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Space Probes Too Slow - Scientists Ask "Why?"
Rudolf writes "Newsweek has an article this week, available here, about NASA calculating that space probes, such as Pioneer 10, 11, and Ulysses, are slowing down more than they should. A team of astronomers and physicists couldn't figure it out, so they published their findings in Physical Review Letters to generate discussion. Several possible causes of the slowing have been discussed, but nothing that completely solves the puzzle. Anyone care to rethink gravity and time?" Update: 09/29 09:00 by H :Thanks to Mark for his link to the original citation.
Maybe the stars we see are just painted on the walls around the solar system ;)
Yeah yeah, working on it... timescape theory page will be up once my Unlogic theory page is re-formatted...
-- 'The' Lord and Master Bitman On High, Master Of All
The physicists at JPL have accounted for this, their not that stupid. It jsut doesn't explain the slowing down enough. However, it could reveal errors in their assumptions about the density of stuff in space (i think it's like 3 hydrogen atoms per cubic meter, or so). BUt it could be something new, like the heliopause ending closer to the sun than thought, or having some non-linear decaying function with distance.
10 seconds. Gravity propgates at the speed of light, like all known forces. Or so physicists would like us to think...!
Impossible, the force they measured was towards the sun, not opposite the probe's line of motion (which would be the case if it were losing velocity to collisions).
:)
To be fair, this was my first thought on the subject too, however
Doug
Venn ist das nurnstuck git und Slotermeyer? Ya! Beigerhund das oder die Flipperwaldt gersput!
Errrr, hate to break it to you, but their does exist a force that repels matter. It is called E&M. You know, same potential as gravity, but it can repel as well as attract. Last I checked it isn't playing hell with our concepts of energy conservation. By the way, it does take an infinite amount of energy to create a point charge (classically speaking). Just make it a footnote and forget about it since ervery thing else works.
:)
Er, yes... but the thing is, with EM, both particles repulse one another (with the strength of repulsion diminishing by the inverse square law). However, with gravity, because of the nature of the force involved, the "normal" particle would still be attracted to the "anti" particle (even though the "anti" particle would be repelling it), and as such, they'd chase each other across the universe with a constant force (ie. constant acceleration, which gives infinite energy). Which is a no-go.
Damn. Wish I hadn't jettisoned most of this stuff from my brain.
I'll work on a full treatment of the problem if you like
Simon
Coming soon - pyrogyra
It could be dust or some other particles, maybe there is a belt out there before the start of the Kyper(sp?) Belt? That should slow a spacecraft down a bit.
It has been suggested that physical constants indicate our lack of understanding of physics. What if the speed of light isn't constant? If you accept the emerging scalar physics, a new school that uses Maxwell's original euqations, than the speed of light should not be constant.
"Luncheon meats make the sawdust in your stomach explode."
Gravity has features akin to elastic after and up to a point. The probe has reached the beginning point of the elasticity-effect of gravity, and will continue to exponentially decellerate as it reaches the extent of the Sun's effect. Obviously, this would create an increased collection of matter at the reaches of this effect, so that is what we test for. Not bad for a 19 year old with no college, eh? ;P Jason jfisher@idmicro.com
Perhaps the orbit is polar so that the orbital plane of the satellite is at 90 degrees to the spin of the earth? (assuming it's spin poles and not magnetic poles).
- Ignore me. Insufficient coffee.
I have heard about this in the past and I remember someone brought up the point that it may not be that the probes have slowed, but the distance being measured from the probe to eath is being measured by radio waves. Anyway, the theory was that radio waves can travel faster when not acted on by the gravity of a near by solar system thus giving a readin of a shorter distance. May not be right but it is a distinct possiblity.
~`'`~-,_,-Jason Wylie-',_,-~`'`~
Was that last bit serious? (I'm not a physics student if you couldn't tell) Sounds like something I read in NS some time ago about a guy who had resolved the universe down to information theory and reakoned that everything was to do with wormholes (explained entanglement and quantum randomness and everything else to boot).
:)
:)
:)
;) (time I got down to the patent office).
;)
That last bit was serious as far as I'm concerned, but other than a few discussions with a friend of mine who was at CERN (who said that I'm correct in principle... but that some of it was out of his field), I've never had the guts to formally write it down. Not to mention that it'd take me a few years to relearn everything I needed to know, and learn enough about quantum mechanics and space-time theory to be able to determine the wormhole structure
Funnily enough, Kip Thorne never replied to my email... not surprised... I probably sounded like a complete kook
Mind you, a number of professors at my uni (way back when) did buy off on the "gravity as knotted spacetime" part of my theory... and on the whole "time as nonlinear for particles" part of it too...
Maybe at some point I'll join the legions of kooks across the world and put something up on my website. It'll all be geometrical arguments though
Mind you, the theory, as it stands, is in pretty good shape. It has the potential to give another explanation as to why there's more matter than antimatter in the universe (without symmetry breaking, which I've always had a slight dislike for), and also gives a possible method of "faster than light" communication (though that's actually a misnomer). However, that depends on whether or not the half-twist in the wormhole between an electron/positron pair has an impedance high enough that it acts as a reflective barrier to signals squirted into it. The good thing though is that it should be reasonable easily testable, now that molecular cages have been created. Just create one hydrogen molecule, one anti-hydrogen molecule, trap them both in cages, and make sure that the electron around the hydrogen and the positron around the anti-hydrogen were both created in the same particle-pair creation event. Then squirt light into one of them; if the theory holds and there is no reflection at the twist, then the other will "ring" in sympathy, no matter how far away it is physically. Think of the applications
This also explains radiation resistance
[Mind you, if the theory was correct it'd explain why the SETI project hasn't picked up anything]
Si
(Joining a legion of kooks...)
Coming soon - pyrogyra
I have heard about this in the past and I remember someone brought up the point that it may not be that the probes have slowed, but the distance being measured from the probe to earth is being measured by radio waves. Anyway, the theory was that radio waves can travel faster when not acted on by the gravity of a near by solar system thus giving a reading of a shorter distance. May not be right but it is a distinct possiblity.
~`'`~-,_,-Jason Wylie-',_,-~`'`~
Clearly, the probes are slowing down because of the load on their systems caused by the Slashdot Effect.
-- Ed Avis ed@membled.com
Your first theory cannot be correct. "it must be concentrated more densely near the sun and less densely farther away" violates one of the leading views on space and time-- that the universe looks and acts the same no matter where you are. The second theory-- If dark matter did exist, I seriously doubt it would have any effect on the space probe because A) It is too sparse B) If it weren't, we'd have found more by now And back in the day, people used the "Ether" theory to explain why light always travels the same speed and similar effects. It is my opinion that the apparent error in this probe's speed and acceleration are due to it's moving through space/time at 27,000 mph. This probably has a small effect locally, but over time it builds up and in effect, moves through time slower than you or I. Of course, that is all Einstein's general theory, and the NASA guys have already looked at that.. I would be really interested in seeing them post all of their equations and work so we can check for errors.
now where is that secret warp factor? I hope the head boss doesn't manifest himself just yet... We haven't even saved our game!
Reminds me of how often I wish I could "save the game" IRL before attempting something risky ("hum, I wonder if brute force will fix the problem" ;)
Not all dust is in orbit, wise-guy.
There's just something not right with the whole picture as they currently know it. It happened with 3 spacecraft so far, so it's getting more and more unlikely to be something correlated with these long-range craft!
make world, not war
- All probes use the same instruments (I can see this for the two pioneers, but ulysses? This'd be easy to find out though I guess, and NASA would've checked it first)
- It's always towards the sun... coincidence?
