What does the detection of gravitational waves mean for us?

I think everyone is already aware that a couple of days ago scientists announced the discovery of gravitational waves for the first time. There was a lot of news about this, on TV, on news sites and everywhere. However, no one bothered to explain accessible language, what this discovery gives us in practical terms.

In fact, everything is simple, just draw an analogy with a submarine:

Source:

Detection of submarines is the first and main task when fighting them. Like any object, a boat with its presence influences environment. In other words, the boat has its own physical fields. The more well-known physical fields of a submarine include hydroacoustic, magnetic, hydrodynamic, electric, low-frequency electromagnetic, as well as thermal and optical. Isolating the physical fields of a boat against the background of the fields of the ocean (sea) underlies the main detection methods.
Methods for detecting submarines are divided according to the type of physical fields: Acoustic, Magnetometric, Radar, Gas, Thermal, etc.

It's the same thing with space. We look at the stars through telescopes, take photographs of Mars, catch radiation and generally try to understand the heavens with everyone accessible ways. And now, after these waves have been recorded, another method of study has been added - gravitational. We will be able to view space based on these vibrations.

That is, just as a submarine passed through the sea and left behind a “trace” by which it can be identified, so too celestial bodies, can now be studied from a different angle for a more complete picture. In the future, we will be able to see how gravitational waves bend around different bodies, galaxies, planets, we will learn to better calculate the cosmic trajectories of objects (And maybe even recognize and predict the approach of meteorites in advance), we will see the behavior of waves under special conditions, and so on.

What will it give?

It's not clear yet. But over time, the equipment will become more accurate and sensitive, and a wealth of material will be collected about gravitational waves. Based on these materials, inquisitive minds will begin to find all sorts of anomalies, mysteries and patterns. These patterns and anomalies, in turn, will serve as either a refutation or confirmation of old theories. Additional mathematical formulas, interesting hypotheses (British scientists have found that pigeons find their way home using gravitational waves!) and much more. And the yellow press will definitely launch some myth, such as a “Gravitational tsunami”, which will one day come, cover our solar system and kill all living things. And Vanga will be dragged in more. In short, it will be fun :]

So what's the result?

As a result, we will have a more advanced field of science that will be able to provide a more accurate and broader picture of our world. And if you are lucky and scientists come across some amazing effect... (Like, if two gravitational waves on a full moon “crashe” into each other at a certain angle with the required speed, then a local source of antigravity occurs, oh-pa!)... then we can hope for serious scientific progress.

The official day of discovery (detection) of gravitational waves is February 11, 2016. It was then, at a press conference held in Washington, that the leaders of the LIGO collaboration announced that a team of researchers had managed to record this phenomenon for the first time in human history.

Prophecies of the great Einstein

The fact that gravitational waves exist was suggested by Albert Einstein at the beginning of the last century (1916) within the framework of his General Theory of Relativity (GTR). One can only marvel at the brilliant abilities of the famous physicist, who, with a minimum of real data, was able to draw such far-reaching conclusions. Among many other predicted physical phenomena that were confirmed in the next century (slowing down the flow of time, changing direction electromagnetic radiation in gravitational fields, etc.) until recently it was not possible to practically detect the presence of this type of wave interaction between bodies.

Is gravity an illusion?

In general, in the light of the Theory of Relativity, gravity can hardly be called a force. disturbances or curvatures of the space-time continuum. A good example A stretched piece of fabric can serve as an illustration of this postulate. Under the weight of a massive object placed on such a surface, a depression is formed. Other objects, when moving near this anomaly, will change the trajectory of their movement, as if being “attracted”. And the greater the weight of the object (the greater the diameter and depth of the curvature), the higher the “force of attraction”. As it moves across the fabric, one can observe the appearance of diverging “ripples”.

