On Thursday presented the discovery of gravitational waves, whose existence Einstein worked out but himself had a hard time believing. The discovery means that we have a new tool to explore the universe, a landmark on a par with the invention of the telescope.
the computer-generated image of two black holes about to collide. Photo: Ligo
Has the universe a sound ? And how would it then leave? It was the American aborigines as in former times la ear to the ground to hear the horses and other animals far, far away. And you can put your ear to the rail trail to hear trains approaching. What if we could put your ear to the universe. What would we hear? Silence, or a world full of life and movement?
The research team Ligo claimed Thursday that they heard the sound of the universe. Ligo stands for Laser Interferometer Gravitational-Wave Observatory. The waves they listen for are not sound waves, but something called gravitational waves. They announce this discovery right now is thus very well designed: it’s almost exactly 100 years ago, Einstein realized that gravity waves was a consequence of his own new theory of gravity. But Einstein himself was not sure if they really existed, or was merely a mathematical artifact.
Einstein really was a genius. But sometimes he appeared a bit like a child who had drawn up the spring in the toy car too much, only to be horrified when he saw how fast the car drove away. So it was with his theory of gravity. Einstein constructed the theory, but was long very skeptical about many of the predictions it brought with it. It truly revolutionary, while difficult to handle only with Einstein’s theory, is that the spacetime is dynamic. But the dynamics went far beyond what even an Einstein could imagine.
According to Einstein’s model universe was no longer static, but could expand. To try to stabilize the universe rummaged Einstein into a new term, the cosmological constant in his equations. Einstein’s theory predicted that there was a possibility that gravity went overboard. If you place too much matter in the same place spacetime collapses to a black hole in the center of which there is a tear in the space-time: a singularity. This was too much for Einstein, and he never thought of the black hole.
But Einstein’s equations had a life of its own, and the predictions they spawned have not gone to arrest. Among other things, it is contemplated that spectacular so-called cataclysmic events could give rise to violent gravitational waves. What is needed is a star that either collapses into a black hole and explodes as a supernova. It can also be about two black holes or two neutron stars that fall into each other. What then happens is similar to the water waves that occur when you throw a heavy stone in the middle of a pond: rumtidsväven deformed so strongly that gravity waves detaching from the system and spread in all directions in space.
is a breathtaking view , and the dream of gravitational waves has been around a long time. The American physicist Joseph Weber claimed in 1969 that he managed to prove their existence. He had constructed an aluminum cylinder that he meant vibrated at its resonant frequency each time a passing gravitational wave. He claimed that he was able to record a pair of such waves per day, but his method never won any recognition. Indirectly, however, we have witnessed the gravitational waves before. In 1993, the Nobel Prize in physics to Americans Joseph Taylor and Russell Hulse for the measurements they made in 1974 of two neutron stars that went into orbit around each other. The track changed in exactly the way you would expect from a system lose energy by radiating gravitational waves.
But no direct detection of gravitational waves have never been done before. How does it actually look when such a wave will still? When an electromagnetic wave is sweeping through the room, the charged particles to move. It’s about as our eyes work when they capture the light reflections, so that we can see. A gravitational wave seems rather directly in the room, and get distances to swell and shrink in different directions. If you meet such a wave will therefore look like the first is short and thick, long and narrow.
To detect a gravitational wave would therefore be very simple. Just two rulers perpendicular to each other. When gravitational wave passes becomes shorter one guide rail, while the other becomes longer. The problem is that these are so incredibly small changes. The room expands to a length only constitute a fraction of the diameter of a proton. Einstein thought for this reason that it would never be possible to perceive the gravity waves.
Ligo team, however, has managed to achieve a tremendous sensitivity in an ingenious way. They have constructed two vacuum tubes, perpendicular to each other. A laser beam is divided and passes through each outlet, hits a mirror, and are brought together again at the origin. Since the system is calibrated so that the pipes get out of tune. It then becomes totally black on the screen. However, if a gravitational wave passes will one tube to be extended and the other tube be shortened. The effect is further enhanced in that each tube is four kilometers long. If everything goes as it should occur is a bright spot – and then the champagne bottles can be uncorked.