The question is: Do other probes experience a similar "problem"? We've sent so many to space, if it's really a phenomen of gravity or whatnot, it should be universally observed.Another quesition would be, at exactly what distance is Ulysses orbiting the sun? If it's closer to the sun, particle density etc. should be relatively easy to determine.
Somehow I seriously doubt the answer can be easily determined or will even pop up to be some instrument fault etc - NASA would check into these things painstakingly before they released such things. They would also not have said something if it was within the "normal error range".
Unfortunately I am not into astrophysics... so I am mostly clueless... Give me a cisco router any day, but I'll have to surrender before a Pioneer probe. :)
Dark matter isn't what you think it is. When folks talk about dark matter, they're talking about stuff near the center of the universe, black holes, stuff that doesn't show up with traditional methods of detection. Dark matter isn't just 'stuff' floating around Venus.
-- Almost an astrophysicist
Oops, typo. That final sentence should be "so it's getting more and more LIKELY to be something correlated with these long-range craft!" Sorry about that.
make world, not war
If I recall correctly, wasn't Pluto reclassified
as a planetisimal (sp?), and therefore not a
planet?
--
Do people really read these?
Which of the current nine planets doesn't actually count as a planet?
At this URL the article mentions that Pioneer 10 will reach the stars of the constellation Taurus in about three million years.
At this URL is presented a star chart showing what is supposed to be the course of an unknown tenth planet in the solar system, which according to this page will pass by the earth in 2003.
What is interesting is that the current location of this "Planet X" is given to be just above Orion, in the leftmost portion of Taurus. Does anybody have more detailed information on exactly where in Taurus Pioneer 10 is, so this correlation could be checked closer?
Marv
I'm not a journalist, but I play one on slashdot
Contrary to mettw's post, the speed of outer stars in a galaxy does not in any way constitute a discrepency in any theory of gravity.
[This is mostly background to redirect many of the wild posts regarding dark matter attached to this article]
When you measure the velocity at which stars orbit the center of a spiral galaxy (mostly external galaxies like Andromeda, but also in more difficult work on our own galaxy), you see that the stars near the center orbit in a pattern which mimics the pattern of stars we see in that galaxy. That is, if we count the stars in the center and calculate what their mass should be, it matches with the velocity at which the stars orbit (that is, gravity is balanced by centripedal force: called Keplerian rotation). But further out from the center of many galaxies, stars orbit faster than what you would predict by counting all the mass from all the stars you can see. If they are going faster than the gravity must be stronger than what you originally predicted. If all the stars you can see can't make enough gravity, then what? Throw out the theory of gravity which has proved so very successful in the past, or postulate that there must be some matter which you can't see, that is, dark matter.
Most astronomers believe the latter. They think there is not enough eveidence to toss the whole theory. Instead, they assume that galaxies are more complicated that we first thought. What causes this dark matter? Well, it must be something that gives off less light than stars. Some folks have suggested that "ordinary" matter (planets and brown dwarfs) make up the difference. Others suggest "strange" matter (stuff not discovered yet). Finally, the flippant sort of people commonly attribute the extra mass to interstellar Volkswagens (i.e. they don't care what it is just yet; they just want to measure the effect for now).
Why am I saying all of this? I just want people to be a little more informed when the term "dark matter" gets thrown into the discussion.
BTW, the "1/r^2" that the previous poster refers to is the pattern of density of dark matter needed in many galaxies to explain the patter of stellar orbits you see. That is, as you go further out from the center of a galaxy, the density of dark matter decreases by the square of the distance. This is NOT a factor thrown into a gravitational equation. It is a feature added to a density model of a galaxy that helps to explain its rotation curve. It's like needing to account for the mass of the passengers when computing the acceleration of a car. It's NOT a feature of physics.
Its the milk doing it!!
Probably lack of sleep, but would that be the 'cosmic constant' that Einstein later removed from the theories because he'd only put it in to keep his theories in line with his own (personal. as opposed ot scientific) views on the universe?
:-)
If not, oops
- Wondering where all that caffenie went.
For those interested, the original articles and articles that cite (and comment) it can be found from the web: gr-qc/9808081
Like maybe there's still infalling dust from the Kuiper belt, or the Oort cloud, and since it's not being swept up by planets or moons, it's fairly constant...and would surely affect a *very* unstreamlined vehicle.
For that matter, if the vehicle was decelerating before, and there was more infalling dust, there might be some backwash (no, I didn't say "something to push against, duhhhh"), radiative or otherwise.
mark "would really prefer something more interesting, Mr. L. Green Man...."
I just hope they don't find a 2100 century equivalent to the old theory claming that space was filled with ether. Perhaps we have a 9'th planet. (not very likely explanation)
As things move from the gravity well of the
solar system, they ought to gain mass.
Spacetime does have an upper limit as to
how much mass can be carried a given location before the surface tension is comprimised and a black hole forms.
Now think of the opposite. As distance increases from a powerful gravity well, there
will be less competition for the limited
tension carrying capacity of spacetime. In
other words, something can make a bigger "dent".
Now, I'm not saying mass will increase exponentially as the distance increase but just
moreso than it would be from within a deep
gravity well. Before some of you guys get
out the beat-down sticks, keep in mind that
quantum gravity doesn't so much as produce a
fart in response to this slowing of the
spacecraft. And "surface tension" is not
such a bad analogy to be used with spacetime.
A "rubber sheet" was Einstein's favorite mental
construct.
These probes have bad aerodinamics, and space isn't a pure vacuum. The poor thing bumps into an area with more hydrogen and slows a bit down. You cant't meassure everything.
Nah. Dark Matter's just the lost socks and things that have fallen behind the fridge of every civilization that's ever existed. Unwanted and unneeded, they create their own wormholes out into the void to be alone with their sorrow.
"Life. Don't talk to me about life."
--
--
The Internet is the Suppository of All Knowledge. You get it in the end.
We don't have precise estimates yet on how many dust and small debris is floating out there. Maybe the impacts of big amounts of small objects slows probes down. (The debris in itself would be moving towards the sun, due to it's gravitation)
It is true that cosmologists are discussing the possibility of a non-zero cosmological constant (Einstein's lambda), but the subtlety of the effect is way to small to be evident on the scale of the solar system and masses like the Sun's. The realm where lambda may be relevent is in very high densities, like just after the the Big Bang, or over very large distances (like the diameter of the observable universe).
Anyway, if lambda (or any odd theory of gravity) could affect Pioneer, then we would likely see it in the orbit of the outer planets, I would think... It seems MUCH more likely to me that something peculiar to the spacecraft (like directional heat dissipation) could cause the effect.
Believe it was 2010, (Arthur C. Clarke) where discovery was droping into Io (I believe) due to a LARGE em tube/field between Jupiter/Io... yes, basing on fiction (that I don't understand completlely) but brings up the point that "The Universe is not only stranger then we imagine, but stranger that we can imagine." Goes to show we have a lot to learn...
Credit to Clarke and Einstien for ideas/quotes, and no credit to a spelling checker cause I didn't use one...
This sig left intentionally blank.
Supposing that there is a nearly constant layer of dark matter throughout the universe (thus gravitational effects would not be present), the slowdown could be caused by the frictional effects of dark matter. This might be a hypothesis. I don't know enough about dark matter and stuff, however.
It's been a long time since I studied any physics but "gain mass"? I thought mass was invariant. Why would it gain mass due to a change in gravity.
trust me, there's nothing so disconcerting as finding your theories and observations conflicting each other! it can drive you nuts!