Something similar happens in outer space. Any rapidly moving massive matter is a source of fluctuations in the density of space and time. A gravitational wave with a significant amplitude is formed by bodies with extremely large masses or when moving with enormous accelerations.

physical characteristics

Fluctuations in the space-time metric manifest themselves as changes in the gravitational field. This phenomenon is otherwise called space-time ripples. The gravitational wave affects the encountered bodies and objects, compressing and stretching them. The magnitude of the deformation is very insignificant - about 10 -21 from the original size. The whole difficulty of detecting this phenomenon was that researchers needed to learn how to measure and record such changes using appropriate equipment. The power of gravitational radiation is also extremely small - for the entire solar system it is several kilowatts.

The speed of propagation of gravitational waves depends slightly on the properties of the conducting medium. The amplitude of oscillations gradually decreases with distance from the source, but never reaches zero value. The frequency ranges from several tens to hundreds of hertz. The speed of gravitational waves in the interstellar medium approaches the speed of light.

Circumstantial evidence

The first theoretical confirmation of the existence of gravitational waves was obtained by the American astronomer Joseph Taylor and his assistant Russell Hulse in 1974. Studying the vastness of the Universe using the Arecibo Observatory radio telescope (Puerto Rico), researchers discovered the pulsar PSR B1913+16, which is a binary system of neutron stars rotating around a common center of mass with a constant angular velocity(quite a rare case). Every year the circulation period, originally 3.75 hours, is reduced by 70 ms. This value is fully consistent with the conclusions from the general relativity equations, which predict an increase in the rotation speed of such systems due to the expenditure of energy on the generation of gravitational waves. Subsequently, several double pulsars and white dwarfs with similar behavior were discovered. Radio astronomers D. Taylor and R. Hulse were awarded the Nobel Prize in Physics in 1993 for discovering new possibilities for studying gravitational fields.

Escaping gravitational wave

The first announcement about the detection of gravitational waves came from University of Maryland scientist Joseph Weber (USA) in 1969. For these purposes, he used two gravitational antennas of his own design, separated by a distance of two kilometers. The resonant detector was a well-vibration-insulated solid two-meter aluminum cylinder equipped with sensitive piezoelectric sensors. The amplitude of the oscillations allegedly recorded by Weber turned out to be more than a million times higher than the expected value. Attempts by other scientists to repeat the “success” of the American physicist using similar equipment did not bring positive results. A few years later, Weber’s work in this area was recognized as untenable, but gave impetus to the development of the “gravitational boom”, which attracted many specialists to this area of ​​research. By the way, Joseph Weber himself was sure until the end of his days that he received gravitational waves.

Improving receiving equipment

In the 70s, scientist Bill Fairbank (USA) developed the design of a gravitational wave antenna, cooled using SQUIDS - ultra-sensitive magnetometers. The technologies existing at that time did not allow the inventor to see his product realized in “metal”.

The Auriga gravitational detector at the National Legnar Laboratory (Padua, Italy) is designed using this principle. The design is based on an aluminum-magnesium cylinder, 3 meters long and 0.6 m in diameter. The receiving device weighing 2.3 tons is suspended in an insulated vacuum chamber cooled almost to absolute zero. To record and detect shocks, an auxiliary kilogram resonator and a computer-based measuring complex are used. The stated sensitivity of the equipment is 10 -20.

Interferometers

The operation of interference detectors of gravitational waves is based on the same principles on which the Michelson interferometer operates. The laser beam emitted by the source is divided into two streams. After multiple reflections and travels along the arms of the device, the flows are again brought together, and based on the final one it is judged whether any disturbances (for example, a gravitational wave) affected the course of the rays. Similar equipment has been created in many countries:

• GEO 600 (Hannover, Germany). The length of the vacuum tunnels is 600 meters.
• TAMA (Japan) with shoulders of 300 m.
• VIRGO (Pisa, Italy) is a joint French-Italian project launched in 2007 with three kilometers of tunnels.
• LIGO (USA, Pacific Coast), which has been hunting for gravitational waves since 2002.

The latter is worth considering in more detail.

