The Pioneer Effect

March 22, 2008 1:26 AM

NASA is baffled by unexplained discrepancies in the velocities of some of its spacecraft. Dubbed the Pioneer Effect, it has been observed before but has now been discovered in more probes. Many theories have been put forward, many disproved, and some are wondering if our understanding of gravity is correct.

I don't know much about this at all but it sounds interesting.

posted by blue shadows (50 comments total)

i've been wondering if this (the peculiar spiraling shapes of planetary nebula) is a reflection of the same phenomena...i've come to a conclusion that there is some major piece of our puzzle missing when it comes to gravity/cosmology. something big, simple, and (once discovered) blindingly obvious. is there a new 'relativity' on the horizon?
posted by sexyrobot at 1:53 AM on March 22

Isaac Asimov said on multiple occasions that the most exciting words in science are never "Eureka, I have it!", but rather, "Hmm, that's funny."
posted by Malor at 2:49 AM on March 22 [38 favorites]

One strain of comments in the Universe Today post is fascinating:

# Brian Says:
January 20th, 2008 at 4:41 pm

Hmm…I was thinking it could have been some sort of stellar wind or current.

Did all of these happen near Earth? Maybe it could have been "pushed" by particles (dust, gas, or whatever) orbiting the planet? Might account for the small boost in acceleration.


# Janus Says:
January 20th, 2008 at 8:45 pm

Maybe it's dark energy. ;-)


# bryant Says:
January 20th, 2008 at 8:45 pm

it must be cold fusion

posted by Anything at 3:43 AM on March 22

it must be cold fusion

No way. We know mathowie is the only person capable of harnessing Cold Fusion, and even then, not all the time...
posted by wendell at 4:07 AM on March 22 [1 favorite]

(the peculiar spiraling shapes of planetary nebula)

I believe this is pretty well explained, and occurs regularly in simulations using the most simple gravitational models: matter coalesces into spinning spherical blobs on various trajectories, when one of these passes by another close enough, material is pulled out from the spinning core in the pattern you mention.
posted by StickyCarpet at 4:45 AM on March 22

Hmm, just looked at the image sexyrobot linked, that's something else, more like an atom bomb explosion.
posted by StickyCarpet at 4:55 AM on March 22

That last link leaves me, in turns, scared, angry and feeling hopelessness for mankind.

One sad side effect of the marvel we call the Internet is that the stupid, ignorant and/or insane people of the world can read untold reams of bad information, compile horrendous "theories" based on flawed conceptions, compile it all with dazzling graphics and co-opted vernacular and publish it for all the world to see, thus repeating the cycle.

In the case of that last link, the thinking is so plainly absurd that it seems it aught to break the cycle. but then again, it's on metafilter linked as a pertinent to the issue under discussion!

Let me just establish why it is silly real quick with an easy to understand illustration: let's imagine a large box filled with millions of little spheres. Now let's break it up a bit: one-third of the spheres are made of lead, another third are glass and the rest are hollow plastic. These balls are all mixed up in the box randomly, so that any random sampling will show roughly equal distribution. now we start shaking the box at a comfortable 60 hertz within the presence of gravity and what do you suppose happens? the heavy balls agitate to the bottom. This is the same effect that is harnessed in a blood fraction centrifuge or the cracking stack of an oil refinery. the agitation is called 'brownian motion' and the amount of gravity or the introduction of centripital forces and/or thermal environment can all be used to speed up or slow down the process.

no magic anti-gravity is needed to explain any of that. someone tell that kook he's fired.
posted by momocrome at 5:35 AM on March 22 [5 favorites]

Silly me- I thought that galaxies were brighter in the middle because there were more stars there.
posted by pjern at 5:44 AM on March 22

...compile it all with dazzling graphics shitty looking, poorly coloured, amateur-hour jpegs and gifs and co-opted....

FTFY etc.