They've been looking hard at this problem for the past several years! and the more attention it's gotten lately has drawn more scientists to study it. All simple calculations thus far cannot account for the full effect noted.
>>Like 'ether', dark matter is not real at all.
I don't believe the 'ether' concept is totally false. I do agree that 'dark matter' is probably not real at all though. Quantum theory has come across the ZPE (Zero point energy) concept. If you carry the concept out a little more, then wouldn't SPACE HAVE MASS. Which loosely ties into the 'ether' concept. Relativity is not 100% correct or the unified field theory would have been solved by now. So perhaps light's constant nature is only contant while moving though space and time. Meaning, if light can propogate through a void, it could be interacting with space itself which gives it the speed properties of 'C'.
We are visually driven in our research and I believe that limits us somewhat.
--Scott 8-}
Physics majors are welcome to correct me here (I'm a bit outside of my field), but I seem to remember reading an article a while back discussing the possibility that gravity warps time/space (Scientific American or Popular Science...I don't remember which). The theory held that large gravitational wells, and especially large rotating gravitational wells, literally pull at the fabric of time/space and stretch it out near the center of the affected area. To prove/disprove the theory, the scientists involved were going to put a satellite into orbit and set a high mass object into a rapid spin. If the theory was correct, spacetime distortion would be detectable around the outer edges of the rotating test object.
Could this be what we're seeing, only on a much larger scale? Perhaps the Sun, with its massive gravity well, has caused time/space to stretch within our solar system, and what we're seeing here is the effect of the probes re-entering "normal" space. From our perspective within the "stretched" area, it would appear that the craft was slowing down.
I would love it if someone could provide more info on this theory, and fill me in on whether or not it could possibly apply here.
There is nothing so pathetic as seeing a beautiful young theory roughed up by a tough gang of facts.
Er, has the person who came up with this argument heard the news that an infinite series can have a finite sum? It's not like this is a new mathematical discovery mentioned on /. last week, after all....
If there is such a thing as gravitational repulsion, and it follows the same inverse square law as gravitational attraction, then the potential energy of two gravitationally repulsive masses equals the escape energy of two corresponding gravitationally attractive masses. Let a block of upsidasium fly off into space, and it will (ignoring air resistance, etc) fly off into space at escape velocity, not "infinitely close to light speed".
/.
/. If the government wants us to respect the law, it should set a better example.
I wasn't thinking straight. If there was enough matter to affect the probes we'd be able to detect its effects on the planets. Crazy theory.
Come to think of it, 27000 miles per hour is not all that fast. That's only a few kfps more than the top speed that the Apollo astronauts travelled at during their lunar transfer.
In order to get all the way out to Jupier, Saturn, etc, the probes must have started out MUCH faster. A tiny relativistic error could throw off NASA's calcuations by a whole lot.
It depends on how they're calculating distance to the probes. Suppose the probes are sending beeps that are known to be 1 second apart. Compare the measured time between beeps and you can find the probe's _speed_. To get the actual distance, you'd probably have to ping it and wait for it to respond while measuring the time it took.
Another possible way that you might determine speed and distance could be for the probe to send precise time from an onboard atomic clock. The clock would measure different time than on earth due to relativisitic speeds; the total difference
between earth time and space probe time would be a history of the probe's entire journey. It's pretty complicated. You'd have to know how far away the probe was in order to figure out how much of the time difference was due to distance and how much was due to time dilation.
So while over long times the energy at a given empty volume in space is zero, for short times you are not sure. In fact for very short times it is unsure enough to allow the creation of virtual particles, like an electron positron pair, that "borrow" their energy from the vacuum, and annihilate after a short time, giving back the energy.
Zero Point Energy
Nope, that term describes the fact, that the lowest possible energy state for a harmonic oscillator in quantumn mechanics is non zero.
Reboot the probe, and it will speed back up (they should be damn glad it didn't just crash!)
Okay, if our sun is radiating energy at something like 3.86*10^26 Joules/second. Then, by E=mc^2, the amount of energy released each second should have an equivalent gravitational force of something like 4.536*10^9 Kilograms. That's one hell of a lot of mass tied up in starlight. And it's in a continually expanding shell.
For a spacecraft at 67 AU, we're talking about a sphere of energy with a radius of something like 10^13 meters. But the energy is not evenly distributed throughout the sphere. Instead, the energy density at any particular point a distance of R from the sun will be inversely proportional to the surface area of a sphere with radius R. Since, presumably, the sun radiates energy equally in all directions. And, therefore, the energy radiated by the sun will be evenly divided across the surface of such a sphere.
It will take some 9 hours, 16 minutes, and 50.67 seconds for light to reach the spacecraft from the sun. In this period of time, the sun will have released some 1.29*10^31 Joules of energy. The gravitational equivalent of some 1.5*10^14 Kilograms.
Now, one can NOT model this sphere of energy as a point source, because gravitational effects fall off at 1/r^2. Energy (mass) nearby will have a more positive effect than energy (mass) far away. And the results will NOT be the equivalent of a single combined mass at the center of the sphere.
However, the energy (and gravitational effects) of a point on the surface of the sphere is falling off at a rate proportional to 1/r^2. (Since the surface area of a sphere is 4*pi*r^2.) So everything may just cancel out and be negligible.
Unfortunately, I am not a mathematician, physicist, nor an astronomer. My old math skills are far too rusty to solve the calculus and resolve this problem. (For all I know, I may have already messed up the math...)
So can anyone out there in slashdot land help? Is there a mathematician in the house?
Also: I have to wonder. Can you imagine the gravitational effects of lightyears of starlight? I mean, scientists did account for the gravitational effects of starlight before they started looking for dark matter, didn't they???
PS> For those wondering how I got started on this thread: Many years ago I read 60's Star Trek. At one point, they mentioned a reference to a planet Vulcan being inside Mercury's orbit. Further investigation revealed that, at one point, folks actually thought there was a planet inside Mercury's orbit. They called it Vulcan, and they needed Vulcan to account for otherwise unexplained oddities in Mercury's orbit. Einstein eventually used E=mc^2 and the gravitational effects of the energy released by the sun to account for Mercury's orbital anomalies. And the Vulcan theory was formally disproved something like three quarters of a century ago.
Man, does that ever take me back....
---
Linux MAPI Server!
http://www.openone.com/software/MailOne/
(Exchange Migration HOWTO coming soon)
Uh, no. There is exactly one equation specified by general relativity, and that is the Einstein field equation. It can have many solutions, but there is only one law. Of course, given any tested law of physics it is always possible to construct infinitely many other laws that also agree with experiment by merely adding in perturbation terms that are too small to distinguish from the original. (See, e.g., scalar-tensor theories like Brans-Dicke theory.)
Yes, it's the same cosmological constant. However, after Einstein "recanted" on it, other physicists found reasons within quantum theory (which Einstein didn't subscribe to) for why it might need to be put back. Furthermore, there now appears to be observational evidence that supports a nonzero cosmological constant (the whole "accelerating universe" deal from a while back). However, as another poster pointed out, the effect is still too small to be responsible for these probe results.
Gravity could be quantized, but the "energy levels" would be so finely distinguished on solar-system (or even atom-sized) scales that they would be effectively continuous, just like classical electromagnetism and such results on large scales as the limit of quantum field theory.
DNA is a Turing machine. You, however, being dynamic and emergent, are not.
