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Dark matter and dark energy in the universe. Dark matter: from initial conditions to the formation of the structure of the Universe

It is known that dark matter interacts with “luminous” (baryonic) matter, at least in a gravitational manner, and represents a medium with an average cosmological density several times higher than the density of baryons. The latter are captured in gravitational holes of dark matter concentrations. Therefore, although dark matter particles do not interact with light, light is emitted from where the dark matter is. This remarkable property of gravitational instability has made it possible to study the amount, state and distribution of dark matter using observational data from radio to X-rays.

Direct study of the distribution of dark matter in galaxy clusters became possible after highly detailed images were obtained in the 1990s. In this case, images of more distant galaxies projected onto the cluster turn out to be distorted or even split due to the effect of gravitational lensing. Based on the nature of these distortions, it becomes possible to reconstruct the distribution and magnitude of mass within the cluster, regardless of observations of the galaxies in the cluster itself. Thus, the presence of hidden mass and dark matter in galaxy clusters is confirmed by a direct method.

A study published in 2012 of the motions of more than 400 stars located at distances of up to 13,000 light-years from the Sun found no evidence of dark matter in the large volume of space around the Sun. According to theoretical predictions, the average amount of dark matter in the vicinity of the Sun should have been approximately 0.5 kg in the volume of the globe. However, measurements gave a value of 0.00±0.06 kg of dark matter in this volume. This means that attempts to detect dark matter on Earth, for example through rare interactions of dark matter particles with “ordinary” matter, are unlikely to be successful.

Dark matter candidates

Baryonic dark matter

The most natural assumption seems to be that dark matter consists of ordinary, baryonic matter, which for some reason weakly interacts electromagnetically and is therefore undetectable when studying, for example, emission and absorption lines. Included dark matter may include many already discovered cosmic objects, such as: dark galactic halos, brown dwarfs and massive planets, compact objects in the final stages of evolution: white dwarfs, neutron stars, black holes. In addition, hypothetical objects such as quark stars, Q stars and preon stars may also be part of baryonic dark matter.

The problems with this approach are manifested in Big Bang cosmology: if all dark matter is represented by baryons, then the ratio of concentrations of light elements after primary nucleosynthesis, observed in the oldest astronomical objects, should be different, sharply different from what is observed. In addition, experiments to search for gravitational lensing of the light of stars in our Galaxy show that a sufficient concentration of large gravitating objects such as planets or black holes is not observed to explain the mass of the halo of our Galaxy, and small objects of sufficient concentration should absorb star light too strongly.

Nonbaryonic dark matter

Theoretical models provide a large selection of possible candidates for the role of nonbaryonic invisible matter. Let's list some of them.

Light neutrinos

Unlike other candidates, neutrinos have a clear advantage: they are known to exist. Since the number of neutrinos in the Universe is comparable to the number of photons, then, even having a small mass, neutrinos may well determine the dynamics of the Universe. To achieve , where is the so-called critical density, neutrino masses of the order of eV are required, where denotes the number of types of light neutrinos. Experiments carried out to date provide estimates of neutrino masses on the order of eV. Thus, light neutrinos are practically excluded as a candidate for the dominant fraction of dark matter.

Heavy neutrinos

From the data on the Z-boson decay width it follows that the number of generations of weakly interacting particles (including neutrinos) is equal to 3. Thus, heavy neutrinos (at least with a mass less than 45 GeV) are necessarily the so-called. “sterile”, that is, particles that do not interact weakly. Theoretical models predict mass in very wide range values (depending on the nature of this neutrino). From the phenomenology for follows a mass range of approximately eV, sterile neutrinos may well constitute a significant part of dark matter.

Supersymmetric particles

In supersymmetric (SUSY) theories, there is at least one stable particle that is a new candidate for dark matter. It is assumed that this particle (LSP) does not participate in electromagnetic and strong interactions. LSP particles can be photino, gravitino, higgsino (superpartners of the photon, graviton and Higgs boson, respectively), as well as sneutrino, wine, and zino. In most theories, an LSP particle is a combination of the above SUSY particles with a mass of the order of 10 GeV.

Cosmions

Cosmions were introduced into physics to solve the problem of solar neutrinos, which consists in a significant difference in the flux of neutrinos detected on Earth from the value predicted by the standard model of the Sun. However, this problem has been resolved within the framework of the theory of neutrino oscillations and the Mikheev-Smirnov-Wolfenstein effect, so cosmions are apparently excluded from candidates for the role of dark matter.

