String theory simple. String theory will become the theory of everything

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.

At school we learned that matter is made up of atoms, and atoms are made up of nuclei around which electrons revolve. The planets revolve around the sun in much the same way, so it’s easy for us to imagine. Then the atom was split into elementary particles, and it became more difficult to imagine the structure of the universe. At the particle scale, different laws apply, and it is not always possible to find an analogy from life. Physics has become abstract and confusing.

But the next step of theoretical physics returned a sense of reality. String theory described the world in terms that are again imaginable and therefore easier to understand and remember.

The topic is still not easy, so let's go in order. First, let's figure out what the theory is, then let's try to understand why it was invented. And for dessert, a little history; string theory has a short history, but with two revolutions.

The universe is made up of vibrating threads of energy

Before string theory, elementary particles were considered points - dimensionless shapes with certain properties. String theory describes them as threads of energy that do have one dimension - length. These one-dimensional threads are called quantum strings.

Theoretical physics

Theoretical physics
describes the world using mathematics, as opposed to experimental physics. The first theoretical physicist was Isaac Newton (1642-1727)

The nucleus of an atom with electrons, elementary particles and quantum strings through the eyes of an artist. Fragment of the documentary "Elegant Universe"

Quantum strings are very small, their length is about 10 -33 cm. This is a hundred million billion times smaller than the protons that collide at the Large Hadron Collider. Such experiments with strings would require building an accelerator the size of a galaxy. We haven't found a way to detect strings yet, but thanks to mathematics we can guess some of their properties.

Quantum strings are open and closed. The open ends are free, while the closed ends close on each other, forming loops. Strings are constantly “opening” and “closing”, connecting with other strings and breaking up into smaller ones.

Quantum strings are stretched. Tension in space occurs due to the difference in energy: for closed strings between the closed ends, for open strings - between the ends of the strings and the void. Physicists call this void two-dimensional dimensional faces, or branes - from the word membrane.

centimeters - the smallest possible size of an object in the universe. It is called the Planck length

We are made of quantum strings

Quantum strings vibrate. These are vibrations similar to the vibrations of the strings of a balalaika, with uniform waves and a whole number of minimums and maximums. When vibrating, a quantum string does not produce sound; on the scale of elementary particles there is nothing to transmit sound vibrations to. It itself becomes a particle: it vibrates at one frequency - a quark, at another - a gluon, at a third - a photon. Therefore, a quantum string is a single building element, a “brick” of the universe.

The universe is usually depicted as space and stars, but it is also our planet, and you and me, and the text on the screen, and berries in the forest.

Diagram of string vibrations. At any frequency, all waves are the same, their number is integer: one, two and three

Moscow region, 2016. There are a lot of strawberries - only more mosquitoes. They are also made of strings.

And space is out there somewhere. Let's go back to space

So, at the core of the universe are quantum strings, one-dimensional threads of energy that vibrate, change size and shape, and exchange energy with other strings. But that's not all.

Quantum strings move through space. And space on the scale of strings is the most interesting part of the theory.

Quantum strings move in 11 dimensions

Theodore Kaluza
(1885-1954)

It all started with Albert Einstein. His discoveries showed that time is relative and united it with space into a single space-time continuum. Einstein's work explained gravity, the movement of planets, and the formation of black holes. In addition, they inspired their contemporaries to make new discoveries.

Einstein published the equations of the General Theory of Relativity in 1915-16, and already in 1919, the Polish mathematician Theodor Kaluza tried to apply his calculations to the theory of the electromagnetic field. But the question arose: if Einsteinian gravity bends the four dimensions of spacetime, what do electromagnetic forces bend? Faith in Einstein was strong, and Kaluza had no doubt that his equations would describe electromagnetism. Instead, he proposed that electromagnetic forces were bending an additional, fifth dimension. Einstein liked the idea, but the theory was not tested by experiments and was forgotten until the 1960s.

