  The LIGO-VIRGO collaboration has detected directly on Earth the gravitational
wave signals generated by the collision and the merger of two massive black
holes at astronomical distance. This major discovery opens up the way to
Gravitational Astronomy, which should revolutionize our comprehension of the
structure of the Universe at large scales, with notably the mechanisms of
formation of black holes and their role in the evolution of the Universe, the
likely emergence of a multi-messenger astronomy joint with electromagnetic
radiation, and a better appraisal of the status of general relativity with
respect to other fundamental interactions. The theoretical and numerical works
on the two-body problem in general relativity play a very important role when
deciphering and interpreting the gravitational wave signals.
