Is string theory the unified theory of everything? String theory in simple terms

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, the physical nature is 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 a new type of connection - 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 according to 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 the mathematical concept that 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 the ability to use mathematical modeling gave hope of 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 publicly available 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, points of parallel worlds can be connected. 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. The big bang hypothesis due to the collision of 2 branes suggests 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 of 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 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” are as follows:

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

Historical reference

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

The main stages of its development:

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

Quantum string theory

The key objects in the new scientific paradigm are the finest objects, which 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, under ordinary laboratory conditions, which do not deal with such small objects, a string is absolutely indistinguishable from a dimensionless point object;
An important characteristic of a string object is orientation. Strings that have it have a pair with the opposite direction. There are also undirected instances.

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

Criticisms

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

Among the most frequently expressed comments:

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

It is perhaps easier to prove Fermat's theorem than in simple words explain the provisions of string theory. 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:

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

Counting from three to ten

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

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

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

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

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

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

Dot, dot, comma

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

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

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

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

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

Each of them will see their comrade like this:

And in this situation:

Our heroes will see each other like this:

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

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

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

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

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

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

The clock is ticking

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

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

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

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

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

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

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

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

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

Very large encyclopedia

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

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

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

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

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

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

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

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

Superstring theory, in popular parlance, envisions the universe as a collection of vibrating strands of energy—strings. They are the basis of nature. The hypothesis also describes other elements - branes. All matter in our world consists of vibrations of strings and branes. A natural consequence of the theory is the description of gravity. That's why scientists believe it holds the key to unifying gravity with other forces.

The concept is evolving

The unified field theory, the theory of superstrings, is purely mathematical. Like all physics concepts, it is based on equations that can be interpreted in certain ways.

Today no one knows exactly what the final version of this theory will be. Scientists have a rather vague idea of its general elements, but no one has yet come up with a final equation that would cover all superstring theories, and it has not yet been possible to confirm it experimentally (although it has also been disproved). Physicists have created simplified versions of the equation, but so far it does not fully describe our universe.

Superstring theory for beginners

The hypothesis is based on five key ideas.

Superstring theory predicts that all objects in our world are composed of vibrating threads and membranes of energy.
She's trying to combine general theory relativity (gravity) with quantum physics.
Superstring theory will allow us to unify all the fundamental forces of the universe.
This hypothesis predicts a new connection, supersymmetry, between two fundamentally various types particles, bosons and fermions.
The concept describes a number of additional, usually unobservable dimensions of the Universe.

Strings and branes

When the theory emerged in the 1970s, the threads of energy in it were considered 1-dimensional objects - strings. The word "one-dimensional" means that the string has only 1 dimension, length, unlike, for example, a square, which has length and height.

The theory divides these superstrings into two types - closed and open. An open string has ends that do not touch each other, while a closed string is a loop with no open ends. As a result, it was found that these strings, called type 1 strings, are subject to 5 main types of interactions.

The interactions are based on the ability of the string to connect and separate its ends. Since the ends of open strings can combine to form looped strings, it is impossible to construct a superstring theory that does not include looped strings.

This turned out to be important because closed strings have properties physicists believe that could describe gravity. In other words, scientists realized that instead of explaining particles of matter, superstring theory could describe their behavior and gravity.

Over the years, it was discovered that, in addition to strings, the theory also needed other elements. They can be thought of as sheets, or branes. Strings can be attached to one or both sides.

Quantum gravity

Modern physics has two basic scientific laws: general relativity (GTR) and quantum. They represent completely different fields of science. Quantum physics studies the smallest natural particles, and general relativity, as a rule, describes nature on the scale of planets, galaxies and the universe as a whole. Hypotheses that attempt to unify them are called theories of quantum gravity. The most promising of them today is the string instrument.

The closed threads correspond to the behavior of gravity. In particular, they have the properties of a graviton, a particle that transfers gravity between objects.

Joining forces

String theory attempts to combine the four forces - electromagnetic force, strong and weak nuclear forces, and gravity - into one. In our world they manifest themselves as four different phenomena, but string theorists believe that in the early Universe, when they were incredibly high levels energy, all these forces are described by strings interacting with each other.

