IPB

Welcome Guest ( Log In | Register )

16 Pages V  « < 2 3 4 5 6 > »   
Reply to this topicStart new topic
The Pioneer Anomaly
Bob Shaw
post Sep 7 2005, 08:47 PM
Post #46


Senior Member
****

Group: Members
Posts: 2488
Joined: 17-April 05
From: Glasgow, Scotland, UK
Member No.: 239



QUOTE (dvandorn @ Sep 7 2005, 07:33 PM)
Oh, that particular scientist-astronaut was well aware of the problem -- for one thing, when the PI found his instrument wouldn't uncage, he *insisted* that this particular scientist-astronaut must have deployed it improperly, must not have leveled it right.  So Houston told him to go back and re-level the experiment -- three times.  When told it would not uncage, Schmitt even kicked it, hard, and then re-leveled it again.  It still did not uncage.

Schmitt was, indeed, *quite* angry that such a screw-up had cost precious lunar surface EVA time.

From what I understand, though, even with the main beam caged, the LSG actexd as a fair one-axis seismometer...

-the other Doug
*


other Doug:

Was the PI's body ever found?

Bob Shaw


--------------------
Remember: Time Flies like the wind - but Fruit Flies like bananas!
Go to the top of the page
 
+Quote Post
edstrick
post Sep 8 2005, 10:49 AM
Post #47


Senior Member
****

Group: Members
Posts: 1870
Joined: 20-February 05
Member No.: 174



"From what I understand, though, even with the main beam caged, the LSG actexd as a fair one-axis seismometer...
-the other Doug"

As far as I know there were no science results whatever published from the instrument in that mode. I think the sensativity was far too low for any signal other than astronauts stomping by.
Go to the top of the page
 
+Quote Post
The Messenger
post Sep 8 2005, 06:21 PM
Post #48


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
Go to the top of the page
 
+Quote Post
Guest_Richard Trigaux_*
post Sep 9 2005, 07:21 AM
Post #49





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.
Go to the top of the page
 
+Quote Post
edstrick
post Sep 9 2005, 07:45 AM
Post #50


Senior Member
****

Group: Members
Posts: 1870
Joined: 20-February 05
Member No.: 174



It has been hoped that cosmic sources of gravitational radiation (as opposed to supernovae and massive object collissions) are stronger than predicted, or that there's unpredicted sources that have relatively frequent events strong enough for the first generation LIGO detection systems, but basically nobody expects it. Detectors have gotten much better than Weber's original cylinders, but my impression is that expectations of predicted source strength-frequency combinations have been such that no detector so far has been expected to detect anything by the general gravitational wave community. LIGI, I believe, works at much too high a frequency for detecting big bang related radiation and the like.

As far as SN1987A goes, we're detecting the blast wave interacting with the inner edge of a lumpy ring which is progressively lighting up as the blast expands. There is still no trace of either a black hole or neutron star in the supernova remenant inside the ring, or of energy being emitted from one. Some models in the past have suggested that in some cases there may be nothing left, but those I think are in disrepute, so the non-observation of a massive object is "A Puzzlement"
Go to the top of the page
 
+Quote Post
Guest_Richard Trigaux_*
post Sep 9 2005, 08:17 AM
Post #51





Guests






QUOTE (edstrick @ Sep 9 2005, 07:45 AM)
As far as SN1987A goes, we're detecting the blast wave interacting with the inner edge of a lumpy ring which is progressively lighting up as the blast expands.  There is still no trace of either a black hole or neutron star in the supernova remenant inside the ring, or of energy being emitted from one. 
*


Thanks for the info, edstrick. The lumpy ring you speak about is the innermost of the three rings, the one which is coplanar with the star.



