The detection of gravitational waves, predicted by general
relativity, requires to detect the relative motion between masses at rest.
An interferometric setup such as the one selected by VIRGO (project between
France and Italy) or LIGO (US observatory) should have the required
sensitivity to see severe astrophysical events. This requires to be able to
control seismic noise, the thermal noise of the masses, the frequency noise
of the laser, the shot noise on the photodiode detector, and to have high
specifications on the mirrors (roughness, losses). Advanced interferometers
will call for even advanced technologies: squeezed light, cryogenic mirrors,
all reflective optical setups, advanced seismic isolations...