Supersymmetry

All particles in the universe can be divided into two types: bosons and fermions. String theory predicts that there is a relationship between them called supersymmetry. Under supersymmetry, for every boson there must be a fermion and for every fermion a boson. Unfortunately, the existence of such particles has not been experimentally confirmed.

Supersymmetry is a mathematical relationship between elements of physical equations. It was discovered in another branch of physics, and its application led to its renaming as supersymmetric string theory (or superstring theory, in popular parlance) in the mid-1970s.

One of the benefits of supersymmetry is that it greatly simplifies equations by eliminating some variables. Without supersymmetry, equations lead to physical contradictions such as infinite values and imaginary

Since scientists have not observed the particles predicted by supersymmetry, it is still a hypothesis. Many physicists believe that the reason for this is the need for a significant amount of energy, which is related to mass by the famous Einstein equation E = mc 2. These particles may have existed in the early universe, but as it cooled and energy spread out after the Big Bang, these particles moved to lower energy levels.

In other words, the strings, which were vibrating as high-energy particles, lost energy, turning them into lower-vibrating elements.

Scientists hope that astronomical observations or particle accelerator experiments will confirm the theory by identifying some of the higher-energy supersymmetric elements.

Additional dimensions

Another mathematical implication of string theory is that it makes sense in a world with more than three dimensions. There are currently two explanations for this:

The extra dimensions (six of them) have collapsed, or, in the terminology of string theory, compacted into incredibly small sizes that will never be perceived.
We are stuck in a 3-dimensional brane, and other dimensions extend beyond it and are inaccessible to us.

An important area of research among theorists is mathematical modeling of how these extra coordinates might relate to ours. The latest results predict that scientists will soon be able to detect these extra dimensions (if they exist) in upcoming experiments, as they may be larger than previously expected.

Understanding the goal

The goal that scientists strive for when studying superstrings is a “theory of everything,” i.e., a unified physical hypothesis that describes all physical reality at a fundamental level. If successful, it could clarify many questions about the structure of our universe.

Explaining Matter and Mass

One of the main tasks modern research- search for solutions for real particles.

String theory began as a concept describing particles such as hadrons by various higher vibrational states of a string. In the majority modern formulations, the matter observed in our universe is the result of the lowest energy vibrations of strings and branes. Higher vibrations generate high-energy particles that currently do not exist in our world.

The mass of these is a manifestation of how strings and branes are wrapped up in compactified extra dimensions. For example, in the simplified case of being folded into a donut shape, called a torus by mathematicians and physicists, the string can wrap around this shape in two ways:

short loop through the middle of the torus;
a long loop around the entire outer circumference of the torus.

A short loop will be a light particle, and a long loop will be a heavy one. When strings are wrapped around torus-shaped compactified dimensions, new elements with different masses are formed.

Superstring theory briefly and clearly, simply and elegantly explains the transition of length to mass. The folded dimensions here are much more complex than a torus, but in principle they work the same way.

It is even possible, although it is difficult to imagine, that the string wraps around the torus in two directions at the same time, resulting in a different particle with a different mass. Branes can also wrap around extra dimensions, creating even more possibilities.

Definition of space and time

In many versions of superstring theory, measurements collapse, making them unobservable at the current level of technology.

It is currently unclear whether string theory can explain the fundamental nature of space and time any further than Einstein did. In it, measurements are a background for the interaction of strings and have no independent real meaning.

Explanations were proposed, not fully developed, concerning the representation of space-time as a derivative of the total sum of all string interactions.

This approach does not correspond to the ideas of some physicists, which led to criticism of the hypothesis. Competitive theory uses the quantization of space and time as its starting point. Some believe that in the end it will turn out to be just a different approach to the same basic hypothesis.

Gravity quantization

The main achievement of this hypothesis, if confirmed, will be the quantum theory of gravity. The current description in General Relativity does not agree with quantum physics. The latter, by imposing restrictions on the behavior of small particles, leads to contradictions when trying to explore the Universe on extremely small scales.