Topological defects of space-time

According to modern cosmological concepts, the vacuum energy is determined by a certain locally homogeneous and isotropic scalar field. This field is necessary to describe the so-called vacuum phase transitions during the expansion of the Universe, during which a consistent violation of symmetry occurred, leading to the separation of fundamental interactions. A phase transition is a jump in the energy of a vacuum field tending to its ground state (the state with minimum energy at a given temperature). Various areas spaces could experience such a transition independently, as a result of which areas with a certain “arrangement” of the scalar field were formed, which, expanding, could come into contact with each other. At the meeting points of regions with different orientations, stable topological defects of various configurations could form: point-like particles (in particular, magnetic monopoles), linear extended objects (cosmic strings), two-dimensional membranes (domain walls), three-dimensional defects (textures). All these objects, as a rule, have colossal mass and could make a dominant contribution to dark matter. At the moment (2012), such objects have not been discovered in the Universe.

Classification of dark matter

Depending on the speeds of the particles that presumably make up dark matter, it can be divided into several classes.

Hot dark matter

Composed of particles moving at close to the speed of light—probably neutrinos. These particles have a very small mass, but still not zero, and given the huge number of neutrinos in the Universe (300 particles per 1 cm³), this gives a huge mass. In some models, neutrinos account for 10% of dark matter.

Due to its enormous speed, this matter cannot form stable structures, but it can influence ordinary matter and other types of dark matter.

Warm dark matter

Matter moving at relativistic speeds, but lower than hot dark matter, is called “warm.” The speeds of its particles can range from 0.1c to 0.95c. Some evidence, particularly temperature variations in background microwave radiation, suggests that this form of matter may exist.

There are no candidates yet for the role of components of warm dark matter, but it is possible that sterile neutrinos, which should move slower than the usual three flavors of neutrinos, could be one of them.

Cold dark matter

Dark matter that moves at classical speeds is called “cold.” This type of matter is of the greatest interest, since, unlike warm and hot dark matter, cold matter can form stable formations, and even entire dark galaxies.

So far, particles suitable for the role of components of cold dark matter have not been discovered. Candidates for the role of cold dark matter are weakly interacting massive particles - WIMPs, such as axions and supersymmetric fermion partners of light bosons - photinos, gravitinos and others.

Mixed dark matter

In popular culture

In the Mass Effect series, dark matter and dark energy in the form of so-called "Element Zero" are necessary for movement at superluminal speeds. Some people, biotics, using dark energy, can control mass effect fields.
In the animated series Futurama, dark matter is used as fuel for the Planet Express spacecraft. Matter is born in the form of feces of the alien race “Zubastilons” and is extremely dense in density.

Notes

Literature

Modern Cosmology website, which also contains a selection of materials on dark matter.
G.W.Klapdor-Kleingrothaus, A.Staudt Non-accelerator physics elementary particles. M.: Nauka, Fizmatlit, 1997.

Links

S. M. Bilenky, Neutrino masses, mixing and oscillations, UFN 173 1171-1186 (2003)
V. N. Lukash, E. V. Mikheeva, Dark matter: from initial conditions to the formation of the structure of the Universe, UFN 177 1023-1028 (2007)
DI. Kazakov "Dark Matter", from a series of lectures in the PostScience project (video)
Anatoly Cherepashchuk. “New forms of matter in the Universe, part 1” - Dark mass and dark energy, from the lecture series “ACADEMIA” (video)

Wikimedia Foundation. 2010.

See what “Dark Matter” is in other dictionaries:

DARK MATTER- (TM) unusual matter of our Universe, consisting not of (see), i.e. not of protons, neutrons, mesons, etc., and discovered by the strongest gravitational effect on cosmic objects of ordinary baryonic nature (stars, galaxies, black … …

Dark Matter The Outer Limits: Dark Matters Genre science fiction ... Wikipedia

This term has other meanings, see Dark Star. A dark star is a theoretically predicted type of star that could have existed early in the formation of the Universe, even before... ... Wikipedia

MATTER - objective reality, existing outside and independently of human consciousness and displayed by it (for example, living and non-living M.). The unity of the world is in its materiality. In physics M. all types of existence (see), which can be in different... ... Big Polytechnic Encyclopedia

A theoretical construct in physics called the Standard Model describes the interactions of all elementary particles known to science. But this is only 5% of the matter existing in the Universe, the remaining 95% is of a completely unknown nature. What is this hypothetical dark matter and how are scientists trying to detect it? Hayk Hakobyan, a MIPT student and employee of the Department of Physics and Astrophysics, talks about this as part of a special project.

