Until last year, Victor Cardoso was linked to the international experience of detection of gravitational waves in the United States, which runs the LIGO observatory, the Laser Interferometer Gravitational-Wave acronym Observatory. That connection existed through the University of Mississippi, which in 2007 created with another colleague a group to participate in the LIGO. But as in recent years the Portuguese physicist won two European superbolsas totaling 2.5 million euros, to investigate Einstein’s equations with the help of a supercomputer, your group on IST grew and, in 2015 ceased to be connected to the University of Mississippi and LIGO. Gravitational waves, including the issue of black holes, very massive stars that died and gave super-dense objects are part of their investigations on the Einstein equations.
Why the detection of gravitational waves is a major scientific news? Why is it so important to be able to detect them?
for many reasons. Gravitational waves are (were) the Holy Grail of physics. They were provided for about a hundred years by Einstein, but have never been detected here on Earth. So this effort is, I think, the longest ever in search science with a theoretical prediction. ! This is really the event of the last century in science
But this demand has other peculiarities: a few years after he predicted gravitational waves, Einstein rejected them, saying that after all perhaps could be an artifact of the calculations . Because of this, only decades later scientists such as Feynman, Bondi and Wheeler, among others, dared to broach the subject and realized that they have to be any theory that is consistent with the theory of relativity [1905, in which Einstein said that there is nothing faster than light] has to predict a maximum propagation speed. Therefore, gravity also has, and this “thing” that carries information about the severity is called “gravitational wave”. It was so in the 1960s began to build the first devices to detect these waves. We are for almost 60 years it!
Finally, despite all of us being convinced that the waves there, there’s nothing like the evidence. And this probe now paves the way for much, because it will be a completely new and different way of looking at our entire universe. These waves travel almost freely from the place where they are produced to us, so we have access to what is happening in the vicinity of black holes, neutron stars and even the beginning of the Universe!
What exactly are these waves, also known as “Einstein’s messengers”?
They are Einstein’s messengers because they carry information about Einstein’s theory. This theory tells us just how gravity works, from the way a stone falls on Earth to how two black holes collide with each other. Albert Einstein was the first person to realize that there had to be a way of gravity propagate and build a solid theory based on this principle (though even Newton have already thought about it). For example, what happens if suddenly the sun disappear? According to Newton’s theory (which was the description of gravity by the end of 1915), we on Earth would be instantaneously affected: we left to have tides, Earth left to walk around the sun and we died all frozen. But Einstein knew that the information has a finite speed, there had to be an entity that takes the information about the disappearance of the sun. To this entity called gravitational waves. By coincidence, they propagate at the speed of light, which means that the Earth would miss the Sun about eight minutes after he disappeared.
The Einstein’s theory of relativity says that space and time they are a single tissue, a single entity, and that gravitational waves are fluctuations of this entity. A good analogy is to imagine that the universe is the fabric of a sweater. And we and everything in the universe are the painted designs on the sweater. Pulling the fabric of the shirt, the designs are more or less stretched. Yanks traveling in tissue are gravitational waves.
Maybe a simple way to think of these waves is like waves that carry forces, like any other waves. For example, if an ocean wave pass by a boat, the boat will swing (and sometimes sinks). If a gravitational wave passed us, does exactly the same: exerts a force on us, stretching in or compressed [in the following image, a NASA illustration of how would the gravitational waves we could see them]
<. p> Why has it been so difficult to “catch them”?
gravitational waves as the waves of the sea, they are all the more important the greater. Gravitational waves are stronger when they are created, for example, by the clash between two black holes, but as these bodies are far from us, the wave is very weak when it comes to earth (just like the sound, the more distant we are from a person speaking, weaker is the sound of that person). To get an idea, a wave of these pass through the Earth will cause the Earth’s radius [over 6350 kilometers] varies around .0000000000001 meters … This is less than the size of an atom! Why is it so difficult to catch them, and that’s why it was necessary to build such a sophisticated device as LIGO.
What kind of gravitational waves is now detected the LIGO observatory?
to detect these waves, we need big waves. Now, big waves are only produced by heavy objects and that move at high speeds, such as black holes, neutron stars or even our universe when I was growing inflationary way [in the first moments after the Big Bang, there are 13,800 million years]. In this particular case, the LIGO detects waves coming from the collision of two black holes. I understand that one of the black holes was about 29 times the mass of our Sun and the other about 36 times.
In March 2014, another group of scientists, BICEP experience 2, at the South Pole, announced that for the first time, had managed to detect gravitational waves directly. But afterwards it was found that this result was wrong and that the error was basic, if data was not removed from the interference of dust our own galaxy. Another result would refuted a large bucket of cold water in the history of gravitational waves?
agree. And the story has even more surprises: already in the 1970s there was detection of ads later found to be forged. However, it also shows the beauty of science: there is no result that is not tested. History will only keep the truth, that is, what other teams and scientists can play. That said, LIGO has been working for decades for this day, and I am convinced that this event was and what they saw was really a gravitational wave.
