Just a few hours ago, news arrived that had been long awaited in the scientific world. A group of scientists from several countries working as part of the international LIGO Scientific Collaboration project say that using several detector observatories they were able to detect gravitational waves in laboratory conditions.
They are analyzing data coming from two laser interferometer gravitational-wave observatories (Laser Interferometer Gravitational-Wave Observatory - LIGO), located in the states of Louisiana and Washington in the United States.
As stated at the LIGO project press conference, gravitational waves were detected on September 14, 2015, first at one observatory, and then 7 milliseconds later at another.
Based on the analysis of the data obtained, which was carried out by scientists from many countries, including Russia, it was found that the gravitational wave was caused by the collision of two black holes with a mass of 29 and 36 times the mass of the Sun. After that, they merged into one large black hole.
This happened 1.3 billion years ago. The signal came to Earth from the direction of the Magellanic Cloud constellation.
Sergei Popov (astrophysicist at the Sternberg State Astronomical Institute of Moscow State University) explained what gravitational waves are and why it is so important to measure them.
Modern theories of gravity are geometric theories of gravity, more or less everything from the theory of relativity. The geometric properties of space affect the movement of bodies or objects such as a light beam. And vice versa - the distribution of energy (this is the same as mass in space) affects the geometric properties of space. This is very cool, because it’s easy to visualize - this whole elastic plane lined in a box has some physical meaning, although, of course, it’s not all so literal.
Physicists use the word "metric". A metric is something that describes the geometric properties of space. And here we have bodies moving with acceleration. The simplest thing is to rotate the cucumber. It is important that it is not, for example, a ball or a flattened disk. It is easy to imagine that when such a cucumber spins on an elastic plane, ripples will run from it. Imagine that you are standing somewhere, and a cucumber turns one end towards you, then the other. It affects space and time in different ways, a gravitational wave runs.
So, a gravitational wave is a ripple running along the space-time metric.
Beads in space
This is a fundamental property of our basic understanding of how gravity works, and people have been wanting to test it for a hundred years. They want to make sure that there is an effect and that it is visible in the laboratory. This was seen in nature about three decades ago. How should gravitational waves manifest themselves in everyday life?
The easiest way to illustrate this is this: if you throw beads in space so that they lie in a circle, and when a gravitational wave passes perpendicular to their plane, they will begin to turn into an ellipse, compressed first in one direction, then in the other. The point is that the space around them will be disturbed, and they will feel it.
"G" on Earth
People do something like this, only not in space, but on Earth.
Mirrors in the shape of the letter “g” [referring to the American LIGO observatories] hang at a distance of four kilometers from each other.
Laser beams are running - this is an interferometer, a well-understood thing. Modern technologies make it possible to measure fantastically small effects. It’s still not that I don’t believe it, I believe it, but I just can’t wrap my head around it - the displacement of mirrors hanging at a distance of four kilometers from each other is less than the size of an atomic nucleus. This is small even compared to the wavelength of this laser. This was the catch: gravity is the weakest interaction, and therefore the displacements are very small.
It took a very long time, people have been trying to do this since the 1970s, they have spent their lives searching for gravitational waves. And now only technical capabilities make it possible to register a gravitational wave in laboratory conditions, that is, it came here, and the mirrors shifted.
Direction
Within a year, if all goes well, there will already be three detectors operating in the world. Three detectors are very important, because these things are very bad at determining the direction of the signal. In much the same way as we are bad at determining the direction of a source by ear. “A sound from somewhere on the right” - these detectors sense something like this. But if three people stand at a distance from each other, and one hears a sound from the right, another from the left, and the third from behind, then we can very accurately determine the direction of the sound. The more detectors there are, the more they are scattered around the globe, the more accurately we will be able to determine the direction of the source, and then astronomy will begin.
After all, the ultimate goal is not only to confirm the general theory of relativity, but also to obtain new astronomical knowledge. Just imagine that there is a black hole weighing ten solar masses. And it collides with another black hole weighing ten solar masses. The collision occurs at the speed of light. Energy breakthrough. This is true. There is a fantastic amount of it. And there’s no way... It’s just ripples of space and time. I would say that detecting the merger of two black holes will be the strongest evidence for a long time that black holes are more or less the black holes we think they are.
