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Methods of Detecting Gravitational Waves I: Resonant-Mass Detectors

2 Jul 2013, 14:00 UTC
Methods of Detecting Gravitational Waves I: Resonant-Mass Detectors
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As the name of this blog suggests, I use LIGO and similar gravitational-wave detectors (like Virgo and GEO). These detectors are all interferometric detectors meaning that they use the interference of light to measure gravitational waves. But interferometers were not the first means used to look for gravitational waves...WEBER BARSIn 1966, Joseph Weber of the University of Maryland constructed a gravitational-wave detector that consisted of a very precisely machined cylinder of aluminum 2 meters long and 1 meter in diameter. The idea was that when a gravitational wave passed over the bar at a specific frequency, the bar would start to ring like a bell. This "ringing" frequency, also called the resonant frequency, for Weber's bars was 1660 Hz (cycles per second).Weber working on one of his bars at the University of Maryland, c. 1965.The way these bars are be used to detect gravitational waves involves the phenomenon of sympathetic resonance. This is when the vibration of something external to an object matches its resonant or "ringing" frequency and causes it to begin vibrating. Even after the external vibration stops, the now vibrating object will continue to ring like a bell (and eventually stop ringing just like a bell as ...

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