LIGO Advanced

The project was created on the initiative of scientists from the Massachusetts and Californian technological institutes. It includes two observatories, separated by 3 thousand km, in and Washington (the cities of Livingston and Hanford) with three identical interferometers. The length of perpendicular vacuum tunnels is 4 thousand meters. These are the largest such structures currently in operation. Until 2011, numerous attempts to detect gravitational waves did not bring any results. The significant modernization carried out (Advanced LIGO) increased the sensitivity of the equipment in the range of 300-500 Hz by more than five times, and in the low-frequency region (up to 60 Hz) by almost an order of magnitude, reaching the coveted value of 10 -21. The updated project started in September 2015, and the efforts of more than a thousand collaboration employees were rewarded with the results obtained.

Gravitational waves detected

On September 14, 2015, advanced LIGO detectors, with an interval of 7 ms, recorded gravitational waves reaching our planet from the largest event that occurred on the outskirts of the observable Universe - the merger of two large black holes with masses 29 and 36 times greater than the mass of the Sun. During the process, which took place more than 1.3 billion years ago, about three solar masses of matter were consumed in a matter of fractions of a second by emitting gravitational waves. The recorded initial frequency of gravitational waves was 35 Hz, and the maximum peak value reached 250 Hz.

The results obtained were repeatedly subjected to comprehensive verification and processing, and alternative interpretations of the data obtained were carefully eliminated. Finally, last year the direct registration of the phenomenon predicted by Einstein was announced to the world community.

A fact illustrating the titanic work of researchers: the amplitude of fluctuations in the size of the interferometer arms was 10 -19 m - this value is the same number of times smaller than the diameter of an atom, as the atom itself is smaller than an orange.

Future prospects

The discovery once again confirms that the General Theory of Relativity is not just a set of abstract formulas, but a fundamentally new look at the essence of gravitational waves and gravity in general.

In further research, scientists big hopes are assigned to the ELSA project: the creation of a giant orbital interferometer with arms of about 5 million km, capable of detecting even minor disturbances in gravitational fields. Activation of work in this direction can tell a lot of new things about the main stages of the development of the Universe, about processes that are difficult or impossible to observe in traditional ranges. There is no doubt that black holes, whose gravitational waves will be detected in the future, will tell a lot about their nature.

To study the cosmic microwave background radiation, which can tell us about the first moments of our world after the Big Bang, more sensitive space instruments will be required. Such a project exists ( Big Bang Observer), but its implementation, according to experts, is possible no earlier than in 30-40 years.

Valentin Nikolaevich Rudenko shares the story of his visit to the city of Cascina (Italy), where he spent a week on the then just built “gravitational antenna” - the Michelson optical interferometer. On the way to the destination, the taxi driver asks why the installation was built. “People here think it’s for talking to God,” the driver admits.

– What are gravitational waves?

– A gravitational wave is one of the “carriers of astrophysical information.” There are visible channels of astrophysical information; telescopes play a special role in “distant vision”. Astronomers have also mastered low-frequency channels - microwave and infrared, and high-frequency channels - X-ray and gamma. In addition to electromagnetic radiation, we can detect streams of particles from Space. For this purpose, neutrino telescopes are used - large-sized detectors of cosmic neutrinos - particles that weakly interact with matter and are therefore difficult to register. Almost all theoretically predicted and laboratory-studied types of “carriers of astrophysical information” have been reliably mastered in practice. The exception was gravity - the weakest interaction in the microcosm and the most powerful force in the macrocosm.

Gravity is geometry. Gravitational waves– geometric waves, that is, waves that change the geometric characteristics of space when they pass through this space. Roughly speaking, these are waves that deform space. Strain is the relative change in the distance between two points. Gravitational radiation differs from all other types of radiation precisely in that it is geometric.

– Did Einstein predict gravitational waves?

– Formally, it is believed that gravitational waves were predicted by Einstein as one of the consequences of his general theory of relativity, but in fact their existence becomes obvious already in the special theory of relativity.

The theory of relativity suggests that, due to gravitational attraction, gravitational collapse is possible, that is, the contraction of an object as a result of collapse, roughly speaking, to a point. Then the gravity is so strong that light cannot even escape from it, so such an object is figuratively called a black hole.

– What is the peculiarity of gravitational interaction?

