Q: What is a gravitational wave
A: A gravitational wave is a tiny ripple of spacetime that propagates in the universe at the speed of light .
These waves have been conceptualized hundred years ago by Albert Einstein, the famous physicist in the wake of his theory of general relativity.
Einstein described gravity as a distortion of space. The masses, like the Sun, for example, curve space. A bit like someone who would be on a trampoline.
If the masses are small, the deformation is small (pea on a trampoline, it does not matter). If the masses are large, the deformation is significant (one person on a trampoline, this distorts the fabric).
If the masses move and are accelerating these deformities will move and spread through space, forming gravitational waves.
We often shows these oscillations by the image of wrinkles that spread to the surface of a pond when you just throw a stone in it. More it is far more the wave becomes.
The gravitational waves that is sought are those produced by violent astrophysical phenomena such as the merger of two black holes or the explosion of massive stars.
The other is too small to hope that we can observe. But they surround us without our being aware and without consequences for us.
Q: Why is it important to reach directly detect these gravitational waves
A: Their detection would provide a direct validation of Einstein’s predictions. That would be one day to mark a milestone among physicists. And its main discoverers could cherish the hope to win a Nobel Prize.
More specifically, it would open the way for a new astronomy, “ gravitational astronomy .”
Besides the various electromagnetic means from which to observe the cosmos now, astrophysicists would have a new tool for observing the violent phenomena in the Universe. The detection of these gravitational waves would see what happens “ within “, during the merger of two black holes, for example.
For each of us, the detection of gravitational waves will not change our lives tomorrow. But technological advances to develop the wave detectors could have ultimately impact on our daily lives.
Q: How is organized the hunt for gravitational waves
A: Albert Einstein was aware that it would be very difficult to observe gravitational waves. For fifty years, it is not much happened. Then, in the 1950s, an American physicist Joseph Weber has made up his mind to flush out the building first detectors.
But in the meantime, indirect evidence of the existence of gravitational waves have been detected.
In 1974, the observation of a pulsar – a neutron star that emits an intense electromagnetic radiation in a given direction, like a lighthouse – in orbit around another star, helped deduce that these waves exist.
Russell Hulse and Joseph Taylor were awarded the Nobel Prize for Physics in 1993 for the discovery of this pulsar.
In the 1990s, the United States decided to build LIGO an ambitious observatory consists of two giant instruments, which use as a light source an infrared laser. One is in Louisiana, the other in Washington.
France and Italy did the same with Virgo, built near Pisa.
In 2007, LIGO and Virgo have decided to work together, exchanging data in real time and analyzing all the results.
In recent years, the LIGO instruments have been significant changes which required them stop.
The detector “ advanced ” LIGO started to operate in September 2015. And it is to him that all eyes are now turned.
Virgo suffered the same kind of transformations but has not yet restarted. It should start functioning in the fall.
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