Experiments
Physicists Russell Hulse and Joseph Taylor explained their observations of a binary neutron star system as the result of the system's emitting gravitational waves in accordance with general relativity, an achievement for which they were awarded the 1993 Nobel Prize in Physics. However, gravitational radiation has never been directly observed -- that is, no one has yet witnessed a physical object actually changing shape as a gravitational wave passes through it -- although there have been a number of unconfirmed reports.
The confirmed observation of gravitational waves would be important further evidence for the validity of general relativity.
One reason for the lack of direct detection so far is that the gravitational waves that we expect to be produced in nature are very weak, so that the signals for gravitational waves, if they exist, are buried under noise generated from other sources. Reportedly, ordinary terrestrial sources would be undetectable, despite their closeness, because of the great relative weakness of the gravitational force. It has been proposed that certian conductors, especially superconductors, could be made to emit gravitational waves in the laboratory, but this work is still considered speculative. See the external link listed at the end of the article for more information.
A number of teams are working on making more sensitive and selective gravitational wave detectors and analysing their results.
A commonly used technique to reduce the effects of noise is to use coincidence detection to filter out events that do not register on both detectors.
There are two common types of detectors used in these experiments:
- laser interferometers, which use long light paths, such as GEO, LIGO, TAMA, VIRGO and ACIGA;
- resonant mass gravitational wave detectors which use large masses at very low temperatures, such as EXPLORER and NAUTILUS.
In November