Let's go through the issues and phenomena that it could reveal.
Do black holes really exist?
The signal expected from the LIGO announcement may have been produced by two merging black holes. Such events are the most energetic ones known; the strength of the gravitational waves emitted by them can briefly outshine all the stars in the observable universe combined. Merging black holes are also quite easy to interpret from their very pure gravitational waves.
A black hole merger occurs when two black holes spiral around each other, emitting energy in the form of gravitational waves. These waves have a characteristic sound (chirp) that can be used to measure the mass of these two objects. After this, black holes usually merge.
“Imagine two soap bubbles that come so close that they form one bubble. The larger bubble is deformed,” says Tybalt Damour, a gravitational theorist at the Institute of Advanced Scientific Research near Paris. The final black hole will be perfectly spherical, but must first emit predictable types of gravitational waves.
One of the most important scientific consequences of detecting a black hole merger will be the confirmation of the existence of black holes - at least perfectly round objects consisting of pure, empty, curved space-time, as predicted by general relativity. Another consequence is that the merger is proceeding as scientists predicted. Astronomers have a lot of indirect evidence of this phenomenon, but so far these have been observations of stars and superheated gas in the orbit of black holes, and not the black holes themselves.
“The scientific community, including myself, doesn’t like black holes. We take them for granted, says France Pretorius, a general relativity simulation specialist at Princeton University in New Jersey. “But when we think about how amazing this prediction is, we need some truly amazing proof.”
Do gravitational waves travel at the speed of light?
When scientists start comparing LIGO observations with those from other telescopes, the first thing they check is whether the signal arrived at the same time. Physicists believe that gravity is transmitted by graviton particles, the gravitational analogue of photons. If, like photons, these particles have no mass, then gravitational waves will travel at the speed of light, matching the prediction of the speed of gravitational waves in classical relativity. (Their speed may be affected by the accelerating expansion of the Universe, but this should be evident at distances significantly greater than those covered by LIGO).
It is quite possible, however, that gravitons have a small mass, which means that gravitational waves will move at a speed less than light. So, for example, if LIGO and Virgo detect gravitational waves and find that the waves arrived on Earth after cosmic event-related gamma rays, this could have life-changing consequences for fundamental physics.
Is space-time made of cosmic strings?
An even stranger discovery could occur if bursts of gravitational waves are found emanating from "cosmic strings." These hypothetical defects in the curvature of spacetime, which may or may not be related to string theories, should be infinitely thin, but stretched to cosmic distances. Scientists predict that cosmic strings, if they exist, may accidentally bend; if the string were to bend, it would cause a gravitational surge that detectors like LIGO or Virgo could measure.
Can neutron stars be lumpy?
Neutron stars are the remains of large stars that collapsed under their own weight and became so dense that electrons and protons began to fuse into neutrons. Scientists have little understanding of the physics of neutron holes, but gravitational waves could tell us a lot about them. For example, the intense gravity on their surface causes neutron stars to become almost perfectly spherical. But some scientists have suggested that there may also be "mountains" - a few millimeters high - that make these dense objects, no more than 10 kilometers in diameter, slightly asymmetrical. Neutron stars typically spin very quickly, so the asymmetric distribution of mass will warp spacetime and produce a persistent gravitational wave signal in the shape of a sine wave, slowing the star's rotation and emitting energy.
Pairs of neutron stars that orbit each other also produce a constant signal. Like black holes, these stars move in a spiral and eventually merge with a characteristic sound. But its specificity differs from the specificity of the sound of black holes.
Why do stars explode?
Black holes and neutron stars form when massive stars stop shining and collapse in on themselves. Astrophysicists think this process underlies all common types of Type II supernova explosions. Simulations of such supernovae have not yet shown what causes them to ignite, but listening to the gravitational wave bursts emitted by a real supernova is thought to provide an answer. Depending on what the burst waves look like, how loud they are, how often they occur, and how they correlate with the supernovae being tracked by electromagnetic telescopes, this data could help rule out a bunch of existing models.