Albert Einstein (1879-1955)

Theodore Kaluza
(1885-1954)

Albert Einstein
(1879-1955)

The first string theory equations produced strange results. Tachyons appeared in them - particles with negative mass that moved faster than the speed of light. This is where Kaluza’s idea of the multidimensionality of the universe came in handy. True, five dimensions were not enough, just as six, seven or ten were not enough. The mathematics of the first string theory only made sense if our universe had 26 dimensions! Later theories had enough of ten, but in the modern one there are eleven of them - ten spatial and time.

But if so, why don't we see the extra seven dimensions? The answer is simple - they are too small. From a distance, a three-dimensional object will appear flat: a water pipe will appear as a ribbon, and a balloon will appear as a circle. Even if we could see objects in other dimensions, we would not consider their multidimensionality. Scientists call this effect compactification.

The extra dimensions are folded into imperceptibly small forms of space-time - they are called Calabi-Yau spaces. From a distance it looks flat.

We can represent seven additional dimensions only in the form of mathematical models. These are fantasies that are built on the properties of space and time known to us. By adding a third dimension, the world becomes three-dimensional and we can bypass the obstacle. Perhaps, using the same principle, it is correct to add the remaining seven dimensions - and then using them you can go around space-time and get to any point in any universe at any time.

measurements in the universe according to the first version of string theory - bosonic. Now it is considered irrelevant

A line has only one dimension - length

A balloon is three-dimensional and has a third dimension—height. But to a two-dimensional man it looks like a line

Just as a two-dimensional man cannot imagine multidimensionality, so we cannot imagine all the dimensions of the universe.

According to this model, quantum strings travel always and everywhere, which means that the same strings encode the properties of all possible universes from their birth to the end of time. Unfortunately, our balloon is flat. Our world is only a four-dimensional projection of an eleven-dimensional universe onto the visible scales of space-time, and we cannot follow the strings.

Someday we will see the Big Bang

Someday we will calculate the frequency of string vibrations and the organization of additional dimensions in our universe. Then we will learn absolutely everything about it and will be able to see the Big Bang or fly to Alpha Centauri. But for now this is impossible - there are no hints on what to rely on in the calculations, and you can only find the necessary numbers by brute force. Mathematicians have calculated that there will be 10,500 options to sort through. The theory has reached a dead end.

Yet string theory is still capable of explaining the nature of the universe. To do this, it must connect all other theories, become the theory of everything.

String theory will become the theory of everything. May be

In the second half of the 20th century, physicists confirmed a number of fundamental theories about the nature of the universe. It seemed that a little more and we would understand everything. However, the main problem has not yet been solved: the theories work great individually, but do not provide an overall picture.

There are two main theories: relativity theory and quantum field theory.

options for organizing 11 dimensions in Calabi-Yau spaces - enough for all possible universes. For comparison, the number of atoms in the observable part of the universe is about 10 80

There are enough options for organizing Calabi-Yau spaces for all possible universes. For comparison, the number of atoms in the observable universe is about 10 80

Theory of relativity
described the gravitational interaction between planets and stars and explained the phenomenon of black holes. This is the physics of a visual and logical world.

Model of gravitational interaction of the Earth and the Moon in Einsteinian space-time

Quantum field theory
determined the types of elementary particles and described 3 types of interaction between them: strong, weak and electromagnetic. This is the physics of chaos.

The quantum world through the eyes of an artist. Video from MiShorts website

Quantum field theory with added mass for neutrinos is called Standard model. This is the basic theory of the structure of the universe at the quantum level. Most of the theory's predictions are confirmed in experiments.

The Standard Model divides all particles into fermions and bosons. Fermions form matter - this group includes all observable particles such as the quark and electron. Bosons are the forces that are responsible for the interaction of fermions, such as the photon and the gluon. Two dozen particles are already known, and scientists continue to discover new ones.

It is logical to assume that the gravitational interaction is also transmitted by its boson. They haven’t found it yet, but they described its properties and came up with a name - graviton.