Unification of forces

Currently, physicists know four fundamental forces: gravity, electromagnetic, weak and strong nuclear interactions. From string theory it follows that they were all once manifestations of one.

According to this hypothesis, as the early universe cooled after the big bang, this single interaction began to break up into different ones that operate today.

High-energy experiments will someday allow us to discover the unification of these forces, although such experiments are far beyond the current development of technology.

Five options

Since the superstring revolution of 1984, development has proceeded at a feverish pace. As a result, instead of one concept, there were five, called type I, IIA, IIB, HO, HE, each of which almost completely described our world, but not completely.

Physicists, going through versions of string theory in the hope of finding a universal true formula, have created 5 different self-sufficient versions. Some of their properties reflected the physical reality of the world, others did not correspond to reality.

M-theory

At a conference in 1995, physicist Edward Witten proposed a bold solution to the five-hypothesis problem. Based on the newly discovered duality, they all became special cases of a single overarching concept, called M-theory of superstrings by Witten. One of its key concepts was branes (short for membrane), fundamental objects with more than 1 dimension. Although the author did not propose a complete version, which still does not exist, M-theory of superstrings briefly consists of the following features:

11-dimensionality (10 spatial plus 1 time dimension);
dualities that lead to five theories explaining the same physical reality;
Branes are strings with more than 1 dimension.

Consequences

As a result, instead of one, 10,500 solutions emerged. For some physicists, this caused a crisis, while others accepted the anthropic principle, which explains the properties of the universe by our presence in it. It remains to be seen that theorists will find another way to navigate superstring theory.

Some interpretations suggest that our world is not the only one. The most radical versions allow for the existence of an infinite number of universes, some of which contain exact copies of ours.

Einstein's theory predicts the existence of a collapsed space called a wormhole or Einstein-Rosen bridge. In this case, two distant areas are connected by a short passage. Superstring theory allows not only this, but also the connection of distant points of parallel worlds. It is even possible to transfer between universes with different laws physics. However, it is likely that the quantum theory of gravity will make their existence impossible.

Many physicists believe that the holographic principle, when all the information contained in a volume of space corresponds to the information recorded on its surface, will allow a deeper understanding of the concept of energy threads.

Some believe that superstring theory allows for multiple dimensions of time, which could lead to travel across them.

In addition, the hypothesis offers an alternative to the big bang model, in which our universe was created by the collision of two branes and goes through repeated cycles of creation and destruction.

The ultimate fate of the universe has always occupied physicists, and the final version of string theory will help determine the density of matter and the cosmological constant. Knowing these values, cosmologists will be able to determine whether the universe will shrink until it explodes, so that it all starts again.

No one knows what it might lead to until it is developed and tested. Einstein, having written the equation E=mc 2, did not assume that it would lead to the emergence of nuclear weapons. The creators of quantum physics did not know that it would become the basis for the creation of lasers and transistors. And although it is not yet known what such a purely theoretical concept will lead to, history indicates that something outstanding will certainly result.

You can read more about this hypothesis in Andrew Zimmerman's book, Superstring Theory for Dummies.

Of course, the strings of the universe are hardly similar to those we imagine. In string theory, they are incredibly small vibrating threads of energy. These threads are more like tiny “rubber bands” that can wriggle, stretch and compress in all sorts of ways. All this, however, does not mean that it is impossible to “play” the symphony of the Universe on them, because, according to string theorists, everything that exists consists of these “threads”.

Physics contradiction

In the second half of the 19th century, it seemed to physicists that nothing serious could be discovered in their science anymore. Classical physics believed that there were no serious problems left in it, and the entire structure of the world looked like a perfectly regulated and predictable machine. The trouble, as usual, happened because of nonsense - one of the small “clouds” that still remained in the clear, understandable sky of science. Namely, when calculating the radiation energy of an absolutely black body (a hypothetical body that, at any temperature, completely absorbs the radiation incident on it, regardless of the wavelength - NS).

