dkomo wrote:

I found an old PBS documentary on VHS from 1991 called _The Astronomers_
at the local public library. One of the programs in the series was
"Waves of the Future" about gravitational waves. In the program Kip
Thorne was shown making a bet with one of his collaborators on gravity
wave theory that these waves would positively be detected by 2000.

I found this both humorous and a touch sad. The program described some
of the early planning for LIGO (Laser Interferometer Gravitational Wave
Observatory). Curious, I went to the LIGO web site to see what was
going on. I found nothing of substance there -- just a lot of slick PR.

So my question is, what are the prospects that gravity waves will be
detected anytime soon? Is LIGO still having technical problems or what?
It is now 2004, after all. Other detection labs are being built around
the world. Are these labs going to have any better luck?


Most likely LIGO will detect gravitational waves.
See: http://www.ligo.caltech.edu/
http:/www.edu-observatory.org/eo/cosmology.html

PHYSICS NEWS UPDATE
The American Institute of Physics Bulletin of Physics News
Number 632 April 9, 2003 by Phillip F. Schewe, Ben Stein, and James
Riordon

FIRST LIGO SCIENTIFIC RESULTS. With two controlling partners, MIT and
Caltech, and two branch offices (two completely independent detectors)
located in Washington State and Louisiana, the Laser Interferometer
Gravitational-Wave Observatory (LIGO) is essentially a giant strain gauge.
In the LIGO setup laser light reflects repeatedly in each of two
perpendicularly oriented 4-km-long pipes. A passing gravity wave will
distort the local spacetime, stretching very slightly one of the paths while
shrinking the other, causing the interference pattern of the two merging
laser light beams to shift in a characteristic way. LIGO does not measure
static gravitational fields, such as those from the sun or the Earth itself.
Rather it strives to see ripples in spacetime radiated by such events as
the inspiral of two neutron stars toward each other, a phenomenon which
would typically produce a strain in the LIGO apparatus as large as one part
in 10^20. That is, a passing gravity wave is expected to change the
distance between mirrors some 4 km apart by about 10^-18 meters, a
displacement 1000 times smaller than a proton. Such a measurement
represents a physics and engineering feat of great delicacy. But at long
last the LIGO team has prepared its instrument and at this week's APS
meeting, reported its first official results from the initial "science" run
conducted over 17 days in September 2002.

In this first run no gravitational wave events were observed, but palpable
knowledge was gained as to what the sky should look like when viewed in the
form of gravity waves. So great is LIGO's sensitivity that it has been able
to set the best upper limit on the output of gravitational waves from three
of the four prime source categories. These four expected waveforms are as
follows: bursts from sources such as supernovas or gamma bursters; chirps
from inspiraling objects such as coalescing binary stars; periodic signals,
perhaps from sources like spherically asymmetric pulsars; and a stochastic
background source arising from gravity waves originating from the big bang
itself. LIGO deputy director Gary Sanders (Caltech,
) said that in three of these four categories,
had set new upper limits on the rate at which gravitational waves were being
produced. In the coalescing binary category, for instance, LIGO has
established an upper limit of 164 per year from the Milky Way, a factor of
26 better than the previous limit. Erik Katsavounidis (MIT,
) said that LIGO could establish an upper limit on
periodic signals from bright pulsars with a sensitivity of about 10^-22.
Sheila Rowan (Stanford Univ and Univ Glasgow) spoke of future operations at
LIGO. First of all, the second scientific run currently underway will be
some ten times more sensitive than the first run, the one being reported at
the meeting. If in the first science run LIGO was essentially sensitive to
gravity waves from the whole of the Milky Way, then in the second science
run (conducted Feb-Apr 2003), featuring a ten-times improvement in
sensitivity, the region of space patrolled would effectively reach out to
about 15 million light years, a realm that includes the nearby Andromeda
galaxy. (For more information about LIGO and a complete collaboration list,
see www.ligo.caltech.edu ) In its search for gravity waves, LIGO (which with
about 440 scientists is as big as the large particle physics experiments
underway at accelerators) is also collaborating with other interferometer
devices such as GEO (in Germany, www.geo600.uni-hannover.de ) and TAMA
(Japan).