The Pioneer Anomaly |
The Pioneer Anomaly |
Aug 16 2005, 04:27 PM
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Rover Driver Group: Members Posts: 1015 Joined: 4-March 04 Member No.: 47 |
http://www.planetary.org/news/2005/pioneer_anomaly_faq.html
The planetary society may be checking it out... QUOTE The Planetary Society has committed to raise the funds to preserve the priceless Pioneer data from destruction.
After years of analysis, but without a final conclusion, NASA, astonishingly, gave up trying to solve the "Pioneer Anomaly" and provided no funds to analyze the data. The Pioneer data exists on a few hundred ancient 7- and 9-track magnetic tapes, which can only be read on "antique" outdated computers. The agency is going to scrap, literally demolish, the only computers able to access and process that data in the next few months! |
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Sep 7 2005, 07:36 AM
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Senior Member Group: Members Posts: 3419 Joined: 9-February 04 From: Minneapolis, MN, USA Member No.: 15 |
Once again, I'm asking a question that I probably ought to just Google up for myself, but it does go along with the thread...
One of the experiments in the Apollo 17 ALSEP was the Lunar Surface Gravimeter. As I recall, it was designed to detect gravity waves. (It failed because it was balanced in 1G and was entirely out of balance, and hence useless, in 1/6G.) Does anyone know what types of waves the LSG was designed to detect? Would it have been more in the LISA range or the LIGO range? I guess I'm wondering what kinds of things we might have been gathering data on for more than 30 years if the instrument had just been designed properly... -the other Doug -------------------- “The trouble ain't that there is too many fools, but that the lightning ain't distributed right.” -Mark Twain
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Guest_Richard Trigaux_* |
Sep 7 2005, 10:28 AM
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#3
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Guests |
QUOTE (dvandorn @ Sep 7 2005, 07:36 AM) Does anyone know what types of waves the LSG was designed to detect? Would it have been more in the LISA range or the LIGO range? I guess I'm wondering what kinds of things we might have been gathering data on for more than 30 years if the instrument had just been designed properly... -the other Doug I think that, even if such an instrument was properly designed, it had far from enough sensitivity to detect expected gravitationnal waves. Gravimeters are very sensitive indeed, they can detect such "low" masses as mountains, and even less (remember the historical Cavendish experiment which measured the effect of a some kilograms mass). But this is very far from enough to detect gravitationnal waves, which are many orders of magnitude under this level of sensitivity. Otherwise it would not be necessary to build such complicated experiments as LIGO, it would be enough to send a gravimeter in the ISS. Perhaps the most powerfull recent gravitationnal event was the supernova in 1978, but who knows what happens in the gravitationnal field. |
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Sep 8 2005, 06:21 PM
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#4
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Member Group: Members Posts: 624 Joined: 10-August 05 Member No.: 460 |
QUOTE (Richard Trigaux @ Sep 7 2005, 03:28 AM) ... Perhaps the most powerfull recent gravitationnal event was the supernova in 1978, but who knows what happens in the gravitationnal field. The failure to observe any evidence of SN1987A by any gravity wave detectors is not a good omen. True, the GW spectrum of a supernova is up-in-the-air, but an explosion of that magnitude, that close, should have created enough broad spectrum transients we should have found something, especially since the timing of the event is well known. I wouldn't pin my life's savings on Advanced LIGO - which seems to be progressing slightly ahead of schedule. Every generation of gravity wave detectors from Weber's work in the '70's on, have been built with the expectation that a GW event was just one pixal below the horizon. Advanced LIGO: http://www.ligo.caltech.edu/docs/G/G050364-00.pdf QUOTE Eventually, with 1-year of data at design sensitivity, the LIGO detectors will be sensitive at a level several times below the nucleosynthesis bound. http://arxiv.org/PS_cache/astro-ph/pdf/0507/0507254.pdf FWI worth, there is still a great deal of contraversy in the supernova community about just what the gamma rays, and expansion RINGs associated with 1987A mean. John Middleditch amoung others, is convinced both the rings and rays reveal a binary event, and he argues most supernovae involve binary systems. This grates against SN Ia theory, but his arguments, (including the 'double humped' light curves observed in many SN Ia spectra.) are strong. http://arxiv.org/abs/astro-ph/0310671 http://arxiv.org/abs/astro-ph/0311484 |
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Guest_Richard Trigaux_* |
Sep 9 2005, 07:21 AM
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Guests |
QUOTE (The Messenger @ Sep 8 2005, 06:21 PM) I wouldn't pin my life's savings on Advanced LIGO - which seems to be progressing slightly ahead of schedule. Every generation of gravity wave detectors from Weber's work in the '70's on, have been built with the expectation that a GW event was just one pixal below the horizon. Advanced LIGO: http://www.ligo.caltech.edu/docs/G/G050364-00.pdf http://arxiv.org/PS_cache/astro-ph/pdf/0507/0507254.pdf Very interesting article, although arduous to read. To summarize, the purpose of LIGO is to detect the cosmic background gravitationnal noise caused by very early cosmological events, far before the electromagnetic background. Today LIGO has not yet achieved this goal, but it made only short runs of data sampling which were rather aimed at improving sensitivity and eliminating instrument noise. With a long run at expected maximum sensitivity they expect to detect the level of gravitationnal waves predicted by the most recent theories of inflation. If they really achieve this design sensitivity and still not fing a gravitationnal background noise, the theories of inflation are at risk. Still only some years of work to let us know... QUOTE (The Messenger @ Sep 8 2005, 06:21 PM) Every generation of gravity wave detectors from Weber's work in the '70's on, have been built with the expectation that a GW event was just one pixal below the horizon. This is often like this in difficult scientifical achievements. Look for instance at the tokamac, the quantum computer, superconduction at ambient temperature... This is also due to the fact that the first researchers were really optimistic. Today evaluations of gravitationnal waves are, alas, much more pessimistic, and if they were know in 1970 Weber would not have started his experiment. Weber simply did what was best possible to do at his epoch, knowing what we knew. QUOTE (The Messenger @ Sep 8 2005, 06:21 PM) FWI worth, there is still a great deal of contraversy in the supernova community about just what the gamma rays, and expansion RINGs associated with 1987A mean. Please remember that the curious set of three non-coplanar rings around SN1987A were already here before the explosion. They were discovered after, with close examination of the place, but such rings are more likely of the planetary nebula family. It was said at this epoch that there will be new hubbub here when the expanding fireball would reach the first ring, 20 years later (2007). Also we are still to detect the predicted blinking of the central object indicating the presence of a pulsar. |
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Sep 12 2005, 01:49 PM
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Member Group: Members Posts: 624 Joined: 10-August 05 Member No.: 460 |
QUOTE (Richard Trigaux @ Sep 9 2005, 12:21 AM) Please remember that the curious set of three non-coplanar rings around SN1987A were already here before the explosion. They were discovered after, with close examination of the place, but such rings are more likely of the planetary nebula family. It was said at this epoch that there will be new hubbub here when the expanding fireball would reach the first ring, 20 years later (2007). Also we are still to detect the predicted blinking of the central object indicating the presence of a pulsar. News to me - can you provide a source? Middleditch based his models on fast rotating binary systems, and the resulting Gamma Rays, so I don't think prior rings cause a conundrum (prior rings being a product of the orbital dog-and-cat fight (?)). |
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