In the 1970's, two European groups initiated investigations into laser-interferometric GW detection. In 1975 the Max-Planck-Institut für Astrophysik in Munich started with a prototype of 3 m armlength, which later (1983), at the Max-Planck-Institut für Quantenoptik in Garching, led to a prototype with 30 m armlength. In 1977 the Department of Physics and Astronomy of the University of Glasgow began similar investigations, and in 1980 started operation of a 10 m prototype. In 1985 the Garching group proposed the construction of a large detector with 3 km armlength, the British group an equivalent project in 1986. The two groups combined their efforts in 1989 - the project GEO was born, with the Harz mountains (Northern Germany) considered an ideal site. The project was, however, not funded, because of financial problems. Thus in 1994 a smaller detector was proposed: GEO 600, to be built in the lowlands near Hannover, with arms of 600 m in length. Since September 1995 this British-German GW detector is under construction. The first test runs have been performed in 2002.
Reliable detection of GW requires the operation of at least two detectors in coincidence. In order to obtain the full information about the GW (source position, polarization), data from at least four detectors have to be compared. Thus, the GEO 600 team collaborates with the GW groups in the USA (LIGO), in France/Italy (VIRGO) and in Japan (TAMA).
GW astronomy provides a totally new look at the Universe. GWs give information on supernovae, black holes, compact binaries and the cosmic background radiation that cannot be obtained by other means. Furthermore, observation of binary systems allows to determine absolute distances and thus an accurate value of the Hubble constant.