String theory is the unified theory of everything.

By comprehensively studying our universe, scientists determine a number of patterns and facts, which subsequently become laws proven by hypotheses. Based on them, other research continues to contribute to a comprehensive study of the world in numbers.

The string theory of the universe is a way of representing the space of the universe, consisting of certain threads, which are called strings and branes. To put it simply (for dummies), the basis of the world is not particles (as we know), but vibrating energy elements called strings and branes. The size of the string is very, very small - approximately 10 -33 cm.

What is this for and is it useful? The theory provided the impetus for the description of the concept of “gravity”.

String theory is mathematical, that is, physical nature described by equations. There are many of them, but there is no one and true one. The hidden dimensions of the universe have not yet been determined experimentally.

The theory is based on 5 concepts:

The world consists of threads in a vibrating state and energy membranes.
The theory is based on the theory of gravity and quantum physics.
The theory unifies all the fundamental forces of the universe.
Particles bosons and fermions have new look connections - supersymmetry.
The theory describes dimensions in the Universe that are unobservable by the human eye.

A comparison with a guitar will help you understand string theory better.

The world first heard about this theory in the seventies of the twentieth century. Names of scientists in the development of this hypothesis:

Witten;
Veneziano;
Green;
Gross;
Kaku;
Maldacena;
Polyakov;
Susskind;
Schwartz.

Energy threads were considered one-dimensional - strings. This means that the string has 1 dimension - length (no height). There are 2 types:

open, in which the ends do not touch each other;
closed - loop.

It was found that they can interact in 5 such ways. This is based on the ability to connect and separate ends. The absence of ring strings is impossible, due to the possibility of combining open strings.

As a result, scientists believe that the theory is capable of describing not the association of particles, but the behavior of gravity. The branes or sheets are considered as the elements to which the strings are attached.

Quantum gravity

In physics there is the quantum law and the general theory of relativity. Quantum physics studies particles on the scale of the universe. The hypotheses in it are called theories of quantum gravity; string gravity is considered the most important.

The closed threads in it work in accordance with the forces of gravity, having the properties of a graviton - a particle that transfers properties between particles.

Joining forces. The theory includes the combined forces into one - electromagnetic, nuclear, gravitational. Scientists believe that this is exactly how it was before, before the forces were divided.

Supersymmetry. According to the concept of supersymmetry, there is a connection between bosons and fermions (structural units of the universe). For each boson there is a fermion, and the converse is also true: for a fermion there is a boson. This was calculated based on equations, but not confirmed experimentally. The advantage of supersymmetry is the possibility of eliminating some variables (infinite, imaginary energy levels).

According to physicists, the reason for the inability to prove supersymmetry is the reason for the large energy associated with mass. It existed earlier, before the period of temperature decline in the universe. After the Big Bang, energy dissipated and particles moved to lower energy levels.

To put it simply, strings that could vibrate with the properties of particles with high energy, having lost it, became low vibration.

When creating particle accelerators, scientists want to identify super symmetrical elements with the required energy level.

Additional dimensions of string theory

A corollary of string theory is mathematical representation, according to which there must be more than 3 dimensions. The first explanation for this is that the additional dimensions have become compact and small, as a result of which they cannot be seen or perceived.

We exist in a three-dimensional brane, cut off from other dimensions. Only opportunity to use mathematical modeling gave hope for obtaining coordinates that would connect them. Recent research in this area makes it possible to assume the emergence of new optimistic data.

Simple understanding of the goal

Scientists around the world, studying super strings, are trying to substantiate the theory regarding the entire physical reality. A single hypothesis could characterize everything at a fundamental level, explaining the structure of the planet.

String theory emerged from the description of hadrons, particles with higher vibrational states of a string. In short, it easily explains the transition from length to mass.

There are many superstring theories. Today it is not known for certain whether it is possible to use it to explain the theory of space-time more accurately than Einstein. The measurements taken do not provide accurate data. Some of them, concerning space-time, were a consequence of the interactions of strings, but were ultimately subject to criticism.