How fast is the Universe expanding?
The expansion of the Universe means that distant objects that move away from our galaxy appear redder than they really are because the light they emit is stretched as they move. Cosmologists estimate the rate of expansion of the Universe by comparing the redshift of galaxies with how far away they are from us. But this distance is usually estimated from the brightness of Type Ia supernovae, and this technique leaves a lot of uncertainties.
If several gravitational wave detectors around the world detect signals from the merger of the same neutron stars, together they can absolutely accurately estimate the volume of the signal, and therefore the distance at which the merger occurred. They will also be able to estimate the direction, and with it, identify the galaxy in which the event occurred. By comparing the redshift of this galaxy with the distance to the merging stars, it is possible to obtain an independent rate of cosmic expansion, perhaps more accurate than current methods allow.
sources
http://www.bbc.com/russian/science/2016/02/160211_gravitational_waves
http://cont.ws/post/199519
Here we somehow found out, but what is and. Look what it looks like The original article is on the website InfoGlaz.rf Link to the article from which this copy was made -On February 11, 2016, an international group of scientists, including from Russia, at a press conference in Washington announced a discovery that sooner or later will change the development of civilization. It was possible to prove in practice gravitational waves or waves of space-time. Their existence was predicted 100 years ago by Albert Einstein in his.
No one doubts that this discovery will be awarded the Nobel Prize. Scientists are in no hurry to talk about its practical application. But they remind us that until quite recently, humanity also did not know what to do with electromagnetic waves, which ultimately led to a real scientific and technological revolution.
What are gravitational waves in simple terms
Gravity and universal gravitation are one and the same thing. Gravitational waves are one of the solutions to GPV. They must spread at the speed of light. It is emitted by any body moving with variable acceleration.
For example, it rotates in its orbit with variable acceleration directed towards the star. And this acceleration is constantly changing. The solar system emits energy on the order of several kilowatts in gravitational waves. This is an insignificant amount, comparable to 3 old color TVs.
Another thing is two pulsars (neutron stars) orbiting each other. They rotate in very close orbits. Such a “couple” was discovered by astrophysicists and observed for a long time. The objects were ready to fall on each other, which indirectly indicated that pulsars emit space-time waves, that is, energy in their field.
Gravity is the force of gravity. We are drawn to the earth. And the essence of a gravitational wave is a change in this field, which is extremely weak when it reaches us. For example, take the water level in a reservoir. The gravitational field strength is the acceleration of free fall at a specific point. A wave runs across our pond, and suddenly the acceleration of free fall changes, just a little.
Such experiments began in the 60s of the last century. At that time, they came up with this: they hung a huge aluminum cylinder, cooled to avoid internal thermal fluctuations. And they waited for a wave from a collision, for example, of two massive black holes to suddenly reach us. The researchers were full of enthusiasm and said that the entire globe could be affected by a gravitational wave coming from outer space. The planet will begin to vibrate, and these seismic waves (compression, shear, and surface waves) can be studied.
An important article about the device in simple terms, and how the Americans and LIGO stole the idea of Soviet scientists and built introferometers that made the discovery possible. Nobody talks about it, everyone is silent!
By the way, gravitational radiation is more interesting from the position of cosmic microwave background radiation, which they are trying to find by changing the spectrum of electromagnetic radiation. CMB and electromagnetic radiation appeared 700 thousand years after the Big Bang, then during the expansion of the universe, filled with hot gas with traveling shock waves, which later turned into galaxies. In this case, naturally, a gigantic, mind-boggling number of space-time waves should have been emitted, affecting the wavelength of the cosmic microwave background radiation, which at that time was still optical. Russian astrophysicist Sazhin writes and regularly publishes articles on this topic.
Misinterpretation of the discovery of gravitational waves
“A mirror hangs, a gravitational wave acts on it, and it begins to oscillate. And even the most insignificant fluctuations with an amplitude less than the size of an atomic nucleus are noticed by instruments” - such an incorrect interpretation, for example, is used in the Wikipedia article. Don’t be lazy, find an article by Soviet scientists from 1962.