The Standard Model of elementary particles, finally confirmed after the discovery of the Higgs boson, describes fundamental interactions(electroweak and strong) ordinary particles known to us: leptons, quarks and interaction carriers (bosons and gluons). However, it turns out that all this huge complex theory describes only about 5–6% of all matter, while the rest does not fit into this model. Observations of the earliest moments of our Universe show us that approximately 95% of the matter that surrounds us is of a completely unknown nature. In other words, we indirectly see the presence of this hidden matter due to its gravitational influence, but we have not yet been able to capture it directly. This hidden mass phenomenon is codenamed “dark matter.”

Modern science, especially cosmology, works according to the deductive method of Sherlock Holmes

Now the main candidate from the WISP group is the axion, which arises in the theory of the strong interaction and has a very small mass. Such a particle is capable of transforming into a photon-photon pair in high magnetic fields, which gives hints on how one might try to detect it. The ADMX experiment uses large chambers that create a magnetic field of 80,000 gauss (that's 100,000 times more magnetic field Earth). In theory, such a field should stimulate the decay of an axion into a photon-photon pair, which detectors should catch. Despite numerous attempts, it has not yet been possible to detect WIMPs, axions or sterile neutrinos.

Thus, we have traveled through a huge number of different hypotheses seeking to explain the strange presence of the hidden mass, and, having rejected all the impossibilities with the help of observations, we have arrived at several possible hypotheses with which we can already work.

A negative result in science is also a result, since it gives restrictions on various parameters of particles, for example, it eliminates the range of possible masses. From year to year, more and more new observations and experiments in accelerators provide new, more stringent restrictions on the mass and other parameters of dark matter particles. Thus, by throwing out all the impossible options and narrowing the circle of searches, day by day we are becoming closer to understanding what 95% of the matter in our Universe consists of.

The term “dark matter” (or hidden mass) is used in various fields of science: cosmology, astronomy, physics. It's about about a hypothetical object - a form of space and time content that directly interacts with electromagnetic radiation and does not allow it to pass through itself.

Dark matter – what is it?

Since time immemorial, people have been concerned about the origin of the Universe and the processes that shape it. In the age of technology were made important discoveries, and the theoretical basis has been significantly expanded. In 1922 British physicist James Jeans and Dutch astronomer Jacobus Kapteyn discovered that most of the galactic matter is invisible. Then the term dark matter was first used - this is a substance that cannot be seen by any of the methods known to mankind. The presence of a mysterious substance is revealed indirect signs– gravitational field, gravity.

Dark matter in astronomy and cosmology

By assuming that all objects and parts in the Universe are attracted to each other, astronomers were able to find the mass visible space. But a discrepancy was discovered in the actual and predicted weights. And scientists have found that there is an invisible mass, which accounts for up to 95% of all unknown essence in the Universe. Dark matter in space has the following characteristics:

subject to gravity;
influences other space objects,
weakly interacts with the real world.

Dark matter - philosophy

Dark matter occupies a special place in philosophy. This science deals with the study of the world order, the foundations of existence, the system of visible and invisible worlds. A certain substance determined by space, time, and surrounding factors was taken as the fundamental principle. The mysterious dark matter of space, discovered much later, changed the understanding of the world, its structure and evolution. In a philosophical sense, an unknown substance, like a clot of energy of space and time, is present in each of us, therefore people are mortal, because they consist of time, which has an end.

Why is dark matter needed?

Only a small part of space objects (planets, stars, etc.) is visible matter. According to the standards of various scientists dark energy and dark matter occupy almost all the space in Space. The first accounts for 21-24%, while energy takes up 72%. Every substance is unclear physical nature has its own functions:

Black energy, which neither absorbs nor emits light, pushes objects away, causing the universe to expand.
Galaxies are built on the basis of hidden mass, its force attracts objects into outer space, keeps them in place. That is, it slows down the expansion of the Universe.

What is dark matter made of?

Dark matter in solar system– this is something that cannot be touched, examined and studied thoroughly. Therefore, several hypotheses are put forward regarding its nature and composition:

Particles unknown to science that participate in gravity are a component of this substance. It is impossible to detect them with a telescope.
The phenomenon is a cluster of small black holes (no larger than the Moon).

It is possible to distinguish two types of hidden mass depending on the speed of its constituent particles and the density of their accumulation.

Hot. It is not enough to form galaxies.
Cold. Consists of slow, massive clots. These components can be axions and bosons known to science.