Seriously, why do all the wacko websites look the same?
posted by kisch mokusch at 5:47 AM on March 22 [1 favorite]

Yes, that last link is pure woo-woo from someone who doesn't understand the first thing about, well, anything.
posted by unSane at 5:53 AM on March 22

kisch, those graphics may seem clumsy to you but they are guaranteed to dazzle the whacko. that's how and why whackos are initially drawn to them. no pun intented.

meanwhile, i am mortified to have omitted a closing tag on my link! i'm also surprised there's no means to edit my own comment. i'm also shamed to have complained about idiots idiotically. sigh.
posted by momocrome at 5:55 AM on March 22

Such a loony - the "Unified Field Theory" is also avaliable on their website as a zip file. Gee, thanks!
posted by monocot at 6:17 AM on March 22

some are wondering if our understanding of gravity is correct

Thanks, that made me laugh and feel better about myself.
posted by zennie at 6:19 AM on March 22

Okaaay, apparently this is all unfunny parody.
posted by monocot at 6:19 AM on March 22

The Economist did a nice piece on this a couple of weeks ago.
posted by ~ at 6:26 AM on March 22

The comments in that UniverseToday thread are just terrifying.

Johnny Blues Says:
January 21st, 2008 at 5:16 am
Asa power boat on a breezy lake, the faster you go, the more skimming effect, further increasing speed capacity. In this case, would gravity waves work as the lake?

*shudder*
posted by unSane at 6:30 AM on March 22

Well, they're discovering planetlike fragments all the time outside the orbit of Pluto... seems to me that this is just a deflection from the minor gravity field of one of them.
posted by mr. creosote at 6:32 AM on March 22

Maybe the craft had to pee. I know I floor it when I'm on the highway and my bladder's full.
posted by not_on_display at 6:34 AM on March 22 [1 favorite]

(The basic phenomenon seems real. The explanation linked to is not. Fox News isn't the least informative source linked in the FPP! And I like it when scientists are described as "baffled". Having a hard time dragging my ass into school this morning to work, and it makes me feel better to think of myself as "baffled" rather than "having no results".)
posted by ~ at 6:35 AM on March 22

The spacecraft are traveling in miles and the measurements are being taken in kilometers. That has to be the answer. This is NASA were talking about, right?
posted by kuujjuarapik at 7:17 AM on March 22 [1 favorite]

from the economist:

...several features of the Pioneer anomalies and the slingshot anomalies suggest they may have a common explanation. Both, for example, involve small objects. By contrast, the data on which Newton and Einstein built their theories were from stars, planets and moons. In addition, the spacecraft in question are all travelling in types of orbit not usually seen in natural systems. Not for them the closed ellipses of Mercury and the other planets; at the whim of their masters in Pasadena they are following much more unusual hyperbolic curves...

and another clue from ars technica: "Oddly enough, this effect is minimized on craft with an orbit symmetric to the equator, and larger for those following an asymmetric orbit."

re: the cat's eye nebula and how "the formation of the beautiful, more complex inner structures is not well understood," curious resonances, viz :P cf. 'Galaxy without dark matter puzzles astronomers' & 'Mysterious web of "dark matter" found'

oh and a (potentially) new CP violation!
posted by kliuless at 7:49 AM on March 22

The spacecraft are traveling in miles and the measurements are being taken in kilometers. That has to be the answer. This is NASA were talking about, right?

Deep space calculations are usually carried out in furlongs per fortnight in order to avoid exactly that problem.
posted by b1tr0t at 7:57 AM on March 22 [1 favorite]

Metafilter: I don't know much about this at all but it sounds interesting.
posted by wheelieman at 7:58 AM on March 22 [1 favorite]

I would comment, but am afraid of leaving other MeFites, in turns, scared, angry and feeling hopelessness for mankind.
posted by KokuRyu at 8:18 AM on March 22 [1 favorite]

lol cats
posted by hortense at 8:34 AM on March 22

Planet X
posted by blue_beetle at 8:55 AM on March 22

It's just the gravitic shield the extraterrestrials have put up around Sol system. Eventually they'll come to a stop.
posted by Henry C. Mabuse at 8:57 AM on March 22 [1 favorite]

That last link is deeply silly. It's not true that hot gas "rises only in the presence of gravity". A bag of hot gas on the moon isn't going anywhere, it'll sit quite happily on the surface. The issue is the presence of a pressure gradient. The energy in a hot gas will expand the boundaries of a balloon and cause it to seek its level in the atmosphere in terms of its mass/volume ratio. And hot gas pressurized at or above the pressure of the surrounding medium will not rise regardless of its temperature.
posted by George_Spiggott at 9:05 AM on March 22 [1 favorite]

from the economist:
...several features of the Pioneer anomalies and the slingshot anomalies suggest they may have a common explanation. Both, for example, involve small objects. By contrast, the data on which Newton and Einstein built their theories were from stars, planets and moons. In addition, the spacecraft in question are all travelling in types of orbit not usually seen in natural systems. Not for them the closed ellipses of Mercury and the other planets; at the whim of their masters in Pasadena they are following much more unusual hyperbolic curves...