Firstly, the mirror must be massive in order to feel the “ripples”. Secondly, it must be cooled to almost absolute zero (Kelvin) to avoid its own thermal fluctuations. Most likely, not only in the 21st century, but in general it will never be possible to detect an elementary particle - the carrier of gravitational waves:
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 had been 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 the 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's an artistic depiction of the tendex lines of two black holes orbiting each other, counterclockwise, and then colliding. 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 shift relative to each other, and these displacements 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 involving 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 record 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, must have left a unique trace in the electromagnetic waves that fill the Universe - 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 advent of a 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 we have witnessed a new era, friends. This is amazing.
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Let us recall that the other day LIGO scientists announced a major breakthrough in the field of physics, astrophysics and our study of the Universe: the discovery of gravitational waves, predicted by Albert Einstein 100 years ago. Gizmodo caught up with Dr. Amber Staver of the Livingston Observatory in Louisiana, a LIGO collaboration, to ask more about what this means for physics. We understand that in just a few articles it will be difficult to achieve a global understanding of a new way of understanding our world, but we will try.
A huge amount of work has been done to detect a single gravitational wave so far, and it was a major breakthrough. It looks like a ton of new possibilities for astronomy are opening up - but is this first detection "simple" proof that the detection is possible in itself, or can you already derive further scientific advances from it? What do you hope to get out of it in the future? Will there be simpler methods for detecting these waves in the future?
This is really a first discovery, a breakthrough, but the goal has always been to use gravitational waves to do new astronomy. Instead of searching the Universe for visible light, we can now sense subtle changes in gravity that are caused by the biggest, strongest, and (in my opinion) most interesting things in the Universe - including some that we could never know about with with the help of light.
We were able to apply this new type of astronomy to the first detection waves. Using what we already know about GTR (general relativity), we were able to predict what gravitational waves from objects like black holes or neutron stars are like. The signal we found matches that predicted for a pair of black holes, one 36 and the other 29 times as massive as the Sun, swirling as they approach each other. Finally, they merge into one black hole. So this is not only the first detection of gravitational waves, but also the first direct observation of black holes, because they cannot be observed using light (only by the matter that orbits around them).
Why are you sure that extraneous effects (like vibration) do not affect the results?
In LIGO, we record much more data related to our environment and equipment than data that might contain a gravitational wave signal. The reason for this is that we want to be as confident as possible that we are not being fooled by extraneous effects or misled into detecting a gravitational wave. If we sense abnormal soil when a gravitational wave signal is detected, we will most likely reject this candidate.
Video: Gravitational waves in a nutshell
Another measure we take to make sure we don't see something random is to have both LIGO detectors see the same signal within the amount of time it takes for the gravitational wave to travel between the two objects. The maximum time for such a trip is approximately 10 milliseconds. To be sure of possible detection, we must see signals of the same shape, at almost the same time, and the data we collect about our environment must be free of anomalies.
There are many other tests that a candidate takes, but these are the main ones.
Is there a practical way to generate gravitational waves that can be detected by such devices? Will we be able to build a gravitational radio or laser?
You are proposing what Heinrich Hertz did in the late 1880s to detect electromagnetic waves in the form of radio waves. But gravity is the weakest of the fundamental forces that hold the Universe together. For this reason, the movement of mass in a laboratory or other facility to create gravitational waves will be too weak to be detected even by a detector such as LIGO. To create strong enough waves, we would have to spin the dumbbell so fast that it would rip through any known material. But there are many large volumes of mass in the Universe that move extremely quickly, so we are building detectors that will search for them.
Will this confirmation change our future? Will we be able to use the power of these waves to explore outer space? Will it be possible to communicate using these waves?
Due to the amount of mass that must move at extreme speeds to produce gravitational waves that detectors like LIGO are able to detect, the only known mechanism for this is pairs of neutron stars or black holes spinning before merging (there may be other sources). The chances that it is some advanced civilization manipulating matter are extremely low. Personally, I don't think it would be great to discover a civilization capable of using gravitational waves as a means of communication, since they could easily kill us off.