Does dark matter exist?

All attempts to measure objects of an unexplored physical nature have not brought success. In 2012, the movement of 400 stars around the Sun was studied, but the presence of hidden matter in large volumes was not proven. Even if dark matter does not exist in reality, it exists in theory. With its help, the location of objects in the Universe in their places is explained. Some scientists are finding evidence of hidden cosmic mass. Its presence in the Universe explains the fact that galaxy clusters do not fly apart into different sides and stick together.

Dark matter - interesting facts

The nature of the hidden mass remains a mystery, but it continues to interest scientific minds around the world. Experiments are regularly carried out with the help of which they try to study the substance itself and its side effects. And the facts about her continue to multiply. For example:

The acclaimed Large Hadron Collider, the world's most powerful particle accelerator, is firing on all cylinders to reveal the existence of invisible matter in space. The world community is awaiting the results with interest.
Japanese scientists create the world's first map of hidden mass in space. It is planned to be completed by 2019.
Recently, theoretical physicist Lisa Randall suggested that dark matter and dinosaurs are connected. This substance sent a comet to Earth, which destroyed life on the planet.

The components of our galaxy and the entire Universe are light and dark matter, that is, visible and invisible objects. If with the study of the first modern technology copes, methods are constantly being improved, then exploring hidden substances is very problematic. Humanity has not yet come to understand this phenomenon. Invisible, intangible, but omnipresent dark matter has been and remains one of the main mysteries of the Universe.

In the articles of the series we examined the structure of the visible Universe. We talked about its structure and the particles that form this structure. About nucleons playing main role, since it is from them that all visible matter consists. About photons, electrons, neutrinos, and also about the supporting actors involved in the universal play that unfolds 14 billion years after the Big Bang. It would seem that there is nothing more to talk about. But that's not true. The fact is that the substance we see is only a small part of what our world consists of. Everything else is something we know almost nothing about. This mysterious “something” is called dark matter.

If the shadows of objects did not depend on the size of these latter,
and if they had their own arbitrary growth, then perhaps
soon there would not be a single bright place left on the entire globe.

Kozma Prutkov

What will happen to our world?

After Edward Hubble's discovery of redshifts in the spectra of distant galaxies in 1929, it became clear that the Universe was expanding. One of the questions that arose in this regard was the following: how long will the expansion last and how will it end? The forces of gravitational attraction acting between individual parts of the Universe tend to slow down the retreat of these parts. What the braking will lead to depends on the total mass of the Universe. If it is large enough, gravitational forces will gradually stop the expansion and it will be replaced by compression. As a result, the Universe will eventually “collapse” again to the point from which it once began to expand. If the mass is less than a certain critical mass, then the expansion will continue forever. It is usually customary to talk not about mass, but about density, which is related to mass by a simple ratio, known from the school course: density is mass divided by volume.

The calculated value of the critical average density of the Universe is approximately 10 -29 grams per cubic centimeter, which corresponds to an average of five nucleons per cubic meter. It should be emphasized that we are talking about average density. The characteristic concentration of nucleons in water, earth and in you and me is about 10 30 per cubic meter. However, in the void that separates clusters of galaxies and occupies the lion's share of the volume of the Universe, the density is tens of orders of magnitude lower. The nucleon concentration averaged over the entire volume of the Universe was measured tens and hundreds of times, carefully calculating different methods number of stars and gas and dust clouds. The results of such measurements differ somewhat, but the qualitative conclusion is unchanged: the density of the Universe barely reaches a few percent of the critical value.

Therefore, until the 70s of the 20th century, the generally accepted forecast was the eternal expansion of our world, which should inevitably lead to the so-called heat death. Heat death is a state of a system when the substance in it is distributed evenly and its different parts have the same temperature. As a consequence, neither the transfer of energy from one part of the system to another, nor the redistribution of matter is possible. In such a system nothing happens and can never happen again. A clear analogy is water spilled on any surface. If the surface is uneven and there are even slight differences in elevation, water moves along it from higher to lower places and eventually collects in the lowlands, forming puddles. The movement stops. The only consolation left was that heat death would occur in tens and hundreds of billions of years. Consequently, you don’t have to think about this gloomy prospect for a very, very long time.

However, it gradually became clear that the true mass of the Universe is much greater than the visible mass contained in stars and gas and dust clouds and, most likely, is close to critical. Or perhaps exactly equal to it.