The theory of gravity will be the main consequence of the described theory if it is confirmed.

Strings and branes became the impetus for the emergence of more than 10 thousand variants of judgments about the universe. Books on string theory are available in public access on the Internet, described in detail and clearly by the authors:

Yau Shintan;
Steve Nadis "String Theory and the Hidden Dimensions of the Universe";
Brian Greene talks about this in The Elegant Universe.

Opinions, evidence, reasoning and all the smallest details can be found by looking at one of the many books that provide information about the world in an accessible and interesting way. Physicists explain the existing universe by our presence, the existence of other universes (even similar to ours). According to Einstein, there is a folded version of space.

In superstring theory, dots can be connected parallel worlds. Established laws in physics give hope for the possibility of transition among universes. At the same time, the quantum theory of gravity eliminates this.

Physicists also talk about holographic recording of data, when they are recorded on a surface. In the future, this will give impetus to understanding the judgment about energy threads. There are judgments about the multiplicity of dimensions of time and the possibility of movement in it. Hypothesis big bang due to the collision of 2 branes, it speaks of the possibility of repeating cycles.

The universe, the emergence of everything and the gradual transformation of everything have always occupied the outstanding minds of mankind. There have been, are and will be new discoveries. The final interpretation of string theory will make it possible to determine the density of matter, the cosmological constant.

Thanks to this, they will determine the ability of the universe to shrink until the subsequent moment of explosion and a new beginning of everything. Theories are developed, proven, and they lead to something. Thus, Einstein’s equation, which describes the dependence of energy on mass and the square of the speed of light E=mc^2, subsequently became the impetus for the emergence nuclear weapons. After this, the laser and transistor were invented. Today we don’t know what to expect, but it will certainly lead to something.

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. The atom was then 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 next step 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 documentary film"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 emptiness two-dimensional dimensional faces, or branes - from the word membrane.

centimeters - minimum possible size 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 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 are electromagnetic forces bending? 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 speed Sveta. 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 balloon- all around. 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
identified 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 alternative theory, capable of uniting 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 Swiss mathematician Leonhard Euler had compiled 200 years earlier. It was strange: in those days the atom was considered indivisible, and Euler’s work solved exclusively math 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 they managed 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 well. 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, naturally follow 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 supersymmetry, and there was no way to know 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 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 theory superstrings

“String theory is a part of twenty-first century physics that accidentally fell into 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 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 strings musical instruments. 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 logically follow from string theory modern science. 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 serious problems there was nothing left in it, and the whole 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 from such obvious absurdity, the German scientist Max Planck in 1900 suggested that visible light, X-rays and others electromagnetic waves can be emitted only 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 famous principle uncertainty.

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 how 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 where exactly a point in space is located. at the moment this or that particle, 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 for a long time considered nothing less than a mathematical curiosity, describes this strong interaction.

What was it really like? The equation was probably the result many years Veneziano's 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 did not have 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 smashing them together. 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 " Maternity Hospital“Scientists have not been 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, even in this perfect theory there was 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 which would allow gravity to be transferred to the quantum level. This is how string theory added gravity to the puzzle, 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 the atom were enlarged to the size solar system, the string would be the size of a tree. Just as the different vibrations of a cello string create what we hear as different musical notes, various ways(modes) vibrations of the 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. Ever since ancient Greece physicists are 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.

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 her, it is the additional dimensions that determine exact value fundamental constants. Some forms of measurement cause one string to vibrate in a certain way, and give rise to 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 within 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 most main problem strings, as already mentioned, it is impossible (at least for now) to prove 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 most, even in a hundred years.