But it is impossible to unite the theories. According to the Standard Model, elementary particles are dimensionless points that interact at zero distances. If this rule is applied to graviton, the equations give infinite results, which makes them meaningless. This is just one of the contradictions, but it illustrates well how far one physics is from another.

Therefore, scientists are looking for an alternative theory that can combine all theories into one. This theory was called the unified field theory, or theory of everything.

Fermions
form all types of matter except dark matter

Bosons
transfer energy between fermions

String theory could unite the scientific world

String theory in this role looks more attractive than others, since it immediately solves the main contradiction. Quantum strings vibrate so that the distance between them is greater than zero, and impossible calculation results for the graviton are avoided. And the graviton itself fits well into the concept of strings.

But string theory has not been proven by experiments; its achievements remain on paper. All the more surprising is the fact that it has not been abandoned in 40 years - its potential is so great. To understand why this happens, let's look back and see how it developed.

String theory has gone through two revolutions

Gabriele Veneziano
(born 1942)

At first, string theory was not at all considered a contender for the unification of physics. It was discovered by accident. In 1968, young theoretical physicist Gabriele Veneziano studied the strong interactions inside the atomic nucleus. Unexpectedly, he discovered that they were described well by Euler’s beta function, a set of equations that the Swiss mathematician Leonhard Euler had compiled 200 years earlier. This was strange: in those days the atom was considered indivisible, and Euler’s work solved exclusively mathematical problems. No one understood why the equations worked, but they were actively used.

The physical meaning of Euler's beta function was clarified two years later. Three physicists, Yoichiro Nambu, Holger Nielsen and Leonard Susskind, suggested that elementary particles might not be points, but one-dimensional vibrating strings. The strong interaction for such objects was described ideally by the Euler equations. The first version of string theory was called bosonic, since it described the string nature of bosons responsible for the interactions of matter, and did not concern the fermions that matter consists of.

The theory was crude. It involved tachyons, and the main predictions contradicted the experimental results. And although it was possible to get rid of tachyons using Kaluza multidimensionality, string theory did not take root.

Gabriele Veneziano
Yoichiro Nambu
Holger Nielsen
Leonard Susskind
John Schwartz
Michael Green
Edward Witten

Gabriele Veneziano
Yoichiro Nambu
Holger Nielsen
Leonard Susskind
John Schwartz
Michael Green
Edward Witten

But the theory still has loyal supporters. In 1971, Pierre Ramon added fermions to string theory, reducing the number of dimensions from 26 to ten. This marked the beginning supersymmetry theory.

It said that each fermion has its own boson, which means that matter and energy are symmetrical. It doesn't matter that the observable universe is asymmetrical, Ramon said, there are conditions under which symmetry is still observed. And if, according to string theory, fermions and bosons are encoded by the same objects, then under these conditions matter can be converted into energy, and vice versa. This property of strings was called supersymmetry, and string theory itself was called superstring theory.

In 1974, John Schwartz and Joel Sherk discovered that some of the properties of strings matched the properties of the supposed carrier of gravity, the graviton, remarkably closely. From that moment on, the theory began to seriously claim to be generalizing.

dimensions of space-time were in the first superstring theory

“The mathematical structure of string theory is so beautiful and has so many amazing properties that it must surely point to something deeper.”

The first superstring revolution happened in 1984. John Schwartz and Michael Green presented a mathematical model that showed that many of the contradictions between string theory and the Standard Model could be resolved. The new equations also related the theory to all types of matter and energy. The scientific world was gripped by fever - physicists abandoned their research and switched to studying strings.

From 1984 to 1986, more than a thousand papers on string theory were written. They showed that many of the provisions of the Standard Model and the theory of gravity, which had been pieced together over the years, follow naturally from string physics. The research has convinced scientists that a unifying theory is just around the corner.

“The moment you are introduced to string theory and realize that almost all the major advances in physics of the last century have flowed—and flowed with such elegance—from such a simple starting point clearly demonstrates the incredible power of this theory.”

