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Fraser
2005-Mar-30, 05:37 PM
SUMMARY: Launched from "Cape Kennedy" just 13 months of one another in 1972/73, Pioneer 10 and 11 are still up there though no longer kicking. But well before last phone home (in 2003 and 1995 respectively), the notes each pair played had changed pitch unexpectedly - they were slowly losing speed. Could the Pioneering Pair have been feeling a bit in the "dark" (as in "dark matter" or "dark energy")? Were they having a "Solar Quadrupole" moment? Could n-dimensional "branes" be behind it? Or has "back-gravity" from behind the Sun played a role? Before things get too exotic, maybe there's a simpler explanation.

View full article (http://www.universetoday.com/am/publish/kuiper_belt_slowing_pioneer.html)

What do you think about this story? Post your comments below.

antoniseb
2005-Mar-30, 05:53 PM
The whole question about what is slowing down the Pioneers is very interesting. It would be great to discover that it is something perfectly normal, and doesn't require new physics or otherwise support some of these Alternative Theories (MoND etc).

lswinford
2005-Mar-30, 07:41 PM
Well, I'm happy with the article. One of my previously expressed 'suspects' was drag. So it was only mentioned in the next-to-last paragraph--it got in there, LOL.

On a slightly more serious note, I was just looking at some illustrations we were considering for a book my company was putting together. The illustration, and associated discussion, described common sound with its pressure zones. Even though we think of space as a vacuum, its not a pure vacuum. After traveling so very far on its momentum, helped with some gravitational assist as I recall, there seem to be ample distance to traverse with the extra trailing vacuum formed by those earth-pointed radio dishes. A little bit, over such a long ways, might add up to some almost-significant momentum sapping.

On the other hand, maybe we got a digit or two transposed in one of the fudge-factors to figure distance or something. I wonder about those mathematicians sometimes. ;)

John L
2005-Mar-30, 07:56 PM
I for one am hoping its new physics! Right now the prospects of rapidly getting people around the solar system and beyond seems remote. If the physics change, though, maybe that change will show us a loophole. I can hope...

imported_JimO
2005-Mar-30, 10:09 PM
Nice story... :D
Pioneer 10 was launched March 3, 1972;
Pioneer 11 was launched April 6, 1973.
The only 'checkable' factuall assertion,
turned out to be wrong. :unsure:

hope the rest of the story was more reliable. :)

Jim Oberg
www.jamesoberg.com

John L
2005-Mar-30, 10:12 PM
That's a minor error on the part of the author of the article. It was the Voyagers that were launched in the 70's within a month of each other.

Fraser
2005-Mar-30, 11:43 PM
Thanks for the catch Jim, I've fixed the article.

The Near-Sighted Astronomer
2005-Mar-31, 01:20 AM
This page:
http://spaceprojects.arc.nasa.gov/Space_Pr...eer/PNStat.html (http://spaceprojects.arc.nasa.gov/Space_Projects/pioneer/PNStat.html)

sites Pioneer 11 launch as

"(Launched 5 April 1973)"

another site says that Pioneer 10 :

http://klabs.org/home_page/pioneer_10.htm

Launch Date/Time: 1972-03-03 at 01:49:00 UTC

"The spacecraft achieved its closest approach to Jupiter on December 3, 1973,"

So yah I'd say the Pioneer launch dates are spot on.

Voyager 1 & 2 dates:

"Launch Date:, September 5, 1977 (Voyager 1). August 20, 1977 (Voyager 2)."

http://nssdc.gsfc.nasa.gov/planetary/voyager.html

I guess time changes with the times - and the sources...

However the two probes went up within 1 month of each other - not 13 just a slip up

Guest
2005-Apr-01, 08:09 AM
I thought that the Pioneers were anomolusly accelerating.

They are according to this from new scientist http://www.newscientist.com/channel/space/.../mg18524911.600 (http://www.newscientist.com/channel/space/mg18524911.600)

antoniseb
2005-Apr-01, 03:54 PM
Originally posted by Guest@Apr 1 2005, 08:09 AM
I thought that the Pioneers were anomolusly accelerating.
The term accelerating is applied scientifically no matter which way the change in velocity is going. In this case, the are accelerating slightly toward the Sun. Considering that they are moving away from the Sun, in common English we would say that they are decelerating faster than expected. Either way, there is a slight difference from the force that was predicted for these craft to be influenced by.

