What physical effect made it possible to detect gravitational waves. Gravitational waves, wave detectors and LIGO

Gravitational Waves - Artist's Image

Gravitational waves are perturbations of the space-time metric that break away from the source and propagate like waves (the so-called "space-time ripples").

In the general theory of relativity and in most other modern theories of gravity, gravitational waves are generated by the movement 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.

Polarized gravitational wave

Gravitational waves are predicted by the general theory of relativity (GR), many others. They were first directly detected in September 2015 by two twin detectors, which recorded gravitational waves, likely resulting from the merger of the two and the formation of one more massive rotating black hole. Indirect evidence of their existence has been known since the 1970s - general relativity predicts the rate of convergence of close systems that coincides with observations due to the loss of energy for 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.

In the framework of general relativity, gravitational waves are described by solutions of the Einstein equations of the wave type, which represent a perturbation of the space-time metric moving at the speed of light (in a linear approximation). The manifestation of this perturbation should be, in particular, a periodic change in the distance between two freely falling (that is, not affected by any forces) test masses. Amplitude h gravitational wave is a dimensionless quantity - a relative change in distance. The predicted maximum amplitudes of gravitational waves from astrophysical objects (for example, compact binary systems) and phenomena (explosions, mergers, captures by black holes, etc.) are very small when measured in ( h=10 −18 -10 −23). A weak (linear) gravitational wave, according to the general theory of relativity, carries 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).

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

Generation of gravitational waves

A system of two neutron stars creates ripples in space-time

A gravitational wave is emitted by any matter moving with asymmetric acceleration. For the emergence of a wave of significant amplitude, an extremely large mass of the emitter or / and huge accelerations are required, the amplitude of the gravitational wave is directly proportional to first derivative of acceleration and the mass of the generator, i.e. ~ . However, if some object is moving at an accelerated rate, then this means that some force is acting on it from the side of another object. In turn, this other object experiences the reverse action (according to Newton's 3rd law), while it turns out that m 1 a 1 = − m 2 a 2 . It turns out that two objects radiate gravitational waves only in pairs, and as a result of interference they are mutually extinguished almost completely. Therefore, gravitational radiation in the general theory of relativity always has the character of at least quadrupole radiation in terms of multipolarity. In addition, for nonrelativistic emitters, the expression for the radiation intensity contains a small parameter where is the gravitational radius of the emitter, r- its characteristic size, T- characteristic period of movement, c is the speed of light in vacuum.

The strongest sources of gravitational waves are:

• colliding (giant masses, very small accelerations),
• gravitational collapse of a binary system of compact objects (colossal accelerations with a fairly large mass). As a special and most interesting case - the merger of neutron stars. In such a system, the gravitational-wave luminosity is close to the highest possible Planck luminosity in nature.

Gravitational waves emitted by a two-body system

Two bodies moving in circular orbits around a common center of mass

Two gravitationally bound bodies with masses m 1 and m 2 , moving nonrelativistically ( v << c) in circular orbits around their common center of mass at a distance r from each other, radiate gravitational waves of the following energy, on average over the period:

As a result, the system loses energy, which leads to the convergence of bodies, that is, to a decrease in the distance between them. Approach speed of bodies:

For the Solar system, for example, the subsystem and produces the greatest gravitational radiation. The power of this radiation is approximately 5 kilowatts. Thus, the energy lost by the solar system to gravitational radiation per year is completely negligible compared to the characteristic kinetic energy of bodies.

Gravitational collapse of a binary system

Any binary star, when its components rotate around a common center of mass, loses energy (as it is assumed - due to the emission of gravitational waves) and, in the end, merges together. But for ordinary, non-compact, binary stars, this process takes a very long time, much more than the present age. If the binary compact system consists of a pair of neutron stars, black holes, or a combination of both, then the merger can occur in several million years. First, the objects approach each other, and their period of revolution decreases. Then at the final stage there is a collision and an asymmetric gravitational collapse. This process lasts a fraction of a second, and during this time, energy is lost into gravitational radiation, which, according to some estimates, is more than 50% of the mass of the system.

