Gravitational waves are fluctuations of the space-time generated by energetic processes in the Universe (like the movement of waves from a stone thrown into the water). Albert Einstein predicted the existence of gravitational waves in 1916 in his general theory of relativity. Gravitational waves are generated by the motion of massive objects (such as neutron stars or black holes orbiting each other) with variable acceleration. For gravitational waves there are no barriers, they travel through everything in the Universe without problems. Their profile carries information about the process that generated them. The strongest gravitational waves are created by events such as colliding black holes, the collapse of stellar cores (supernovae), the rotation of neutron stars, and the remnants of gravitational radiation created by the birth of the Universe itself.
On 14 September 2015, the Advanced LIGO observatory detected a gravitational wave generated by merging two black holes with masses of 29 and 36 solar masses in a distant galaxy about 1.3 billion light-years away.
In 2017, the Nobel Prize in Physics was awarded to Rainer Weiss, Kip Thorne and Barry Barish for their role in the detection of gravitational waves.