Seminarium KMMF "Teoria Dwoistości"

The recent detection of gravitational waves by the LIGO/VIRGO team is anincredibly impressive achievement of experimental physics. It is also atremendous success of the theory of General Relativity. It confirms theexistence of black holes; shows that binary black holes exist; that they maycollide and that during the merging process gravitational waves are produced.These are all predictions of General Relativity theory in its fully nonlinearregime.The existence of gravitational waves was predicted by Albert Einstein in 1916within the framework of linearized Einstein theory. Contrary to common belief,even the very definition of a gravitational wave in the fully nonlinearEinstein theory was provided only after Einstein's death. Actually, Einsteinhad arguments against the existence of nonlinear gravitational waves (theywere erroneous but he did not accept this), which virtually stoppeddevelopment of the subject until the mid 1950s. This is what we refer to asthe Red Light for gravitational waves research.In the following years, the theme was picked up again and studied vigorouslyby various experts, mainly Herman Bondi, Felix Pirani, Ivor Robinson andAndrzej Trautman, where the theoretical obstacles concerning gravitationalwave existence were successfully overcome, thus giving the `Green Light'for experimentalists to start designing detectors, culminating in therecent LIGO/VIRGO discovery.In this lecture we tell the story of this theoretical breakthrough. Particularattention will be given to the fundamental 1958 papers of Trautman, whichseem to be lesser known outside the circle of General Relativity experts.