A feature of gravitational interaction is the principle of equivalence. According to it, the dynamic response of a test body in a gravitational field does not depend on the mass of this body. Simply put, all bodies fall with the same acceleration.

Gravitational interaction is the weakest we know today.

– Who was the first to try to catch a gravitational wave?

– The gravitational wave experiment was first conducted by Joseph Weber from the University of Maryland (USA). He created a gravitational detector, which is now kept in the Smithsonian Museum in Washington. In 1968-1972, Joe Weber conducted a series of observations on a pair of spatially separated detectors, trying to isolate cases of "coincidences". The coincidence technique is borrowed from nuclear physics. The low statistical significance of the gravitational signals obtained by Weber caused a critical attitude towards the results of the experiment: there was no confidence that gravitational waves had been detected. Subsequently, scientists tried to increase the sensitivity of Weber-type detectors. It took 45 years to develop a detector whose sensitivity was adequate to the astrophysical forecast.

During the start of the experiment, many other experiments took place before fixation; impulses were recorded during this period, but their intensity was too low.

– Why was the signal fixation not announced immediately?

– Gravitational waves were recorded back in September 2015. But even if a coincidence was recorded, before announcing it, it is necessary to prove that it is not accidental. The signal taken from any antenna always contains noise bursts (short-term bursts), and one of them can accidentally occur simultaneously with a noise burst on another antenna. It is possible to prove that the coincidence did not occur by chance only with the help of statistical estimates.

– Why are discoveries in the field of gravitational waves so important?

– The ability to register the relict gravitational background and measure its characteristics, such as density, temperature, etc., allows us to approach the beginning of the universe.

What's attractive is that gravitational radiation is difficult to detect because it interacts very weakly with matter. But, thanks to this same property, it passes without absorption from the objects most distant from us with the most mysterious, from the point of view of matter, properties.

We can say that gravitational radiation passes without distortion. The most ambitious goal is to study the gravitational radiation that was separated from the primordial matter in the Big Bang Theory, which was created at the creation of the Universe.

– Does the discovery of gravitational waves rule out quantum theory?

The theory of gravity assumes the existence of gravitational collapse, that is, the contraction of massive objects to a point. At the same time, the quantum theory developed by the Copenhagen School suggests that, thanks to the uncertainty principle, it is impossible to simultaneously indicate exactly such parameters as the coordinate, speed and momentum of a body. There is an uncertainty principle here; it is impossible to determine the exact trajectory, because the trajectory is both a coordinate and a speed, etc. It is only possible to determine a certain conditional confidence corridor within the limits of this error, which is associated with the principles of uncertainty. Quantum theory categorically denies the possibility of point objects, but describes them in a statistically probabilistic manner: it does not specifically indicate coordinates, but indicates the probability that it has certain coordinates.

The question of unifying quantum theory and the theory of gravity is one of the fundamental questions of creating a unified field theory.

They continue to work on it now, and the words “quantum gravity” mean a completely advanced area of ​​science, the border of knowledge and ignorance, where all the theorists in the world are now working.

– What can the discovery bring in the future?

Gravitational waves must inevitably form the foundation of modern science as one of the components of our knowledge. They play a significant role in the evolution of the Universe and with the help of these waves the Universe should be studied. Discovery promotes general development science and culture.

If you decide to go beyond the scope of today's science, then it is permissible to imagine gravitational telecommunication lines, jet devices using gravitational radiation, gravitational-wave introscopy devices.

– Do gravitational waves have anything to do with extrasensory perception and telepathy?

Dont Have. The described effects are the effects of the quantum world, the effects of optics.

Interviewed by Anna Utkina

Yesterday, the world was shocked by a sensation: scientists finally discovered gravitational waves, the existence of which Einstein predicted a hundred years ago. This is a breakthrough. Distortion of space-time (these are gravitational waves - now we’ll explain what’s what) was discovered at the LIGO observatory, and one of its founders is - who do you think? - Kip Thorne, author of the book.

