Three space vehicles, separated by five million kilometers from each other, will shoot laser beams at each other across empty space in order to prove whether a theory proposed by Albert Einstein is correct
The European Space Agency did publish an announcement about a project called LISA. It is not a beautiful girl with that name, but three synchronized detectors that bear the initials of "space antenna using laser interferometry". LISA is a joint mission between NASA and the European Space Agency (ESA/NASA). NASA will provide the three space vehicles, the launch vehicle, the operations, the use of the deep space network and elements of the MtD. Whereas ESA will be responsible for the entire MDT and the three propulsion units.
Lisa's goal is to hunt down Einstein's gravitational waves. It consists of three detectors that will cruise at the vertices of an equilateral triangle structure as they orbit the sun. Each of the three detectors will have floating masses. Each detector fired laser beams at the other detector. These laser beams will be used to measure slight changes in the distances between each mass, changes caused by weak gravitational waves. This mission will allow physicists to prove the existence of gravitational waves, the last part of general relativity that has not yet been proven true.
Gravitational waves
Einstein's theory of general relativity predicts that movements of masses create vibrations that move through space-time at the speed of light. These gravitational waves are created a lot in the universe and they spread in the entire space. Einstein's theory of relativity predicts that when large objects collide, such as massive black holes, these ripples propagate through space-time.
Measuring these waves will add an important layer and a new way to investigate what is happening in the universe: instead of investigating the expansion and particles and conventional fields in space-time, as scientists have done until now, Lisa will feel the ripples and vibrations in the fabric of space-time itself. Investigating this new form of energy will convey rich and new information about the behavior, structure and history of the universe. Of course, this research will open new horizons for physics itself. The assumption is that when we can measure the gravitational waves and observe them with measuring means, they will provide a new, unique and powerful tool for the study of the universe. It will be a means of research for extreme situations occurring in the universe, from the big bang to black holes.
It is possible that gravitational waves could even help answer deep and disturbing questions arising from Einstein's view of the universe: What drives the Big Bang? What happens to space and time inside black holes? And a particularly troubling question in recent years, what is that mysterious dark energy accelerating the expansion of the universe?
Why is it important to measure gravity waves in the sky and not in the land?
The LISA mission will aim to discover, measure and observe gravitational waves from astronomical sources such as massive black holes and especially galactic binary star systems in the very low frequency range. LISA will consist of three spacecraft that will act as a giant interferometer in the sky with an arm length of five million kilometers. The plane that will be spread by the three space vehicles - an equilateral triangle - will consist of a very large gravitational wave antenna. And so LISA will be the largest detector ever built.
It is not possible to obtain a gravitational wave detector and antenna on Earth with a distance of five million kilometers... therefore the range of low frequencies, i.e. the long wavelengths, of Lisa is inaccessible for interferometers located on the ground. Interferometers on the ground are physically limited in length to two kilometers. This limits their coverage to frequencies that include events such as supernovae core collapses and neutron star binary mergers. In addition, on the ground on Earth there is local gravitational noise, which results from atmospheric effects and seismic activity. In LISA's low frequency band, it will detect signals from many astronomical sources that are inaccessible to detectors on Earth.
How does Lisa work?
Lisa contains two elements for detecting and measuring gravitational waves:
- Masses floating undisturbed in any of the three spacecraft: the perturbations to the masses should be small enough. Otherwise the resulting movements will be greater than the visible changes in the gravitational waves that we want to detect. The masses are protected from disturbances by the fact that they are in free fall, when there is instrumentation around them that constantly monitors their free fall. There is a system that prevents the spacecraft from exerting forces and disturbances on the masses in free fall.
- Laser distance measurement system: The distance measurement system is an interferometric laser system. At the end of each space vehicle arm of the three, a laser operates in a "responding" manner. One space vehicle will shoot a laser beam at the other vehicle that is far away from it. The laser in the second remote spacecraft will be phase locked to the incoming beam from the first vehicle. The second space vehicle will return to the first space vehicle a laser beam with great intensity and in the same phase. When this beam returns to the original spacecraft, it hits the local laser. And so the three space vehicles will exchange laser beams between them. In the end, after each round, the impact of the lasers on the various space vehicles is compared. These laser beams will be used to measure changes in the distances between each floating mass, changes caused by weak gravitational waves.
The constellation of three spacecraft will orbit the sun in a year. During this rotation there is a Doppler shift of the observed gravity waves as a result of the orbital motion. In addition, the non-isotropic antenna pattern of the detectors causes amplitude modulation of the gravitational waves. This allows determination of the direction of the source and verification of some of its properties. For example, it is possible to deduce the direction of the source and whether the signal is periodic and what the signal-to-noise ratio is, whether it is large. It will be possible to determine the exact location from which the gravitational wave comes with an accuracy of up to a minute of arc depending on the strength of the source.
