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What's up with gravity wave detection?
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? Also, what are people's opinions about gravity waves? Is it possible that these are a scientific dead end like the decay of the proton turned out to be? If gravity waves are never detected, what are the implications for the general theory of relativity? |
#2
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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). |
#3
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Most likely LIGO will detect gravitational waves.
See: http://www.ligo.caltech.edu/ http:/www.edu-observatory.org/eo/cosmology.html It is very interesting how institutions would spend millions of dollars trying to detect something that has not been thoroughly understood. As I read in Scientific American a year or two ago, LIGO was chosen to be built in places where noise generated by human activities are at near maximum. This means LIGO's detection of gravitational waves is subjected to broad and creative interpretations of data which can easily be explained by something else. |
#4
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"Australopithecus Afarensis" wrote in message news:zQXTc.100010$sh.86278@fed1read06...
Most likely LIGO will detect gravitational waves. See: http://www.ligo.caltech.edu/ http:/www.edu-observatory.org/eo/cosmology.html It is very interesting how institutions would spend millions of dollars trying to detect something that has not been thoroughly understood. The theory of gravitational radiation has been well established for several decades. Details can usually be found in any GR textbook. Weinberg's book is probably the best in this regard. As I read in Scientific American a year or two ago, LIGO was chosen to be built in places where noise generated by human activities are at near maximum. This means LIGO's detection of gravitational waves is subjected to broad and creative interpretations of data which can easily be explained by something else. Why do you think they built two of them in entirely separate locations? |
#6
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Dear Australopithecus Afarensis:
"Australopithecus Afarensis" wrote in message news:zQXTc.100010$sh.86278@fed1read06... Most likely LIGO will detect gravitational waves. See: http://www.ligo.caltech.edu/ http:/www.edu-observatory.org/eo/cosmology.html It is very interesting how institutions would spend millions of dollars trying to detect something that has not been thoroughly understood. Like AIDS? Money is spent to find out about things that are not yet known. That is what research is for. That is what theories are about, predict and test. David A. Smith |
#7
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On Mon, 16 Aug 2004 07:07:28 -0700, "N:dlzc D:aol T:com \(dlzc\)" N:
dlzc1 D:cox wrote: Like AIDS? Money is spent to find out about things that are not yet known. Or which are well known but denied by an advocacy group? |
#8
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"Australopithecus Afarensis" wrote in message news:zQXTc.100010$sh.86278@fed1read06...
Most likely LIGO will detect gravitational waves. See: http://www.ligo.caltech.edu/ http:/www.edu-observatory.org/eo/cosmology.html It is very interesting how institutions would spend millions of dollars trying to detect something that has not been thoroughly understood. As I read in Scientific American a year or two ago, LIGO was chosen to be built in places where noise generated by human activities are at near maximum. This means LIGO's detection of gravitational waves is subjected to broad and creative interpretations of data which can easily be explained by something else. They will detect nothing but thermal noise and geo vibrations. Signal to noise ratio will be too low to make anything out of that. Any signal processing applied will open the room to subjectivity. Another one bites the dust. Gravity will always stay a mystery. Mike |
#9
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#10
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"Australopithecus Afarensis" wrote in message news:zQXTc.100010$sh.86278@fed1read06...
Most likely LIGO will detect gravitational waves. See: http://www.ligo.caltech.edu/ http:/www.edu-observatory.org/eo/cosmology.html It is very interesting how institutions would spend millions of dollars trying to detect something that has not been thoroughly understood. As I read in Scientific American a year or two ago, LIGO was chosen to be built in places where noise generated by human activities are at near maximum. This means LIGO's detection of gravitational waves is subjected to broad and creative interpretations of data which can easily be explained by something else. It's not that interesting since scientists usually spend billions of dollars doing nothing. And since saying that gravity waves are thoroughly understod is the same thing as gravity particles are thoroughly understood, both statements which are quark-quantum crapola, the experiment is obviously not meant to be understood by quantum-chemists, or astro-physicists, since it has no magents involved. Since to be being with the experiment is not even detecting waves. The wave detection is a third order effect of the entire setup. Since Laser interferometry can't "detect" ANYTHING, nevermind a gravity wave. |
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