We tell you why the discovery of gravitational waves is so important, what Mark Zuckerberg said and, of course, share the story from the first person. Kip Thorne, like no one else, knows how the project works, what makes it unusual and what significance LIGO has for humanity. Yes, yes, everything is so serious.

Discovery of gravitational waves

The scientific world will forever remember the date February 11, 2016. On this day, participants in the LIGO project announced: after so many futile attempts gravitational waves found. This is reality. In fact, they were discovered a little earlier: in September 2015, but yesterday the discovery was officially recognized. The Guardian believes that scientists will certainly receive Nobel Prize in physics.

The cause of gravitational waves is the collision of two black holes, which occurred already... a billion light years from Earth. Can you imagine how huge our Universe is! Since black holes are very massive bodies, they send ripples through space-time, distorting it slightly. So waves appear, similar to those that spread from a stone thrown into the water.

This is how you can imagine gravitational waves coming to the Earth, for example, from a wormhole. Drawing from the book “Interstellar. Science behind the scenes"

The resulting vibrations were converted into sound. Interestingly, the signal from gravitational waves arrives at approximately the same frequency as our speech. So we can hear with our own ears how black holes collide. Listen to what gravitational waves sound like.

And guess what? More recently, black holes are not structured as previously thought. But there was no evidence at all that they exist in principle. And now there is. Black holes really “live” in the Universe.

This is what scientists believe a catastrophe looks like—a merger of black holes.

On February 11, a grandiose conference took place, which brought together more than a thousand scientists from 15 countries. Russian scientists were also present. And, of course, there was Kip Thorne. “This discovery is the beginning of an amazing, magnificent quest for people: the search and exploration of the curved side of the Universe - objects and phenomena created from distorted space-time. Black hole collisions and gravitational waves are our first remarkable examples,” said Kip Thorne.

The search for gravitational waves has been one of the main problems in physics. Now they have been found. And Einstein's genius is confirmed again.

In October, we interviewed Sergei Popov, a Russian astrophysicist and famous popularizer of science. He looked like he was looking into water! In the fall: “It seems to me that we are now on the threshold of new discoveries, which is primarily associated with the work of the LIGO and VIRGO gravitational wave detectors (Kip Thorne made a major contribution to the creation of the LIGO project).” Amazing, right?

Gravitational waves, wave detectors and LIGO

Well, now for a little physics. For those who really want to understand what gravitational waves are. Here artistic image Tendex lines of two black holes that orbit each other counterclockwise and then collide. Tendex lines generate tidal gravity. Go ahead. The lines, which emanate from the two points furthest apart from each other on the surfaces of a pair of black holes, stretch everything in their path, including the artist’s friend in the drawing. The lines emanating from the collision area compress everything.

As the holes rotate around one another, they carry along their tendex lines, which resemble streams of water from a spinning sprinkler on a lawn. In the picture from the book “Interstellar. Science behind the scenes" - a pair of black holes that collide, rotating around each other counterclockwise, and their tendex lines.

Black holes merge into one big hole; it is deformed and rotates counterclockwise, dragging tendex lines with it. A stationary observer far from the hole will feel vibrations as the tendex lines pass through him: stretching, then compression, then stretching - the tendex lines have become a gravitational wave. As the waves propagate, the black hole's deformation gradually decreases, and the waves also weaken.

When these waves reach the Earth, they look like the one shown at the top of the figure below. They stretch in one direction and compress in the other. The extensions and compressions oscillate (from red right-left, to blue right-left, to red right-left, etc.) as the waves pass through the detector at the bottom of the figure.

Gravitational waves passing through the LIGO detector.

The detector consists of four large mirrors (40 kilograms, 34 centimeters in diameter), which are attached to the ends of two perpendicular pipes, called detector arms. Tendex lines of gravitational waves stretch one arm, while compressing the second, and then, on the contrary, compress the first and stretch the second. And so again and again. As the length of the arms changes periodically, the mirrors move relative to each other, and these movements are tracked using laser beams in a way called interferometry. Hence the name LIGO: Laser Interferometer Gravitational-Wave Observatory.