A similar question has already been asked here:

But I’ll try to tell you about it in my signature style;)

We have a very long conversation ahead of us, but I hope that you will find it interesting, bro. In general, listen to what the point is here. The main idea is already visible in the name itself: instead of point elementary particles (such as electrons, photons, etc.), this theory proposes strings - sort of microscopic vibrating one-dimensional threads of energy that are so small that they cannot be detected with any modern equipment (specifically they are on the Planck length, but that’s not the point). Not to say that particles consist made of strings, they and there is strings, simply due to the imperfection of our equipment, we see them as particles. And if our equipment is able to reach the Planck length, then, as expected, we will find strings there. And just as a violin string vibrates to produce different notes, a quantum string vibrates to produce different particle properties (such as charges or masses). This, in general, is the main idea.

However, it is important to note here that string theory has very big ambitions and it claims nothing less than the status of a “theory of everything”, combining gravity (the theory of relativity) and quantum mechanics (that is, the macroworld - the world of large objects familiar to us, and the microworld - world of elementary particles). Gravity appears elegantly on its own in string theory, and here's why. Initially, string theory was generally perceived only as a theory of the strong nuclear force (the interaction due to which protons and neutrons are held together in the nucleus of an atom), nothing more, since some types of vibrating strings resembled the properties of gluons (particles that carry the strong force). However, in addition to gluons, there were other types of string oscillations in it, reminiscent of other particles that carried some kind of interaction, which had nothing to do with gluons. Having studied the properties of these particles, scientists discovered that these vibrations exactly coincide with the properties of a hypothetical particle - a graviton - a particle that carries gravitational interaction. This is how gravity appeared in string theory.

But here again (what are you going to do!) a problem called “quantum fluctuations” arises. Don't be afraid, this term is scary only in appearance. So, quantum fluctuations are associated with the constant birth and destruction of virtual (those that cannot be seen directly due to their continuous appearance and disappearance) particles. The most significant process in this sense is annihilation - the collision of a particle and an antiparticle with the formation of a photon (particle of light), which subsequently generates another particle and antiparticle. What is gravity, essentially? It is a smoothly curved geometric fabric of space-time. The key word here is smoothly. And in the quantum world, because of these same fluctuations, space is not at all smooth and smooth, there is such chaos going on there that it’s even scary to imagine. As you probably already understand, the smooth geometry of space of the theory of relativity is completely incompatible with quantum fluctuations. Confused, but physicists have found a solution, saying that the interaction of strings smooths out these fluctuations. How, you ask? But imagine two closed strings (for there are also open ones, which are a kind of small thread with two open ends; closed strings, accordingly, are a kind of loops). These two closed strings are on a collision course and at some point collide, turning into one larger size string. This string continues to move for some time, after which it breaks up into two smaller strings. Now the next step. Let's imagine this whole process in filmed footage: we will see that this process has acquired a certain three-dimensional volume. This volume is called the "world surface". Now let’s imagine that you and I are looking at this whole process from different angles: I’m looking straight, and you’re looking at a slight angle. We will see that from your point of view and from my point of view the strings will collide in different places, since for you these string “loops” (let's call them that) will move slightly at an angle, but for me they will move straight. However, this is the same process, the same two colliding strings, the difference lies only in two points of view. This means that there is a certain “smearing” of the interaction of the strings: from the position of different observers, they interact in different places. However, despite these different points of view, the process is nevertheless the same, and the point of interaction is the same. Thus, different observers will record the same place of interaction of two point particles. Just like that! Do you understand what's happening? We have smoothed out quantum fluctuations and thus united gravity and quantum mechanics! Look!

Okay, let's move on. Are you tired yet? Well, listen. Now I’ll talk about something that I personally don’t really like about string theory. And this is called “mathematization”. Somehow the theorists got too carried away with mathematics... but the point here is simple: how many dimensions of space do you know? That's right, three: length, width and height (time is the fourth dimension). So, the mathematics of string theory gets along very poorly with these four dimensions. And with five too. And with ten. But he gets along well with eleven. And the theorists decided: well, since mathematics requires it, let there be eleven dimensions. You see, mathematics requires! Mathematics, not reality! (Exclamation aside: if I'm wrong, someone convince me! I want to change my mind!) Well, where, one might ask, did the other seven dimensions go? The theory answers this question by saying that they are “compactified”, rolled up into microscopic formations at the Planck length (that is, at a scale that we are not able to observe). These formations are called the “Calabi-Yau manifold” (after the names of two prominent physicists).