Basic exact solutions of the Einstein equations for gravitational waves

Body waves of Bondi - Pirani - Robinson

These waves are described by a metric of the form . If we introduce a variable and a function , then from the GR equations we obtain the equation

Takeno metric

has the form , -functions, satisfy the same equation.

Rosen metric

Where satisfy

Perez metric

Wherein

Einstein-Rosen Cylindrical Waves

In cylindrical coordinates, such waves have the form and are fulfilled

Registration of gravitational waves

Registration of gravitational waves is rather complicated due to the weakness of the latter (small distortion of the metric). The instruments for their registration are gravitational wave detectors. Attempts to detect gravitational waves have been made since the late 1960s. Gravitational waves of detectable amplitude are produced during the collapse of a binary . Similar events take place in the vicinity approximately once a decade.

On the other hand, general relativity predicts an acceleration of the mutual rotation of binary stars due to the loss of energy for the emission of gravitational waves, and this effect has been reliably recorded in several known systems of binary compact objects (in particular, pulsars with compact companions). In 1993, "for the discovery of a new type of pulsar that gave new possibilities in the study of gravity" to the discoverers of the first double pulsar PSR B1913+16, Russell Hulse and Joseph Taylor Jr. was awarded the Nobel Prize in Physics. The acceleration of rotation observed in this system completely coincides with the predictions of general relativity for the emission of gravitational waves. The same phenomenon was recorded in several other cases: for the pulsars PSR J0737-3039, PSR J0437-4715, SDSS J065133.338+284423.37 (usually abbreviated as J0651) and the binary RX J0806 system. For example, the distance between the two components A and B of the first binary star of the two pulsars PSR J0737-3039 decreases by about 2.5 inches (6.35 cm) per day due to energy loss to gravitational waves, and this happens in accordance with general relativity . All these data are interpreted as indirect confirmation of the existence of gravitational waves.

According to estimates, the strongest and most frequent sources of gravitational waves for gravitational telescopes and antennas are catastrophes associated with the collapse of binary systems in nearby galaxies. It is expected that in the near future, advanced gravitational detectors will register several such events per year, distorting the metric in the vicinity by 10 −21 -10 −23 . The first observations of the optical-metric parametric resonance signal, which makes it possible to detect the effect of gravitational waves from periodic sources of the close binary type on the radiation of cosmic masers, may have been obtained at the Radio Astronomy Observatory of the Russian Academy of Sciences, Pushchino.

Another possibility for detecting the background of gravitational waves filling the Universe is high-precision timing of distant pulsars - analysis of the arrival time of their pulses, which characteristically changes under the action of gravitational waves passing through the space between the Earth and the pulsar. According to estimates in 2013, the timing accuracy needs to be increased by about one order of magnitude to be able to detect background waves from multiple sources in our universe, and this task can be solved before the end of the decade.

According to modern concepts, our Universe is filled with relic gravitational waves that appeared in the first moments after. Their registration will provide information about the processes at the beginning of the birth of the Universe. On March 17, 2014 at 20:00 Moscow time at the Harvard-Smithsonian Center for Astrophysics, an American group of researchers working on the BICEP 2 project announced the detection of non-zero tensor perturbations in the early Universe by polarization of the CMB, which is also the discovery of these relic gravitational waves . However, almost immediately this result was disputed, since, as it turned out, the contribution of . One of the authors, J. M. Kovats ( Kovac J.M.), acknowledged that "with the interpretation and coverage of the data of the BICEP2 experiment, the participants in the experiment and science journalists were a little hasty."

