The discovery announced by Harvard University is the one hoped for by the scientists of all the world: the BICEP2 (Background Imaging of Cosmic Extragalactic Polarization) experiment has detected the gravitational wave in the perturbations of the cosmic microwave background (CMB) radiation existing in the universe. It’s a kind of echo from the period of what is called cosmic inflation, which occurred immediately after the Big Bang.

The idea of cosmic inflation was developed independently in the late ’70s and early ’80s by Alexei Starobinski and Alan Guth. It expects that an extremely small fraction of second after the Big Bang the universe expanded very rapidly in a very short time, another extremely small fraction of a second.

This very brief cosmic inflation was enough to make the universe very homogeneous, as is also evident from the last map. This is indirect evidence, instead detecting the gravitational waves created during the period of inflation would have been a smoking gun.

The BICEP and the subsequent BICEP2 experiments were carried out precisely in order to detect these gravitational waves. In simple words, the scientists led by astrophysicists John Kovac and Chao-Lin Kuo examined the different strength of the gravitational waves at different wavelengths. This allowed them to distinguish gravitational waves from density fluctuations in the universe.

Because of the homogeneity of the universe the detection of gravitational waves has been difficult and required very sophisticated instruments. In fact, the BICEP2 experiment’s instruments are located at the South Pole, where the environmental conditions make those observations simpler.

Inevitably, the full results are complex but the essence is that they have a degree of probability of being correct extremely high. In scientific terms, it’s an almost unassailable proof, the best you can get in a world where nothing can be taken for granted.

This is an important result because it proves that the structure of the universe is really due to cosmic inflation. Now astrophysicists are investigating directly a time when the universe was just born, when it was still opaque. This will allow to create more accurate models of the evolution of the universe to also understand what will happen to it in the future.

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