Constructor working with the four-kilometer-long tubes at Ligo Observatory, near Richland in Washington, USA. Photo: Tracy Montauk / AP
Though initially not much happened. In the years 2002-2010 was a man constantly ready with cork screw, but never got to use it. Only noise was heard. It has therefore been the past five years made various upgrades to further enhance sensitivity. In September 2015 struck it on again, and then it became the jackpot immediately. Measurements officially began on 18 September, but the signal be unveiled Thursday is derived from 14 September. The months since then have been used in the best way, to analyze and re-analyze the signal to ensure that it can not be confused with a trivial event.
Ligo said to be the most sensitive instruments ever designed, so potential interference is the rule rather than the exception. It is said that sometimes pattered to the detector at very strange times, even after having filtered out the known confounding factors such as earthquakes and other seismic events. In the end, they went up on the roof and looked around him with binoculars. It turned out that when the trucks drove into the pits on a nearby road reacted to the detector. The detector is actually so sensitive that you also need to consider the radiation pressure of the laser beam, which pushes the mirror.
However, the signal from the September 14, 2015 has not been able to explain away, on the contrary, have become increasingly confident that it is the first direct detection of gravitational wave ever made. Numerical and analytical studies of Einstein’s equations have enabled an exact match to the likely astrophysical sources. To say that the conclusion is astounding is the understatement of the century. There are two black holes, which captured another in a cosmic ring game, a dance that lasted for billions of years. But the black hole is dangerous to dance: their paths destabilization of the energy is lost in the radiated gravitational energy, to eventually completely collapse.
For a few tenths of a second, for 1.3 billion years ago, gave the collision between the black holes emit more energy per unit of time than the universe gathered stars together. The system lost overall energy equivalent to three solar masses, which is incredibly much. Gravitational waves have since been moving towards us, to the end of September 14 to pass through the earth and Ligo detector.
You can not emphasize enough how amazing this discovery really is, in so many ways at the same time. Again, Einstein proved to be more right than he ever could have imagined: gravitational waves exist, black holes are real and Einstein’s field equations are valid far beyond the svagfältsapproximationer hitherto been used and tested.
Can we trust Ligo-earnings ? Ligo team has two detectors: one in Hanford, Washington, and one in Livingston, Louisiana. Both looked exactly the same signal with the delay expected. This, they say, is convincing proof that it is seen not just a smokescreen, but for real. It is the same standard as particle physics laboratory Cern used when it was discovered the Higgs boson. When did you two separate experiments along the accelerator ring, which both came to the same result. Neither Ligo or CERN can be said to have two completely independent experiments, but they still appear in both cases have done the best they could. The prestigious physics magazine Physical Review Letters, has reviewed and approved Ligo article.
The human ear has an outer ear that picks up sound waves. They led into the eardrum which vibrates. Ligo has instead two giant arms begin to vibrate when the gravitational wave passes. Ear drum vibration can be transmitted to the audio and the same applies to Ligo arms. In fact, Ligo team gladly plays the sound of the colliding black holes for those who want to hear it. It sounds like the chirping of birds, which is increasing in both frequency and amplitude as the intensification of the black hole dance, then quickly calm down when the two holes merged into one.
Ligo detectors are our two new ears to space, and more are on the way. 400 years ago saw Galileo Galilei first stars through his telescope, and after it became the world never the same again. This year could be the starting point for a similar revolution in the observational cosmology. With gravitational waves, we have gained a new tool for exploring the Universe. We have been deaf, but can now for the first time to listen to the universe. And no one really knows what more we will hear.
Michael Smedbäck is a PhD in theoretical physics.
Read more on Ligos website
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