Evidence for dark matter

The first indication that something was wrong with the calculation of the mass of the Universe appeared in the mid-30s of the 20th century. Swiss astronomer Fritz Zwicky measured the speeds at which the galaxies of the Coma cluster (which is one of the largest clusters known to us, it includes thousands of galaxies) move around general center. The result was discouraging: the velocities of the galaxies turned out to be much greater than could be expected based on the observed total mass of the cluster. This meant that the true mass of the Coma cluster was much greater than the apparent mass. But the main amount of matter present in this region of the Universe remains, for some reason, invisible and inaccessible to direct observations, manifesting itself only gravitationally, that is, only as mass.

The presence of hidden mass in galaxy clusters is also evidenced by experiments on the so-called gravitational lensing. The explanation for this phenomenon follows from the theory of relativity. In accordance with it, any mass deforms space and, like a lens, distorts the rectilinear path of light rays. The distortion that galaxy clusters cause is so great that it is easy to notice. In particular, from the distortion of the image of the galaxy that lies behind the cluster, it is possible to calculate the distribution of matter in the lens cluster and thereby measure its total mass. And it turns out that it is always many times greater than the contribution of the visible matter of the cluster.

40 years after Zwicky’s work, in the 70s, American astronomer Vera Rubin studied the speed of rotation around the galactic center of matter located on the periphery of galaxies. In accordance with Kepler's laws (and they directly follow from the law of universal gravitation), when moving from the center of a galaxy to its periphery, the rotation speed of galactic objects should decrease in inverse proportion to square root from the distance to the center. Measurements have shown that for many galaxies this speed remains almost constant at a very significant distance from the center. These results can be interpreted only in one way: the density of matter in such galaxies does not decrease when moving from the center, but remains almost unchanged. Since the density of visible matter (contained in stars and interstellar gas) rapidly falls towards the periphery of the galaxy, the missing density must be supplied by something that for some reason we cannot see. To quantitatively explain the observed dependences of the rotation rate on the distance to the center of galaxies, it is required that this invisible “something” be approximately 10 times larger than ordinary visible matter. This “something” was called “dark matter” (in English “ dark matter") and still remains the most intriguing mystery in astrophysics.

Another important piece of evidence for the presence of dark matter in our world comes from calculations simulating the process of galaxy formation that began about 300,000 years after the Big Bang. These calculations show that the forces of gravitational attraction that acted between the flying fragments of the matter generated during the explosion could not compensate for the kinetic energy of the expansion. The matter simply should not have gathered into the galaxies that we nevertheless observe in the modern era. This problem is called the galactic paradox, and for a long time it was considered a serious argument against the Big Bang theory. However, if we assume that particles of ordinary matter in the early Universe were mixed with particles of invisible dark matter, then everything falls into place in the calculations and the ends begin to meet - the formation of galaxies from stars, and then clusters of galaxies, becomes possible. At the same time, as calculations show, at first a huge number of dark matter particles accumulated in galaxies and only then, due to gravitational forces, elements of ordinary matter were collected on them, the total mass of which was only a few percent of the total mass of the Universe. It turns out that the familiar and seemingly studied in detail visible world, which we quite recently considered almost understood, is only small addition to something that the Universe is actually made of. Planets, stars, galaxies and you and me are just a screen for a huge “something” about which we have not the slightest idea.

Photo fact

The galaxy cluster (at the lower left of the circled area) creates a gravitational lens. It distorts the shape of objects located behind the lens - stretching their images in one direction. Based on the magnitude and direction of the stretch, an international group of astronomers from the Southern European Observatory, led by scientists from the Paris Institute of Astrophysics, constructed a mass distribution, which is shown in the bottom image. As you can see, the cluster contains much more mass than can be seen through a telescope.

Hunting dark, massive objects is a slow process, and the results don't look the most impressive in photographs. In 1995, the Hubble Telescope noticed that one of the stars in the Large Magellanic Cloud flashed brighter. This glow lasted for more than three months, but then the star returned to its natural state. And six years later, a barely luminous object appeared next to the star. It was a cold dwarf that, passing at a distance of 600 light years from the star, created a gravitational lens that amplified the light. Calculations have shown that the mass of this dwarf is only 5-10% of the mass of the Sun.

Finally, the general theory of relativity unambiguously connects the rate of expansion of the Universe with the average density of the matter contained in it. Assuming that the average curvature of space is zero, that is, the geometry of Euclid and not Lobachevsky operates in it (which has been reliably verified, for example, in experiments with cosmic microwave background radiation), this density should be equal to 10 -29 grams per cubic centimeter. The density of visible matter is approximately 20 times less. The missing 95% of the mass of the Universe is dark matter. Note that the density value measured from the expansion rate of the Universe is equal to the critical value. Two values, independently calculated completely in different ways, coincided! If in fact the density of the Universe is exactly equal to the critical density, this cannot be a coincidence, but is a consequence of some fundamental property of our world, which has yet to be understood and comprehended.