Experimental confirmation of existence

The first recorded gravitational wave signal. On the left, data from the detector at Hanford (H1), on the right, at Livingston (L1). The time is counted from September 14, 2015, 09:50:45 UTC. To visualize the signal, it was filtered with a frequency filter with a bandwidth of 35-350 Hz to suppress large fluctuations outside the high sensitivity range of the detectors; band-pass filters were also used to suppress the noise of the installations themselves. Top row: voltages h in the detectors. GW150914 first arrived at L1 and after 6 9 +0 5 −0 4 ms at H1; for visual comparison, the data from H1 are shown in the L1 plot inverted and time-shifted (to take into account the relative orientation of the detectors). Second row: voltages h from the gravitational wave signal, passed through the same bandpass filter 35-350 Hz. The solid line is the result of numerical relativity for a system with parameters compatible with those found on the basis of studying the GW150914 signal, obtained by two independent codes with a resulting match of 99.9. The gray thick lines are the 90% confidence intervals of the waveform recovered from the detector data by two different methods. The dark gray line models the expected signals from black hole mergers, the light gray line does not use astrophysical models, but represents the signal as a linear combination of sinusoidal-gaussian wavelets. Reconstructions overlap by 94%. Third row: Residual errors after extracting the filtered prediction of the numerical relativity signal from the filtered signal of the detectors. Bottom row: voltage frequency map representation showing the increase in the dominant frequency of the signal over time.

February 11, 2016 by LIGO and VIRGO collaborations. The signal of the merger of two black holes with an amplitude at a maximum of about 10 −21 was detected on September 14, 2015 at 09:51 UTC by two LIGO detectors in Hanford and Livingston 7 milliseconds apart, in the region of maximum signal amplitude (0.2 seconds) combined the signal-to-noise ratio was 24:1. The signal was designated GW150914. The shape of the signal matches the prediction of general relativity for the merger of two black holes with masses of 36 and 29 solar masses; the resulting black hole should have a mass of 62 solar masses and a rotation parameter a= 0.67. The distance to the source is about 1.3 billion , the energy radiated in tenths of a second in the merger is the equivalent of about 3 solar masses.

Story

The history of the term "gravitational wave" itself, the theoretical and experimental search for these waves, as well as their use to study phenomena inaccessible to other methods.