QUOTE (edstrick @ Sep 9 2005, 07:45 AM)
  Some models in the past have suggested that in some cases there may be nothing left, but those I think are in disrepute, so the non-observation of a massive object is "A Puzzlement"
*


Yes there are some models predicting a nuclear explosion of the star, without gravitationnal collapse. In this case all the mass is blasted away and nothing remains in the centre. But this is for peculiar cases of binary stars, I do not think it fits for SN1987A, which is believed to be basically a gravitationnal collapse of a massive star which exhausted all its nuclear power. But the process leading from a star to a neutron star or black hole is not yet understood. The only thing sure is that there was a blast of neutrinos detected, indicating very high temperatures reached in the core. But we do not know if a black hole or a neutron star was created. By the way this star was not very massive, it could have given only a white dwarf (an idea of mine, without any waranty). I remember that the detection of a blinking light was expected 10 years after. Now 18 years passed by...
Go to the top of the page
 
+Quote Post
The Messenger
post Sep 12 2005, 01:49 PM
Post #52


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 (?)).
Go to the top of the page
 
+Quote Post
Guest_Richard Trigaux_*
post Sep 12 2005, 02:23 PM
Post #53





Guests






QUOTE (The Messenger @ Sep 12 2005, 01:49 PM)
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 (?)).
*



This set of three non-coplanar rings was photographied just after the blast was extinct, some months after the supernova, when astronomers began to examine the place. I remember well that it was in all the science reviews (Here in France "Science et Avenir", "Science et Vie", "Pour la science" , and also in amateur astronomy reviews. At that time the fireball from the explosion was just an unresolved point at the centre of the well resolved three rings. Previous photos of the same place showed the parent star, but were not large enough to show the rings. These rings much puzzled the astronomers, and they played a role in the planetary nebula theory (since it was found one or several planetary nebula looking like hour glasses, ressembling the rings of 1987A). They are now expected to form from binary systems. But I never heard of a companion star of SN1987A, with my opinion if it exists it must be a very weak star, white dwarf, neutron star or black hole. Anyway it puzzles me that today some people (and even scientists) seem to think that the three rings resulted from the explosion. Today the fireball of the explosion is just catching the innermost ring.


Another curious thing is that, while the fireball was still very bright, days of weeks after the explosion,I heard mentioned that just nearby there was a huge transcient infrared source, most powerfull than the entire Magellanic cloud. But I never heard of this again, perhaps it was just an observation error. Often unexplained facts are considered as mistakes and forgotten. But there may be some new thing about. Today people may think that it was the effect of a focused gamma ray beam like those predicted by some supernova theories.

Sorry, I have no other sources than my memories of the scientific press at this epoch. If you want more precise sources, I think you should look in the archives of science and astronomy reviews (like the "scientific American" in the months following the supernova, I think you cannot miss the images of the three rings.
Go to the top of the page
 
+Quote Post
The Messenger
post Sep 12 2005, 06:56 PM
Post #54


Member
***

Group: Members
Posts: 624
Joined: 10-August 05
Member No.: 460



QUOTE (Richard Trigaux @ Sep 12 2005, 07:23 AM)
But I never heard of a companion star of SN1987A, with my opinion if it exists it must be a very weak star, white dwarf, neutron star or black hole. Anyway it puzzles me that today some people (and even scientists) seem to think that the three rings resulted from the explosion. Today the fireball of the explosion is just catching the innermost ring.


Thanks -

Nisenson argues the 'spots' are indeed likely supernova remnants, but I am not sure if he is arguing the rings are actual remnants or "spotlighted" illuminations of existing nebula.

http://arxiv.org/abs/astro-ph/9904109

You are correct in stating a companion star for 1987A has never been discovered. The column of energy released was so enormous, Middleditch speculates a high volume of the star may have undergone 'unidirectional weak interactions'. A relativistic laser(?)