What is this?

What do we know today about dark matter, which makes up 95% of the mass of the Universe? Almost nothing. But we still know something. First of all, there is no doubt that dark matter exists - this is irrefutably evidenced by the facts given above. We also know for certain that dark matter exists in several forms. After the beginning of the 21st century, as a result of many years of observations in experiments SuperKamiokande(Japan) and SNO (Canada) it was established that neutrinos have mass, it became clear that from 0.3% to 3% of the 95% of the hidden mass lies in neutrinos that have long been familiar to us - even if their mass is extremely small, but their quantity is in The universe has about a billion times the number of nucleons: each cubic centimeter contains an average of 300 neutrinos. The remaining 92-95% consists of two parts - dark matter and dark energy. A small fraction of dark matter consists of ordinary baryonic matter, built from nucleons; the remainder is apparently accounted for by some unknown massive weakly interacting particles (the so-called cold dark matter). Energy balance in modern universe is presented in the table, and the story about its last three columns is below.

Baryonic dark matter

A small (4-5%) part of dark matter is ordinary matter that emits little or no radiation of its own and is therefore invisible. The existence of several classes of such objects can be considered experimentally confirmed. The most complex experiments, based on the same gravitational lensing, led to the discovery of so-called massive compact halo objects, that is, located on the periphery of galactic disks. This required monitoring millions of distant galaxies over several years. When a dark, massive body passes between an observer and a distant galaxy, its brightness is short time decreases (or increases because dark body acts as a gravitational lens). As a result of painstaking searches, such events were identified. The nature of massive compact halo objects is not completely clear. Most likely, these are either cooled stars (brown dwarfs) or planet-like objects that are not associated with stars and travel around the galaxy on their own. Another representative of baryonic dark matter is hot gas recently discovered in galaxy clusters using X-ray astronomy methods, which does not glow in the visible range.

Nonbaryonic dark matter

The main candidates for nonbaryonic dark matter are the so-called WIMPs (short for English Weakly Interactive Massive Particles- weakly interacting massive particles). The peculiarity of WIMPs is that they show almost no interaction with ordinary matter. This is why they are the real invisible dark matter, and why they are extremely difficult to detect. The mass of WIMP must be at least tens of times greater than the mass of a proton. The search for WIMPs has been carried out in many experiments over the past 20-30 years, but despite all efforts, they have not yet been detected.

One idea is that if such particles exist, then the Earth, as it orbits the Sun with the Sun around the galactic center, should be flying through a rain of WIMPs. Despite the fact that WIMP is an extremely weakly interacting particle, it still has a very small probability of interacting with an ordinary atom. At the same time, in special installations - very complex and expensive - a signal can be recorded. The number of such signals should change throughout the year because, as the Earth moves in orbit around the Sun, it changes its speed and direction relative to the wind, which consists of WIMPs. The DAMA experimental group, working at Italy's Gran Sasso underground laboratory, reports observed year-to-year variations in signal count rates. However, other groups have not yet confirmed these results, and the question essentially remains open.

Another method of searching for WIMPs is based on the assumption that during billions of years of their existence, various astronomical objects (Earth, Sun, the center of our Galaxy) should capture WIMPs, which accumulate in the center of these objects, and, annihilating each other, give rise to a neutrino stream . Attempts to detect excess neutrino flux from the center of the Earth towards the Sun and the center of the Galaxy were made on underground and underwater neutrino detectors MACRO, LVD (Gran Sasso Laboratory), NT-200 (Lake Baikal, Russia), SuperKamiokande, AMANDA (Scott Station -Amundsen, South Pole), but have not yet led to a positive result.

Experiments to search for WIMPs are also actively carried out at particle accelerators. In accordance with Einstein's famous equation E=mс 2, energy is equivalent to mass. Therefore, by accelerating a particle (for example, a proton) to a very high energy and colliding it with another particle, one can expect the creation of pairs of other particles and antiparticles (including WIMPs), the total mass of which is equal to the total energy of the colliding particles. But accelerator experiments have not yet led to a positive result.