• 1900 - Lorentz suggested that gravity "... can propagate at a speed no greater than the speed of light";
• 1905 - Poincare first introduced the term gravitational wave (onde gravifique). Poincaré, on a qualitative level, removed the well-established objections of Laplace and showed that the corrections associated with gravitational waves to Newton's generally accepted laws of gravity of the order cancel, so the assumption of the existence of gravitational waves does not contradict observations;
• 1916 - Einstein showed that, within the framework of GR, a mechanical system would transfer energy to gravitational waves and, roughly speaking, any rotation relative to fixed stars must stop sooner or later, although, of course, under normal conditions, energy losses of the order are negligible and practically cannot be measured (in In this work, he still mistakenly believed that a mechanical system that constantly maintains spherical symmetry can radiate gravitational waves);
• 1918 - Einstein derived a quadrupole formula in which the radiation of gravitational waves turns out to be an order effect, thereby correcting the error in his previous work (there was an error in the coefficient, the wave energy is 2 times less);
• 1923 - Eddington - questioned the physical reality of gravitational waves "... propagate ... at the speed of thought." In 1934, when preparing a Russian translation of his monograph The Theory of Relativity, Eddington added several chapters, including chapters with two options for calculating energy losses by a rotating rod, but noted that the methods used for approximate calculations of general relativity, in his opinion, are not applicable to gravitationally coupled systems. so doubts remain;
• 1937 - Einstein, together with Rosen, investigated cylindrical wave solutions of the exact equations of the gravitational field. In the course of these studies, they had doubts that gravitational waves might be an artifact of approximate solutions to the GR equations (there is a known correspondence regarding the review of the article by Einstein and Rosen "Do gravitational waves exist?"). Later, he found an error in the reasoning, the final version of the article with fundamental edits was already published in the Journal of the Franklin Institute;
• 1957 - Herman Bondy and Richard Feynman proposed a "cane with beads" thought experiment in which they substantiated the existence of the physical consequences of gravitational waves in general relativity;
• 1962 - Vladislav Pustovoit and Mikhail Gertsenshtein described the principles of using interferometers to detect long-wavelength gravitational waves;
• 1964 - Philip Peters and John Matthew theoretically described gravitational waves emitted by binary systems;
• 1969 - Joseph Weber, founder of gravitational wave astronomy, reports detection of gravitational waves using a resonant detector - a mechanical gravitational antenna. These reports give rise to a rapid growth of work in this direction, in particular, Rene Weiss, one of the founders of the LIGO project, began experiments at that time. To date (2015), no one has been able to obtain reliable confirmation of these events;
• 1978 - Joseph Taylor reported the detection of gravitational radiation in the binary system of the pulsar PSR B1913+16. The work of Joseph Taylor and Russell Hulse earned the 1993 Nobel Prize in Physics. At the beginning of 2015, three post-Keplerian parameters, including the decrease in the period due to the emission of gravitational waves, were measured for at least 8 such systems;
• 2002 - Sergey Kopeikin and Edward Fomalont made dynamic measurements of light deflection in the gravitational field of Jupiter using radio wave interferometry with an extra long baseline, which for a certain class of hypothetical extensions of general relativity allows estimating the speed of gravity - the difference from the speed of light should not exceed 20% (this interpretation does not generally accepted);
• 2006 - the international team of Martha Burgay (Parks Observatory, Australia) reported much more accurate confirmation of general relativity and the correspondence to it of the magnitude of gravitational wave radiation in the system of two pulsars PSR J0737-3039A/B;
• 2014 - Astronomers at the Harvard-Smithsonian Center for Astrophysics (BICEP) reported the detection of primordial gravitational waves in measurements of CMB fluctuations. At the moment (2016), the detected fluctuations are considered not to be of relict origin, but are explained by the radiation of dust in the Galaxy;
• 2016 - LIGO international team announced the detection of the event of the passage of gravitational waves GW150914. For the first time, direct observation of interacting massive bodies in superstrong gravitational fields with superhigh relative velocities (< 1,2 × R s , v/c >0.5), which made it possible to verify the correctness of general relativity with an accuracy of several high-order post-Newtonian terms. The measured dispersion of gravitational waves does not contradict the previous measurements of the dispersion and the upper limit of the mass of the hypothetical graviton (< 1,2 × 10 −22 эВ), если он в некотором гипотетическом расширении ОТО будет существовать.



It looks like we'll be talking a lot about gravitational waves in the coming days. But why are they sometimes mistakenly called "gravity waves"? In this world of social media, where brevity is most often valued first, it might seem that reducing the phrase "gravity waves" to "gravity waves" is not such a big deal. Especially since it saves a few extra characters for Twitter lovers!

And you will most likely see many headlines in the news foreshadowing "gravitational waves of science" replaced by the word "gravity", but don't fall into that trap. While both words carry weight, in essence, gravitational waves and gravity waves are completely different "creatures". Read on and you'll find out how they differ, and you can even show off your gravity knowledge next time in front of your friends at the pub.

Gravitational waves are, in the most general sense, a kind of ripples in space and time. Einstein's theory of general relativity predicted their existence over a hundred years ago, and they are formed by the acceleration (or actually deceleration) of massive objects in space. If a star explodes as a supernova, then gravitational waves carry away energy from the detonation at the speed of light. If two black holes collide, they will cause ripples in space and time, reminiscent of ripples in a pond where a pebble has been thrown. If two neutron stars orbit each other very closely, their energy that is carried away from the system is – you guessed it – called gravitational waves. If we could detect and observe these waves, which the new era of gravitational wave astronomy might allow, then we would be able to recognize gravitational waves and work with the phenomena that produced them. For example, a sudden burst of gravitational waves could indicate they were coming from a supernova explosion, while a continuous oscillating signal could indicate the tight orbit of two black holes before they merge.

