisely because of their shapes. After all, if we assume, for example, that one string vibrates inside a jug, and the other inside a curved post horn, these will be completely different vibrations. However, if you believe string theory, in reality the forms of additional dimensions look much more complex than a jug.
How the world works
Science today knows a set of numbers that are the fundamental constants of the Universe. They are the ones who determine the properties and characteristics of everything around us. Among such constants are, for example, the charge of an electron, the gravitational constant, the speed of light in a vacuum... And if we change these numbers even by an insignificant number of times, the consequences will be catastrophic. Suppose we increased the strength of the electromagnetic interaction. What happened? We may suddenly find that the ions begin to repel each other more strongly, and nuclear fusion, which makes stars shine and emit heat, suddenly fails. All the stars will go out.
But what does string theory with its extra dimensions have to do with it? The fact is that, according to it, it is the additional dimensions that determine the exact value of the fundamental constants. Some forms of measurement cause one string to vibrate in a certain way, and produce what we see as a photon. In other forms, the strings vibrate differently and produce an electron. Truly, God is in the “little things” - it is these tiny forms that determine all the fundamental constants of this world.
Superstring theory
In the mid-1980s, string theory took on a grand and orderly appearance, but inside the monument there was confusion. In just a few years, as many as five versions of string theory have emerged. And although each of them is built on strings and extra dimensions (all five versions are combined into the general theory of superstrings - NS), these versions diverged significantly in details.
So, in some versions the strings had open ends, in others they resembled rings. And in some versions, the theory even required not 10, but as many as 26 dimensions. The paradox is that all five versions today can be called equally true. But which one really describes our Universe? This is another mystery of string theory. That is why many physicists again gave up on the “crazy” theory.
But the main problem of strings, as already mentioned, is the impossibility (at least for now) of proving their presence experimentally.
Some scientists, however, still say that the next generation of accelerators has a very minimal, but still opportunity to test the hypothesis of additional dimensions. Although the majority, of course, are sure that if this is possible, then, alas, it will not happen very soon - at least in decades, at maximum - even in a hundred years.