The analogy between gravitational waves and (say) water waves can't be pushed that far. It could be possible of course that the probe is running into some gravitational waves, but the effects wouldn't be what are observed (constant unidirectional force). I also suspect that waves large enough to have this kind of effect would've been seen by now by the gravitational wave detectors that are being brought into test mode now.
Sadly, none of us can probably make a useful suggestion on this topic (one that would have eluded all the physicists that have been working on this). Unless the next Einstein is reading Slashdot,we can only make narrow conjectures. How many of us have the knowledge and data required? We might as well try to diagnose a medical condition based on a cursory discussion. It's fun to talk about, though.
They are both really moving out of the system, are they showing the same effect?
l
8 29 4 08
From:
http://vraptor.jpl.nasa.gov/voyager/voyager.htm
They are both speeding out of the system at:
...............................Voyager 1 Voyager 2
Velocity Relative to Sun
(Km/sec)..........................17.294....15.
Velocity Relative to Sun
(Mi/hr)...........................38,684....35,
Distance from the Sun (Km)
......................11,196,000,000 8,776,000,000
Distance from the Sun (Mi)
.......................6,957,000,000 5,453,000,000
not true. As a poster after you on the original parent thread noted, repulsive forces do exist, as you'll study in any E&M class. You basically forgot a negative sign in your account. You're correct in observing that these two particles (if repulsive) will travel to infinite distance from each other (in a closed system). However, it is this infinite distance which has relative zero potential energy. You INCREASE your potential energy as you bring the two particles together (for this hypothetical repulsive case). Just like with two attractive bodies, potential energy increases as you separate them, here potential energy decreases as you separate them.
As a final note, if everything was repulsive, you wouldn't eventually have everything travelling at speeds of light, but instead equally and infinitely spread out from each other. Everything would be at rest relatively to everything else.
make world, not war
Those gerbils on those treadmills powering the probes can't run forever, you know.
IF there are no other explanations, like the contribution from heat emissions etc, then perhaps we are seeing an effect from some locally trapped dark matter in the solar system. Like a minor version of the concentration within the galactic halo. Not enough to be noticable calculating planetary orbits, but with a decades long radial trajectory (well more radial than planets) there would be a detectable cumulative effect.
Just my 2 cents.
Bitter and proud of it.
Just proving that on the web, folks can grab an Old News story and run with it. /. should hang their head for not researching the story.
Don't sweat it. You get what you pay for.
People gripe when the same article is posted twice a week apart. A year apart can be forgiven, and, after all, it's not the same URL
It's Because the universe is expanding. And seeing as Earth is at it's centre anything travelling away from Earth will be subject to this effect, the more distance between Earth and the moving object - the more dramatic the effect.....
I would be really interested in seeing them post all of their equations and work so we can check for errors
Cool. Open Physics. So long as ESR doesn't get involved. He's even been deleting entries from the jargon file, y'know...
axolotl
Do you actually understand anything more about dark matter than "it's got mass and we can't see it"? Your dark matter hypothesis (where the dark matter effect permeates space) would be essentially the same as conventional Hot Dark Matter theories, an example of which would be massive (but still very light!) neutrinos. Unfortunately HDM theories alone can explain observations no better than Cold Dark Matter theories on their own. It's a lot more complicated than just "we can't see all the mass that's out there".
Relativity is not 100% correct or the unified field theory would have been solved by now
Er. Calculus is not 100% correct or we would be able to symbolically integrate sinc(x). (cough)bullshit(/cough).
You can't necessarily solve any given equation. Of course, I'm not saying relativity is necessarily right, just that your logic is flawed.
We are visually driven in our research and I believe that limits us somewhat
Oh, I suppose we should just listen to the stars instead?
Yes, it would be nice to be able to sense gravitational fields directly in the brain or the like. But we can't and never will be able to. It's not an important consideration since we can't change it. What is far more limiting is that we are also economically driven in our research, so the important things often don't get funded because they are not of short-term commercial importance.
axolotl
PS. Sorry if this comes across as flamage, but it irritates me a little when people try to convince others of their ideas when those ideas are half-formed, have no supporting evidence or theory and don't even fit with existing data, let alone predict anything. It's nothing more than cargo cult science and achieves only the spread of people with little clue about real science.
Did you ever wonder why a candle's flame is hotter at the top where hardly any light is put out than at the base? That answers why the corona of the sun is hotter than the surface.
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Do you even know anything about perl? -- AC Replying to Tom Christiansen post.
Actually, the universe ends just outside the orbit of the moon. "the diety" to which you refer has gathered-up the space probes, and positioned holy radio transmitting sources at the locations where the probes should be and they are broadcasting data, spoofing what NASA expects to be hearing from the probes.
When we finally send men to Mars, "the diety" is going to have to drug them and hypnotize them into believing they actually travelled to Mars, when in reality, they landed on the dark side of the moon, and went into a secret complex with a big room with walls painted on the inside to resemble Mars, so that the photographic equipment and such broadcasts the expected pictures. Mockups of Pathfinder and Viking will probably also be present.
"The number of suckers born each minute doubles every 18 months."
These are my friends, See how they glisten. See this one shine, how he smiles in the light.
Now, who was it who was arguing with me a few weeks ago about how flawless newtonian physics was, and how we (mankind) had complete understanding and mastery of the laws of nature?
"The number of suckers born each minute doubles every 18 months."
These are my friends, See how they glisten. See this one shine, how he smiles in the light.
Space (the stuff between matter) is more densely packed the more mass there is.
Space is very dense inside the sun.
Space is less dense outside the sun.
Space is even less dense 1M miles from the sun.
Space is made up of regions of densely packed space and not so densely packed space.
If you are traveling through a less dense subject, you travel slower (relatively)...the further away from the local source you go, the greater your acceleration in the opposite direction would appear to be from a distant reference.
Here's a kitchen reference: sound travels about 700 mph in air at sea level and 680mph about 10,000 feet up where the air is less dense.
From alt.sci.physics.acoustics Speed of sound in water is
" Fresh water at 20 degrees C is 1481 m/sec.
Seawater at 13 degrees C is 1500 m/sec.
"
Seawater is ....yes, that's right...MORE dense then fresh water.
Now there are some variables here such as heat from the sun creating a less dense "atmosphere" at the surface of the sun and into regions close by, but i think that matter ejected would have much greater effects on the satellite and therefor would be a more noticeable acceleration.
not that I'm an expert or anything though :)
As a question to the more physics and cosmology oriented slashdotters: This makes sense to me in a Newtonian view of gravity - is this effect already accounted for in an Einsteinian view of space and gravity? Is this a plausible explanation for the observed effect?
Note: There was an earlier, more tongue-in-cheek, post about the expansion of the universe which includes a reply stating that this would result in an increase in the observed effect. [The vague wording is intentional.] It is true that the expansion would lead to an increase in the measured velocity of the spacecraft, but it would not effect the measured deceleration. [Although a decrease in the rate of the expansion of the universe would.]