But string theory was in no hurry to reveal its secrets. In place of solved problems, new ones arose. Scientists have discovered that there is not one, but five superstring theories. The strings in them had different types of supersymmetry, and there was no way to understand which theory was correct.

Mathematical methods had their limits. Physicists are accustomed to complex equations that do not give accurate results, but for string theory it was not possible to write even accurate equations. And approximate results of approximate equations did not provide answers. It became clear that new mathematics was needed to study the theory, but no one knew what kind of mathematics it would be. The ardor of scientists has subsided.

Second superstring revolution thundered in 1995. The stalemate was brought to an end by Edward Witten's talk at the String Theory Conference in Southern California. Witten showed that all five theories are special cases of one, more general theory of superstrings, in which there are not ten dimensions, but eleven. Witten called the unifying theory M-theory, or the Mother of all theories, from the English word Mother.

But something else was more important. Witten's M-theory described the effect of gravity in superstring theory so well that it was called the supersymmetric theory of gravity, or supergravity theory. This encouraged scientists, and scientific journals again filled with publications on string physics.

space-time measurements in modern superstring theory

“String theory is a part of twenty-first century physics that accidentally ended up in the twentieth century. It may take decades, or even centuries, before it is fully developed and understood."

The echoes of this revolution can still be heard today. But despite all the efforts of scientists, string theory has more questions than answers. Modern science is trying to build models of a multidimensional universe and studies dimensions as membranes of space. They're called branes—remember the void with open strings stretched across them? It is assumed that the strings themselves may turn out to be two- or three-dimensional. They even talk about a new 12-dimensional fundamental theory - F-theory, the Father of all theories, from the word Father. The history of string theory is far from over.

String theory has not yet been proven, but it has not been disproved either.

The main problem with the theory is the lack of direct evidence. Yes, other theories follow from it, scientists add 2 and 2, and it turns out 4. But this does not mean that the four consists of twos. Experiments at the Large Hadron Collider have not yet discovered supersymmetry, which would confirm the unified structural basis of the universe and would play into the hands of supporters of string physics. But there are no denials either. Therefore, the elegant mathematics of string theory continues to excite the minds of scientists, promising solutions to all the mysteries of the universe.

When talking about string theory, one cannot fail to mention Brian Greene, a professor at Columbia University and a tireless popularizer of the theory. Green gives lectures and appears on television. In 2000, his book “Elegant Universe. Superstrings, Hidden Dimensions, and the Search for the Ultimate Theory" was a finalist for the Pulitzer Prize. In 2011, he played himself in episode 83 of The Big Bang Theory. In 2013, he visited the Moscow Polytechnic Institute and gave an interview to Lenta-ru.

If you don’t want to become an expert in string theory, but want to understand what kind of world you live in, remember this cheat sheet:

The universe is made up of threads of energy—quantum strings—that vibrate like the strings of a musical instrument. Different vibration frequencies turn strings into different particles.
The ends of the strings can be free, or they can close on each other, forming loops. The strings are constantly closing, opening and exchanging energy with other strings.
Quantum strings exist in the 11-dimensional universe. The extra 7 dimensions are folded into elusively small forms of space-time, so we don't see them. This is called dimension compactification.
If we knew exactly how the dimensions in our universe are folded, we might be able to travel through time and to other stars. But this is not possible yet - there are too many options to go through. There would be enough of them for all possible universes.
String theory can unite all physical theories and reveal to us the secrets of the universe - there are all the prerequisites for this. But there is no evidence yet.
Other discoveries of modern science logically follow from string theory. Unfortunately, this doesn't prove anything.
String theory has survived two superstring revolutions and many years of oblivion. Some scientists consider it science fiction, others believe that new technologies will help prove it.
The most important thing: if you plan to tell your friends about string theory, make sure that there is no physicist among them - you will save time and nerves. And you'll look like Brian Greene at the Polytechnic:

Have you ever thought that the universe is like a cello? That's right - she didn't come. Because the universe is not like a cello. But that doesn't mean it doesn't have strings.

