Weber bar
Encyclopedia
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 theoretical gravitational waves.
Around 1968, Weber collected what he concluded to be "good evidence" 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 until recently widely considered 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. However, recent analysis has suggested that his claim may be in need of reassessment.
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.
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.
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
Joseph Weber
Joseph Weber
Joseph Weber was an American physicist. He gave the earliest public lecture on the principles behind the laser and the maser and developed the first gravitational wave detectors .-Early education:...
at the University of Maryland
University of Maryland, College Park
The University of Maryland, College Park is a top-ranked public research university located in the city of College Park in Prince George's County, Maryland, just outside Washington, D.C...
. The device consisted of multiple aluminium
Aluminium
Aluminium or aluminum is a silvery white member of the boron group of chemical elements. It has the symbol Al, and its atomic number is 13. It is not soluble in water under normal circumstances....
cylinders, 2 meters in length and 1 meter in diameter
Diameter
In geometry, a diameter of a circle is any straight line segment that passes through the center of the circle and whose endpoints are on the circle. The diameters are the longest chords of the circle...
, antennae
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
for detecting theoretical gravitational waves.
Around 1968, Weber collected what he concluded to be "good evidence" 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 until recently widely considered 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. However, recent analysis has suggested that his claim may be in need of reassessment.
Weber's first "Gravitational Wave Antenna" was on display in the Smithsonian Institution
Smithsonian Institution
The Smithsonian Institution is an educational and research institute and associated museum complex, administered and funded by the government of the United States and by funds from its endowment, contributions, and profits from its retail operations, concessions, licensing activities, and magazines...
as part of "Einstein: a Centenary Exhibit" from March 1979 to March 1980.
Mechanism
These massive aluminium cylinders vibrated at a resonance frequencyResonance
In physics, resonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies...
of 1660 hertz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
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.
Further reading
- Weber, Joseph. How I discovered Gravitational Waves, Popular SciencePopular SciencePopular Science is an American monthly magazine founded in 1872 carrying articles for the general reader on science and technology subjects. Popular Science has won over 58 awards, including the ASME awards for its journalistic excellence in both 2003 and 2004...
, Bonnier Corporation, May 1972, Vol. 200, No. 5, pp. 106–107 & 190–192, ISSN 0161-7370.