Sources such as interacting black holes, coalescing compact
binary systems, stellar collapses and pulsars are all possible
candidates for detection; observing signals from them will
significantly boost our understanding of the Universe. New
unexpected sources will almost certainly be found and time will
tell what new information such discoveries will bring.
Gravitational waves are ripples in the curvature of space-time
and manifest themselves as fluctuating tidal forces on masses in
the path of the wave. The first gravitational wave detectors were
based on the effect of these forces on the fundamental resonant
mode of aluminium bars at room temperature. Initial instruments
were constructed by Joseph Weber [104,
105
] and subsequently developed by others. Reviews of this early
work are given in [102,
29]. Following the lack of confirmed detection of signals,
aluminium bar systems operated at and below the temperature of
liquid helium were developed and work in this area is still
underway [74
,
77
,
9
,
47
]. However the most promising design of gravitational wave
detectors, offering the possibility of very high sensitivities
over a wide range of frequency, uses widely separated test masses
freely suspended as pendulums on earth or in a drag free craft in
space; laser interferometry provides a means of sensing the
motion of the masses produced as they interact with a
gravitational wave.
Ground based detectors of this type, based on the pioneering
work of Bob Forward and colleagues (Hughes Aircraft) [71], Rai Weiss and colleagues (MIT) [107], Ron Drever and colleagues (Glasgow/Caltech)[31,
30
] and Heinz Billing and colleagues (MPQ Garching) [13
], will be used to observe sources whose radiation is emitted at
frequencies above a few Hz, and space borne detectors, as
originally envisaged by Peter Bender and Jim Faller [27,
35] at JILA will be developed for implementation at lower
frequencies.
Already gravitational wave detectors of long baseline are
being built in a number of places around the world; in the USA
(LIGO project led by a Caltech/MIT consortium) [11,
1], in Italy (VIRGO project, a joint Italian/French
venture) [20,
2], in Germany (GEO 600 project being built by a
collaboration centred on the University of Glasgow, the
University of Hannover, the Max Planck Institute for Quantum
Optics, the Max Planck Institute for Gravitational Physics
(Albert Einstein Institute), Golm and the University of Wales,
Cardiff) [52,
3] and in Japan (TAMA 300 project) [100,
4]. A space-borne detector, LISA, [26,
5
,
6
] - proposed by a collaboration of European and US research
groups - has been adopted by ESA as a future Cornerstone Mission.
When completed, this detector array should have the capability of
detecting gravitational wave signals from violent astrophysical
events in the Universe, providing unique information on testing
aspects of General Relativity and opening up a new field of
astronomy.
We recommend a number of excellent books for reference. For a popular account of the development of the gravitational wave field the reader should consult Chapter 10 of `Black Holes and Time Warps' by Kip S. Thorne [98]. A comprehensive review of developments toward laser interferometer detectors is found in `Fundamentals of Interferometric Gravitational Wave Detectors' by Peter Saulson [88], and discussions relevant to the technology of both bar and interferometric detectors are found in `The Detection of Gravitational Waves' edited by David Blair [14]. In addition to the home site of this journal and the sites listed above there is a very informative general site maintained by the National Centre for Supercomputing Applications [7].
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Gravitational Wave Detection by Interferometry (Ground
and Space)
Sheila Rowan and Jim Hough http://www.livingreviews.org/lrr-2000-3 © Max-Planck-Gesellschaft. ISSN 1433-8351 Problems/Comments to livrev@aei-potsdam.mpg.de |