Pioneer anomaly

[drwayne]

Acceleration is not in fact a constant as a function of time. The spacecraft is moving away from a non-uniform, non-steady-state distribution of mass.<br /><br />Wayne <div class="Discussion_UserSignature"> <p>"1) Give no quarter; 2) Take no prisoners; 3) Sink everything."  Admiral Jackie Fisher</p> </div>

 

[remcook]

my point exactly. if thye pioneer anomaly is indeed a CONSTANT acceleration it would indicate that it is not caused by a small uncertainty in the mass of the planets, since they are moving, hence their force is changing.<br /><br />And yes, the effects of movement of the planets decrease with distance. So, again my point: the pioneer anomaly appears to be a CONSTANT acceleration, so not caused by a uncertainty in the gravity of the solar system.

 

[mrmorris]

<font color="yellow">"So, again my point: the pioneer anomaly appears to be a CONSTANT acceleration..."</font><br /><br />In actuality --they know diddly about instantaneous acceleration of the Pioneer craft over time. What they were able to determine was <b>position</b> and changes therein. From the changes in position that occured during the lifetime of the craft, it's possible to generate calculations to estimate acceleration and velocity that happened between (hypothetical) 'Checkpoint 1238' and 'Checkpoint 1239', but there is no way to determine those values empirically. There was no constant monitoring of the craft. Mathematically they couldn't *prove* that Pioneer hadn't come to a dead stop at CP1238 and 'teleported' to CP1239 immediately before it was queried for telemetry.<br /><br />The mathematical model used almost assuredly assumes acceleration to be constant (primarily because that's both the easiest and most mainstream assumption) -- but it's entirely possible that factors are at work which periodically vary it -- be it clumps of interstellar dust or unknown gravitational effects.

 

[duress]

Clarification please!!!<br /><br />I think I need to clear up one point, it’s decelerating, yes? Because early in the article it reads “That's how much farther the probes should have travelled in their 34 years”, ergo, slowing down, and later it reads “anomalous acceleration of the Pioneer spacecraft”. I’m taking it as acceleration opposite to it’s steady state (One that it should be).<br /><br />“Another idea is that gravity tugs slightly harder at things farther away. That radical suggestion, if proved true, would force a modification of Einstein's general theory of relativity and might eliminate dark matter as a player”<br />The Anti-Cosmological Constant…Einstein’s revenge for uncertainty, what a prick!<br /><br />“Turyshev is the first to admit that the most obvious explanation would be an unknown onboard effect. Perhaps excessive internal heat or leaks of propulsion gas are providing a wee bit of thrust that adds up over the years”<br />Perhaps it’s accruing ice and dust faster than anticipated. It stands to reason that the closer to the Oort cloud you get the greater the congregation of ice and dust, even if they’re only a fraction of the way.<br /><br />PS. http://www.solarviews.com/eng/oort.htm<br /><br />

 

[CalliArcale]

No, the Pioneers are actually still accelerating (presumably, since no further measurements of them can be made). It's just that the rate of acceleration appears to have changed over time in a way not consistent with simple Newtonian physics. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[mrmorris]

<font color="yellow">"No, the Pioneers are actually still accelerating"</font><br /><br />I'm not sure what you're getting at here, Calli. Duress asked if the probes are decelerating, and you said 'no' -- they're accelerating.<br /><br />Acceleration is a generic term meaning a change in velocity. Deceleration is a specific term meaning negative acceleration (i.e. the velocity is decreasing). Since the probes are no longer supplying any motive force of their own -- presumably the only forces acting on them are gravity from objects in the solar system and insterstellar matter in their path (i.e. dust, etc.). Both of these would tend to reduce the velocity of the Pioneeer probes (i.e. negative acceleration or deceleration).<br /><br />Are you saying there's something still increasing the velocity ot the Pioneer probes, or am I missing something in your post?

