When I was a postgraduate student at the University of Glasgow I was sometimes taken down into the basement to see a remarkable experiment. It was a Gravitational Wave Detector and at that time in 1982 it was the state of the art. They never recorded any positive signal but since then some more impressive GWDs have been constructed including the two LIGO detectors and VIRGO which have arms several kilometers long.
One talk at ICHEP that I could not see because it was not webcast was “Gravitational wave detectors: First astrophysical results and path to next generation” by Fabien Cavalier. The slides end with a nice quote from Kip Thorn who has been one of the major players in getting LIGO up and running: “[I]nterferometers should detect the first waves in 2001 or several years thereafter (…)” It is now 2010 and still no gravitational waves have been detected.
To be fair to Kip Thorn we need to quote at least the full sentence from which this quote was taken. We find it in gr-qc/9506086: “If the source estimates described in this review article are approximately correct, then the planned interferometers should detect the first waves in 2001 or several years thereafter, thereby opening up this rich new window onto the Universe.” So the fair interpretation is that the estimates of gravitational waves used in 1995 were not approximately correct. LIGO and VIRGO have set upper limits on how many gravitational wave sources there are. These are the “First astrophsysical results” from the title. Unfortuneatly nobody ever got a Nobel Prize for negative observational results even though they can be very important constraints for theorists.
The most promising sources for GWDs are inspiraling black hole pairs of neutron stars. These would produce a very characteristic signature in the detectors.