Quantum string theory in simple words. Briefly about string theory

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

Need

As is known, physical laws 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 macrocosm and at the level of the microcosm, 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 new type particles that cannot exist in nature - tachyons, the square of whose mass 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, graviton - gravitational, or the same Higgs boson, propagating the 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.

Key questions:

What are the fundamental components of the Universe - the “first bricks of matter”? Are there theories that can explain all basic physical phenomena?

Question: is this real?

Currently and for the foreseeable future, direct observation on such a small scale is not possible. Physics is in search, and experiments are being carried out, for example, to detect supersymmetric particles or search for additional dimensions accelerators may indicate that string theory is on the right track.

Whether string theory is the theory of everything or not, it gives us a unique set of tools to peer into the deeper structures of reality.

String theory

Macro and micro

When describing the Universe, physics divides it into two seemingly incompatible halves - the quantum microworld, and the macroworld, within which gravity is described.

String theory is a controversial attempt to combine these halves into a "Theory of Everything".

Particles and interactions

The world is made of two kinds elementary particles- fermions and bosons. Fermions are all observable matter, and bosons are carriers of the four known fundamental interactions: weak, electromagnetic, strong and gravitational. Using a theory called the Standard Model, physicists have been able to elegantly describe and test the three fundamental interactions, all but the weakest - gravitational forces. Today, the Standard Model is the most accurate and experimentally confirmed model of our world.

Why do we need string theory?

The Standard Model does not include gravity, cannot describe the center of a black hole and the Big Bang, and does not explain the results of some experiments. String theory is an attempt to resolve these problems and unify matter and interactions by replacing elementary particles with tiny vibrating strings.

String theory is based on the idea that all elementary particles can be represented as one elementary “first brick” - a string. The strings can vibrate and different fashions Such oscillations at a great distance will look to us like various elementary particles. One mode of vibration will make the string look like a photon, another will make it look like an electron.

There is even a mode that describes the carrier of gravitational interaction - the graviton! Variants of string theory describe strings of two types: open (1) and closed (2). Open strings have two ends (3) located on membrane-like structures called D-branes, and their dynamics describe three of the four fundamental interactions- everything except gravitational.

Closed strings resemble loops, they are not tied to D-branes - it is the vibrational modes of closed strings that are represented by a massless graviton. The ends of an open string can join to form a closed string, which in turn can break to become an open string, or converge and split into two closed strings (5) - thus in string theory, gravitational interaction is combined with all others

Strings are the smallest of all objects that physics operates on. The range of sizes V of the objects shown in the picture above extends to 34 orders of magnitude - if the atom were the size of solar system, then the string size could be a little larger atomic nucleus.

Additional dimensions

Consistent string theories are only possible in higher-dimensional space, where in addition to the familiar 4th space-time dimensions, 6 additional ones are required. Theorists believe that these extra dimensions are folded into elusively small forms - Calabi-Yau spaces. One of the problems with string theory is that there is almost infinite number options for convolution (compactification) of Calabi-Yau, which allows us to describe any world, and so far there is no way to find that version of compactification that would allow us to describe what we see around us.

Supersymmetry

Most versions of string theory require the concept of supersymmetry, which is based on the idea that fermions (matter) and bosons (interactions) are manifestations of the same object, and can turn into each other.

The theory of everything?

Supersymmetry can be included in string theory in various ways, which leads to 5 various types string theory, which means that string theory itself cannot claim to be the “theory of everything.” All five of these types are related to each other by mathematical transformations called dualities, and this has led to the understanding that all of these types are aspects of something more general. This more general theory is called M-Theory.

There are 5 different formulations of string theory, but upon closer examination, it turns out that all of them are manifestations of more general theory

At the beginning of the 20th century, two load-bearing supports of the modern scientific knowledge. 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, in new theory additional measurements are introduced;
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 background

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 Garibrele Veneziano proposed a double resonance model to describe strong interactions. Yoshiro Nambu developed this idea and described nuclear forces like 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

Key objects in the new scientific paradigm are the finest objects, which are 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, in 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 possessing it are paired with opposite direction. There are also undirected instances.

Strings can exist either in the form of a segment limited at both ends, or 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 represent 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;
Most important variety are D-branes. They are attached to their surfaces endpoints open string at the moment when it passes through space.

Criticisms

Like any scientific revolution, this one breaks 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 huge amount universes. According to mathematician Peter Volt, this leads to the impossibility of predicting any processes or phenomena. Every experiment starts large number different scenarios that can be interpreted in different ways;
There is no confirmation option. Modern level technological developments do 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 yes, then a wonderful thing awaits us. new world 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:

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 to be 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. For similar experiments with strings, one would have to build 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 vibration quantum string does not make sound, there is nothing to transmit on the scale of elementary particles sound vibrations. 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 theories.

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 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 who were moving 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 so far this is impossible - there are no hints on what to rely on in the calculations and find the numbers you need It's only possible 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 gravitational interaction Earth and Moon in Einsteinian spacetime

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 theory fields with added mass for neutrinos are 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. By Standard model, elementary particles - dimensionless points, which 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 unified theory fields, 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 the distance between them greater than zero, and impossible calculation results for the graviton can be 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. It was strange: in those days the atom was considered indivisible, and Euler’s work solved exclusively math problems. Nobody understood why the equations worked, but they were actively used.

Physical meaning Euler's beta functions were discovered 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 mathematical model, which showed that many contradictions between string theory and the Standard Model can be resolved. The new equations also related the theory to all types of matter and energy. Scientific world A fever struck - 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 supersymmetry, and there was no way to know which theory was correct.

Mathematical methods had their limits. Physicists are accustomed to complex equations, which do not give exact results, but for string theory it was not possible to write even exact 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 inspired scientists, and scientific journals published publications on string physics again.

space-time measurements in modern theory superstrings

“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're even talking about a new 12-dimensional fundamental theory— F-theories, 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.

Main problem theories - in the absence 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 a single structural basis 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 final theory" became a finalist Pulitzer Prize. In 2011, he played himself in the 83rd episode of Theories Big Bang" 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 bring everything together 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:

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. Main idea is already visible in the name itself: instead of point-like 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 there is no modern equipment they cannot be detected (specifically, they are located at the Planck length, but this is 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 various properties particles (for example, 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 interaction(the interaction by which protons and neutrons are held together in the nucleus of an atom), no more, since some types of vibrating strings resembled the properties of gluons (carrier particles strong interaction). 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 quantum world Because of these very fluctuations, space is not smooth and smooth at all, 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. Confusion, but physicists found a solution, saying that the interaction of strings smoothes 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 under 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 From a perspective, the process is nevertheless one, and the point of interaction is one. 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 infinite number 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 be different sizes, 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: parallel universe) or somehow see her. 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.