It occurred to me that perhaps the probes were slowing because their trajectories were too linear, trying to escape the solar system, while natural objects travel in orbits and join the dance of the system. Perhaps this acceleration discrimination is related to the organizational force which clearly exists, but which isn't fully explained by the traditional gravity theory. In other words, if you try to leave the dancefloor, someone pulls you back into the fray. This would explain phenomena on both a quantum and super-galactic scale.
a prophet on the burning shore
(not a personal slam at teraflop, you obviously understand the issues) I just want to caution Slashdot readers (some of whom seem to be posting a lot) that one scientist's hypothesis does not a solution make. Clearly there is room for debate on this issue, particularly since actually going out to Pioneer and taking measurements is ... somewhat impractical. So, Scientists A&B say, we have something odd here, and nothing we've investigated explains it (first article in physics journal, reported in NS). Scientists C&D say, it looks to us like the probe's excess heat, using these calculations (2nd NS article). That doesn't mean that A&B will automatically agree with C&D (they don't). It's often said, not entirely tongue-in-cheek, that scientists (who have careers at stake) never admit they're wrong, and that the only way new theories become accepted is for all the old scientists to die off! In any case, the Pioneer conundrum is a very interesting one. It's not, in itself, evidence of a new force, but it is dramatic example of how complex something as "simple" as a spaceship trajectory can be, and how we don't understand everything yet. (Which to that I say: Thank God, what a boring universe it would be if we understood everything.) [As for the slashdot kiddies complaining "we heard about this already", maybe Slashdot should stop reporting on, say, Microsoft vs. the DOJ. After all, it was first reported on over a year ago, the fact that they're still arguing is irrelevant. We heard it all last year, we know what we think. It's old news!]
lake effect weblog
{Network engineer in Chicago--looking for work!}
(not a personal slam at teraflop, you obviously understand the issues)
... somewhat impractical.
I just want to caution Slashdot readers (some of whom seem to be posting) that one scientist's hypothesis does not a solution make. Clearly there is room for debate on this issue, particularly since actually going out to Pioneer and taking measurements is
So, Scientists A&B say, we have something odd here, and nothing we've investigated explains it (first article in physics journal, reported in NS). Scientists C&D say, it looks to us like the probe's excess heat, using these calculations (2nd NS article). That doesn't mean that A&B will automatically agree with C&D (they don't).
It's often said, not entirely tongue-in-cheek, that scientists (who have careers at stake) never admit they're wrong, and that the only way new theories become accepted is for all the old scientists to die off!
In any case, the Pioneer conundrum is a very interesting one. It's not, in itself, evidence of a new force, but it is dramatic example of how complex something as "simple" as a spaceship trajectory can be, and how we don't understand everything yet. (Which to that I say: Thank God, what a boring universe it would be if we understood everything.)
[As for the slashdot kiddies complaining "we heard about this already", maybe Slashdot should stop reporting on, say, Microsoft vs. the DOJ. After all, it was first reported on over a year ago, the fact that they're still arguing is irrelevant. It's old news!]
lake effect weblog
{Network engineer in Chicago--looking for work!}
Apparently they now think there is another planetoid beyond pluto causing this.
d _460000/460095.stm
http://news.bbc.co.uk/hi/english/sci/tech/newsi
Just to throw around more theories, why wouldn't there be more "space particles" once you get out of the immediate solar system? Most of the hydrogen WITHIN the system has been either pulled into a planet or the sun.
Gosling was sent back in time to install a Java Virtual Machine in the probe. Clearly, this accounts for its slowness. Expect it to blow up before 2003 when it runs out of memory.
I once read a book I got out of the library at UConn (Univ. Connecticut). Found it totally by accident one day.
The author(s) purported that if you take the geologic age of Earth and map out the "disasters" that they form a definite period, something like roughly every 30,000 years or so.
The supposition was that we actually live in a BINARY solar system, with the sun's twin being a black dwarf, and that it and the sun were drifting apart.
The answer as to why it hadn't been seen yet was simple: we've only had astronomy for (at most) 10,000 years, and only recently (300 years) had telescopes at all. If at this time this body was at the furthest point out of the orbit, we'd not have seen it.
The book was published in the 70s, I think. I wonder if the Hubble has dismissed such a theory, or if it's even been up long enough (13 years?) to have mapped enough of the "local galaxy" to have done so? Hmm...
46. The Hobo smiles, his eyes glaze over, and he burps. "Beware the man who has lived longer than the Wasteland."
I don't know about there being a lot more than was originally expected, but I do recall reading that most matter in the universe is dark matter. Something along the lines of 99%. Basically if the only matter that existed in the universe were "light" matter then the universe would be too "light"(weight-wise) and would be expanding at such a rate that single atoms would never have had the oppurtunity to form into anything.
This is an interesting idea though. The only thing I'm thinking is that if the problem is dark matter, shouldn't it effect planets too?
-matt
If yer a member of the church of the sub-genius, yer diety is "Bob". I think you can see him by executing "xscreensaver -mode bob" or something like that (my xscreensaver is borken, so I cannot check :^( )
--- Journals are boring; Go to my web page instead
This is data collected with tax payer money, they horde the information for 20 years, hoping to win a nobel or something, and now they release it because the failed and are all getting ready to retire.
If I was king they would all be thrown in prison for such anti-mankind selfish behavior
"after pursuing an answer for 20 years and not finding it, we felt it was important to get it out for discussion."
OTH Wasn't there a
As I noted in my other post, if it was gravity effects it would show up not as *constant* acceleration but acceleration that drops. Remember newtons law of universal gravitation? The acceleration due to gravity changes with square of the distance.
Simon.
Zecharia Sitchen has written a series of books that cover the existance of Nibiru, a planet with an elliptical orbit that comes close to the earth every 3,600 years. The return of this planet closely parallels jumps in the human experience(beginnings of agriculture, metalworking, etc).
Just how well have they calc'd friction effects?
Friction in a vaccuum is notoriously difficult to predict correctly, even if you get the density correct. What if the mean-free-path velocity distribution is _NOT_ anisotropic? (the same in all directions)
-- Robert
I wonder if there is a strange spacetime drag going on here
It's funny how explanations like this pop up readily; my own first thoughts were along similar lines. I blame Star Trek.
The problem with any sort of drag is that it doesn't seem to affect everything. In order to get to Saturn Cassini has to fly around a whole bunch of planets (Venus twice), and that sort of calculation wouldn't be possible. The V'gers would also have missed out on the outer planets.
If this drag is a feature of spacetime, however, and acts only on accelerating bodies, it may be negated by gravity. Which is why we can't detect it near the sun.
Usual warning:IANAA and I'm making it all up.
IIRC dark matter refers to matter that must exist for our current theories to work but cannot be detected for whatever reason. So it could very well be floating around Venus, or there could be a huge chunk of it on my monitor. The point is we can't detect it (yet) so we really don't know where it hangs out, why it hangs out there, or if it hangs out anywhere at all.
-matt
FWIW: The principle of Occam's Razor states that the simplest explaination is usually the correct one, lacking other data. Granted, in this case, we lack an awful lot of data, but I think the principle still holds. Assuming that there must be an undiscovered branch of physics at work is a bit extreme, I think. You might as well say there are giants pushing on the probes, or dragons blowing them off course. (Read Issac Asimov's Nightfall for the reference.)
/.'er: Adding fuel to the fire. :-)
I'm not saying you are right or wrong. I am just doing my part as a
dragonhawk@iname.microsoft.com
I do not like Microsoft. Remove them from my email address.
Time is Nature's way of keeping everything from happening at once... the bitch.
Not a physics majour, but I didn't think the ether theory existed to explain why light always travels at the same speed. IIRC, the ether theory was discarded for the precise reason that light always travels at the same speed.
This was the famous Michelson-Morey intraferometer experiment. The ether theory suggested that the ether was an absolute reference frame, and they were trying to measure the speed of the Earth's movement through the ether by comparing the time it took two light beams to travel the same distance in different directions. Of course, no matter which way they did it, those two light beams always traveled the same distance in the same time. So, either Earth moves immeasurably slowly through the ether (kinda strange since we're spinning round the sun rather quickly), or light goes the same speed no matter which way you look at it.