So far, gravitational waves are theoretical, despite the existence of strong circumstantial evidence. Interestingly, as gravitational waves propagate through space, they will physically deform the "fabric" of space, that is, shrink or expand the space between two objects very slightly. The effect is negligible, but using a laser interferometer such as the Gravitational Wave Observatory Laser Interferometer or LIGO (LIGO), which measures the slightest disturbance in lasers reflected through 2.5 km L-shaped vacuum tunnels, the propagation of gravitational waves through our planet can be detected. In the case of LIGO, there are 2 stations located on opposite sides of the US, separated by almost 2000 miles. If the gravitational wave signal is real, its signature will be observed at both locations; if it is a false signal (that is, a truck just passed by), then only one station will detect the signal. Although LIGO started operations in 2002, it has yet to detect gravitational waves. But in September 2015, the system was upgraded to Advanced LIGO and it is hoped that physicists will finally give us some good news on Thursday.

Bonus: Primordial gravitational waves. You may remember the turmoil with BICEP2's "discovery" (and then non-detection) of gravitational waves in the faint primordial "glow" of the Big Bang known as the cosmic microwave background (CMB). Although the "discovery" of BICEP2 turned out to be hopeless, it is believed that tiny gravitational disturbances around the time of the Big Bang may leave their "imprint" in this ancient radiation as a special kind of polarized light. If the imprint of primordial gravitational waves (those produced by the Big Bang) is observed, then some models of cosmic inflation and quantum gravity can be confirmed.

However, these are not the gravitational waves that LIGO is after. LIGO (and similar observatories) is looking for gravitational waves that are generated by energy events currently taking place in our modern universe. Hunting for primordial gravitational waves is like archeological excavations of the past of our universe.

Gravity waves are physical disturbances driven by the restoring gravity in the planetary environment. In other words, gravity waves are characteristic only for planetary atmospheres and water bodies. In the case of atmospheres, the air blows across the ocean, and then, hitting an island, for example, is forced to rise. Downwind, the air will be forced to a lower altitude by gravity, but its buoyancy will work against gravity, causing it to rise again. As a result, often a region of oscillating air in the atmosphere can produce clouds at the crests of waves. Examples of gravity waves are wind waves, tides, and tsunamis.

Thus, it turns out that the force of gravity drives both gravitational waves and gravity waves, but they have very different properties that should not be confused.

Valentin Nikolaevich Rudenko shares the story of his visit to the city of Kashina (Italy), where he spent a week on the newly built "gravitational antenna" - Michelson's optical interferometer. On the way to the destination, the taxi driver is interested in what the installation was built for. “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, a special role in "far vision" belongs to telescopes. Astronomers have also mastered low-frequency channels - microwave and infrared, and high-frequency - X-ray and gamma. In addition to electromagnetic radiation, we can register particle flows from the Cosmos. To do this, neutrino telescopes are used - large-sized detectors of cosmic neutrinos - particles that weakly interact with matter and therefore are difficult to register. Almost all theoretically predicted and laboratory-studied types of "carriers of astrophysical information" are reliably mastered in practice. The exception was gravitation - the weakest interaction in the microcosm and the most powerful force in the macrocosm.

Gravity is geometry. Gravitational waves are geometric waves, that is, waves that change the geometric characteristics of space as they travel through that space. Roughly speaking, these are waves that deform space. Deformation is the relative change in distance between two points. Gravitational radiation differs from all other types of radiation precisely in that they are 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, into a point. Then 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 the gravitational interaction?

A feature of the gravitational interaction is the principle of equivalence. According to him, 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.

The gravitational force 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 the gravitational detector, which is now kept in the Smithsonian Museum in Washington. In 1968-1972, Joe Weber made a series of observations with a pair of spaced apart detectors in an attempt to isolate instances of "coincidences". The reception of coincidences is borrowed from nuclear physics. The low statistical significance of the gravitational signals received by Weber caused a critical attitude towards the results of the experiment: there was no certainty that gravitational waves could be detected. In the future, 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 prediction.