The Near-Sighted Astronomer
2005-Apr-02, 02:53 AM
Its interesting that the factor of "blue shift" caused by the infall of the carrier signals toward the Earth from further out away from the Sun's gravity well was not cited by anyone as contributing to the apparent deceleration (or more scientifically "negative acceleration"). Doesn't light "blue shift" as it "falls" inward from the perspective of an observer deeper inside a garvitational well?

nobody
2005-Apr-14, 06:30 AM
Originally posted by antoniseb+Apr 1 2005, 03:54 PM--></div><table border='0' align='center' width='95%' cellpadding='3' cellspacing='1'><tr><td>QUOTE (antoniseb @ Apr 1 2005, 03:54 PM)</td></tr><tr><td id='QUOTE'> <!--QuoteBegin-Guest@Apr 1 2005, 08:09 AM
I thought that the Pioneers were anomolusly accelerating.
The term accelerating is applied scientifically no matter which way the change in velocity is going. In this case, the are accelerating slightly toward the Sun. Considering that they are moving away from the Sun, in common English we would say that they are decelerating faster than expected. Either way, there is a slight difference from the force that was predicted for these craft to be influenced by. [/b][/quote]
The article at NewScientist says "speeding up." It&#39;s clear they meant that it&#39;s going faster as time goes by not slower.

antoniseb
2005-Apr-14, 03:52 PM
Originally posted by nobody@Apr 14 2005, 06:30 AM
The article at NewScientist says "speeding up." It&#39;s clear they meant that it&#39;s going faster as time goes by not slower.
I enjoy New Scientist, and have a great deal of admiration for them in both the stories they choose, and how they write them up, but if they said it is speeding up, then the journalist who wrote the story and his editor both missed an important fact in the story. These spacecraft are slowing down faster than expected, they are NOT speeding up. Let me say it one more time a little differently. These craft are moving AWAY from the Sun because of rockets and slingshot effect, but are experiencing an acceleration TOWARD the Sun (all or mostly gravity). This acceleration slows their movement away from the Sun more than expected (based on the mass of the Sun and planets), and that larger acceleration is thought (in this news item) to be a result of the combined gravitational influence of the objects in the Kuiper Belt.

Greg
2005-Apr-14, 04:19 PM
The objects are inded slowing down due to negative acceleration towards the sun. When you hear the term "blue-shifted," this is what is is meant. The effect is very very small and will not significantly effect the probes velocity in interstellar space. The article is a good one, but is speculative. We simply do not know what the mass and distribution of mass is in the Kuiper belt and beyond. This explanation is more plausible than a more popular one that Gravity may have an increasingly strong hold over long distances, an effect unknown before since we have never been able to measure it directly before. We will not know which explanation is right unless someone sends another probe specifically on a mission to asnwer this question. Such a mission has been proposed recently by the ESA.

The Near-Sighted Astronomer
2005-Apr-28, 10:28 PM
I wonder, Have we seen this with Voyager too?

If not why not?

Nereid
2005-Apr-28, 11:48 PM
No (we have not seen this wrt the Voyagers), but not for want of looking&#33;

The original paper (by Anderson?) reporting the Pioneer anomaly, plus (maybe) some follow-ups, go into considerable detail as to why the Voyager (and Ulysses, and ...) do not show this effect (or rather, why the effect would be hard to detect).

It&#39;s all so very exciting, yet frustrating at the same time&#33; (a bit like the 40 year history of tracking down the &#39;solar neutrino problem&#39; really).

The only thing that should brighten everyone&#39;s day is that whatever it is, LISA is sure to detect it, to ~<1%&#33;

Duane
2005-Apr-29, 07:14 PM
Originally posted by The Near-Sighted Astronomer@Apr 28 2005, 03:28 PM
I wonder, Have we seen this with Voyager too?

If not why not?
No, different propulsion on the Voyagers vrs the Pioneers.