I thought the ether theory existed because physicists felt that all waves required a medium to travel in. The ether was the medium that EM wave traveled in. But, ether would have been an absolute reference frame, which contradicted Newton (no absolute reference frames). Anyway, no need for ether anymore...
---
-- Will quantum computers run imaginary-time operating systems?
Sorry about that. I had a proxy time-out.
lake effect weblog
{Network engineer in Chicago--looking for work!}
then wouldn't SPACE HAVE MASS
It could, if it wasn't just a convenient abstraction.
Relativity is not 100% correct or the unified field theory would have been solved by now
You presume that there is a unified field theory to be discovered. It may be that the very small and the very large operate in different universes.
Yeah, I'm a Mac programmer. You got a problem with that?
-- thinkyhead software and media
It seems obvious to me.
The probes are slowing down as they penetrate the membrane more commonly referred to as the Cell Wall.
Gallileo (at least), as well as perhaps another of the probes listed, are not in interstellar space. IIRC, Gallileo was sent to Jupiter to study Jupiter, and has not left Jupiter because it's studying Jupiter. I must emphasize, that Jupiter is not in interstellar space. Jupiter is the 5th planet from the sun, just outside of the asteroid belt.
:-) (Keywords bolded for effect)
--
Internet Explorer (n): Another bug -- that is, a feature that can't be turned off -- in Windows.
perhaps the probe are slightly magnetically attracted to the Sun, which, I understand has an incredibly powerful magnetic field...
What I meant is why dont they think that they are wrong? They should be quicker to accept that they could have messed up some calculations.
---------------------------
"I'm not gonna say anything inspirational, I'm just gonna fucking swear a lot"
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i must say this definately relates directly to Y2K and the second coming of god's red headed stepchild
This all came up about 2 months ago.
Much "new force" and "new fangled gravity theories needed" abounded. As I recall the discrepancies were resolved without resorting the such stuff.
Dig around on space news and the like for the articles.
Cameron Simpson, DoD#743 cs@cskk.id.au http://www.cskk.ezoshosting.com/cs/
Just kidding! :)
I just wanted to see how many old sci.physics junkies still exist....
But seriously, we'll probably never know the answer as to why it's slowing down. Those old probes weren't designed for experiments such as this (I don't think....)
Let's send out another one, this time specifically designed for precise gravitational measurements, with current technology, and with a couple of ion thrusters (yes they do bloody exist) on the back to catch up to the others, and let's have a look!
Oh wait, that would cost money, and we can't spend money on anything that doesn't make more money for Unca To^H^HSam.
Blech. Signatures.
and the probes are begining to run into it :-) :-)
What about this dark matter that you hear mutterings about on occasion. IIRC, they came out a while back with the theory that there was a lot more of it than they had originally thought.
Left shift 1 for e-mail...
I suppose it depends on how big a neighborhood you take into consideration. The part of the universe around my neck doesn't much resemble the part of the universe about two feet in front of it, which is monitor-like. Of course there are *local* variations, they're pretty much inevitable. Matter clumps in some spots, not in others, so that principle is already "violated" (by which i mean, not really) in the sun's vicinity.
My proposed revision: Any sufficiently large chunk of space pretty much resembles any other similarly sized and shaped chunk of space, for an appropriate value of "sufficiently large"
"Oh, I hope he doesn't give us halyatchkies," said Heinrich.
Thanks for the back-up info!
Somehow I changed 30 million to 30,000. Mea Culpa.
46. The Hobo smiles, his eyes glaze over, and he burps. "Beware the man who has lived longer than the Wasteland."
I assume (sorry, havn't had time to check this) that the distance to those probes is measured with a radiosignal these critters emit. Now imagine for a second that the speed of light is NOT a constant (don't forget that Einstein postulated that it was, and he, nor someone else, has ever proven it is). The distance measured based on the assumption Time_to_reach_us * speed_of_light = distance_to_probe would be wrong. I have assumed that the distance to a probe is measured in the same manner the distance to GPS-sattelite is measured (basically the sattelite emits time based on his on board nuclear clock and that emitted time is compared to the reception time). If this assumption is wrong just smile and neglect this comment (Oh, and send me how it's done too)
Einstein's first set of solutions to the General Relativity problem included a constant (lambda) which allowed for Gravity, at a very great distance to be a repulsive rather than attractive force. The term was included for mathematical completeness, but most people have always set it to zero.
If it is a non-zero term, than it could explain what is being seen, though you would expect the satellites to be experience an anomolous acceleration rather than a deacceleration.
It actually isn't surprising at all that this might occur. There are a number of models that would argue that there are spacetime features in a gravity well (like that of the sun) that would not be present in relatively flat spacetime. The further we get from the sun's well, the more likely we are to begin observing these effects.
In illa quae ultra sunt
27,000 mph is pretty trivial compared to the speed of light...I wouldn't expect anything too weird would happen at that speed (27,000 ~ 12 km/s compared to c ~ 300 km/s, about %4 of speed of light).
It's 10 PM. Do you know if you're un-American?
From page 2 of the article
Jonathan Katz, an astronomer at Washington University in St. Louis, thinks he's worked out where the rest of the push is coming from.
George
Wouldn't the dark matter then also be concentrated near the Earth? I think we would have seen it by now.
--
rde > If this is the case, dark matter has to exert a force other than gravity. And if that's the case, the Pioneers' acceleration
;-)
rde> away from the sun should increase as it moves out of the dark matter's influence.
Actualy Pioneer is accelerating towards the sun, this is normal for a body that is in free fall, it just happens to have been thrown very hard away from the sun at the start >escape velocity but the suns gravity still slows it down. This accerlation is comonly called deceleration but thats just accelerating with a minus sign. The rate of (de)acceleration certainly does slow as it moves away from the suns influence. However without another force on it (engine, planet further out, other star etc) the thing will not accelerate away from the sun.
The rate of (de)acceleration is reducing but they have found that the pull towards the sun is larger than predicted and thus the acceleration towards the sun is higher.
rde> Of course, I could be talking bollocks.
Afraid it looks like you were
R.
Maybe you live in interesting times
The experiment will check, very precisely, tiny changes in the direction of spin of four gyroscopes contained in an Earth satellite orbiting at 400-mile altitude directly over the poles.
Okay, maybe I'm not up on my astrophysics, but.. How the hell do you orbit something over the poles? I thought a geosync orbit had to be roughly equatorial. Do they mean a geosync orbit, hanging over the poles? Or am I being stupid again?
---
- Give a man a fire and he's warm for a day, but set him on fire and he's warm for the rest of his life.
Yup. Sep. 26, 1999.
so there are aliens messing with our spaceship. so what? they are probably not any more interesting than the people living down the street from you that you have little evidence of either. maybe they have a crack for some h0t w4r3z tho. imagine an alien race that specializes in w4r3z. thats all they do. warez 24 / 7. the best w4r3z d00dz in the g4l4x33. hahaha.
The most interesting prospect that occurs to me is that it could be an example of dark matter in the form of Weakly Interacting Massive Particles (WIMPs). Particles which do not interact via the electromagnetic force would not scatter light nor be affected by inter-atomic forces, and those which do not interact via the strong force would go right through nuclei as well; such particles would be phantoms, only feeling the weak nuclear force and gravity. The planets orbitting in the inner system would tend to eject such particles which ventured in too close, but those in a halo outside the outer planets would be undisturbed. As the probes passed out of the planetary zone and into the halo, they would begin to feel the pull of its mass (there is zero pull inside of a spherical shell). This would manifest itself as an increase in gravity, just as is being observed.