I'm a humanist, but this sounds strange to me. Isn't the whole point of Newtonian physics that the size of the objects (as long as we're not talking about things on an atomic scale, when forces other than gravity comes into play) and the shape of the orbit are not important? The same rules apply to billiard balls, satellites and planets.
posted by Termite at 9:12 AM on March 22

The spacecraft are traveling in miles and the measurements are being taken in kilometers ..

There's a passing suggestion here that the problem may actually be the use of the Astronomical Unit, which supposedly isn't as constant as once thought.
posted by wilko at 9:27 AM on March 22

(Here, even)
posted by wilko at 9:29 AM on March 22

Isn't the whole point of Newtonian physics that the size of the objects (as long as we're not talking about things on an atomic scale, when forces other than gravity comes into play) and the shape of the orbit are not important?

It takes a lot less force to move a small thing a measurable distance than a big thing. And planets are several million times heavier than satellites. I am not an astrophysicist though and have no idea what the limits of our measuring equipment is these days for either planets or satellites.
posted by public at 9:39 AM on March 22

It's just the gravitic shield the extraterrestrials have put up around Sol system. Eventually they'll come to a stop.
posted by Henry C. Mabuse

Ahh, Hogan. A pity he can't write for shit, because my God the quality of his ideas . . .
posted by Ryvar at 9:48 AM on March 22

Planet X

Nah, it's probably Nemesis. That fucking thing gets blamed for everything.
posted by quin at 10:13 AM on March 22

That last link is indeed riddled with wrong - they don't understand what a flat rotation curve is - galaxies don't rotate like a solid disk as it says to take one paragraph at random. And I took a few more paragraphs at random to try to find one that might not be totally incorrect but I'm yet to get lucky. I'm not going to keep looking either as my level of frustration with crackpots is about to become gravitationally unbound.

That said, the Pioneer anomaly is interesting, but not necessarily indicative of our understanding of gravity being wrong. There's also plenty of other reasons for wondering if our theory of gravity is correct, particularly at very small and very large scales, but not really so much at solar system scales.
posted by edd at 11:03 AM on March 22

Metafilter: pure woo-woo from someone who doesn't understand the first thing about, well, anything.

(Actually, this is interesting stuff; I hadn't heard of this phenomenon before, and no doubt the explanation will be simple yet profound - as some many of these things are).
posted by never used baby shoes at 11:38 AM on March 22

Centuries old Newtonian-physics model - deemed by any serious scientist as "good enough for interplanetary trajectories and pub billiards, for now"- based on calculations derived from unrealistic, non-existent Platonic solids, breaks down when applied to fuzzy, hoary, non-Newtonian real life.

Film at eleven.
posted by loquacious at 11:49 AM on March 22

I kind of like that last link. It is so screwed that even a non-scientist like me can debunk it and feel like I know something. The Archimedes part, for instance, where the guy confuses mass and volume. And all that stuff about gas rising because of anti-gravity -- which is why salad dressing separates, too, right? All that energy packed into the oil or something. See, if people didn't use external energy sources, like rockets, but just internalized all that energy instead, why then, we'd all just rise and float free of Earth's surly bonds. And the Pioneer Effect proves it. Yes.
posted by CCBC at 1:04 PM on March 22

Now that you mention it, yes, what the world needs is a Salad Dressing Theory of Everything. http://salad-dressing-toe.net/ is available, we just need someone to come up with the funky pixelart tha will sweep the masses' imagination.
posted by Iosephus at 3:22 PM on March 22

For some reason, all I could think of was the luminiferous ether.
posted by tommasz at 6:11 PM on March 22

Isn't the whole point of Newtonian physics that the size of the objects [...] and the shape of the orbit are not important? The same rules apply to billiard balls, satellites and planets.

Yes. Well, really, that's the point of all physics. But anyway, it's wrong to think that gravity has only been measured on large scales; Cavendish's original experiment to determine the value of G used masses of a few hundred pounds.
posted by hattifattener at 7:29 PM on March 22

Time is not invariant. They're looking at the acceleration, but velocity is acceleration × time. Time is the result of entropy caused by the expansion of the universe¹. As the expansion of the universe slows, so does time. However, due to the presence of gravity, the expansion of the universe does not slow uniformly². We haven't observed this effect, because all of our measurements of the speed of light have been based on observations made within the solar system. What this actually means is that many of our extrasolar observations involving redshifting and blueshifting are incorrect, and indeed obviates much of the need for "dark matter" explanations.