LIGO control center, from where they send commands to the detector and monitor the received signals. LIGO's gravity detectors are located in Hanford, Washington, and Livingston, Louisiana. Photo from the book “Interstellar. Science behind the scenes"

Now LIGO is an international project in which 900 scientists from different countries, with headquarters located at the California Institute of Technology.

The Curved Side of the Universe

Black holes, wormholes, singularities, gravitational anomalies and higher order dimensions are associated with curvatures of space and time. That's why Kip Thorne calls them "the twisted side of the universe." Humanity still has very little experimental and observational data from the curved side of the Universe. This is why we pay so much attention to gravitational waves: they are made of curved space and provide the most accessible way for us to explore the curved side.

Imagine if you only saw the ocean when it was calm. You wouldn't know about currents, whirlpools and storm waves. This is reminiscent of our current knowledge of the curvature of space and time.

We know almost nothing about how curved space and curved time behave "in a storm" - when the shape of space fluctuates violently and when the speed of time fluctuates. This is an incredibly alluring frontier of knowledge. Scientist John Wheeler coined the term "geometrodynamics" for these changes.

Of particular interest in the field of geometrodynamics is the collision of two black holes.

Collision of two non-rotating black holes. Model from the book “Interstellar. Science behind the scenes"

The picture above shows the moment when two black holes collide. Just such an event allowed scientists to detect gravitational waves. This model is built for non-rotating black holes. Top: orbits and shadows of holes, as seen from our Universe. Middle: curved space and time, as seen from the bulk (multidimensional hyperspace); The arrows show how space is involved in movement, and the changing colors show how time is bent. Bottom: The shape of the emitted gravitational waves.

Gravitational waves from the Big Bang

Over to Kip Thorne. “In 1975, Leonid Grischuk, my good friend from Russia, made a sensational statement. He said that at the moment of the Big Bang, many gravitational waves arose, and the mechanism of their origin (previously unknown) was as follows: quantum fluctuations (random fluctuations - editor's note) gravitational fields during the Big Bang were greatly enhanced by the initial expansion of the Universe and thus became the original gravitational waves. These waves, if detected, could tell us what happened at the birth of our Universe."

If scientists find the primordial gravitational waves, we will know how the Universe began.

People have solved far all the mysteries of the Universe. There's more to come.

In subsequent years, as our understanding of the Big Bang improved, it became obvious that these primordial waves must be strong at wavelengths commensurate with the size of the visible Universe, that is, at lengths of billions of light years. Can you imagine how much this is?.. And at the wavelengths that LIGO detectors cover (hundreds and thousands of kilometers), the waves will most likely be too weak to be recognized.

Jamie Bock's team built the BICEP2 apparatus, with which the trace of the original gravitational waves was discovered. The device located at the North Pole is shown here during twilight, which occurs there only twice a year.

BICEP2 device. Image from the book Interstellar. Science behind the scenes"

It is surrounded by shields that shield the device from radiation from the surrounding ice cover. In the upper right corner there is a trace discovered in the cosmic microwave background radiation - a polarization pattern. Electric field lines are directed along short light strokes.

Trace of the beginning of the universe

In the early nineties, cosmologists realized that these gravitational waves, billions of light years long, would have left a unique imprint on electromagnetic waves filling the Universe - in the so-called cosmic microwave background, or cosmic microwave background radiation. This began the search for the Holy Grail. After all, if we detect this trace and deduce from it the properties of the original gravitational waves, we can find out how the Universe was born.

In March 2014, while Kip Thorne was writing this book, the team of Jamie Bok, a cosmologist at Caltech whose office is next door to Thorne's, finally discovered this trace in the cosmic microwave background radiation.

This is an absolutely amazing discovery, but there is one controversial point: the trace found by Jamie's team could have been caused by something other than gravitational waves.

If a trace of the gravitational waves that arose during the Big Bang is indeed found, it means that a cosmological discovery has occurred on a level that happens perhaps once every half century. It gives you a chance to touch the events that occurred a trillionth of a trillionth of a trillionth of a second after the birth of the Universe.