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 “Elastic Bands”, capable of wriggling, stretching and compressing 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”.

A contradiction in physics.
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 must be infinitely large. To escape Because of such obvious absurdity, the German scientist Max Planck proposed in 1900 that visible light, X-rays and other electromagnetic waves could only be emitted by certain discrete portions of energy, which he called quanta. With their help, he was able to solve the particular blackbody problem. However, the consequences The quantum hypothesis for determinism was not yet understood until another German scientist, Werner Heisenberg, formulated the famous uncertainty principle in 1926.

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 “Spread” 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.

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 “Crazy Hooligan” - quantum mechanics, and, as a result, the macroworld cannot “make peace” with the microworld. This is where string theory comes to the rescue.

Theory of everything.
String theory embodies the dream of all physicists to unify the two fundamentally contradictory theories of quantum mechanics and quantum mechanics, a dream that haunted the greatest “Gypsy and the 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.

Oto 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, the young Italian theoretical physicist Gabriele Veneziano searched 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, he once accidentally stumbled upon a dusty book on the history of mathematics, in which he found a two-hundred-year-old equation first written down by the Swiss mathematician Leonhard Euler. Imagine Veneziano's surprise when he discovered that Euler's equation, which had long been considered nothing more than a mathematical curiosity, described this strong interaction.

What was it really like? The equation 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 equation, which miraculously explained the strong force, took on new life.

In the end, it caught the eye of the young American physicist and theorist 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. Graduate students from physics universities 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 operating in nature could also be explained in terms of particles. That is, there are particles of matter, and there are particles that are carriers of interactions. Such, for example, is a photon - a particle of light. The more of these particles - carriers - the same photons that are exchanged by particles of matter, the brighter the light. Scientists predicted that it is this exchange of particles - carriers - that 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.

Scientists believe that if we travel back 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, then 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 did not have 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 suggesting that strings are billions and billions of times smaller than an atom, the Stringers turned the theory's flaw 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 intractable 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 the 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 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.

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, and 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 hidden 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.

At the beginning of the 20th century, two supporting pillars of modern scientific knowledge were formed. One of them is Einstein's general theory of relativity, which explains the phenomenon of gravity and the structure of space-time. The other is quantum mechanics, which describes physical processes through the prism of probability. String theory is intended to combine these two approaches. It can be explained briefly and clearly using analogies in everyday life.

String theory in simple terms

The main provisions of one of the most famous “theories of everything” boil down to the following:

The basis of the universe is made up of extended objects that are shaped like strings;
These objects tend to perform various vibrations, as if on a musical instrument;
As a result of these vibrations, various elementary particles (quarks, electrons, etc.) are formed.
The mass of the resulting object is directly proportional to the amplitude of the perfect vibration;
The theory helps provide new insight into black holes;
Also, with the help of the new teaching, it was possible to reveal the force of gravity in the interactions between fundamental particles;
In contrast to the currently dominant ideas about the four-dimensional world, the new theory introduces additional dimensions;
Currently, the concept has not yet been officially accepted by the wider scientific community. There is not a single experiment known that would confirm this harmonious and verified theory on paper.

Historical reference

The history of this paradigm spans several decades of intensive research. Thanks to the joint efforts of physicists around the world, a coherent theory was developed that included the concepts of condensed matter, cosmology and theoretical mathematics.

The main stages of its development:

1943-1959 Werner Heisenberg's doctrine of the s-matrix appeared, within which it was proposed to discard the concepts of space and time for quantum phenomena. Heisenberg was the first to discover that participants in strong interactions are extended objects, not points;
1959-1968 Particles with high spins (moments of rotation) were discovered. Italian physicist Tullio Regge will propose grouping quantum states into trajectories (which were named after him);
1968-1974 Garibral Veneziano proposed a double resonance model to describe strong interactions. Yoshiro Nambu developed this idea and described nuclear forces as vibrating one-dimensional strings;
1974-1994 The discovery of superstrings, largely thanks to the work of the Russian scientist Alexander Polyakov;
1994-2003 The emergence of M-theory allowed for more than 11 dimensions;
2003 - present V. Michael Douglas developed landscape string theory with the concept false vacuum.