It is also interesting that string theory leads us to the Multiverse, that is, to the idea of the existence of an infinite number of parallel Universes. The whole point here is that in string theory there are not only strings, but also branes (from the word “membrane”). Branes can have different dimensions, up to nine. We are supposed to live on a 3-brane, but there may be others near this brane, and they may collide periodically. But we don’t see them because open strings are tightly attached to the brane at both ends. These strings with their ends can move along the brane, but they cannot leave it (get unhooked). And if you believe string theory, then all matter and all of us consist of particles that at the Planck length look like strings. Consequently, since open strings cannot leave the brane, then we cannot interact in any way with another brane (read: a parallel Universe) or somehow see it. The only particle that, in principle, does not care about this limitation and can do this is the hypothetical graviton, which is a closed string. However, no one has yet been able to detect a graviton. Such a Multiverse is called a “brane Multiverse” or a “brane world scenario.”

By the way, due to the fact that not only strings, but also branes were discovered in string theory, theorists began to call it “M-theory”, but no one really knows what this “M” means;)

Just like that. This is the story. I hope you found it interesting, bro. If something remains unclear, ask in the comments and I’ll explain.

Theoretical physics is obscure to many, but at the same time it is of paramount importance in the study of the world around us. The task of any theoretical physicist is to construct mathematical model, a theory capable of explaining certain processes in nature.

Need

As you know, the physical laws of the macrocosm, that is, the world in which we exist, differ significantly from the laws of nature in the microcosm - within which atoms, molecules and elementary particles live. An example would be a difficult-to-understand principle called carpuscular-wave dualism, according to which micro-objects (electron, proton and others) can be both particles and waves.

Like us, theoretical physicists want to describe the world briefly and clearly, which is the main purpose of string theory. It can help explain some physical processes, both at the level of the macroworld and at the level of the microworld, which makes it universal, uniting other previously unrelated theories (general relativity and quantum mechanics).

The essence

According to string theory, the entire world is built not from particles, as is believed today, but from infinitely thin objects 10-35 m long that have the ability to vibrate, which allows us to draw an analogy with strings. Using a complex mathematical mechanism, these vibrations can be associated with energy, and therefore with mass; in other words, any particle arises as a result of one or another type of vibration of a quantum string.

Issues and Features

Like any unconfirmed theory, string theory has a number of problems that indicate that it requires improvement. These problems include, for example, the following: as a result of calculations, mathematically, there was a new type of particles that cannot exist in nature - tachyons, the square of whose mass is less than zero, and the speed of movement exceeds the speed of light.

The other one important issue, or rather the peculiarity is the existence of string theory only in 10-dimensional space. Why do we perceive other dimensions? “Scientists have come to the conclusion that on very small scales these spaces fold and close in on themselves, making it impossible for us to identify them.

Development

There are two types of particles: fermions - particles of matter, and bosons - carriers of interaction. For example, a photon is a boson that carries electromagnetic interaction, a graviton is gravitational, or the same Higgs boson that carries interaction with the Higgs field. So, if string theory took into account only bosons, then superstring theory also took into account fermions, which made it possible to get rid of tachyons.

The final version of the superstring principle was developed by Edward Witten and is called "m-theory", according to which to unite all different versions superstring theory should introduce the 11th dimension.

We can probably end here. Theoretical physicists are diligently working to solve problems and refine the existing mathematical model different countries peace. Perhaps soon we will finally be able to understand the structure of the world around us, but looking back at the scope and complexity of the above, it is obvious that the resulting description of the world will not be understandable without a certain base of knowledge in the field of physics and mathematics.