I was looking for a mechanism to explain the relativistic accelerations Nisenson is trying to interpret, when I stumbled across the possibly 'non-Newtonian' trend in the solar system I outlined above. FWIW, I haven't convinced anyone in the field this could be a real aspect of gravity, but I haven't found anyone who's eyes don't glaze over the second they realize the implications, either.
Go to the top of the page
 
+Quote Post
Guest_Richard Trigaux_*
post Sep 13 2005, 10:15 AM
Post #55





Guests






QUOTE (The Messenger @ Sep 12 2005, 06:56 PM)
You are correct in stating a companion star for 1987A has never been discovered.
*


Such a companion is deemed necessary to explain the existence of the rings (some planetary nebulae geometries are suposed to appear in binary systems). Alas we don not have precise spectra of 1987A before the explosion (it was just a blue spot among thousands of others). To explain the "disappearance" of the companion, we can suppose:
-it is very weak (white dwarf, neutron star, black hole. But I think we cannot expect the presence of a white dwarf as a companion to a large star)
-it was blasted away during the explosion
-it was absorbed some thousands years ago when 1987A was a red giant, just after involving in the rings. Eventually such three-ring geometry would be the signature of this kind of event.

Remember also that a blue star exploding as a supernova was a surprise; astronomers were thinking of SN1987A as being an ordinary blue star on its main sequence, not the likely candidate for a supernova. (It was the first time the star forming the supernova was known). The generaly retained explanation is that 1987A had undergone a red giant stage earlier, but since some thousand years it had subsided into a smaller blue star. Such variations in near-death stars are expected by theories and supported by observations.
Go to the top of the page
 
+Quote Post
ljk4-1
post Sep 13 2005, 01:17 PM
Post #56


Senior Member
****

Group: Members
Posts: 2454
Joined: 8-July 05
From: NGC 5907
Member No.: 430



QUOTE (Richard Trigaux @ Sep 13 2005, 05:15 AM)
Such a companion is deemed necessary to explain the existence of the rings (some planetary nebulae geometries are suposed to appear in binary systems). Alas we don not have precise spectra of 1987A before the explosion (it was just a blue spot among thousands of others). To explain the "disappearance" of the companion, we can suppose:
-it is very weak (white dwarf, neutron star, black hole. But I think we cannot expect the presence of a white dwarf as a companion to a large star)
-it was blasted away during the explosion
-it was absorbed some thousands years ago when 1987A was a red giant, just after involving in the rings. Eventually such three-ring geometry would be the signature of this kind of event.

Remember also that a blue star exploding as a supernova was a surprise; astronomers were thinking of SN1987A as being an ordinary blue star on its main sequence, not the likely candidate for a supernova. (It was the first time the star forming the supernova was known). The generaly retained explanation is that 1987A had undergone a red giant stage earlier, but since some thousand years it had subsided into a smaller blue star. Such variations in near-death stars are expected by theories and supported by observations.
*


Perhaps it was an industrial accident.

From the article "Detectability of Extraterrestrial Technological Activities"
by Guillermo A. Lemarchand:

http://www.coseti.org/lemarch1.htm


FIGURE 2: Concept of an "artificial" blue straggler star according to Reeves (1985). In this figure, a series of hydrogen bombs or powerful laser beams are aimed at the surface of a star, creating a "hot point" and rejuvenating the unused hydrogen, thus keeping the star on the Main Sequence for a longer period of time than would be natural.

http://www.coseti.org/images/lefig_2.gif

Reeves (1985) speculated on the origin of mysterious stars called blue stragglers. This class of star was first identified by Sandage (1952). Since that time, no clear consensus upon their origins has emerged. This is not, however, due to a paucity of theoretical models being devised. Indeed, a wealth of explanations have been presented to explain the origins of this star class. The essential characteristic of the blue stragglers is that they lie on, or near, the Main Sequence, but at surface temperatures and luminosities higher than those stars which define the cluster turnoff. A review of current thinking about these stars in the light of recent visible and ultraviolet Hubble Space Telescope observations assigns an explanation to stellar mergers occurring in the dense stellar environment of globular clusters (Bailyn, 1994).

