A Weber bar is a device used in the detection of gravitational waves first devised and constructed by physicist Joseph Weber at the University of Maryland. The device consisted of multiple aluminium cylinders, 2 meters in length and 1 meter in diameter, antennae for detecting gravitational waves.[1]
History
Around 1968, Weber collected what he concluded to be "good evidence"[1] of the theorized phenomenon. However, his experiments were duplicated many times, always with a null result.
Such experiments conducted by Joseph Weber were very controversial, and his positive results with the apparatus, in particular his claim to have detected gravitational waves from SN1987A in 1987, were widely discredited. Criticisms of the study have focused on Weber's data analysis and his incomplete definitions of what strength vibration would signify a passing gravitational wave.
Weber's first "Gravitational Wave Antenna" was on display in the Smithsonian Institution as part of "Einstein: a Centenary Exhibit" from March 1979 to March 1980.[2] A second is on display at the LIGO Hanford Observatory.[3]
Eight large aluminum bars organized in an arch around a sign that says "Weber Memorial Garden" with a picture of Weber working on the detectors. The Garden can be found at the University of Maryland.
The Weber Memorial Garden at the University of Maryland.
Weber Memorial Garden was dedicated 2019 at the University of Maryland, where Weber was a faculty member. The garden contains eight of the cores of Weber's bar detectors.[4]
Mechanism
These massive aluminium cylinders vibrated at a resonance frequency of 1660 hertz and were designed to be set in motion by gravitational waves predicted by Weber. Because these waves were supposed to be so weak, the cylinders had to be massive and the piezoelectric sensors had to be very sensitive, capable of detecting a change in the cylinders' lengths by about 10−16 meters.[1]
References
Lindley, David. "A Fleeting Detection of Gravitational Waves". Retrieved 2006-05-06.
Einstein: A Centenary Exhibition. Edited by the National Museum of History and Technology. Washington, D.C.: Smithsonian Institution Press, 1979.
"Resonant Bar Detector Dedicated at Hanford". The LIGO web newsletter. Retrieved 2012-03-29.
"Weber Garden Dedication Held March 12 - UMD Physics". umdphysics.umd.edu. Retrieved 2019-05-09.
Further reading
Gretz, Darrell J. (2018), "Early History of Gravitational Wave Astronomy: The Weber Bar Antenna Development" (PDF), History of Physics Newsletter, 13 (6): 1–16
Weber, J. (1967), "Gravitational radiation", Physical Review Letters, 18 (13): 498–501, Bibcode:1967PhRvL..18..498W, doi:10.1103/PhysRevLett.18.498
Weber, J. (1968), "Gravitational-wave-detector events", Physical Review Letters, 20 (23): 1307–1308, Bibcode:1968PhRvL..20.1307W, doi:10.1103/PhysRevLett.20.1307
Weber, J. (1969), "Evidence for discovery of gravitational radiation", Physical Review Letters, 22 (24): 1320–1324, Bibcode:1969PhRvL..22.1320W, doi:10.1103/PhysRevLett.22.1320
Weber, Joseph. How I discovered Gravitational Waves, Popular Science, Bonnier Corporation, May 1972, Vol. 200, No. 5, pp. 106–107 & 190–192, ISSN 0161-7370.
vte
Gravitational-wave astronomy
Gravitational wave Gravitational-wave observatory
Detectors
Resonant mass
antennas
Active
NAUTILUS (IGEC) AURIGA (IGEC) MiniGRAIL Mario Schenberg
Past
EXPLORER (IGEC) ALLEGRO (IGEC) NIOBE (IGEC) Stanford gravitational wave detector ALTAIR GEOGRAV AGATA Weber bar
Proposed
Past proposals
GRAIL (downsized to MiniGRAIL) TIGA SFERA Graviton (downsized to Mario Schenberg)
Ground-based
Interferometers
Active
AIGO (ACIGA) CLIO Fermilab holometer GEO600 Advanced LIGO (LIGO Scientific Collaboration) KAGRA Advanced Virgo (European Gravitational Observatory)
Past
TAMA 300 TAMA 20, later known as LISM TENKO-100 Caltech 40m interferometer
Planned
INDIGO (LIGO-India)
Proposed
Cosmic Explorer Einstein Telescope
Past proposals
AIGO (LIGO-Australia)
Space-based
interferometers
Planned
LISA
Proposed
Big Bang Observer DECIGO TianQin
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Data analysis
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List of observations First observation (GW150914) GW151012 GW151226 GW170104 GW170608 GW170729 GW170809 GW170814 GW170817 (first neutron star merger) GW170818 GW170823 GW190412 GW190521 (first-ever light from bh-bh merger) GW190814 (first-ever "mass gap" collision)
Methods
Direct detection
Laser interferometers Resonant mass detectors Proposed: Atom interferometers Indirect detection
B-modes of CMB Pulsar timing array Binary pulsar
Theory
General relativity Tests of general relativity Metric theories Graviton
Effects / properties
Polarization Spin-flip Redshift Travel with speed of light h strain Chirp signal (chirp mass) Carried energy
Types / sources
Stochastic
Cosmic inflation-quantum fluctuation Phase transition Binary inspiral
Supermassive black holes Stellar black holes Neutron stars EMRI Continuous
Rotating neutron star Burst
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