 

[CalliArcale]

D'oh. That's what I get for posting before my morning Dew. <img src="/images/icons/tongue.gif" /><br /><br />I'm not sure what my brain was doing there. But yes, they are accelerating negatively (or should be). So Duress is actually right. But the rate does not appear to be consistent with what would be expected from purely Newtonian physics. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[duress]

Cheers mrmorris / CalliArcale.<br /><br />I’m finding it very difficult to believe that so many studies into G over the past decade, defining it to the ‘inth’ degree, have not picked up the same anomaly. Nothing. I’m all for the obvious answers first, it saves time at work. So just for now, I’m going to rule out gravitational influence altogether and stick to the basics. I doubt that any venting fuel would go undetected and I’m sure that every perceivable scenario involving external influences, such as Solar Winds V’s Cosmic Rays, has been fully discussed and mathematically plotted. It may well be something very simple and quite obvious…once realised or proven that is. I wonder if anyone has plotted the amount of mass accumulation over time needed to fit the neg acceleration profile that these craft are experiencing. If average rate is in the order of 1lb/yr over the past 30 years, well that’s 30lb (568 lb all up), that's 5%. Increasing the spacecraft’s all up weight could easily be mistaken for an increase in acceleration. Especially if the vehicle itself is in a steady state but under a gravitational influence, or four. Another obvious clue would be if it’s a steady acceleration, as that would be a strong indication of mass accumulation. I would just love to know exactly what rate of accumulation would be required to mirror the same effect.<br />

 

[mrmorris]

<font color="yellow">"I’m finding it very difficult to believe that so many studies into G over the past decade, defining it to the ‘inth’ degree, have not picked up the same anomaly."</font><br /><br />There have been <b>no</b> studies on G at distances comparable to this. Thinking you completely understand how gravity works at interstellar distances because of earth-based studies is akin to thinking you know everything about the ocean depths because you've been to the beach. Scientists only have mathematical models for how it's believed gravity should behave at thses distances -- and it looks like those models may be wrong.<br /><br /><font color="yellow">"I wonder if anyone has plotted the amount of mass accumulation over time..."</font><br /><br />You think the Pioneers are collecting samples on their way out of the solar system? Admittedly, trinkets from Earth might be quite valuable whenever (if ever) they make it to another solar system in a few hundred thousand years. Antique value alone would do it... but then when you add in the shipping charges... <img src="/images/icons/smile.gif" /><br /><br />

 

[duress]

It’s a good thing I haven’t made any wild claims then, merely hypothesised.<br /><br />“It looks like those models may be wrong”<br />Wouldn’t this mean that even the wildest claims have merit?<br /><br />“You think the Pioneers are collecting samples on their way out of the solar system?” Yeah, I hear there’s some really COOL shopping.<br />

 

[CalliArcale]

Incidentally, it's worth pointing out that this effect may not be real. It is extraordinarily difficult to get good measurements. Pioneer 10 and Pioneer 11 are the only probes that provided data accurate enough -- and it's still only barely accurate enough. It's still possible that this is an error in the data. Theories for what's causing the effect (if it's real) are at present little better than speculation; there's no other spacecraft capable of giving us the data to test them, and the Pioneers provided only a very small data set.<br /><br />My hope is that New Horizons will be able to continue this study. It's the next probe slated to go into the great beyond. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[duress]

Yeah, I wonder if the calculations were done in metric or imperial…it could happen again.

 

[remcook]

"There have been no studies on G at distances comparable to this. Thinking you completely understand how gravity works at interstellar distances because of earth-based studies is akin to thinking you know everything about the ocean depths because you've been to the beach. "<br /><br />how about double-stars, etc. they are large distances apart right?

 

[mrmorris]

<font color="yellow">"how about double-stars, etc. they are large distances apart right? "</font><br /><br />Understand that I'm a computer nerd with an interest in space, rather than an astrophysicist. I don't even play one on TV.<br /><br />However -- it's my understanding that when studying distant objects like this, the calculations are made using the the effects of gravity as a known value. Since the masses of the objects themselves are unknown -- distance, velocity and the 'known' value of gravity are used to determine the unknown mass. If the current understanding of gravitational effects at a distance are wrong, there is going to be a *whole* lot of recalculating required.

 

[remcook]

ah of course. that makes sense.

 

[duress]

*WARNING, extreme hypothetical, hot weapons to safe please*<br /><br />Wouldn't it be terrible if gravitational forces over vast distances had an inherent level of uncertainty built into them too? Much the same as the quantum world for position and velocity/energy. I know its wild, but imagine what that would do to the future possibilities of interstellar travel. One could argue that that would cause all manner of inconsistencies in the macro world, true, but we find inconsistencies in the micro world also. We navigate around these by applying varying mathematical and physical rules to suit each individual situation in each discipline. There is no reason for disscluding the possibility of such a scenario, nor string theory for that matter, if a true anomaly existed. If it were true, it would seem that we are somehow conveniently sheltered on an island in the centre of it all.<br />