The science behind LISA was summarized in a 2007 assessment by NASA in its program "NASA's Beyond Einstein Program: Architecture for Implementation - September 2007". The program says: "On purely scientific grounds Lisa is the most promising and least scientifically risky mission. Even under pessimistic assumptions about the percentage of events, it should provide decisive and clean tests of general relativity in the dynamic field of the strong field and be able to perform detailed mappings of the space-time near black holes. Therefore, the committee gives Lisa the highest scientific rating."
There are five types of gravitational wave sources expected to be discovered by LISA in the frequency band where LISA will have useful sensitivity, from 0.1 to 103 MHz. These are: merging massive black holes and non-rotating massive black holes (between 107 and XNUMX solar masses), compact bodies with the mass of a star. These spin into supermassive black holes in galactic nuclei, binary systems of compact objects and possibly background bursts from cosmological or astrophysical sources.
Scientists have already started building the instruments for Lisa, but the Lisa system will not be launched until 2020.
34 תגובות
Agree with A. Ben Ner from response 20 that there should be four detectors and not three. With four detectors, four triangles will be created and not one. The phenomenon will be measured in four triangles. It will make it easier to pinpoint its location in the space of the source of the waves. The additional cost is another third and you will receive a fourfold amount of information with the possibility of verifying the phenomenon. Note that even if there is a random reading in one of the detectors that does not result from a gravitational wave, there will always be a triangle of detectors (opposite the deviated detector) that will prove that it is a casual reading because a reading will not appear for it.
So the anonymous from comment 21 can laugh and insult as much as he wants but he's the wretch.
good week
Sabdarmish Yehuda
A. This is a clear prediction of relativity.
B. Listen, the assumption that there are such things as gravitational waves is based on the theory of relativity and it predicts as mentioned that their speed was exactly the speed of light - if it turns out that they exist but their speed is different from the speed of light it will be surprising and very strange - in fact it will say that the theory of relativity is wrong and another theory is the correct one and by chance creates Exactly the same phenomenon predicted by the theory of relativity. I don't know how possible it is because there is no theory that explains everything that the theory of relativity explains and yet predicts gravitational radiation at a speed different from the speed of light - if I were able to think of such a theory I would send it to an important scientific monthly before I would present it to you 🙂 .
deer
A]. Is the prediction of the speed of gravitational waves as the speed of light a conclusion of the theory of relativity or an assumption?
B]. Is it not possible that the prediction regarding the very existence of gravitational waves will come true but their speed, when measured,
Will it be different from the speed of light?
Your answer (No. 27) is worded as a dictation, but unfortunately in a way that did not make me understand the idea better.
I admit that other physicists I have discussed with you on the subject, (including my son) formulated their answer similarly to you,
In complete reliance on the theory of relativity but ignoring the possibility that the measurement results may be
variance.
Michael and Zvi
Thanks so much for the detailed answers!
deer
In your response No. 6, you rejected Daniel's proposal by "Many and Me" because it is possible that speed
Gravitational waves are faster than the speed of light.
I suggest not taking such a decisive position regarding a phenomenon that has not yet been measured.
If and when gravitational waves are measured, their speed will also be measured. the result
may be surprising, like many discoveries in the history of science.
Are gravitational waves electromagnetic waves?
Is the answer to this question absolute and absolute for science?
Maybe just measuring their speed will help in answering this question?
Not if the gravitational waves are not waves that propagate in space like waves
A.M. rather, waves of space itself, from which there are no density waves of space,
(in a simplistic analogy to sound waves in a gaseous medium), then there is no theoretical obstacle because
Their speed will exceed the speed of light.
This is perhaps also the reason for the technical difficulty in detections and their measurement.
I would love to read comments. Thanks
Mr. Anonymous,
My decision simply stems from the fact that according to the theory of general relativity there is no doubt that gravitational waves will propagate at exactly the speed of light - since the theory of relativity is the source of the idea of gravitational waves and if it is wrong then there is no reason to think that such waves exist, it is also correct to think that if they exist they will probably behave according to the theory that predicts them.
For your other questions:
Are gravitational waves electromagnetic waves? - No, they are gravitational waves, which means they are not disturbances in the electromagnetic field but in something else (the matrix).
Is the answer to this question absolute and absolute for science? - Yes!
Maybe just measuring their speed will help in answering this question? - Irrelevant!