Quantum string theory

The key objects in the new scientific paradigm are the finest objects, which, with their oscillatory movements, impart mass and charge to any elementary particle.

The main properties of strings according to modern ideas:

Their length is extremely small - about 10 -35 meters. At this scale, quantum interactions become discernible;
However, under ordinary laboratory conditions, which do not deal with such small objects, a string is absolutely indistinguishable from a dimensionless point object;
An important characteristic of a string object is orientation. Strings that have it have a pair with the opposite direction. There are also undirected instances.

Strings can exist both in the form of a segment limited at both ends, and in the form of a closed loop. Moreover, the following transformations are possible:

A segment or loop can "multiply" to give rise to a pair of corresponding objects;
A segment gives rise to a loop if part of it “loops”;
The loop breaks and becomes an open string;
Two segments exchange segments.

Other fundamental objects

In 1995, it turned out that not only one-dimensional objects are the building blocks of our universe. The existence of unusual formations was predicted - branes- in the form of a cylinder or volumetric ring, which have the following features:

They are several billion times smaller than atoms;
Can propagate through space and time, have mass and charge;
In our Universe they are three-dimensional objects. However, it is suggested that their shape is much more mysterious, since a significant part of them can extend into other dimensions;
The multidimensional space that lies beneath the branes is hyperspace;
These structures are associated with the existence of particles that carry gravity - gravitons. They freely separate from branes and flow smoothly into other dimensions;
Electromagnetic, nuclear and weak interactions are also localized on branes;
The most important type are D-branes. The end points of the open string are attached to their surface at the moment when it passes through space.

Criticisms

Like any scientific revolution, this one makes its way through the thorns of misunderstanding and criticism from adherents of traditional views.

Among the most frequently expressed comments:

The introduction of additional dimensions of space-time creates the hypothetical possibility of the existence of a huge number of universes. According to mathematician Peter Volt, this leads to the impossibility of predicting any processes or phenomena. Every experiment triggers a large number of different scenarios that can be interpreted in different ways;
There is no confirmation option. The current level of technological development does not allow desk research to be experimentally confirmed or refuted;
Recent observations of astronomical objects do not fit the theory, which forces scientists to reconsider some of their conclusions;
A number of physicists express the opinion that the concept is speculative and inhibits the development of other fundamental concepts.

It is perhaps easier to prove Fermat's theorem than to explain string theory in simple words. Its mathematical apparatus is so extensive that only seasoned scientists from the largest research institutes can understand it.

It is still not clear whether the discoveries made at the tip of a pen over the past decades will find real application. If so, then a brave new world awaits us with antigravity, multiple universes and clues to the nature of black holes.

Video: string theory brief and accessible

In this video, physicist Stanislav Efremov will tell you in simple words what string theory is:

Ecology of knowledge: The biggest problem for theoretical physicists is how to combine all the fundamental interactions (gravitational, electromagnetic, weak and strong) into a single theory. Superstring theory claims to be the Theory of Everything

Counting from three to ten

The biggest problem for theoretical physicists is how to combine all the fundamental interactions (gravitational, electromagnetic, weak and strong) into a single theory. Superstring theory claims to be the Theory of Everything.

But it turned out that the most convenient number of dimensions required for this theory to work is as many as ten (nine of which are spatial, and one is temporal)! If there are more or less dimensions, mathematical equations give irrational results that go to infinity - a singularity.

The next stage in the development of superstring theory - M-theory - has already counted eleven dimensions. And another version of it - F-theory - all twelve. And this is not a complication at all. F-theory describes 12-dimensional space with simpler equations than M-theory describes 11-dimensional space.

