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Mysterious Force Affects Pioneer 10 & 11 Probes
JabbaTheFart writes "The Guardian is writing that something strange is tugging at America's oldest spacecraft. As the Pioneer 10 and 11 probes head towards distant stars, scientists have discovered that the craft - launched more than 30 years ago - appear to be in the grip of a mysterious force that is holding them back as they sweep out of the solar system.
Some researchers say unseen 'dark matter' may permeate the universe and that this is affecting the Pioneers' passage. Others say flaws in our understanding of the laws of gravity best explain the crafts' wayward behaviour."
exactly what was AFFECTED?
It is also thought that dark matter is at the centre of galaxies Could explain a lot of things, e.g. the expansion/contraction of the universe. Judging by the amount of "tangible" matter in the universe, there is no way to halt the expansion, and it will go on forever. However, if there is dark matter, it could hold enough gravity to halt expansion and force the big crunch. Lots of info on this sort of stuff here
Note to Hemos: The verb is spelled "affect". You know, with an "a". The noun is spelled "effect", but it's the verb needed in the title.
Sorry, don't mean to sound curmudgeonly and grumpy and so forth, but so few people get this right that I can't stand by and let it slide.
I'll put the cantankerous old grouch away now...
Daar is nie 'n lepel nie
No, this was explained more than a year ago. Radiation pressure from the spacecraft (I think from an RTG) is causing a very small asymetrical thrust.
Nothing new here
http://michaelsmith.id.au
Bit of an old story this.
wot no sig
Link to the Physics Web article: http://physicsweb.org/article/world/17/9/3
But expecting /. editors to recall that would be like expecting them to get effect and affect correct.
Here's an affect/effect primer with which they can practice.
Dont be such a dipshit. All scientist are aware we dont know that much of the overall picture. You learn that in highschool.
RELEASE: 03-082HQ PIONEER 10 SPACECRAFT SENDS LAST SIGNAL After more than 30 years, it appears the venerable Pioneer 10 spacecraft has sent its last signal to Earth. Pioneer's last, very weak signal was received on Jan. 22, 2003. NASA engineers report Pioneer 10's radioisotope power source has decayed, and it may not have enough power to send additional transmissions to Earth. NASA's Deep Space Network (DSN) did not detect a signal during the last contact attempt Feb. 7, 2003. The previous three contacts, including the Jan. 22 signal, were very faint with no telemetry received. The last time a Pioneer 10 contact returned telemetry data was April 27, 2002. NASA has no additional contact attempts planned for Pioneer 10.
Bush Lies On the Record.
Well, our understanding of the laws of gravitation _is_ better than the link in the article might suggest. Look: http://en.wikipedia.org/wiki/General_relativity.
Greetings from the physics department.
As it happens, The Economist ran an article in 1997 addressing some of these issues. The article also provides context and perspective that should be of interest to those participating in this discussion. For convenience, the full text is reproduced below; it is also accessible online (may require paid subscription).
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A space oddity
Sep 24th 1998
From The Economist print edition
A tiny error in the paths of two spacecraft may require the rewriting of some of the laws of physics
OUT in the far reaches of the solar system, beyond the orbits of Neptune and Pluto, something strange is going on. Two space probes, now speeding away into the interstellar void, are not behaving as they should. They appear to be experiencing an unexplained extra tug from the sun--raising the possibility that there is something amiss with the laws of gravity.
Physicists are used to predicting spacecraft trajectories with great accuracy. For the Pioneer 10 and Pioneer 11 probes, launched towards Jupiter in 1972 and 1973 and now heading away from the sun in opposite directions, they have done it with the help of a piece of computer software called the Orbit Determination Program (ODP). This calculates how the gravitational influence of the sun and the planets--suitably tweaked to fit with the general theory of relativity--affects each probe's motion.
At the same time, by analysing radio signals from the two probes, precise measurements of the Pioneers' actual trajectories can be made. As each craft zooms away from the solar system, the radio waves it transmits back to earth are slightly stretched out, causing a change in frequency (known as a Doppler shift) that depends on the craft's speed relative to the earth. With enough number-crunching--taking into account the motion of the earth around the sun and its wobbles as it spins on its axis--the position and acceleration of each Pioneer can then be worked out.
The trouble is that the predicted and measured trajectories do not match. Instead, there seems to be an additional pull (in effect, an acceleration) in the direction of the sun that is not predicted by the ODP. The anomaly is almost imperceptible: about one ten-billionth of the acceleration due to gravity at the earth's surface (at that rate, an apple would take a day to drop to the ground from the branch of a tree). But that is still big enough to raise questions.