It is very difficult for me to respond to the rest of your words because they indicate a basic misunderstanding of what gravitational waves are - an understanding that stems from your lack of knowledge and not from a lack of knowledge in the scientific world - these waves are a theoretical prediction and therefore their properties (if they do exist) are known - including the speed (the speed of light) ), the nature of the disturbance (traffic jam disturbance), etc.
To all my knowledgeable friends
I usually identify myself as A. Ben-Ner when I respond from my computer.
I wrote the previous response (No. 25) from the computer in the entrance lobby of the Shenkar building
(Physics) at Tel Aviv University. And here I saw that this computer identifies itself as:
"By an anonymous (unidentified) user". It is possible, then, because a large number respond in this name
of "knowers", who are some and who are others. Please refer accordingly below. A. Ben-Ner
deer
In your response No. 6, you rejected Daniel's proposal by "Many and Me" because it is possible that speed
Gravitational waves are faster than the speed of light.
I suggest not taking such a decisive position regarding a phenomenon that has not yet been measured.
If and when gravitational waves are measured, their speed will also be measured. the result
may be surprising, like many discoveries in the history of science.
Are gravitational waves electromagnetic waves?
Is the answer to this question absolute and absolute for science?
Maybe just measuring their speed will help in answering this question?
Not if the gravitational waves are not waves that propagate in space like waves
A.M. rather, waves of space itself, from which there are no density waves of space,
(in a simplistic analogy to sound waves in a gaseous medium), then there is no theoretical obstacle because
Their speed will exceed the speed of light.
This is perhaps also the reason for the technical difficulty in detections and their measurement.
I would love to read comments. Thanks.
questionnaire
I'm afraid you've made a salad of several topics, so I'm having trouble answering you.
In the meantime, we have not yet seen gravitational radiation, so there is nothing to talk about its gravitational decay - such a phenomenon may exist, but I am not aware of any discussion about it.
Gravitational radiation as described in the article is quite different from gravitational dimming which is an optical phenomenon and they know how to calculate very well what happens when the light source passes not directly behind the lens - in fact what will happen is a non-infinite increase in the intensity of the light (as would happen if the source passed directly behind the lens).
21 - I really liked your response. It's just that you didn't specify whether it was a grand piano - or a domestic one? Please specify.
The question is over:
If we observe gravitational blur when the light source is not in a straight line
Behind the center of the curved body (and we the viewers), does this mean that the light observed around that body will reach us in different instances like in a giant interferometer?
And if this is possible, is it possible to understand something about the gravity waves that cause the irradiance?
Thanks.
A. Ben Ner, you are very wrong. Should include not 4 vertices but 58.3 double piano.
And I would also recommend you to look for life there if you don't have any on Earth.
The question is over
It seems to me that the experiment should include 4 vertices and not just 3. in order to have a uniform sensitivity for all
Closer to space. is not it ?
sympathetic,
As far as I understand Michael is right about the reason for the location of three detectors:
Furthermore:
Gravitational radiation is not equivalent to electromagnetic dipole radiation - but rather to quadrupole radiation, for a very simple reason:
The relevant point of reference in the case of masses is the center of mass, under this definition since there is no negative gravitational charge, there will inevitably never be a gravitational dipole and the highest moment will be the quadrupole moment (another factor in lowering its strength). Note that the determination of the coordinate system according to the center of mass system is the natural determination according to the law of conservation of momentum which has a tremendous meaning (I assume you know that it actually derives from the symmetry of the world for displacements).
By the way, a source of gravitational radiation must not be spheric (according to a law called Birkhof's theorem)
This answers both your question about the binary pulsar and about the impossibility of a radiating accelerated particle (as Michael pointed out) - by the way, I don't know how to intuitively explain (maybe I'll have enough time to go through the course notebooks again tonight and try to find an explanation) why but the radiation intensity in the case of a binary pair does not go like the second derivative of the moment of inertia (corresponding to the acceleration) but like the third derivative.
The spectrum of gravitational radiation is determined by the nature of the astrophysical source and I think that one day when gravitational waves are discovered it will turn out that there are many uncertainties regarding the interpretation of gravitational waves and their spectrum.
Finally, as for the Newtonian limit - I have never heard of a Newtonian approximation of gravitational radiation - in fact gravitational radiation is itself a linear approximation (first order) of non-linear equations. Under the 0th order approximation (which I think corresponds to the Newtonian limit) you get a situation where there are no gravitational waves at all because Trika is simply flat.
sympathetic:
I don't know how to answer all your questions, but I will try to answer some of them (Zvi should also go online at this point):
The three satellites are necessary to determine the direction of the radiation source (and it says that this is what they intend to do).
