35 years ago Baade and Minkowski (1954) suggested that a galaxy collision - diagnosed from the peculiar appearance of the parent object and its strong emission lines - is responsible for the strong radio-source CygA. This was the first time that gravitational interactions between galaxies were suggested to trigger nuclear activity. Over the following decades after the detection of the quasars and the gradual realization that quasars, comparable to the Seyfert phenomenon, are events at the

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... of seemingly isolated galaxies, the collision hypothesis was abandoned. Efforts concentrated on the understanding of the activity as internal processes in the host galaxies, possibly aided by infall of gas from the intergalactic medium (cf. Rees, 1978; Gunn, 1979).