During the beginning of the experiment before fixation, many other experiments took place, impulses were recorded during this period, but they had too little intensity.

- Why was the fixing of the signal not announced immediately?

– Gravitational waves were recorded back in September 2015. But even if a coincidence was recorded, it is necessary to prove before declaring that it is not accidental. In the signal taken from any antenna, there are always 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 happen 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.

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

We can say that gravitational radiations pass without distortion. The most ambitious goal is to investigate the gravitational radiation that was separated from the primary matter in the Big Bang Theory, which was created at the moment of 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 into 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 specify exactly such parameters as the position, velocity and momentum of a body at the same time. There is an uncertainty principle here, it is impossible to determine exactly the trajectory, because the trajectory is both a coordinate and a speed, etc. It is possible to determine only a certain conditional confidence corridor within 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 way: it does not specifically indicate the coordinates, but indicates the probability that it has certain coordinates.

The question of the unification of quantum theory and the theory of gravity is one of the fundamental questions of the creation of 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 theorists of the world are now working.

– What can the discovery give in the future?

Gravitational waves must inevitably form the foundation of modern science as one of the components of our knowledge. They are assigned a significant role in the evolution of the Universe and with the help of these waves the Universe should be studied. The discovery contributes to the overall development of science and culture.

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

- Do gravitational waves have any relation to extrasensory perception and telepathy?

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

Interviewed by Anna Utkina

“Recently, a series of long-term experiments to directly observe gravitational waves has sparked strong scientific interest,” theoretical physicist Michio Kaku wrote in his 2004 book Einstein’s Cosmos. - The LIGO (Laser Interferometer for Observing Gravitational Waves) project may be the first to "see" gravitational waves, most likely from the collision of two black holes in deep space. LIGO is a physicist's dream come true, the first facility with enough power to measure gravitational waves."

Kaku's prediction came true: on Thursday, a group of international scientists from the LIGO observatory announced the discovery of gravitational waves.

Gravitational waves are fluctuations in space-time that "run away" from massive objects (such as black holes) moving with acceleration. In other words, gravitational waves are a propagating perturbation of space-time, a running deformation of absolute emptiness.

A black hole is a region in space-time whose gravitational attraction is so strong that even objects moving at the speed of light (including light itself) cannot leave it. The boundary separating a black hole from the rest of the world is called the event horizon: everything that happens inside the event horizon is hidden from the eyes of an external observer.

Erin Ryan Photo of the cake posted online by Erin Ryan.

Scientists began to catch gravitational waves half a century ago: it was then that the American physicist Joseph Weber became interested in Einstein's general theory of relativity (GR), took a sabbatical and began to study gravitational waves. Weber invented the first device to detect gravitational waves, and soon claimed to have recorded "the sound of gravitational waves." However, the scientific community denied his message.

However, it was thanks to Joseph Weber that many scientists turned into “wave chasers”. Today Weber is considered the father of the scientific direction of gravitational wave astronomy.

"This is the beginning of a new era of gravitational astronomy"

The LIGO observatory, where scientists recorded gravitational waves, consists of three laser installations in the United States: two are located in Washington state and one in Louisiana. Here is how Michio Kaku describes the operation of laser detectors: “The laser beam is split into two separate beams, which then go perpendicular to each other. Then, reflected from the mirror, they reconnect. If a gravitational wave passes through the interferometer (measuring device), the path lengths of the two laser beams will be perturbed and this will be reflected in their interference pattern. To make sure that the signal registered by the laser installation is not random, the detectors should be placed at different points on the Earth.

Only under the influence of a giant gravitational wave, much larger than our planet, will all detectors work simultaneously.

Now the LIGO collaboration has detected gravitational radiation caused by the merger of a binary system of black holes with masses of 36 and 29 solar masses into an object with a mass of 62 solar masses. “This is the first direct (it is very important that it is direct!) measurement of the action of gravitational waves,” Sergey Vyatchanin, a professor at the Faculty of Physics of Moscow State University, commented to the correspondent of the science department of Gazeta.Ru. - That is, a signal was received from the astrophysical catastrophe of the merger of two black holes. And this signal is identified - this is also very important! It is clear that this is from two black holes. And this is the beginning of a new era of gravitational astronomy, which will allow obtaining information about the Universe not only through optical, X-ray, electromagnetic and neutrino sources, but also through gravitational waves.