Even a single body that is accelerated creates gravitational waves, but what reason can there be for its acceleration if not the existence of another body?
It should be remembered that in order for the gravity waves to be strong, the accelerations will also be strong, therefore the two bodies must be close.
Beyond that, another advantage of gravitational waves created by two bodies orbiting each other rapidly is the fact that they repeat themselves many times - which increases the chances of detection.
Noam:
The answer to your question is of course the word "conceit"
Amichai
Gravity is not radiation that propagates in waves, but it can be shown that a small perturbation of the gravitational field turns Einstein's equations into a wave equation. Therefore, small perturbations of the gravitational field will proceed in the form of a wave. All this in analogy to the progress of electromagnetic interference. Unlike electromagnetic radiation, Einstein's equations are not linear and only under linearization (i.e. a small disturbance) do they take on the character of wave equations. I don't know if Einstein was right or wrong, but it is appropriate to understand what he said before assuming that he was wrong. In addition, there is considerable experimental evidence that confirms the theory of general relativity. Regarding Newton's laws, the situation is not the same even in cases where relative effects can be neglected.
Amichai,
Please explain what brings you to Luther's nonsense here about the special and general theory of relativity that has been confirmed by so many observations and experiments?
sympathetic:
In my opinion, it is necessary and appropriate to assume that gravitational waves will not be detected.
We will have to accept that gravity is not radiation that spreads in waves.
It is possible that as a result we will have to separate from general relativity and find an alternative theory of gravity.
Another implication will be to upgrade the accepted wave theory again, which means replacing special relativity as well.
(In such a state of affairs, it is clear that analogies of the type you brought up are not relevant.)
Although we have already gotten used to Einstein, I am sure that when this happens everyone will eventually get used to it.
including Dr. Gali Weinstein.
I would appreciate it if someone could answer.
Why are there three detectors and two are not enough?
Is radiation through gravitational waves of a binary pulsar analogous to dipole radiation in an electromagnetic field?
Why is there no radiation from a single charge, i.e. a single star, in analogy to the radiation emitted by an accelerated charged particle in the electromagnetic case?
What determines the spectrum of gravitational waves?
What happens to gravitational waves in the Newtonian limit?
Thanks.
A comprehensive answer to those who asked above: the existence of gravitational waves is a direct consequence of the theory of general relativity and in fact an unavoidable consequence of all relativistic theories of gravity with finite propagation velocities. Maxwell's electromagnetic theory predicted electromagnetic waves and Einstein's general theory of relativity and relativistic gravity theories predict the existence of gravitational waves. Gravitational waves propagate through space-time while others create ripples in the geometry of space-time. The role of gravitational waves in gravitational physics is like the role of electromagnetic waves in physics. The importance of the discovery of gravitational waves is mainly that they can be used to study fundamental physics and cosmology, especially black hole physics and ancient cosmology.
According to the binary pulsar theory of relativity, a binary star should emit energy in the form of gravitational waves. The loss of energy is expressed in a smaller orbit and a shorter orbital cycle. Observed some relativistic binary pulsar for thirty years and found that it was indeed consistent with the relativistic prediction of gravitational radiation emission. But Rabak, what if we discover gravitational waves?... That's why they started building gravitational wave detectors. And what are they? Usually amplitude sensors, not energy sensors. They sense frequency characteristics. Then ground sensors and space sensors arose and tried to time the pulsars and methods to test the cosmic background radiation in the microwave field. And what are you looking for? After all, in electromagnetic waves we have radio waves and microwave waves and waves in the visible range. Gravitational waves also arrive in the same way at all kinds of frequencies. A detector has been designed for each frequency.
And here we come to dark energy. Dark energy models can be tested by gravitational waves. Observations on a supernova of the type…. show that our universe is currently undergoing accelerated expansion. That is, the gravitational constant is not zero. It is now expected that gravitational waves from binary black holes can be used to learn about the accelerated expansion of the universe. The amplitude, frequency and flicker rate of the binary can be measured from the observation of the gravitational wave. The illumination distance is deduced (the maximum distance from which light can reach us) and there is a red shift.
So how does all this even have anything to do with the lady Lisa I wrote the article about above? Lisa Danan is very accurate regarding the illumination distance and Lisa has a very high signal to noise ratio. And this helps determine an equation called the dark energy equation of state. A high signal-to-noise ratio gives high angular resolution and this allows redshift determination. Lisa is also a dark energy measurer and is able to determine the parameters (illumination distance) in the equation of state of the dark energy with a high level of accuracy.