Of course, theoretical physics is not called theoretical for nothing. All her achievements exist so far only on paper. So, to explain why we can only move in three-dimensional space, scientists started talking about how the unfortunate remaining dimensions had to shrink into compact spheres at the quantum level. To be precise, not into spheres, but into Calabi-Yau spaces. These are three-dimensional figures, inside of which there is their own world with its own dimension. A two-dimensional projection of such a manifold looks something like this:

More than 470 million such figures are known. Which of them corresponds to our reality is currently being calculated. It is not easy to be a theoretical physicist.

Yes, this seems a little far-fetched. But maybe this is precisely what explains why the quantum world is so different from the one we perceive.

Dot, dot, comma

Start over. The zero dimension is a point. She has no size. There is nowhere to move, no coordinates are needed to indicate the location in such a dimension.

Let's place a second one next to the first point and draw a line through them. Here's the first dimension. A one-dimensional object has a size - length, but no width or depth. Movement within one-dimensional space is very limited, because an obstacle that arises on the way cannot be avoided. To determine the location on this segment, you only need one coordinate.

Let's put a dot next to the segment. To fit both of these objects, we will need a two-dimensional space with length and width, that is, area, but without depth, that is, volume. The location of any point on this field is determined by two coordinates.

The third dimension arises when we add a third coordinate axis to this system. It is very easy for us, residents of the three-dimensional universe, to imagine this.

Let's try to imagine how the inhabitants of two-dimensional space see the world. For example, these two people:

Each of them will see their comrade like this:

And in this situation:

Our heroes will see each other like this:

It is the change of point of view that allows our heroes to judge each other as two-dimensional objects, and not one-dimensional segments.

Now let’s imagine that a certain volumetric object moves in the third dimension, which intersects this two-dimensional world. For an outside observer, this movement will be expressed in a change in two-dimensional projections of the object on the plane, like broccoli in an MRI machine:

But for an inhabitant of our Flatland such a picture is incomprehensible! He can't even imagine her. For him, each of the two-dimensional projections will be seen as a one-dimensional segment with a mysteriously variable length, appearing in an unpredictable place and also disappearing unpredictably. Attempts to calculate the length and place of origin of such objects using the laws of physics of two-dimensional space are doomed to failure.

We, inhabitants of the three-dimensional world, see everything as two-dimensional. Only moving an object in space allows us to feel its volume. We will also see any multidimensional object as two-dimensional, but it will change in surprising ways depending on our relationship with it or time.

From this point of view it is interesting to think, for example, about gravity. Everyone has probably seen pictures like this:

They usually depict how gravity bends space-time. It bends... where? Exactly not in any of the dimensions familiar to us. And what about quantum tunneling, that is, the ability of a particle to disappear in one place and appear in a completely different one, and behind an obstacle through which in our realities it could not penetrate without making a hole in it? What about black holes? What if all these and other mysteries of modern science are explained by the fact that the geometry of space is not at all the same as we are used to perceiving it?

The clock is ticking

Time adds another coordinate to our Universe. In order for a party to take place, you need to know not only in which bar it will take place, but also the exact time of this event.

Based on our perception, time is not so much a straight line as a ray. That is, it has a starting point, and movement is carried out only in one direction - from the past to the future. Moreover, only the present is real. Neither the past nor the future exists, just as breakfasts and dinners do not exist from the point of view of an office clerk during his lunch break.

But the theory of relativity does not agree with this. From her point of view, time is a full-fledged dimension. All events that have existed, exist and will exist are equally real, just like the sea beach is real, regardless of where exactly the dreams of the sound of the surf took us by surprise. Our perception is just something like a spotlight that illuminates a certain segment on a straight line of time. Humanity in its fourth dimension looks something like this:

But we see only a projection, a slice of this dimension at each individual moment in time. Yes, yes, like broccoli in an MRI machine.