Calculations showed that the total radiation energy of any absolutely black body should be infinitely large. To get away from such obvious absurdity, the German scientist Max Planck in 1900 suggested that visible light, X-rays and other electromagnetic waves can only be emitted by certain discrete portions of energy, which he called quanta. With their help, it was possible to solve the particular problem of an absolutely black body. However, the consequences of the quantum hypothesis for determinism were not yet realized. Until, in 1926, another German scientist, Werner Heisenberg, formulated the famous uncertainty principle.

Its essence boils down to the fact that, contrary to all previously dominant statements, nature limits our ability to predict the future on the basis of physical laws. We are, of course, talking about the future and present of subatomic particles. It turned out that they behave completely differently from the way any things do in the macrocosm around us. At the subatomic level, the fabric of space becomes uneven and chaotic. The world of tiny particles is so turbulent and incomprehensible that it defies common sense. Space and time are so twisted and intertwined in it that there are no ordinary concepts of left and right, up and down, or even before and after.

There is no way to say for sure at what point in space a particular particle is currently located, and what is its angular momentum. There is only a certain probability of finding a particle in many regions of space-time. Particles at the subatomic level seem to be “smeared” throughout space. Not only that, but the “status” of the particles itself is not defined: in some cases they behave like waves, in others they exhibit the properties of particles. This is what physicists call the wave-particle duality of quantum mechanics.

Levels of the structure of the world: 1. Macroscopic level - matter 2. Molecular level 3. Atomic level - protons, neutrons and electrons 4. Subatomic level - electron 5. Subatomic level - quarks 6. String level /©Bruno P. Ramos

In the General Theory of Relativity, as if in a state with opposite laws, the situation is fundamentally different. Space appears to be like a trampoline - a smooth fabric that can be bent and stretched by objects with mass. They create warps in space-time—what we experience as gravity. Needless to say, the harmonious, correct and predictable General Theory of Relativity is in an insoluble conflict with the “eccentric hooligan” - quantum mechanics, and, as a consequence, 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 general relativity and quantum mechanics, a dream that haunted the greatest “gypsy and tramp” Albert Einstein until the end of his days.

Many scientists believe that everything from the exquisite dance of galaxies to the crazy dance of subatomic particles can ultimately be explained by just one fundamental physical principle. Maybe even a single law that unites all types of energy, particles and interactions in some elegant formula.

General relativity describes one of the most famous forces of the Universe - gravity. Quantum mechanics describes three other forces: the strong nuclear force, which glues protons and neutrons together in atoms, electromagnetism, and the weak force, which is involved in radioactive decay. Any event in the universe, from the ionization of an atom to the birth of a star, is described by the interactions of matter through these four forces.

By using the most complex mathematics It was possible to show that electromagnetic and weak interactions have a common nature, combining them into a single electroweak interaction. Subsequently, strong nuclear interaction was added to them - but gravity does not join them in any way. String theory is one of the most serious candidates for connecting all four forces, and, therefore, embracing all phenomena in the Universe - it is not for nothing that it is also called the “Theory of Everything”.

In the beginning there was a myth

Until now, not all physicists are delighted with string theory. And at the dawn of its appearance, it seemed infinitely far from reality. Her very birth is a legend.

In the late 1960s, a young Italian theoretical physicist, Gabriele Veneziano, was searching for equations that could explain the strong nuclear force—the extremely powerful “glue” that holds the nuclei of atoms together, binding protons and neutrons together. According to legend, one day he accidentally stumbled upon a dusty book on the history of mathematics, in which he found a two-hundred-year-old function first written down by the Swiss mathematician Leonhard Euler. Imagine Veneziano's surprise when he discovered that the Euler function, which for a long time considered nothing more than a mathematical curiosity, describes this strong interaction.

What was it really like? The formula was probably the result for long years Veneziano's work, and chance only helped take the first step towards the discovery of string theory. Euler's function, which miraculously explained the strong force, has found new life.

