Resonant Mass Detectors

Joseph Weber [Picture, Photo, Photograph]; middle age; three-quarter view; viewing equipment; laboratory; Joseph Weber checking the wires that connect the crystals on the 38 bar, in the gravity building, around 1969.; Weber Joseph F1

Joseph Weber working on a resonant mass detector.
Image courtesy of AIP Emilio Segrè Visual Archives

Joseph Weber built the first resonant mass detector in the late 1960s. Many similar detectors have been built, but they have not detected gravitational waves yet.

Most resonant mass detectors are made of large, cylindrical aluminum bars. When a gravitational wave passes through the bar, it changes the distance between the two ends of the bar. The bar then absorbs energy from the wave and this makes it vibrate. Then, sensors around the bar detect the vibrations and turn them into electrical signals that researchers can analyze. The bars are often suspended in a vacuum and kept at low temperatures to reduce noise.

The size of the vibrations depends on the strength of the gravitational wave. Therefore, scientists can figure out the strength of a wave that passed through by measuring the size of the vibration.

Resonant mass detectors are less expensive to build than laser interferometer detectors. However, they are only sensitive to waves from specific sources and have lots of background noise. Most of the new gravitational wave detection projects are using laser interferometers instead of resonant mass detectors because they are more sensitive.

Schematics of a gravitational wave bar detector: Image courtesy of AURIGA Detector.

There are a number of resonant mass detectors in use, below are links to some of them.