The Pioneer Anomaly |
The Pioneer Anomaly |
Aug 16 2005, 04:27 PM
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#101
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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 The Pioneer data exists on a few hundred ancient 7- and 9-track magnetic tapes, which can only be read on "antique" outdated computers.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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Jan 26 2006, 07:30 PM
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#102
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Member Group: Members Posts: 124 Joined: 23-April 05 Member No.: 358 |
From New Scientist -> http://www.newscientistspace.com/article.ns?id=dn8631
Gravity theory dispenses with dark matter A modified theory of gravity that incorporates quantum effects can explain a trio of puzzling astronomical observations – including the wayward motion of the Pioneer spacecraft in our solar system, new studies claim. The work appears to rule out the need to invoke dark matter or another alternative gravity theory called MOND (Modified Newtonian Dynamics). But other experts caution it has yet to pass the most crucial test – how to account for the afterglow of the big bang. Astronomers realised in the 1970s that the gravity of visible matter alone was not enough to prevent the fast-moving stars and gas in spiral galaxies from flying out into space. They attributed the extra pull to a mysterious substance called dark matter, which is now thought to outweigh normal matter in the universe by 6 to 1. But researchers still do not know what dark matter actually is, and some have come up with new theories of gravity to explain the galaxy observations. MOND, for example, holds that there are two forms of gravity. Above a certain acceleration, called a0, objects move according to the conventional form of gravity, whose effects weaken as two bodies move further apart in proportion to the square of distance. But below a0, objects are controlled by another type of gravity that fades more slowly, decreasing linearly with distance. But critics point out that MOND cannot explain the observed masses of clusters of galaxies without invoking dark matter, in the form of almost massless, known particles called neutrinos. http://www.newscientistspace.com/article.ns?id=dn8631 |
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Jan 27 2006, 01:41 AM
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#103
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Member Group: Members Posts: 477 Joined: 2-March 05 Member No.: 180 |
QUOTE (hal_9000 @ Jan 26 2006, 02:30 PM) From New Scientist -> http://www.newscientistspace.com/article.ns?id=dn8631 Gravity theory dispenses with dark matter Sounds like a version of the theory that general relativity needs to be applied to gravitational models, instead of simpler Newtonian physics. That theory hclaims to be able to do away with dark matter entirely and still explain both small-scale and very large-scale systems. I just imagine the thought of doing away with dark matter is unappealing to some people, as I'm sure some have made the study of dark matter their life's work. Another way of looking at it though is that they're just inadvertently referring to "the effects of general relativity" as "dark matter". |
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Jan 27 2006, 06:34 PM
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#104
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Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
Paper: astro-ph/0601581
Date: Wed, 25 Jan 2006 21:28:29 GMT (15kb) Title: Globular Clusters as a Test for Gravity in the Weak Acceleration Regime Authors: Riccardo Scarpa, Gianni Marconi, and Roberto Gilmozzi Comments: Comments: To Appear in the proceeding of the "First crisis in cosmology" conference, published in the American Institute of Physiscs' proceedings series, Vol. 822. (includes 3 pages and 1 fig) \\ Non-baryonic Dark Matter (DM) appears in galaxies and other cosmic structures when and only when the acceleration of gravity, as computed considering only baryons, goes below a well defined value a0=1.2e-8 cm/s/s. This might indicate a breakdown of Newton's law of gravity (or inertia) below a0, an acceleration smaller than the smallest probed in the solar system. It is therefore important to verify whether Newton's law of gravity holds in this regime of accelerations. In order to do this, one has to study the dynamics of objects that do not contain significant amounts of DM and therefore should follow Newton's prediction for whatever small accelerations. Globular clusters are believed, even by strong supporters of DM, to contain negligible amounts of DM and therefore are ideal for testing Newtonian dynamics in the low acceleration limit. Here, we discuss the status of an ongoing program aimed to do this test. Compared to other studies of globular clsuters, the novelty is that we trace the velocity dispersion profile of globular clusters far enough from the center to probe gravitational accelerations well below a0. In all three clusters studied so far the velocity dispersion is found to remain constant at large radii rather than follow the Keplerian falloff. On average, the flattening occurs at the radius where the cluster internal acceleration of gravity is 1.8+-0.4 x 10^{-8} cm/s/s, fully consistent with MOND predictions. \\ ( http://arXiv.org/abs/astro-ph/0601581 , 15kb) -------------------- "After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance. I see that such intercourse long continued would make one thoroughly prosaic, hard, and coarse. But the longest intercourse with Nature, though in her rudest moods, does not thus harden and make coarse. A hard, sensible man whom we liken to a rock is indeed much harder than a rock. From hard, coarse, insensible men with whom I have no sympathy, I go to commune with the rocks, whose hearts are comparatively soft." - Henry David Thoreau, November 15, 1853 |
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Feb 1 2006, 04:02 AM
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#105
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Senior Member Group: Members Posts: 2454 Joined: 8-July 05 From: NGC 5907 Member No.: 430 |
From The Planetary Society update:
Our strategy for the upcoming analysis of the newly available data can be summed up as follows: First, studying the early mission data may help us unambiguously determine whether the acceleration points towards the Earth, the Sun, or some other direction. Second, we hope to find out how the anomaly begins or if it was present throughout the mission. Third, we hope to be able to determine how this anomalous acceleration changed over time. Fourth, we will compare data from the two Pioneers to see if we can discern any notable differences in their behavior. Lastly, we will use the MDRs to develop a better engineering model of the spacecraft, making use, for instance, of finite element analysis methods to understand its thermal behavior. In March 2006, for the very last time the Earth will be in a favorable position to receive Pioneer 10's radio signal. It is possible that Pioneer 10 is still able to transmit, despite the age of its electronics, the extreme coldness of deep space, and the diminishing amount of electrical power on board. The possibility that the Deep Space Network will attempt to reacquire Pioneer 10's weak signal is currently being investigated, raising the hope, however faint, that we may yet have another data point to aid in our investigation of the Pioneers' enigmatic behavior. The rest is here: http://planetary.org/programs/projects/pio...ate_200601.html -------------------- "After having some business dealings with men, I am occasionally chagrined,
and feel as if I had done some wrong, and it is hard to forget the ugly circumstance. I see that such intercourse long continued would make one thoroughly prosaic, hard, and coarse. But the longest intercourse with Nature, though in her rudest moods, does not thus harden and make coarse. A hard, sensible man whom we liken to a rock is indeed much harder than a rock. From hard, coarse, insensible men with whom I have no sympathy, I go to commune with the rocks, whose hearts are comparatively soft." - Henry David Thoreau, November 15, 1853 |
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Guest_Richard Trigaux_* |
Feb 1 2006, 08:27 AM
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#106
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Guests |
QUOTE (ljk4-1 @ Feb 1 2006, 04:02 AM) From The Planetary Society update: Our strategy for the upcoming analysis of the newly available data ... The rest is here: http://planetary.org/programs/projects/pio...ate_200601.html So this data was recovered and is now safe. Good move. Now serious work can begin. |
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