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Huge jolt in the scientific world for a major discovery in store at the top of the biggest breakthroughs of knowledge. For the first time, vibrations from outer space and a strange kind were detected on Earth, confirming a prediction of Albert Einstein a century old.
These tremors, called “waves gravitational “compress and expand at the speed of light in space-time around us, as its does with the air. ” Or like veal in aspic quivers when shaken “, likes to say Thibault Damour, a specialist in general relativity at the Institute of Advanced scientific studies in Bures-sur-Yvette (Essonne). Space-time, that is to say the very fabric of the world we live in, is an elastic container, which may undulate like the ripples on the surface of water disturbed by the launch of a pebble.
the detection of this first cosmic lapping is detailed in the journal Physical review Letters of 11 February by the team of the LIGO instrument, the United States in collaboration with those of Virgo detector essentially Franco-Italian and built near Pisa, and GEO600, Germany. “This detection is the beginning of a new era of astronomy of gravitational waves has now become a reality,” , launched Gabriela Gonzalez, spokeswoman for the LIGO team professor astrophysics at Louisiana State University.
Finishing
the researchers spotted the tiny effect of the passage of such a wave, which has the amazing ability to distort distances to lengthen or reduce slightly. No other wave can do. The effect is small, on the order of a variation of ten-thousandth the size of an elementary particle (about 10 -19 m). In other words, as if the nearest star, Proxima Centauri, which is more than four light-years from Earth, approached us with a hair semidiameter …
To measure such a tiny distance, the researchers constructed twenty years of “amplifiers” giants. LIGO is thus made of two perpendicular tunnels four kilometers long each. Inside, two laser beams, perfectly synchronized with each other, conduct dozens of back and forth between the mirrors. Then these two beams are recombined at the output to verify synchronization. If a gravitational wave shakes the space-time and spreads far, it stretches a light path before the other, desynchronizing lasers.
this is what happened September 14, 2015 at 11 am 51 (French time) on the twin US sites built in Louisiana and Washington state in 3000 kilometers. The “seismographs” fussed with 7 milliseconds of lag. “It was too good to be true! “, recalls Jean-Yves Vinet, former head of Virgo (2007-2011), today CNRS Research Director at the Observatoire de la Cote d’Azur. But after weeks of checking, discarding any errors, confirmation arrived. “This is the culmination of a very big job. It’s exciting, “ says Eric Chassande-Mottin, CNRS researcher Astroparticle and Cosmology Laboratory.
The signal recorded by the researchers says, further, the origin of the tremor, bringing a second major discovery. This is the merger of two black holes in a new, twice as big. The duo, respectively twenty-nine and thirty-six times more massive than the Sun and located more than a billion light years from Earth. “It’s amazing. When I started this work, in the 1970s, black holes were just a hypothesis “, recalls Jean-Yves Vinet.
Even better, the researchers breathe seen these giants from which no light nor matter can escape. When two black holes come together, gravitational waves are created, maddening periodically LIGO detectors. Then, when they merge, the potato-shaped object that results do not immediately adopt a stable form. It vibrates like a bell, and shook up the cosmic jelly terrestrial sensors, differently from the previous sarabande. A new black hole being born. “The final black hole mass is 62 times that of the sun. This is less than the sum of the two black holes; the surplus was converted into gravitational waves “ says Nicolas Arnaud (CNRS) Laboratory of the linear accelerator in Orsay.
It was at this show and many others that dream to attend more often astronomers now. “This opens a great new and exciting time. The universe is driven by gravity, but it is observed that with the light. We finally see things never seen because they do not emit light said Pierre Binétruy, professor at the University of Paris VII. We change time. “” Whenever we shine a new instrument to the sky, we see and we understand new things. This was the case with Galileo pointed his telescope at Jupiter and discovering its satellites “ says Jean-Yves Vinet.
A new astronomical window
only events involving large moving objects can oscillate cosmic calf jelly. Like stars exploding as a supernova; or dying stars and contracting in the black hole or neutron stars, also called “pulsars”, which condense the equivalent of the Sun’s mass to just ten kilometers; or the violent origin of the universe in the Big Bang, there are over thirteen billion years.
This first discovery therefore opens a new astronomical window on these phenomena, expanding the spectrum means of observation after visible light, X-rays, infrared, ultraviolet, radio waves or even neutrinos (particles with almost no mass that interact with matter).
following , Virgo is currently makeover to be as accurate as his American colleague and resume service before the end of 2016. its coupling with LIGO will allow a precise location of sources in the sky. The Japanese Kagra complete; Indians rely on LIGO India. And researchers see even further. Terrestrial instruments are indeed limited to the observation of some massive and closer objects, relatively speaking.
The more the “pebbles” waving the space-time are bigger, the ridges the created waves are more remote and requires large arm to grasp the passage. Black holes millions of times heavier than the Sun, like the heart of our galaxy will actually invisible to LIGO and Virgo.
Rumors rustle already that the LIGO detector would be other
shaking his sleeve
the result will be to install Elisa in orbit, a kind of laser beams triangle whose ” arm “one million kilometers throughout budge under the effect of gravitational waves. Launch planned in the 2030s The European Space Agency has orbited, December 3, 2015, LISA Pathfinder, a satellite designed to test necessary for ELISA technology.
The detection of gravitational waves, as complicated as it is, is not a surprise. General relativity is reliable and proven for many years: most strange phenomena under this theory have already been observed. For example, large objects deflect the light rays, which effectively shifts the position of the stars in the sky. Or a clock slower tempo beats aloft than at the surface (essential information for correcting GPS signals).
As for gravitational waves themselves, their presence was spotted in 1978 and hailed a Nobel prize in 1993: the rotation of two pulsars detected in 1974 and turning around was accelerating because of the emission of gravitational waves between the two objects. However, these waves had never been experienced on Earth. Rumors already rustle on the fact that LIGO would be other shocks in his bag.
While there is no doubt that the Nobel Prize will crown this discovery, the winners will be difficult to choose . The American Rainer Weiss of MIT is responsible, in the 1970s, the first detailed studies on the challenges for future instruments. Kip Thorne, charismatic American physicist, has pushed for the realization of LIGO in the 1990s Ronald Drever, a Scot, was one of the key ideas for increasing the power of lasers. European side, the French Alain Brillet and Italian Adalberto Giazotto have contributed to optical and mechanical techniques for the proper functioning of Virgo. And, of course, the spokesman for LIGO, Gabriela Gonzalez, or Virgo, Fulvio Ricci, are also in the running. What still shake the scientific landerneau
Read also:. On the track of gravitational waves
A century of waiting
Albert Einstein by his dual theory of relativity (1905) and General (1915) upset the intuitive notions of time, space and energy.
According to the first theory, the full and proper description of the universe must not separate the time and positions in space but considered together: a point in space-time is actually an event, that is to say a position attached to a time. The absolute time does not exist. It depends on the relative speeds between observers, for example. . A clock that displays a moving time passes more slowly than another immobile
A second consequence of the theory is that this space is structured by the gravitational force: heavy objects bend the space-time, like a ball goes into a taut sheet. In return, the structure of space-time forces the matter and light to follow her curves. It is in this elastic space we live and spread the gravitational waves that distort the distances, as the sound is a compression of the air.
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