We can say that 90 percent of black holes have ceased to be hypothetical objects. Some doubt remains, but still, the signal that is caught fits painfully well with what is predicted by countless simulations of the merger of two black holes in accordance with the general theory of relativity.

This is a strong argument that black holes exist. There is no other explanation for such a signal yet. Therefore, it is assumed that black holes exist.”

"Einstein would be very happy"

Gravitational waves were predicted by Albert Einstein (who, by the way, was skeptical about the existence of black holes) within the framework of his general theory of relativity. In general relativity, time is added to three spatial dimensions, and the world becomes four-dimensional. According to a theory that turned physics on its head, gravity is a consequence of the curvature of space-time under the influence of mass.

Einstein proved that any matter moving with acceleration creates a perturbation of space-time - a gravitational wave. This perturbation is the greater, the higher the acceleration and mass of the object.

Due to the weakness of gravitational forces compared to other fundamental interactions, these waves should have a very small magnitude, which is difficult to register.

When explaining general relativity to the humanities, physicists often ask them to imagine a stretched sheet of rubber on which massive balls are lowered. The balls push through the rubber, and the stretched sheet (which represents space-time) is deformed. According to general relativity, the entire universe is rubber, on which every planet, every star and every galaxy leave dents. Our Earth revolves around the Sun like a small ball rolled around the cone of a funnel formed as a result of the “punching” of space-time by a heavy ball.

HANDOUT/Reuters

The heavy ball is the Sun

It is likely that the discovery of gravitational waves, which is the main confirmation of Einstein's theory, claims the Nobel Prize in physics. “Einstein would be very happy,” said Gabriella Gonzalez, spokesperson for the LIGO collaboration.

According to scientists, it is too early to talk about the practical applicability of the discovery. “Although, did Heinrich Hertz (a German physicist who proved the existence of electromagnetic waves. - Gazeta.Ru) think that there would be a mobile phone? Not! We can’t imagine anything right now,” said Valery Mitrofanov, professor at the Faculty of Physics of Moscow State University. M.V. Lomonosov. - I am guided by the movie "Interstellar". He is criticized, yes, but even a wild man could imagine a magic carpet. And the flying carpet turned into a plane, and that's it. And here it is already necessary to imagine something very complex. In Interstellar, one of the moments is related to the fact that a person can travel from one world to another. If so, do you believe that a person can travel from one world to another, that there can be many universes - anything? I can't answer no. Because a physicist cannot answer such a question with “no”! Only if it contradicts some conservation laws! There are options that do not contradict known physical laws. So, travel around the worlds can be!

What does the detection of gravitational waves mean for us.

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

In fact, everything is simple, it is enough to draw an analogy with a submarine:

Source:

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

With space the same garbage. We look at the stars through telescopes, take photographs of Mars, catch radiation and generally try to know the heavens in all available ways. And now, after these waves have been fixed, another method of study has been added - gravitational. We will be able to view space based on these fluctuations.

That is, just as a submarine passed through the sea and left a "trail" behind it, by which it can be calculated, in the same way 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 go around different luminaries, galaxies, planets, we will learn how to calculate the cosmic trajectories of objects even better (And maybe even recognize and predict the approach of meteorites in advance), we will see the behavior of waves in special conditions, well, and all that.

What will it give?

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

And what is the result?

As a result, we will get a more perfect field of science, which will be able to give a more accurate and broader view of our world. And if you're lucky and scientists come across some amazing effect... (Like, if two gravitational waves on a full moon "crash" into each other at a certain angle with the right speed, then a local center of antigravity happens, oh-pa!)... then we can hope for serious scientific progress.