Eventually, it caught the eye of the young American theoretical physicist Leonard Susskind, who saw that, first of all, the formula described particles that 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 colliding them at high speeds and studying the consequences of these collisions. It turned out that the Universe is much richer than one could imagine. It was a real “population explosion” elementary particles. Physics graduate students ran through the corridors shouting that they had discovered a new particle - there weren’t even enough letters to designate them. But, alas, in the “maternity hospital” of new particles, scientists were never able to find the answer to the question - why are there so many of them and where do they come from?

This prompted physicists to make an unusual and startling prediction - they realized that the forces at work in nature could also be explained in terms of particles. That is, there are particles of matter, and there are particles that carry interactions. For example, a photon is a particle of light. The more of these carrier particles - the same photons that matter particles exchange - the brighter the light. Scientists predicted that this particular exchange of carrier particles is nothing more than what we perceive as force. This was confirmed by experiments. This is how physicists managed to get closer to Einstein’s dream of uniting forces.

Interactions between various particles in the Standard Model /

Scientists believe that if we fast forward to just after the Big Bang, when the Universe was trillions of degrees hotter, the particles that carry electromagnetism and the weak force will become indistinguishable and combine into a single force called the electroweak force. And if we go back even further in time, the electroweak interaction would combine with the strong one into one total “superforce.”

Even though all this is still waiting to be proven, quantum mechanics suddenly explained how three of the four forces interact at the subatomic level. And she explained it beautifully and consistently. This coherent picture of interactions ultimately became known as the Standard Model. But, alas, this perfect theory had one big problem - it did not include the most famous macro-level force - gravity.

Graviton

For string theory, which had not yet had time to “bloom,” “autumn” has come; it contained too many problems from its very birth. For example, the theory's calculations predicted the existence of particles, which, as was soon established, do not exist. This is the so-called tachyon - a particle that moves in a vacuum faster than light. Among other things, it turned out that the theory requires as many as 10 dimensions. It's not surprising that this has been very confusing to physicists, since it's obviously bigger than what we see.

By 1973, only a few young physicists were still grappling with the mysteries of string theory. One of them was the American theoretical physicist John Schwartz. For four years, Schwartz tried to tame the unruly equations, but to no avail. Among other problems, one of these equations persisted in describing a mysterious particle that had no mass and had not been observed in nature.

The scientist had already decided to abandon his disastrous business, and then it dawned on him - maybe the equations of string theory also describe gravity? However, this implied a revision of the dimensions of the main “heroes” of the theory – strings. By assuming that strings are billions and billions of times smaller than an atom, the “stringers” turned the theory’s disadvantage into its advantage. The mysterious particle that John Schwartz had so persistently tried to get rid of now acted as a graviton - a particle that had long been sought and that would allow gravity to be transferred to the quantum level. This is how string theory completed the puzzle with gravity, which was missing in the Standard Model. But, alas, even to this discovery the scientific community did not react in any way. String theory remained on the brink of survival. But that didn't stop Schwartz. Only one scientist wanted to join his search, ready to risk his career for the sake of mysterious strings - Michael Green.

Subatomic nesting dolls

Despite everything, in the early 1980s, string theory still had insoluble contradictions, called anomalies in science. Schwartz and Green set about eliminating them. And their efforts were not in vain: scientists were able to eliminate some of the contradictions in the theory. Imagine the amazement of these two, already accustomed to the fact that their theory was ignored, when the reaction of the scientific community exploded scientific world. In less than a year, the number of string theorists has jumped to hundreds of people. It was then that string theory was awarded the title of Theory of Everything. The new theory seemed capable of describing all the components of the universe. And these are the components.

Each atom, as we know, consists of even smaller particles - electrons, which swirl around a nucleus consisting of protons and neutrons. Protons and neutrons, in turn, consist of even smaller particles - quarks. But string theory says it doesn't end with quarks. Quarks are made of tiny, wriggling strands of energy that resemble strings. Each of these strings is unimaginably small.

So small that if 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...