There. I have officially blown your mind. Or proven myself batshit insane. Personally, I hope it's both, but I anticipate we'll all be dead before I'm proved right.

¹ Entropy increases as volume increases. Take two chambers, separated by a valve. Put purple gas molecules into one, leave the other evacuated. Now open the valve. The tendency of the purple gas molecules is to "spread out", eventually filling both chambers.

² Picture the 3-D universe as the 2-D surface of a balloon. Draw little galaxies all over the balloon. As you blow into the balloon, the galaxies spread out. This is the traditionally accepted principle used to explain the redshifting of galaxies; that the universe is expanding. Now gravity is like a pressure on the 2-D membrane of the balloon's skin. If you zoomed in on the surface of the balloon til it looked like a flat rubber sheet, you could put a large ball in the middle to represent a mass (say, the sun). If you tried to roll a ball past the larger mass, you'd notice it curved around the larger mass due to the deflection it caused in the surface of the sheet. This is the Physics 101 demo of General Relativity. Ok, now zoom out again. This time, use the fingers of your hand to represent massive objects by gripping the balloon as you blow into it. If you've done it right, you'll notice your fingers push into the balloon ("inwards" and "outwards" on the balloon represent our fourth dimension—NOT to be confused with time in this case) deflecting the rubber surface just like the large ball on our giant rubber sheet. The area bounded by your fingers will not expand at the same rate as the unbounded area. As you move further away from massive objects, the rate of expansion in the universe changes.
posted by Eideteker at 8:26 PM on March 22

sorry if i was fuzzy headed when i last posted ...it was late. it just seemed to have something to do with off-axis rotation...(im an artist but i did study physics for a few years (straight a's in six semesters of calculus...now, sadly, mostly forgotten...) i find they tend to mix well for me, but most scientists think i'm sloppy, and most artists think i'm crazy. me, i lump it all under 'nature')

so forgive my rambling...

things poorly understood by science that i think might be related if there is indeed a common cause: (with possible explanations):

-Pioneer effect (solar/planetary magnetism? (i mean these things are metal, right?) stronger/more polarized above and below the equatorial plane, neutral at the center...remember the iron filings? also, have these craft become magnetized? is there any way to tell? i know the pioneers and v'gers are 'boresighted' on the earth now...i forget if they are rotating on that axis, though, or whether or not that would affect any magnetic build-up...)

-the 'Dynamo' effect that causes these magnetic fields (for this all i have is a shape from my subconcious, a molten cylinder (not a perfect cylinder, mind you) aligned with the field girdled with a molten 'donut' or disk in the middle, but tilted off the equator by about 20 degrees. they rotate in the same direction, but at different speeds, and though they seem to have their own identity (the disc and the cylinder), they blend and share material, like the two lobes of a Lorenz attractor, with lots of shearing. oh, and the disc doesnt rotate, just its material (ie, the 'higher' side stays in the same place...imagine a vertical line with a diagonal slash through it, sloping down from left to right...thats the side view...if they rotated together, the slope would go the other way and back again...it doesn't do that...except maybe sloooowly. the path of any individual particle is very spirally...up and down the cylinder and around and around the disc. like i said, though...its just something from my subconcious.)

-"Dark Matter" (oy vey. i flatly just don't believe in it. at least not in the enormous quantities they're talking about. one article i read claimed that the galactic motions that seem to require it (ie, not flying into bits) are being figured with Newtonian mechanics, and that if you use relatavistic mechanics, you don't need dark matter. another possibility i haven't heard addressed: magnetism. stars are just big magnets, right? of course, since magnetism is about 10^36 times stronger than gravity, we'd need an explanation of why the galaxies aren't just totally collapsing, right? and finally another possibility to explain some missing mass, this one from chemistry: mixtures are cloudy, solutions are clear. maybe, we're just looking through some of this missing mass...though i imagine it would still register spectroscopically, no?)

that's all i got.

eiderteker: that is indeed a mindfuck...it reminds me of the search for the shape of the universe based on the variations in the cosmic background radiation...cosmology is so screwed...its like trying to figure out what you're looking at in a funhouse mirror, without knowing the shape or the mirror...