Hope I explained well :).
Kudos to this site that uploads interesting materials and not yellow trash, reality TV, celebrities and everything related to the Israeli subculture that brings our children towards me even less
well done !
Dr. Gali Weinstein
Kvalies tóna nisht mágé a bisl kneidels
Dr. Gali Weinstein
You will hear!
Nicht du qualies!
LISA is the direct continuation of LIGO, which is a national observatory for measuring gravitational waves - it consists of two different facilities in the USA (on the east and west coasts), each of which fires two perpendicular lasers over long distances and then brings them together and measures the interference pattern.
The idea is that gravitational waves cause movements in space-time, so if a gravitational wave passes through the earth, it will cause a change in the distance that the laser will have to travel (along one axis, but not perpendicular to it) and will therefore result in a change in the interference pattern. The point is that gravitational waves are also limited in their speed, therefore there will be a time difference between the recording of one observatory and the *exactly same* recording in the other observatory, and then it can be concluded that a gravitational wave has passed.
The main disadvantage of LIGO is the sensitivity of the lasers to the interferences originating from the DHA, and of course the short distances at our disposal (each arm is 4 km long). LISA is designed to solve all these problems (but presents other problems such as satellite orbit drift over time) and is considered the great hope in the field of gravitational waves
Zvi - thank you. Unfortunately, I don't have any additional information other than the fact that I was very surprised when I read that article - ten years ago - and that's why I remember it. This may have been written by sensation-seekers and has no scientific basis. I would love to get another opinion.
Daniel,
The description you provided is not informative enough and there is a chance that this is a one-off article that fell apart as quickly as it appeared.
As far as I know - with a very high degree of certainty, gravitational waves moving at a speed higher than the speed of light are not known.
After all, the gravitational waves discussed in the article here move exactly at the speed of light
Question - about ten years ago I read about gravitational waves moving in the universe at a speed higher than the speed of light - are these the same gravitational waves in the article? Is it possible? Thanks in advance.
Mickey,
As a result, there is always a theoretical possibility that gravitational waves will not be found, but this possibility will probably not be realized.
Gravitational waves are one of the fundamental predictions of the theory of relativity, which has already been proven in countless experiments - to this day, gravitational waves have not been detected directly, since their power is very small (according to Wikipedia - the power of the gravitational waves emitted by the Sun during its rotation around the Sun is equivalent to an energy of 200 watts - two and a half standard light bulbs).
Indirect proof of the existence of gravitational waves was already found in 1974 in the form of the approach of two neutron stars to each other (the gravitational system loses energy and this exactly in accordance with the predictions of gravitational radiation) - a discovery following which the Nobel Prize was awarded in 1993 to a pair named Halls and Taylor (http://en.wikipedia.org/wiki/Hulse-Taylor_binary) - the awarding of a Nobel Prize for something usually indicates that it is proven with a very large degree of certainty (unless you are an American president receiving a Nobel Peace Prize).
Note that from the moment the detector is built we will still have to wait for a gravitational event large enough to pick up the gravitational waves and this can take time.
Gideon,
Like many other things, it may not contribute to your bank account and certainly not on the immediate level - on the other hand there are many other things that will not contribute to your bank account and yet a lot of money is invested in them.
jelly,
You mentioned that the discoveries of gravitational radiation can have many implications for understanding the nature of dark energy - could you elaborate (I will certainly understand if you tell me that you are not that knowledgeable on the subject and simply quoted some article - I know how much such knowledge requires specific expertise).
Will all this contribute to my bank account.
Let me give you an answer from a philosopher who knows nothing about any experiment carried out in the field.
Let's say there is a theory and the theory predicts something and we are going to perform an experiment. The experiment does not find what the theory predicts. Does it say anything about the theory? According to Karl Popper, the theory should be discarded if a refutation is found. That is, if we find a decisive experiment whose result will contradict the prediction of the theory... we throw the theory away. Of course this is an extreme statement and we always try to save a theory. Women hang here and hang there... but we will go to the extremes. After all, in our country, everything is extreme, isn't it? 🙂 Now suppose we perform an experiment to see if we can discover something that the theory predicts. And the experiment does not find what the theory predicts. There is no unequivocal rebuttal. But we just couldn't find out... what do we do in such a case? They will come and claim that it's because of interference or the measuring device and all... Then they try to perform a more elaborate experiment, maybe next time... Maybe because it's hard to separate from Einstein 🙂
I wonder what it means for Einstein's theory of relativity if no gravitational waves are found