Are gravitational waves coherent? Is it possible to make them coherent? Is it possible to focus them? What will happen to a massive object that is affected by a focused beam of gravity? Could this effect be used to improve particle accelerators?
Some types of gravitational waves can be coherent. Let's imagine a neutron star that is almost perfectly spherical. If it rotates quickly, small deformations of less than an inch will produce gravitational waves of a certain frequency, which will make them coherent. But focusing gravitational waves is very difficult because the Universe is transparent to them; gravitational waves travel through matter and come out unchanged. You need to change the path of at least some of the gravitational waves to focus them. Perhaps an exotic form of gravitational lensing could at least partially focus gravitational waves, but it would be difficult, if not impossible, to harness them. If they can be focused, they will still be so weak that I can't imagine any practical use for them. But they've also talked about lasers, which are essentially just focused coherent light, so who knows.
What is the speed of a gravitational wave? Does it have mass? If not, can it travel faster than the speed of light?
Gravitational waves are believed to travel at the speed of light. This is the speed limited by general relativity. But experiments like LIGO should test this. Perhaps they move a little slower than the speed of light. If so, then the theoretical particle associated with gravity, the graviton, will have mass. Since gravity itself acts between masses, this will add complexity to the theory. But not impossibility. We use Occam's razor: the simplest explanation is usually the most correct.
How far do you need to be from a black hole merger to be able to talk about them?
In the case of our binary black holes, which we detected from gravitational waves, they produced a maximum change in the length of our 4-kilometer arms of 1 x 10 -18 meters (that's 1/1000 the diameter of a proton). We also believe that these black holes are 1.3 billion light years from Earth.
Now suppose that we are two meters tall and we are floating at the distance of the Earth to the Sun from the black hole. I think you'd experience alternating flattening and stretching of about 165 nanometers (your height changes by more throughout the day). This can be survived.
In a new way to hear the cosmos, what are scientists most interested in?
The potential is not fully known, in the sense that there may be many more places than we thought. The more we learn about the Universe, the better we will be able to answer its questions using gravitational waves. For example, these:
- What causes gamma-ray bursts?
- How does matter behave under the extreme conditions of a collapsing star?
- What were the first moments after the Big Bang?
- How does matter behave in neutron stars?
But I'm more interested in what unexpected things can be discovered using gravitational waves. Every time people observed the Universe in a new way, we discovered many unexpected things that turned our understanding of the Universe upside down. I want to find these gravitational waves and discover something that we had no idea about before.
Will this help us make a real warp drive?
Since gravitational waves interact weakly with matter, they can hardly be used to move that matter. But even if you could, a gravitational wave only travels at the speed of light. They are not suitable for warp drive. It would be cool though.
What about anti-gravity devices?
To create an anti-gravity device, we need to turn the force of attraction into a force of repulsion. And although a gravitational wave propagates changes in gravity, the change will never be repulsive (or negative).
Gravity always attracts because negative mass doesn't seem to exist. After all, there is positive and negative charge, a north and south magnetic pole, but only positive mass. Why? If negative mass existed, the ball of matter would fall up instead of down. It would be repelled by the positive mass of the Earth.
What does this mean for the ability to time travel and teleportation? Can we find a practical application for this phenomenon, other than studying our Universe?
Currently, the best way to travel in time (and only to the future) is to travel at near-light speed (remember the twin paradox in General Relativity) or to go to an area with increased gravity (this kind of time travel was demonstrated in Interstellar). Because a gravitational wave propagates changes in gravity, it will produce very small fluctuations in the speed of time, but since gravitational waves are inherently weak, so are the time fluctuations. And while I don't think this can be applied to time travel (or teleportation), never say never (I bet it took your breath away).
Will there come a day when we stop validating Einstein and start looking for strange things again?