Reeves (1985) suggested the intervention of the inhabitants that depend on these stars for light and heat. According to Reeves, these inhabitants could have found a way of keeping the stellar cores well-mixed with hydrogen, thus delaying the Main Sequence turn-off and the ultimately destructive, red giant phase.

Beech (1990) made a more detailed analysis of Reeves' hypothesis and suggested an interesting list of mechanisms for mixing envelope material into the core of the star. Some of them are as follows:

* Creating a "hot spot" between the stellar core and surface through the detonation of a series of hydrogen bombs. This process may alternately be achieved by aiming "a powerful, extremely concentrated laser beam" at the stellar surface.

* Enhanced stellar rotation and/or enhanced magnetic fields. Abt (1985) suggested from his studies of blue stragglers that meridional mixing in rapidly rotating stars may enhance their Main Sequence lifetime.

If some of these processes can be achieved, the Main Sequence lifetime may be greatly extended by factors of ten or more. It is far too early to establish, however, whether all the blue stragglers are the result of astroengineering activities.


--------------------
"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

Go to the top of the page
 
+Quote Post
The Messenger
post Sep 13 2005, 04:16 PM
Post #57


Member
***

Group: Members
Posts: 624
Joined: 10-August 05
Member No.: 460



Suggestions, by anyone, of engineering on this scale, is not productive and not scientifically motivated.
Go to the top of the page
 
+Quote Post
Guest_Richard Trigaux_*
post Sep 13 2005, 06:06 PM
Post #58





Guests






QUOTE (The Messenger @ Sep 13 2005, 04:16 PM)
Suggestions, by anyone, of engineering on this scale, is not productive and not scientifically motivated.
*


I mostly agree with you, but...


Imagine a million years old civilization, with technologies such as self-reproducing machines, fusion energy, etc... and plenty of time. Soon within reach of us.

Unless such a civilisation turns more ethical/spiritual than technological, there is no limit with such a technology, and it is not impossible we discover stars and even galaxies which were engineered over millions (or billions) of years. Simply we have not yet evidences (and even not suspicion) of it. There is alway this temptation when we discover something we do not understand: and if it was artificial? Remember the first pulsars: their extreme accuracy was not yet understood, and many scientists seriously considered they could be some interstellar beacons...

Coalescence of stars are a sufficient explanation for blue stragglers. A catastrophe which could happpen in some years, projecting all their planets (inhabited?) into blaze or into the darkness of space. Living into a dense star cluster may offer aver beautiful night sky, but it is also a ver dangerous place where most plants are ejected from their orbit by star encounters. so it is not the most likely place to find evolved life.
Go to the top of the page
 
+Quote Post
The Messenger
post Sep 14 2005, 03:31 PM
Post #59


Member
***

Group: Members
Posts: 624
Joined: 10-August 05
Member No.: 460



Returning to the Pioneer Anomally:

You may or may not be aware of the curious brightening phenomenon being studied by Ann Verbiscer, per the Planetary Weblog:

QUOTE (Emily L)
"We see three different views of Saturn on different dates. The globe of Saturn hardly looks different at all at these small differences in phase angle. But look at the rings! With the minutest difference in phase angle -- from 0.13 degrees down to 0.02 degrees -- the rings suddenly flash into brilliant light. Anne told me that she saw similar effects on Saturn's icy satellites, especially Enceladus. The size of the opposition surge she saw was "drastically higher, 40% higher, than previously published values."

I'm not an astronomical observer myself so Anne had to explain to me what causes the opposition surge. One explanation is "shadow hiding" -- at any non-zero phase angle, the particles in the rings cast shadows across other particles in the rings, so that darkens the surface. But at zero phase, you see no shadows at all, and the surface looks brighter. But Anne said that "it doesn't work" to explain all of the observed opposition effect. You need something more, like coherent backscatter: that is, constructive interference of the light being reflected from the rings and Enceladus. 


