Gravitational waves

Gravitational Waves: A new area in the observation of space

February 11th 2017 will remain an important date for humanity. On this day, the American Collaboration Laser Interferometer Gravitational-Wave Observatory (LIGO) officially announced the first detection of gravitational waves detected September 14th 2015, at approximately 9:50 am. The gravitational waves came from the fusion of two black holes. This fusion released an unimaginable amount of energy in only 20 milliseconds. This event released an amount of energy equal to 3.6*1049 watts which represents more energy than all the energy produced by stars in the entire observable universe (sphere of 13.8 billion light years). The result of this event created a black hole with a mass of 62 Suns (Gravitational wave page 128). Space time was then violently shaken which generated gravitational waves that traveled one billion and three hundred millions years to reach us. Albert Einstein was therefore right; he was the first one to dream in 1916 about gravitational waves after the creation in 1916 of his gravitational theory (YouTube). This dream was not a hallucination and this is one more reason to know more about gravitational waves.

Scientists verified in many ways the General Relativity discovered by Einstein. The Newton's law of universal gravitation works perfectly in many cases. However, when the gravitational field becomes too intense calculations start to become wrong. The General Relativity that describes the curvature of the space-time brought a solution to this problem. Thanks to this theory we understood why the period of revolution of Mercury was wrong when calculated with Newton’s theory. Among the numerous advantages that Einstein’s theory had to offer, it was capable to predict events of a new kind. Thus, scientists were able to predict events such as black holes, neutron stars, or gravitational waves before we made observations.

According to General Relativity, stellar bodies are attracted to one another not because of a force but because of the curvature they inflict on the space-time. Indeed, our world is composed of three dimensions of space (x, y, z) and one of time. A gravitational wave is a deformation of space time. Calculations undertaken by Einstein on his theory let him think that gravitational waves could occur during very energetic events such as the fusion of two black holes or the collision of a neutron star couple. A neutron star is a celestial object with a small radius and a very high density. However, at this period of time no concrete observation had been made, neutron stars and black holes are only theoretical mathematical objects. It was necessary to wait until 1974 for the discovery of the pulsar couple (PSR B1913+16) and the work undertaken by Russell Hulse and Joseph Taylor (“PSR B1913+16.”), a pulsar being a neutron star that rotates quickly on itself at a steady rhythm(YouTube). When those two scientists found that this pulsar couple was losing energy, the only explanation of this phenomenon was the emission of gravitational waves. Both received in 1993 the Nobel price of physics and their work gave a serious clue to the scientific community.

In 1994, the United States and Europe decided to start the construction of a two detectors able to detect gravitational waves(YouTube). The difficulty to overcome was gigantic, gravitational waves emit a length deformation of 10-20 meter which is the

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