Certainly! Since gravity is the weakest of the forces, it is also difficult to experiment with. Until now, every time scientists tested general relativity, they received exactly predicted results. Even the discovery of gravitational waves once again confirmed Einstein's theory. But I believe that when we start testing the smallest details of the theory (maybe with gravitational waves, maybe with something else), we will find “funny” things, like the experimental result not exactly matching the prediction. This will not mean that GTR is erroneous, only the need to clarify its details.
Video: How did gravitational waves blow up the Internet?
Every time we answer one question about nature, new ones arise. Eventually we will have questions that are cooler than the answers that general relativity can provide.
Can you explain how this discovery might relate to or affect unified field theory? Are we closer to confirming it or debunking it?
Now the results of our discovery are mainly devoted to testing and confirming general relativity. Unified field theory seeks to create a theory that explains the physics of the very small (quantum mechanics) and the very large (general relativity). Now these two theories can be generalized to explain the scale of the world in which we live, but no more. Because our discovery focuses on the physics of the very large, on its own it will do little to advance us toward a unified theory. But that's not the question. The field of gravitational wave physics has just been born. As we learn more, we will certainly expand our results into the realm of unified theory. But before you run, you need to walk.
Now that we're listening to gravitational waves, what do scientists have to hear to literally blow a brick? 1) Unnatural patterns/structures? 2) Sources of gravitational waves from regions that we thought were empty? 3) Rick Astley - Never gonna give you up?
When I read your question, I immediately thought of the scene from Contact in which the radio telescope picks up patterns of prime numbers. This is unlikely to be found in nature (as far as we know). So your option with an unnatural pattern or structure would be most likely.
I don't think we will ever be sure that there is a void in a certain region of space. In the end, the black hole system we discovered was isolated and no light was coming from the region, but we still detected gravitational waves there.
Regarding music... I specialize in separating gravitational wave signals from the static noise that we constantly measure in the background environment. If I found music in a gravitational wave, especially music that I had heard before, it would be a hoax. But music that has never been heard on Earth... It would be like with simple cases from “Contact”.
Since the experiment detects waves by changing the distance between two objects, is the amplitude of one direction greater than the other? Otherwise, wouldn't the data being read mean that the Universe is changing in size? And if so, does this confirm the expansion or something unexpected?
We need to see many gravitational waves coming from many different directions in the Universe before we can answer this question. In astronomy, this creates a population model. How many different types of things are there? This is the main question. Once we have a lot of observations and start to see unexpected patterns, for example that gravitational waves of a certain type come from a certain part of the Universe and nowhere else, this will be an extremely interesting result. Some patterns could confirm expansion (of which we are very confident) or other phenomena that we are not yet aware of. But first we need to see a lot more gravitational waves.
It is completely incomprehensible to me how scientists determined that the waves they measured belong to two supermassive black holes. How can one determine the source of the waves with such accuracy?
Data analysis methods use a catalog of predicted gravitational wave signals to compare with our data. If there is a strong correlation with one of these predictions, or patterns, then we not only know that it is a gravitational wave, but we also know what system produced it.
Every single way a gravitational wave is created, be it black holes merging, stars spinning, or stars dying, the waves all have different shapes. When we detect a gravitational wave, we use these shapes, as predicted by general relativity, to determine their cause.
How do we know that these waves came from the collision of two black holes and not some other event? Is it possible to predict where or when such an event occurred with any degree of accuracy?
Once we know which system produced the gravitational wave, we can predict how strong the gravitational wave was close to where it originated. By measuring its strength as it reaches Earth and comparing our measurements to the predicted strength of the source, we can calculate how far away the source is. Since gravitational waves travel at the speed of light, we can also calculate how long it took the gravitational waves to travel towards Earth.
In the case of the black hole system we discovered, we measured the maximum change in the length of the LIGO arms per 1/1000th of the proton diameter. This system is located 1.3 billion light years away. The gravitational wave, discovered in September and announced recently, has been moving towards us for 1.3 billion years. This happened before animal life formed on Earth, but after the emergence of multicellular organisms.
At the time of the announcement, it was stated that other detectors would look for waves with longer periods - some of them even cosmic. What can you tell us about these large detectors?