There is an explanation that is consistent, actually a necessary constraint, upon the permeability hypothesis I entered above:

The rings of Saturn, the highly reflective surfaces of some of the moons, are more like mirrors than nominal planetary surfaces. The sunlight reflected by the rings, therefore, more closely resembles a mirrored reflection of the sun, and will return a loosely coherant image of the sun.

When the Earth passes exactly between the Sun and Saturn, the rings and more reflective moons brighten. Why would the reflection be brighter at the very center?

If and ony if there is curvature of space. The image of the sun is focused only at the center, at anyother position of the Earth relative to the sun and Saturn, the image is deconvoluted.

When the Earth is exactly positioned in front of the sun, a perfectly curved lens would return a much brighter reflection of the sun. That is exactly what is happening.

And why would there be curvature? If and only if the permeability of space varies, increasing the speed of light with increasing distance from the center of the solar system, and this would be true if and only if the permeability of space is a function of MASS.

OK, There may be other solutions: Fressnel lensing, for example, but the solution is a lensing solution because the amount of brightening is also a function of wavelength, as would be expected with any single density lensing element.

The curvature has to be very slight...almost undetectable, but not quite, because it produces this brilliant mirror effect exactly in the center - just as a gravitational lens should. But the Earth is too far from the sun to experience this kind of curvature, with GR, as formulated by Einstein, to be the cause. (Also the mass of the Earth is not great enough to cause a GR bending of the light.)

This also explains why there are so many 'Gravitational' lenses, and 'micro quasar' lenses in the galaxy: There is a not-so-new physical principle being manifest: The permeability of space is a function of mass, the speed of light is only a constant in an ideal vacuum that includes the absence of any matter.

Returning to the Pioneer Accelerations, they are an artifact: We use the two-way time and speed of light to determine the distance to the probes. As the speed of light increases at a rate of ~1X10^-9m/s^2, the time it takes light to reach the probes and return is less than if the speed of light were constant. We interpret this as an acceleration of the probes towards the sun, when it is actually a slight acceleration of light away from the sun. (Of course both the speed of light, and the acceleration of the probes are not independently constrained at this time, so the true acceleration of the probes is unknown.) cool.gif
Go to the top of the page
 
+Quote Post
Guest_Richard Trigaux_*
post Sep 14 2005, 03:46 PM
Post #60





Guests






Messenger, yes the Earth does have a "gravitationnal lens" effect, but it can significantly concentrates light only at a distance of several thousand light-years. This was put at work in the search of "machos" (massive objects such as blue dwarf stars, planets, brown dwarfs, black holes... explaining the dark matter around the galaxy). But the "machos" detected were very far, for instance in the Magellanic cloud, and the most common mass was around half what of the Sun, much larger than Earth. So I think the effect of gravitationnal lens is undetectable from Saturn. The opposition effect is well explained in terms of shadow hiding and back reflection from ice crystals, an effect we can also see on earth clouds (from above). The best evidence is that it was also photographied by Cassini (see somewhere on Cassini site or on this site) and from here it appears as a bright spot on the rings.
Go to the top of the page
 
+Quote Post

16 Pages V  « < 2 3 4 5 6 > » 
Reply to this topicStart new topic

 



RSS Lo-Fi Version Time is now: 29th March 2024 - 07:36 AM
RULES AND GUIDELINES
Please read the Forum Rules and Guidelines before posting.

IMAGE COPYRIGHT
Images posted on UnmannedSpaceflight.com may be copyrighted. Do not reproduce without permission. Read here for further information on space images and copyright.

OPINIONS AND MODERATION
Opinions expressed on UnmannedSpaceflight.com are those of the individual posters and do not necessarily reflect the opinions of UnmannedSpaceflight.com or The Planetary Society. The all-volunteer UnmannedSpaceflight.com moderation team is wholly independent of The Planetary Society. The Planetary Society has no influence over decisions made by the UnmannedSpaceflight.com moderators.
SUPPORT THE FORUM
Unmannedspaceflight.com is funded by the Planetary Society. Please consider supporting our work and many other projects by donating to the Society or becoming a member.