It's been known for many years that galaxies have a lot of mass that isn't visible. Maybe the Pioneers have revealed some of it in our own back yard. Now wouldn't that be cool!
Time is Nature's way of keeping everything from happening at once... the bitch.
They should have used Energizers
A month later New Scientist published this story, suggesting that the slowing was due to the reaction from heat radiated from the probes RTG power plant.
They still appear to be arguing over whether this effect is big enough. Measurements involving heat are notoriously difficult, as the cold fusion debacle showed.
I tend to agree with the others that say we don't know as much about outer space as we think we do. There could be pockets of gasses that slow things down, because space isnt a complete vacuum, right? There could also perhaps be wind that nobody cared to observe. Also, where did they get this measurement of how fast a probe should go? Maybe that is flawed. Possibly again because of different gasses. And perhaps gravity has a further reaching effect that we think. But why is it that these scientists get a number, and beleive it to be correct under conditions they beleive are correct, and then complain about it when either one of the numbers can be very wrong?
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"I'm not gonna say anything inspirational, I'm just gonna fucking swear a lot"
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I'm posting for him because he doesn't want to get mail from "you cranks" and refuses to believe that Anonymous is anonymous.
If you want to do your poor old pops a favour, tell them you pops is A. S. Liu, one of Anderson's co-investigators along with Phil Laing. Both Phil and I think the effect is caused by minute gas leaks from the hydrozine thrusters that control Pio. 10 attitude. It is difficult to get an exact proof because the engineering details and engineers have long disappeared. This effect has been seen on every one of JPL spacecrafts and just by Occam's razor principle, a gas leak is the most likely explanation, as they all have the same attitude systems.
Pio 11 is just a twin of Pio 10 and should (and do) show similar (but not identical) behavior. Ulysses orbit is so badly messed up because the nutation dampers are gone and JPL is constantly firing atttitude control jets to compensate. Galileio did not go far enough out of the solar system (only 5 AUs) so that we could not separate the small force with solar radiation effects. (Pio 10 and 11 are so far out that solar radiation effects are effectively gone.)
I don't think it's dust, or hydrogen, or heat radiation. If you read the original paper, it refers to an "anomalous, constant acceleration (my boldies).
I initially balked at the idea of 'new physics' to explain this, but when you consider how narrow our field of vision is, there cannot but be more than is dream't of in our philosophy.
These probes have travelled farther than pretty much anything else created by man; anything funky with gravity may only begin to manifest itself over billions of klicks.
My own wild and unsupported theory must go unpublished lest the drooling masses call to my door armed with pitchforks and flaming torches.
One of the discrepancies that drives the dark matter theories is that the universe appears to contain much more mass than we can see. Dark matter is just a theoretical substance that has not been proven to exist; many people would say that it's a fake thing made up to explain weird phenomena (like the ether theory 100 years ago).
Now we've got additional symptoms of the universe being more massive than it ought to be. The probes are slowing down faster than expected, as if there was 'dark matter' collected near the sun.
From these *observations* I propose 2 hypotheses---
1. If dark matter is real, it must be concentrated more densely near the sun and less densely farther away. Otherwise the distribution of dark matter would not slow the probes. This makes sense because dark matter, being massive and subject to normal physical laws, would tend to collect near stars and other massive objects. In any case, why heck can't we see it?
2. Like 'ether', dark matter is not real at all. There is an unkown phenomena manifesting itself here. If so, the unknown force(s) could very well be the same ones that caused the observations that led people to propose dark matter in the first place.
How would _you_ solve the Dirac Equation?
Oh yes... quick note:
even anti-matter is gravitationally attractive; an anti-particle has positive energy.
This Anti-materia you speak of would need to have negative energy (which you can just about create using the Casimir effect). But it's definitely not every day stuff -- and my other argument still holds...
Simon
Coming soon - pyrogyra
The distance and motion relative to the Sun might have a funny average with all the mass of this solar system.
Someone might have forgot something in a calculation and it is still forgotten.
Spacecraft are not yet able to solar sail well on just what is available.
Bill Nye mentioned there is more gravity between you and your TV than there is between you and astrological signs.
Those spacecraft aren't able to maintain themselves in some ways like biological organisms, so the machines wear out or break.
There could have been an escaped solar flare or something from a rare event.
Radioactive elements might not decay if you could stop them from moving.
On a large scale there could be gravity poles.
Something like symmetrical magnets wouldn't destroy each other, but that is like an absolute value.
Naturally light might not be able to go faster, but mankind can make planes fly.
There might be an effect like in a car race with cars having less drag together.
Recalculate Pi, add earthquake prediction, cancel celestial humm, or find some sort of deep cold space polarity.
The effects of heat and cold while in space could begin to crystalyze a vehicle as a whole. Ice still can flow, so an independant probe might get a little disfigured.
The universe simply doesn't exist
outside the borders of our solar system.
The probes are slowing down because
they are literally hitting the "wall";
Our solar system system was created
by a diety that didn't want to go
through all the fuss that comes with
creating a complete universe.
Breaking through the borders of our
solar system will let us reach the
realm of the gods.
SEND ME ALL YOUR MONEY AND GET
A SEAT ON MY SPACESHIP TO JESUS!
How do we know there isn't some kind of "wind resistance" in space, or maybe an antigravity source outside the solar system? All that physicists have been going on until now is math, this could be the first evidence that we are wrong. Nobody contradicted the ether theory or the belief that the earth was flat until contradictory evidence was presented, so this could just be history repeating itself. It's 5:30 in the morning, so this will probably read like gibberish after I get some sleep. {##}
--
Win98 sux without these 1337 toolz !!
This BBC article yesterday about the discovery of yet another Kuiper Belt object by Pioneer, mentions at the bottom:
Earlier this year, scientists were puzzled by what was described as a mysterious force acting on the probe. It led to speculation that there was something wrong in our understanding of the force of gravity.
Eventually the effect was tracked down to the probe itself, which was unexpectedly pushing itself in one particular direction.
I expect this new theory will also be dispelled by minor impacts, leaking remainders of fuel, and the fact that space isn't a true vaccuum. I'd be delighted to be proved wrong, of course.
--
Andrew Oakley - www.aoakley.com
Surely the effect of this second object would be to speed up the probe?
perhaps they have more pulling power than has been calculated...
I doubt anyone will ever come up with the answer cos there is no-one out there to take accurate readings.... perhaps the 20 year old instruments are just knackered.... *shrugs*
-~ Given a choice between two theories, take the one which is funnier. ~-
Hey, I've switched to decaf.
:)
Actually many Quantum theories are among the best supported experimentally of any of our theories, due in part to the electronics industry and the immense commercial incentives to research in the field of the very small. Obviously they can be replaced by something better if it comes along, but it hasn't yet. Note that quantum theories should be kept distinct from interpretations of quantum mechanics (the many worlds model, the Copenhagen interpretation etc) which are just pet ideas and are mainly hogwash. They don't tell us anything and are just items of faith in the same way as vi/emacs wars until the time when one interpretation leads to a prediction that other interpretations do not make, and this prediction can be checked.
But even such theories as quantum entanglement have been well documented and observed many times in the laboratory.
There are theories that include particles with FTL characteristics, and in fact General Relativity doesn't preclude them. Einstein thought they didn't make sense since he'd been working with Special Relativity for too long, so he chose a special set of General Relativity equations that ruled them out. But it's not necessary. The only proviso is that any particle travelling slower than the speed of light cannot attain the speed of light, and any partcle travelling faster than the speed of light (which would have zero energy when travelling infinitely fast) could never decelerate to the speed of light. This essentially says that particles can never reverse the way they are going through time, so I suppose although it breaks causality in the traditional sense you could actually have two independent causalities going on at once in the same time-stream, one for subluminal particles and one for superluminal particles. Of course, time does not pass at all for those particles (photons) which travel exactly at the speed of light.