There is indeed a space detector in development. It's called LISA (Laser Interferometer Space Antenna). Since it will be in space, it will be quite sensitive to low-frequency gravitational waves, unlike earth-based detectors, due to the natural vibrations of the Earth. It will be difficult because the satellites will have to be placed further from the Earth than humans have ever been. If something goes wrong, we won't be able to send astronauts out for repairs like we did with Hubble in the 1990s. To test the necessary technologies, the LISA Pathfinder mission was launched in December. So far, she has completed all her tasks, but the mission is far from over.
Is it possible to convert gravitational waves into sound waves? And if so, what will they look like?
Can. Of course, you won't just hear a gravitational wave. But if you take the signal and pass it through the speakers, you can hear it.
What should we do with this information? Do other astronomical objects with significant mass emit these waves? Can waves be used to find planets or simple black holes?
When searching for gravitational values, it's not just mass that matters. Also the acceleration that is inherent to an object. The black holes we discovered were spinning around each other at 60% the speed of light when they merged. That's why we were able to detect them during the merger. But now there are no more gravitational waves coming from them, since they have merged into one inactive mass.
So anything that has a lot of mass and moves very quickly creates gravitational waves that can be detected.
Exoplanets are unlikely to have sufficient mass or acceleration to produce detectable gravitational waves. (I'm not saying they don't create them at all, only that they won't be strong enough or at a different frequency). Even if the exoplanet were massive enough to produce the necessary waves, the acceleration would tear it apart. Don't forget that the most massive planets tend to be gas giants.
How true is the analogy of waves in water? Can we ride these waves? Do gravitational “peaks” exist, like the already known “wells”?
Since gravitational waves can move through matter, there is no way to ride them or harness them for propulsion. So no gravitational wave surfing.
"Peaks" and "wells" are great. Gravity always attracts because there is no negative mass. We don't know why, but it has never been observed in the laboratory or in the universe. Therefore, gravity is usually represented as a “well”. The mass that moves along this “well” will fall deeper; This is how attraction works. If you have a negative mass, then you will get repulsion, and with it a “peak”. A mass that moves at the “peak” will bend away from it. So “wells” exist, but “peaks” do not.
The analogy with water is fine, as long as we talk about the fact that the strength of the wave decreases with the distance traveled from the source. The water wave will become smaller and smaller, and the gravity wave will become weaker and weaker.
How will this discovery affect our description of the inflationary period of the Big Bang?
At the moment, this discovery has virtually no impact on inflation. To make statements like this, one must observe the relic gravitational waves of the Big Bang. The BICEP2 project thought it had indirectly observed these gravitational waves, but it turned out that cosmic dust was to blame. If he gets the right data, it will also confirm the existence of a short period of inflation shortly after the Big Bang.
LIGO will be able to see these gravitational waves directly (this will also be the weakest type of gravitational waves we hope to detect). If we see them, we will be able to look deep into the past of the Universe, as we have not looked before, and judge inflation from the data obtained.
The first direct detection of gravitational waves was revealed to the world on February 11, 2016 and generated headlines around the world. For this discovery, physicists received the Nobel Prize in 2017 and officially launched a new era of gravitational astronomy. But a team of physicists at the Niels Bohr Institute in Copenhagen, Denmark, question the finding, based on their own independent analysis of the data over the past two and a half years.
One of the most mysterious objects in history, black holes, regularly attract attention. We know that they collide, merge, change brightness, and even evaporate. And also, in theory, black holes can connect Universes with each other using . However, all our knowledge and assumptions about these massive objects may turn out to be inaccurate. Recently, rumors have appeared in the scientific community that scientists have received a signal emanating from a black hole, the size and mass of which is so enormous that its existence is physically impossible.
The first direct detection of gravitational waves was revealed to the world on February 11, 2016 and generated headlines around the world. For this discovery, physicists received the Nobel Prize in 2017 and officially launched a new era of gravitational astronomy. But a team of physicists at the Niels Bohr Institute in Copenhagen question the finding, based on their own independent analysis of the data over the past two and a half years.