b1tr0t: we must have taken the same introdution to physics...i remember the 'furlongs per fortnight' question from the homeworkings...it was to find the speed of light, right?
posted by sexyrobot at 12:20 AM on March 23

(OF the mirror, not OR the mirror...)
posted by sexyrobot at 12:23 AM on March 23

Centuries old Newtonian-physics model ... based on calculations derived from unrealistic, non-existent Platonic solids

Careful, there, you're getting Newton mixed up with Kepler.
posted by anewc2 at 4:22 AM on March 23

sexyrobot, just wanted to weigh in on a couple of the Dark Matter issues you brought up:

"if you use relatavistic mechanics, you don't need dark matter"

As far as I know, that's pretty much an urban legend. In fact, studies using gravitational lensing, which relies on the effects of general relativity to determine mass without the use of dynamics, have confirmed dark matter, not contradicted it. And one of the big problems with the theories that say that problem is with our understanding of gravity rather than matter, such as MOND theory, is that they're extremely hard to reconcile with relativity. MOND theory postulates that gravitational force becomes stronger than the Newtonian approximation at great distances or in weak fields, and would be a neat solution to both dark matter and, I would imagine, the Pioneer effect, but the current evidence seems to be against it rather than for it.

"since magnetism is about 10^36 times stronger than gravity, we'd need an explanation of why the galaxies aren't just totally collapsing"

Well, not really. Think about that for a minute. First, if you put a powerful magnet in the center of your house, you don't need an explanation of why your house isn't totally collapsing. Magnetism is stronger than gravity, but also a lot more selective in what it effects. Second, stars really aren't big magnets anyway, at least in the sense you probably mean. They produce a ton of electromagnetic energy, but that's very different from being a magnet. Stars do also have an electromagnetic field, which is a lot closer to what you mean, and those can have very interesting effects (such as flares), but they're WAY weaker than the gravity well of the star - far too weak to affect another star light-years away. Magnetic force is technically stronger all things being equal, but they're not equal here. Stars have a lot of mass.
posted by kyrademon at 6:00 AM on March 23 [1 favorite]

What kyrademon says, except it's not an urban legend exactly. There was a paper claiming that galaxy rotation curves could be explained by a relativistic model, and that's where this 'myth' arises from, but basically it was wrong.
posted by edd at 7:27 AM on March 23

yeah, it definitely wasnt this mond business...dammit i wish i could find that article!...it was pretty simple and straightforward and made a lot of sense (haha the opposite of me!) ...i recall it had something to do with how the models of galactic mass were made based on apparent motion...gah!
but wrong, really? is there a refutation somewhere? i'd like to see it...

and yeah i've seen the computer-inferred photos of the dark matter around certain galaxies, still, i'm gonna wait until they've caught some in a jar before i stop shaving with occam's razor...

and i'm not talking about 'electromagnetic energy' ie, light, i'm talking about the magnetic fields ...the ones that make compasses spin around, the one that the voyagers are currently penetrating as they move into the galactic magnetic field, that one being the combined magnetic field of all the stars in the galaxy...sure, they're individually weak, but they are damn persistent, and i'm betting that we're going to find that more stars are generally aligned with this field than not, like magnetic marbles on the skylab ...i actually came up with a process to try to photograph a galaxys magnetic field, but i dont have access to the equiptment...basically i want to take a series of images through a polarizer (ideally 360) at different angles and use additive image stacking to bring out structure ...they might have to be overexposed to show the field lines in the halo...does anybody have access to a reasonable large telescope and a good polarizer?

also i checked on the progress of gravity probe b to see if they were picking up this effect, interestingly, they seem to be having some trouble with their data... also, there was another frame-dragging or gravity mission i recall, possibly japanese...a cluster of (i think 3) ships, shaped like a ball with a geodesic arrangement of holes with mirrors inside...as i recall they were going to orbit the earth and bounce lasers back and forth...does anyone remember what that mission was called?
posted by sexyrobot at 12:51 AM on March 24

also, LOVE the asimov quote!...i have to agree, whatever this is, it's going to be BIG!
posted by sexyrobot at 12:54 AM on March 24

sexyrobot: I think this is a refutation - not sure of it, not read that myself, but the description of a singular disk fits with what I'd heard about it.
posted by edd at 6:20 AM on March 24