Fifth Dimension

Although many scientists call string theory a triumph of mathematics, some problems still remain with it - most notably, the lack of any possibility of testing it experimentally in the near future. Not a single instrument in the world, neither existing nor capable of appearing in the future, is capable of “seeing” the strings. Therefore, some scientists, by the way, even ask the question: is string theory a theory of physics or philosophy?.. True, seeing strings “with your own eyes” is not at all necessary. Proving string theory requires, rather, something else—what sounds like science fiction—confirmation of the existence of extra dimensions of space.

What is it about? We are all accustomed to three dimensions of space and one – time. But string theory predicts the presence of other—extra—dimensions. But let's start in order.

In fact, the idea of the existence of other dimensions arose almost a hundred years ago. It came to the mind of the then unknown German mathematician Theodor Kaluza in 1919. He suggested the possibility of another dimension in our Universe that we do not see. Albert Einstein learned about this idea, and at first he really liked it. Later, however, he doubted its correctness, and delayed the publication of Kaluza for two whole years. Ultimately, however, the article was published, and the additional dimension became a kind of hobby for the genius of physics.

As you know, Einstein showed that gravity is nothing more than a deformation of space-time dimensions. Kaluza suggested that electromagnetism could also be ripples. Why don't we see it? Kaluza found the answer to this question - the ripples of electromagnetism can exist in an additional, hidden dimension. But where is it?

The answer to this question was given by Swedish physicist Oskar Klein, who suggested that Kaluza's fifth dimension is folded billions of times stronger than the size of a single atom, which is why we cannot see it. The idea of this tiny dimension that is all around us is at the heart of string theory.

One of the proposed forms of additional twisted dimensions. Inside each of these forms, a string vibrates and moves - the main component of the Universe. Each form is six-dimensional - according to the number of six additional dimensions /

Ten dimensions

But in fact, the equations of string theory require not even one, but six additional dimensions (in total, with the four we know, there are exactly 10 of them). They all have a very twisted and curved complex shape. And everything is unimaginably small.

How can these tiny measurements influence our Big world? According to string theory, it's decisive: for it, shape determines everything. When you press different keys on a saxophone, you get different sounds. This happens because when you press a particular key or combination of keys, you change the shape of the space in the musical instrument where the air circulates. Thanks to this, different sounds are born.

String theory suggests that additional curved and twisted dimensions of space manifest themselves in a similar way. The shapes of these extra dimensions are complex and varied, and each causes the string located within such dimensions to vibrate differently precisely because of their shapes. After all, if we assume, for example, that one string vibrates inside a jug, and the other inside a curved post horn, these will be completely different vibrations. However, if you believe string theory, in reality the forms of additional dimensions look much more complex than a jug.

How the world works

Science today knows a set of numbers that are the fundamental constants of the Universe. They are the ones who determine the properties and characteristics of everything around us. Among such constants are, for example, the charge of an electron, the gravitational constant, the speed of light in a vacuum... And if we change these numbers even by an insignificant number of times, the consequences will be catastrophic. Suppose we increased the strength of the electromagnetic interaction. What happened? We may suddenly find that the ions begin to repel each other more strongly, and nuclear fusion, which makes stars shine and emit heat, suddenly fails. All the stars will go out.

But what does string theory with its extra dimensions have to do with it? The fact is that, according to it, it is the additional dimensions that determine the exact value of the fundamental constants. Some forms of measurement cause one string to vibrate in a certain way, and produce what we see as a photon. In other forms, the strings vibrate differently and produce an electron. Truly, God is in the “little things” - it is these tiny forms that determine all the fundamental constants of this world.

Superstring theory

In the mid-1980s, string theory took on a grand and orderly appearance, but inside the monument there was confusion. In just a few years, as many as five versions of string theory have emerged. And although each of them is built on strings and extra dimensions (all five versions are combined into the general theory of superstrings - NS), these versions diverged significantly in details.

So, in some versions the strings had open ends, in others they resembled rings. And in some versions, the theory even required not 10, but as many as 26 dimensions. The paradox is that all five versions today can be called equally true. But which one really describes our Universe? This is another mystery of string theory. That is why many physicists again gave up on the “crazy” theory.

But the most the 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 maximum - even in a hundred years.