Now on to dark matter...
The problems dark matter theories are postulated to explain are (1) the distribution of velocities of stars within galaxies; Newtonianally (which is good enough here because the stars are non-relativistic) we would expect the velocities to tail off with distance from the centre of the galaxy, in the same way that Pluto orbits the sun more slowly than Mercury. Actually this is not observed to happen in galaxies, requiring that either there is a large amount of matter at great distances from the nucleus that we can't see, or that our entire understanding of gravity is wrong.
Since physicists never like to abandon a successful theory, a lot of time is spent looking for this matter.
The other problem is (2) the large-scale structure of the Universe. In our current understanding of things, it is very hard to model the Universe in such a way that galaxies will have formed by now. They simply don't collapse fast enough. Also, we can't explain the very large-scale structure where galaxies form along the walls of vast bubble-like structures with huge utter voids within these bubbles. This cannot be predicted by conventional theory, but dark matter theories can (albeit in a not entirely satisfactory yet manner) start to offer an explanation.
According to any good cosmologist there are two speeds in the Universe: stationary, and the speed of light.
Broadly, hot dark matter is composed of very light massive particles travelling at approximately the speed of light. An example of this might be massive neutrinos. These theories are all very well, but simulations of them on big iron don't give rise to the large-scale structures we see in the Universe.
Cold dark matter is composed of very massive objects which are essentially stationary. Examples of these might be black holes, quark nuggets[0] etc.
For various reasons these do not fit with experimental observations either (to explain the velocity distributions of mass within galaxies you would need an unusual distribution of the cold dark matter, with lots of black holes further out in the galactic halo and not very many in at the centre). A hybrid theory encompassing both types of dark matter can be teased out to give slightly more realistic models, and the ideas can be further extended with exotic dark matter types such as incredibly massive 1D filaments and 2D sheets embedded within space, like fractures in it. These might explain the very large scale bubble-like structure of space, but are completely hypothetical.
Anyway, I hope this interests you and makes amends for my earlier post. But if I'd really wanted to be insulting, of course, I would have posted:
"Your mother was a 'amster and your father smelt of elderberries!"
:-)
axolotl
[0] Quark nuggets are large aggregates of quarks, big enough to see with the naked eye, but very much denser than normal matter.
Aparently P10 has discovered a new planetoid http://news.bbc.co.uk/hi/english/sci/tech/newsid_4 60000/460095.stm
So why is a candles flame hotter at the top then?
There may still be some good explanations so we should not wet our pants, but still it is interesting to speculate a little about possibilities of a new physical theory or phenomenon.
One must remember, that gravity is the only physical fundamental force we have not been able to quantisize. As quantum theory has been a very good explanator and predicter for electric, optic and magnetic phenomenons, I think it could also do something to gravity also.
Gravity has been extremely difficult to quantisize, though. You may have heard of gravitons, but that is still only a name without shape. It seems gravity can not be explained with linear differential equations (like Scrödinger's or Dirac's for electromagnetism) but with nonlinear DE:s. These can not be usually calculated analytically, but only numerically.
So is this a quantum effect of gravity? Maybe we know it someday.
-------------------------------------------------
and you thought he was just a clueless media whore!
tune in for the next article on this subject, where our hero postulates that the effect is due to a new era of Internet-Based Geek Astronomy that will change the whole paradigm of human existence. and also his book on the subject will now be available. on slashdot.
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-- in china, chinese food is just called food.
Everything else in the universe is quantized and non-continuous, why not gravity? Gravitational orbital theory....hm... Or.. space bugs splattering on the windshield. That could slow anything down. eh?
Some people are talking about dark matter as being the culprit, although dark matter is very elusive and we have no proof of it.
Einstein described how gravity, caused by mass, can warp spacetime, like ripples in a pond. But what about these "ripples"? Could not space-time itself not be infinitely fluid, but instead have a "viscosity"? For instance...take a planet and throw it accross space-time. What you would expect is that it leaves a trail of warped space-time. For how long does this trail exist? Could we perhaps just be stumbling into the wake of residual gravitation? Could space-time be "wrinkled" and we are just stumbling into the wrinkles? Have any claims or hypotheses been made about the "viscosity" (my term) of space-time? Am I just a nut?
It's 10 PM. Do you know if you're un-American?
These calculations always make me wonder what the speed of gravity would be. Consider the following thought experiment. You create a universe with an object, just like the earth. The next day, at 10 lightsecs away you place a copy of the sun. How long wil it take before sun.bak starts pulling at earth.bak
I dont know much about physics, but I wonder if this problem is related to the problem of why its hotter further from the sun than at the surface of the sun.
They probably miss Earth and they're slowing down to come back.
Various measures of gravity in the vicinity of the earth, used in resource exploration and navigation, seem to be off the r-squared gravitation attraction law. Since r-squared seemed to hold for astronomical bodies in mostly empty space, some physicists postualated a mysterious fifth force that operated on limited scales. Not so absurd because the nuclear strong force is limited range and was unbelieved for some years. However, the fifth force was eventually attributed to complicated exprimental data analysis error.
Star Trek has done so much to encourage the imagination of scientists, but it also destroys the scientific literacy of non-scientists. Dark matter is definitely one of the casualties.
"Dark Matter" is a loose term referring to mass in the universe that should exist but has not been accounted for yet. The last time I studied astronomy, two of the biggest theories were WIMPs (unknown subatomic particles) and MACHOs (planet-sized junk out in the void). An excellent essay on the subject is available at Berkeley.
i wonder if they considered the gravity of the asteroid belt in their calculations.Any astrophysicist who neglected the mass of asteroids, Oort, etc, would be a public laughingstock and unable to show their face in public for a long time. BTW, at reasonably large distances, the gravitation for any collection of objects (such as the asteroid belt, or the entire solar system for that matter) is identical to the sum of their masses located at their center of mass. The calculations are high school AP physics/calc, no big deal.
Maybe our Solar System is surround by anti-materia which repulse any materia?
It should be noted that general relativity
doesn't specify a single equation for gravity,
it specifies a set of conditions that an infinite
number of equations fullfill. Einstein just
chose the simplest equation, which may infact
be the wrong choice.
There are a number of known discrepancies in the
current theory such as the speed of the outer
stars in a galaxy and even the outer planets in
our solar system. It has been shown that by
adding a 1/r^2 factor to the gravitational
equation then both of the problems above are
accounted for.
My personal beleif is that astronomers will
eventually give up on the dark matter theories.
The Newsweek article quotes both Jon Katz and Eddie Murphy. Wow!
This could mean only one thing...
Murphy also has two more important laws to remember in a situation like this: "Anything that can go wrong will go wrong." and "If anything simply cannot go wrong, it will anyway." No matter how much meticulous planning and calculation you go through, it's a given fact that something somewhere won't work out as planned. Even rocket scientists aren't infallible.
"If you give a man a fire he's warm for a day, but if you set him on fire he's warm for the rest of his life."
Yeap, and I'm about to type 'YOKE' :) The hole ripples in space stuff, thats when something hits the big black cloth with some LEDs sown in. Mlk
Wow, I should not post when knackered.
Dosn't this Murphy guy have a law ?
Maybe this is an example of it.
When we look harder at this problem it will go away.