In the experiment BICEP 2 was thought that they had detected gravitational waves, not caused by very massive objects such as black holes, but coming from the beginnings of the universe produced by the Big Bang. The detection of primordial gravitational waves, having been confirmed, it would be more important than the waves created by massive objects? Ie the detection of primordial gravitational waves would have solved most cosmological problems?
Surely the detection of primordial gravitational waves could have illuminated some problems in cosmology, such as the existence of an inflationary period [ in the early universe] or even quantum nature of gravity. However, this detection of LIGO is, in my opinion, much more important. It shows that there are black holes colliding in our Universe, and shows that the technology works. What this means in practice is that we can now improve the technology with confidence, and the wave detection will be as trivial as picking up a telescope and look at the moon: in a few years we will be able to enjoy astronomy of gravitational waves, and see hundreds of collisions between black holes, which will allow us, for example, test Einstein’s theory, but also realize what populates the universe … And maybe have some more clues about dark matter, matter that we know only by the action of its gravity. Finally, the fact that we know that this type of technology works can, and will surely open the door to other detectors that are sensitive to primary waves, and then yes, we can learn more about the origin of the universe.
Einstein did not speak of primordial gravitational waves. Neither could have said, because at the time they developed the theory of general relativity had been the view (wrongly) that the universe was static: there had been no Big Bang and the Universe as we know it has always been and would always be so .. .
that just shows how err is human. In fact, as I said, the great beauty of science and why scientific building has endured for thousands of years is because the walls of this house only science are the bricks that other scientists check be solid. Even Einstein made mistakes, but that does not stop the progress of science, which is done through dialogue and tests and experiments, as all problems that must be solved rationally. To paraphrase Newton. Errors are not in the art, but the artists
How does the LIGO, which consists of two large detection facilities in the US, looking for gravitational waves
As gravitational waves carry the force of gravity, the easiest way to detect them is to measure the movement of objects through which they pass. Of course this is easier said than done. I connect two arms are L-shaped with a mirror at the end of each arm. Each arm has about four kilometers and within each circulates a laser beam, which is reflected in the mirror. The LIGO basically measures the variation in the laser path when it passes a gravitational wave, that is, measures the change in length of the arms of the L. Unfortunately, a gravitational wave in passing changes the length of the arms by about the size of an electron … Until aircraft or trains to pass at the foot of the detector have much greater effects. Therefore, it is necessary to isolate all too well. This L is within a tube, where it made the most perfect vacuum of the universe, and the tube is based on shock absorbers to isolate the seismic noise.
In addition, the LIGO also built another same detector separated by thousands of kilometers: one is in Louisiana and the other in Washington state. Thus, if a gravitational wave passes, it will move the four arms simultaneously (or nearly so) and the same. We’re convinced that a wave passed if both L vary in the same way and at the same time.
Almost a year ago, had said in an interview with Publico that he believed that LIGO would make first direct detection of these waves in a year or two. And that if nothing was detected until 2017, then either the universe was quite different from how we see now or Einstein’s theory was seriously wrong. Why was so “sure” that the detection of gravitational waves would happen soon?
In fact, I had a secret hope that would not be detected and that everything we think we know about the universe had to be revised. But indirect evidence existed for gravitational waves were stronger. For decades, Russell Hulse and Joseph Taylor measured very carefully the orbital motion of two neutron stars [about one another]. They measured the course of one of these stars, and saw that it was decreasing! What could cause this? If we look at our solar system, Mercury has a smaller year than the Earth, and Mercury is closer to the sun. This means that the stars Hulse and Taylor were observed approaching each other. And they remembered that perhaps it was because the system was emitting gravitational waves. As these waves carry energy, so the two stars were losing power and therefore had to get closer … and this gave them the Nobel Prize in 1993 because the prediction of Einstein’s theory corresponded very precisely to what they observed. Therefore, there was strong evidence of these waves, though they had never been measured directly, here on Earth.
The LIGO started functioning for years. Until now, I had not been able to detect gravitational waves. What has changed so that it was possible?
LIGO however got better. About two years ago, he stopped to be improved. The damping system, which isolates the L from the rest of the world became more sophisticated and even how to measure the length of variation became more sophisticated and came to the quantum limit. Less than a year, the enhanced version of LIGO put into operation and could wave measuring three times smaller than previously. And that made the difference!
As black holes and dark matter, gravitational waves are part of their research work?
My group tries to understand a more conceptual part: to detect waves that come from black holes, what does this tell us about Einstein’s theory? For example, these black holes are even predicted by Einstein’s theory? And we are sure that they are even black holes? It is this kind of issues we try to tackle now. We have a great European project among several universities approved in this area and we are submitting another specifically about gravitational waves. The coming years will be incredibly exciting and fun, no doubt about!
Given announcement that gravitational waves were finally detected, which imagines that now tell us Einstein, he who even doubted that they exist?
suppose to open a bottle of champagne and toasting the universe and its theory … As he said himself, “if ever erraste is because they never tried anything new.”
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