Until now, all theories worked with a large number of spatial dimensions, and the temporal one was always the only one. But why does space allow multiple dimensions for space, but only one time? Until scientists can answer this question, the hypothesis of two or more time spaces will seem very attractive to all philosophers and science fiction writers. And physicists, too, so what? For example, American astrophysicist Itzhak Bars sees the root of all troubles with the Theory of Everything as the overlooked second time dimension. As a mental exercise, let's try to imagine a world with two times.

Each dimension exists separately. This is expressed in the fact that if we change the coordinates of an object in one dimension, the coordinates in others may remain unchanged. So, if you move along one time axis that intersects another at a right angle, then at the intersection point the time around will stop. In practice it will look something like this:

All Neo had to do was place his one-dimensional time axis perpendicular to the bullets' time axis. A mere trifle, you will agree. In reality, everything is much more complicated.

Exact time in a universe with two time dimensions will be determined by two values. Is it difficult to imagine a two-dimensional event? That is, one that is extended simultaneously along two time axes? It is likely that such a world would require specialists in mapping time, just as cartographers map the two-dimensional surface of the globe.

What else distinguishes two-dimensional space from one-dimensional space? The ability to bypass an obstacle, for example. This is completely beyond the boundaries of our minds. A resident of a one-dimensional world cannot imagine what it is like to turn a corner. And what is this - an angle in time? In addition, in two-dimensional space you can travel forward, backward, or even diagonally. I have no idea what it's like to pass through time diagonally. Not to mention the fact that time underlies many physical laws, and it is impossible to imagine how the physics of the Universe will change with the advent of another time dimension. But it’s so exciting to think about it!

Very large encyclopedia

Other dimensions have not yet been discovered and exist only in mathematical models. But you can try to imagine them like this.

As we found out earlier, we see a three-dimensional projection of the fourth (time) dimension of the Universe. In other words, every moment of the existence of our world is a point (similar to the zero dimension) in the period of time from the Big Bang to the End of the World.

Those of you who have read about time travel know what an important role the curvature of the space-time continuum plays in it. This is the fifth dimension - it is in it that four-dimensional space-time “bends” in order to bring two points on this line closer together. Without this, travel between these points would be too long, or even impossible. Roughly speaking, the fifth dimension is similar to the second - it moves the “one-dimensional” line of space-time into a “two-dimensional” plane with all that it implies in the form of the ability to turn a corner.

A little earlier, our particularly philosophically minded readers probably thought about the possibility of free will in conditions where the future already exists, but is not yet known. Science answers this question this way: probabilities. The future is not a stick, but a whole broom of possible scenarios. We will find out which one will come true when we get there.

Each of the probabilities exists in the form of a “one-dimensional” segment on the “plane” of the fifth dimension. What is the fastest way to jump from one segment to another? That's right - bend this plane like a sheet of paper. Where should I bend it? And again correctly - in the sixth dimension, which gives this entire complex structure “volume”. And, thus, makes it, like three-dimensional space, “finished”, a new point.

The seventh dimension is a new straight line, which consists of six-dimensional “points”. What is any other point on this line? The whole infinite set of options for the development of events in another universe, formed not as a result of the Big Bang, but under other conditions, and operating according to other laws. That is, the seventh dimension is beads from parallel worlds. The eighth dimension collects these “straight lines” into one “plane”. And the ninth can be compared to a book that contains all the “sheets” of the eighth dimension. This is the totality of all the histories of all universes with all the laws of physics and all the initial conditions. Period again.

Here we hit the limit. To imagine the tenth dimension, we need a straight line. And what other point could there be on this line if the ninth dimension already covers everything that can be imagined, and even that which is impossible to imagine? It turns out that the ninth dimension is not just another starting point, but the final one - for our imagination, at least.

String theory states that it is in the tenth dimension that strings vibrate—the basic particles that make up everything. If the tenth dimension contains all universes and all possibilities, then strings exist everywhere and all the time. I mean, every string exists both in our universe and in any other. At any time. Straightaway. Cool, yeah? published