Dark energy

At the beginning of the last century, Albert Einstein, wanting to provide a cosmological model in general theory relativity, independence of time, introduced the so-called cosmological constant into the equations of the theory, which he designated by the Greek letter “lambda” - Λ. This Λ was a purely formal constant, in which Einstein himself did not see any physical meaning. After the expansion of the Universe was discovered, the need for it disappeared. Einstein very much regretted his haste and called the cosmological constant Λ his biggest scientific mistake. However, decades later it turned out that the Hubble constant, which determines the rate of expansion of the Universe, changes with time, and its dependence on time can be explained by selecting the value of that very “erroneous” Einstein constant Λ, which contributes to the hidden density of the Universe. This part of the hidden mass came to be called “dark energy”.

Even less can be said about dark energy than about dark matter. First, it is evenly distributed throughout the Universe, unlike ordinary matter and other forms of dark matter. There is as much of it in galaxies and galaxy clusters as outside of them. Secondly, it has several very strange properties, which can only be understood by analyzing the equations of the theory of relativity and interpreting their solutions. For example, dark energy experiences antigravity: due to its presence, the rate of expansion of the Universe increases. Dark energy seems to push itself away, accelerating the scattering of ordinary matter collected in galaxies. Dark energy also has negative pressure, due to which a force arises in the substance that prevents it from stretching.

The main candidate for dark energy is vacuum. The vacuum energy density does not change with the expansion of the Universe, which corresponds to negative pressure. Another candidate is a hypothetical super-weak field, called quintessence. Hopes for clarifying the nature of dark energy are associated primarily with new astronomical observations. Progress in this direction will undoubtedly bring radically new knowledge to humanity, since in any case, dark energy must be a completely unusual substance, completely different from what physics has dealt with so far.

So, 95% of our world consists of something about which we know almost nothing. One can have different attitudes towards such a fact that is beyond any doubt. It can cause anxiety, which always accompanies a meeting with something unknown. Or disappointment because such a long and difficult path to building physical theory, describing the properties of our world, led to the statement: most of the Universe is hidden from us and unknown to us.

But most physicists are now feeling encouraged. Experience shows that all the riddles that nature posed to humanity were sooner or later resolved. Undoubtedly, the mystery of dark matter will also be resolved. And this will certainly bring completely new knowledge and concepts that we have no idea about yet. And perhaps we will meet new mysteries, which, in turn, will also be solved. But this will be a completely different story, which readers of “Chemistry and Life” will not be able to read until a few years later. Or maybe in a few decades.

What's happened dark matter and dark energy The Universe: structure of space with photos, volume in percentage, influence on objects, research, expansion of the Universe.

About 80% of the space is represented by material that is hidden from direct observation. It's about dark matter– a substance that does not produce energy or light. How did the researchers realize that it was dominant?

In the 1950s, scientists began to actively study other galaxies. During the analyzes they noticed that the Universe is filled a large number material than can be captured on “ visible eye" Proponents of dark matter emerged every day. Although there was no direct evidence of its existence, theories grew, as did workarounds for observation.

The material we see is called baryonic matter. It is represented by protons, neutrons and electrons. It is believed that dark matter is capable of combining baryonic and non-baryonic matter. For the Universe to remain in its usual integrity, dark matter must be present in an amount of 80%.

The elusive substance can be incredibly difficult to find if it contains baryonic matter. Among the candidates are brown and white dwarfs, as well as neutron stars. Supermassive black holes can also add to the difference. But they must have contributed more influence than what scientists saw. There are also those who think that dark matter must consist of something more unusual and rare.

Combined image Hubble telescope, showing a ghostly ring of dark matter in the galaxy cluster Cl 0024+17

Most scientific world believes that the unknown substance is represented mainly by non-baryonic matter. The most popular candidate is WIMPS (weakly interacting massive particles), whose mass is 10-100 times greater than that of a proton. But their interaction with ordinary matter is too weak, making it more difficult to find.

Neutrinos, massive hypothetical particles that are larger in mass than neutrinos, but are characterized by their slowness, are now being examined very carefully. They haven't been found yet. As possible options the smaller neutral axiom and intact photons are also taken into account.

Another possibility is that knowledge about gravity is outdated and needs to be updated.

Invisible dark matter and dark energy

But if we don’t see something, how can we prove that it exists? And why did we decide that dark matter and dark energy are something real?

The mass of large objects is calculated from their spatial movement. In the 1950s, researchers looking at spiral galaxies assumed that material close to the center would move much faster than material farther away. But it turned out that the stars were moving at the same speed, which meant there was much more mass than previously thought. The gas studied in elliptical types showed the same results. The same conclusion suggested itself: if you focus only on visible mass, then the galaxy clusters would have collapsed long ago.

