Sounds of Silence: Listening to the Universe with Gravitational Waves

One hundred years after Einstein predicted the existence of gravitational waves on the basis
of his theory of General Relativity, LIGO announced the first observation of gravitational waves passing
through the Earth emitted by the collision of two black holes one billion three-hundred million light years
away. The detection of gravitational waves constitutes a major scientific discovery, as it permits a new
kind of observation of the cosmos, quite different from electromagnetic and particle observations. In
this talk I will review the gravitational-wave signals detected up to now by LIGO and discuss the theoretical
groundwork that allows to identify and interpret those signals. I will also highlight how those new astronomical messengers are used and will be used in the future to unveil the properties of the most extreme astrophysical objects in the universe and probe fundamental physics.