This discovery confirms theories that the expansion of the Universe at that moment was extremely fast, in the slang of cosmologists - inflationary fast. And heralds the coming new era in cosmology.

Gravitational waves and Interstellar

Yesterday, at a conference on the discovery of gravitational waves, Valery Mitrofanov, head of the Moscow LIGO collaboration of scientists, which includes 8 scientists from Moscow State University, noted that the plot of the film “Interstellar,” although fantastic, is not so far from reality. And all because Kip Thorne was the scientific consultant. Thorne himself expressed hope that he believes in future manned flights to a black hole. They may not happen as soon as we would like, but today it is much more real than it was before.

The day is not too far off when people will leave the confines of our galaxy.

The event stirred the minds of millions of people. The notorious Mark Zuckerberg wrote: “The discovery of gravitational waves is the biggest discovery in modern science. Albert Einstein is one of my heroes, which is why I took the discovery so personally. A century ago, within the framework of the General Theory of Relativity (GTR), he predicted the existence of gravitational waves. But they are so small to detect that it has come to look for them in the origins of events such as the Big Bang, stellar explosions and black hole collisions. When scientists analyze the data obtained, a completely new view of space will open before us. And perhaps this will shed light on the origin of the Universe, the birth and development of black holes. It is very inspiring to think about how many lives and efforts have gone into unveiling this mystery of the Universe. This breakthrough was made possible thanks to the talent of brilliant scientists and engineers, people of different nationalities, as well as the latest computer technologies that have appeared only recently. Congratulations to everyone involved. Einstein would be proud of you."

This is the speech. And this is a person who is simply interested in science. One can imagine what a storm of emotions overwhelmed the scientists who contributed to the discovery. It seems that we have witnessed a new era, friends. This is amazing.

P.S.: Did you like it? Subscribe to our newsletter on horizons. Once a week we send educational letters and give discounts on MYTH books.

• Gravitational waves are changes in the gravitational field that propagate like waves. They are emitted by moving masses, but after radiation they are separated from them and exist independently of these masses. Mathematically related to the perturbation of spacetime metrics and can be described as "spacetime ripples".

  In general relativity and most others modern theories In gravity, gravitational waves are generated by the motion of massive bodies with variable acceleration. Gravitational waves propagate freely in space at the speed of light. Due to the relative weakness of gravitational forces (compared to others), these waves have a very small magnitude, which is difficult to register.

  Gravitational waves are predicted by the general theory of relativity (GR) and many other theories of gravity. They were first directly detected in September 2015 by LIGO's twin detectors, which detected gravitational waves likely produced by two black holes merging to form a single, more massive, rotating black hole. Indirect evidence of their existence has been known since the 1970s - General Relativity predicts rates of convergence of close systems of double stars that coincide with observations due to the loss of energy due to the emission of gravitational waves. Direct registration of gravitational waves and their use to determine the parameters of astrophysical processes is an important task of modern physics and astronomy.

  Within the framework of general relativity, gravitational waves are described by solutions of wave-type Einstein equations, which represent a perturbation of the space-time metric moving at the speed of light (in the linear approximation). The manifestation of this disturbance should be, in particular, a periodic change in the distance between two freely falling (that is, not influenced by any forces) test masses. The amplitude h of a gravitational wave is a dimensionless quantity - a relative change in distance. Predicted maximum amplitudes of gravitational waves from astrophysical objects (for example, compact binary systems) and phenomena (supernova explosions, neutron star mergers, star captures by black holes, etc.) when measured in solar system very small (h=10−18-10−23). A weak (linear) gravitational wave, according to the general theory of relativity, transfers energy and momentum, moves at the speed of light, is transverse, quadrupole and is described by two independent components located at an angle of 45° to each other (has two directions of polarization).

  Different theories predict the speed of propagation of gravitational waves differently. In general relativity, it is equal to the speed of light (in the linear approximation). In other theories of gravity, it can take any value, including infinity. According to the first registration of gravitational waves, their dispersion turned out to be compatible with a massless graviton, and the speed was estimated to be equal to the speed of light.