Albert Einstein was able to prove that large universal objects are capable of bending and distorting light rays. This allowed them to be used as a natural magnifying lens. By studying this process, scientists were able to create a map of dark matter.

It turns out that most of our world is represented by a still elusive substance. You will learn more interesting things about dark matter if you watch the video.

Dark matter

Physicist Dmitry Kazakov about the overall energy balance of the Universe, the theory of hidden mass and dark matter particles:

If we talk about matter, then dark matter is certainly the leader in percentage. But overall it takes up only a quarter of everything. The universe abounds dark energy.

Since the Big Bang, space has begun a process of expansion that continues today. The researchers believed that eventually the initial energy would run out and it would slow down. But distant supernovae demonstrate that space does not stop, but picks up speed. All this is only possible if the amount of energy is so huge that it overcomes the gravitational influence.

Dark matter and dark energy: a mystery explained

We know that the Universe is mostly dark energy. This is a mysterious force that causes space to increase the rate of expansion of the Universe. Another mysterious component is dark matter, which maintains contact with objects only through gravity.

Scientists can't see dark matter through direct observation, but the effects can be studied. They manage to capture light that is bent by the gravitational force of invisible objects (gravitational lensing). They also notice moments when the star rotates around the galaxy much faster than it should.

All this is explained by the presence huge amount an elusive substance that affects mass and speed. In fact, this substance is shrouded in mystery. It turns out that researchers can rather say not what is in front of them, but what “it” is not.

This collage shows images of six different galaxy clusters taken using space telescope NASA Hubble. The clusters were discovered during attempts to study the behavior of dark matter in galaxy clusters during their collision

Dark matter... dark. It does not produce light and is not observable in direct view. Therefore, we exclude stars and planets.

It does not act as a cloud of ordinary matter (such particles are called baryons). If baryons were present in dark matter, it would show up in direct observation.

We also exclude black holes, because they act as gravitational lenses that emit light. Scientists don't observe sufficient quantity lensing events to calculate the volume of dark matter that must be present.

Although the Universe is a huge place, it all began with the smallest structures. It is believed that dark matter began to condense to create "building blocks" with normal matter, producing the first galaxies and clusters.

To find dark matter, scientists use various methods:

Large Hadron Collider.
instruments like WNAP and the Planck space observatory.
direct view experiments: ArDM, CDMS, Zeplin, XENON, WARP and ArDM.
indirect detection: gamma ray detectors (Fermi), neutrino telescopes (IceCube), antimatter detectors (PAMELA), X-ray and radio sensors.

Methods for searching for dark matter

Physicist Anton Baushev on weak interactions between particles, radioactivity and the search for traces of annihilation:

Delving deeper into the mystery of dark matter and dark energy

Scientists have never been able to literally see dark matter, because it does not contact baryonic matter, which means it remains elusive to light and other varieties electromagnetic radiation. But researchers are confident in its presence, as they observe the impact on galaxies and clusters.

Standard physics says that stars located at the edges of a spiral galaxy should slow down. But it turns out that stars appear whose speed does not obey the principle of location in relation to the center. This can only be explained by the fact that the stars feel the influence of invisible dark matter in the halo around the galaxy.

The presence of dark matter can also decipher some of the illusions observed in the depths of the universe. For example, the presence of strange rings and arcs of light in galaxies. That is, light from distant galaxies passes through the distortion and is amplified by an invisible layer of dark matter (gravitational lensing).

So far we have a few ideas about what dark matter is. Main idea- These are exotic particles that do not come into contact with ordinary matter and light, but have power in the gravitational sense. Now several groups (some using the Large Hadron Collider) are working on creating dark matter particles to study them in the laboratory.

Others think the influence can be explained by a fundamental modification of gravitational theory. Then we get several forms of gravity, which differs significantly from the usual picture and the laws established by physics.

The Expanding Universe and Dark Energy

The situation with dark energy is even more confusing and the discovery itself became unpredictable in the 1990s. Physicists have always thought that the force of gravity works to slow down and one day may stop the process of universal expansion. Two teams took on the task of measuring speed and both, to their surprise, detected acceleration. It's like you throw an apple into the air and know that it is bound to fall down, but it moves further and further away from you.

It became clear that acceleration was influenced by a certain force. Moreover, it seems that the wider the Universe, the more “power” this force gains. Scientists decided to call it dark energy.