Send for the detectives
Astronomical discoveries often hinge on the analysis of wobbles, discrepancies and errors. The existence of Neptune was deduced from minute deviations between the predicted and observed orbits of Uranus. An anomaly in the orbit of Mercury provided one of the first clues that the laws of gravity as described by Newton were incomplete, which, in turn, led Einstein to general relativity. So John Anderson, one of the members of the Pioneer 10 navigation team at the Jet Propulsion Laboratory in Pasadena, California, says he feels a professional responsibility to make his sums add up. His latest attempts to explain the anomalous acceleration will be published next month in Physical Review Letters.
Dr Anderson and his team start by considering all the possible forces that might be acting on the Pioneer craft but have not been included in the ODP. Could any of them account for the slight acceleration towards the sun? Gas leaks, and the minuscule push provided by infra-red radiation from the crafts' electricity generators, were ruled out. Both would be too feeble, and would be unlikely to press in the sun's direction anyway. Similarly, the pressure exerted by sunlight, and the force exerted by the emissions from each probe's radio antenna, were dismissed: again, both are too weak, and they would tend to push the probes away from the sun, not towards it.
Next, the gravitational influence of objects
Certainly in his anthology "The River of Time" there was a story called " The Crystal Spheres"
I like the following explanation of the anomalous acceleration. No dark matter/20 dimensions/new gravity theory needed here. A small amount of dust in the kuiper-belt that transfers momentum with the probe should be enough to explain the slowdown. Look at: http://www.newtonphysics.on.ca/Anomalous/Accelerat ion.html
Also, quite a few stories require that the spacecraft be a certain distance from the gravity well of the solar system before they can use their FTL engines.
This doesn't quite quench my thirst for information: does this mean the probes are still sending radio waves/signals, or just irradiating passively?
Article at physicsweb says:
When the craft were at distances of between 20 and 70 astronomical units, researchers found that the Doppler frequency of microwave signals that were bounced off the craft drifted at a small, constant rate
So, passive it seems.
The most exciting phrase to hear in science, the one that heralds new discoveries, is not "Eureka!" but "That's funny..."'
I have it on the wall over my bench. It helps when the data goes all weird on me.
There is a reason for everything. Sometimes that reason just sucks.
You mean "bremstrahlung," as in braking, not "brenstrahlung," as in burning, right?
"Give a man fire, and he'll be warm for a day; set a man on fire, and he'll be warm for the rest of his life
Affect and effect are two different verbs, with related but quite different meanings.
Affect is the more common. To affect something is to alter it, usually but not always in a harmful way.
Effect is less common. To effect something is to cause it to happen. I noticed people starting to use this more commonly about eight years ago. Soon afterwards, people started to use the verb "to effect" instead of the verb "to affect", unaware of the difference in meaning. The difference is so strong that these people often end up saying the opposite of what they mean.
here is a good reference.
It would be hard to imagine that the behavior of light would not change as it crossed these boundaries. I would expect some sort of refraction, etc. as it changed from one medium to another. Observations do not bear this out, although I know of nothing off of the top of my head that would disprove your idea.
For all we know the formula for the gravitational force has a couple more terms. I seem to remember coming across an advanced formula for the electric force that contained a couple of more terms, that were generally insignifcant compared to the main term kq1q2/e^2 that most people recognize. Why not the gravitational too? I have heard some physicists advocate for a 1/r term I believe. Can anybody back up any of what I said about the electric force or arguments for an extra term in the gravitational force?
Let's go Hurricanes!!! 2006 Stanley Cup Champions!!!
Quite a lot of them, specially considering there are few really massive ones. No such objects with a mass greater than 1% of earth have been discovered.
But even if such an object would exist, it would not affect two probes in different locations in a similar way. Even if there were many massive undiscoverd objects out there, chances to these effects are very slim.
The Pioneer probes are currently also way beyond the Kuiper belt, so the influence of a pluto-like object would be very very small.
There are big problems with all of these techniques.
Worm holes: the problem is described in the article -- even if it can be achieved from an engineering perspective, and even if the theory is correct, you need to travel to your destination by conventional means to open the wormhole up in the first place.
Alcubierre's warp drive: several problems exist; primarily what is referred to as "negative energy" in the article can be thought of more easily as "negative mass". It's quite likely that no such entity can exist in our universe, we certainly have no idea how to produce it. And you need a lot of it, too. Second, the control problem referred to in the article is much more serious than it sounds. The problem is that the apparatus to control the warp effect would, essentially, need to operate on the unwarped universe outside of the travelling region; based on our current understanding, if the region were travelling at or faster than light, then the rest of the universe would be causally isolated from it, so whoever was travelling inside the warp ship would not be able to control it.
Negative mass: probably can't exist. There's no evidence to support it.
Millis space drives: these have less problems, but aren't actually FTL drives; they're "reactionless" traditional drive systems. This allows you to accelerate to significant fractions of c, but you'll take a while to get there.
Lets assume two objects are spaceship A and spaceship B. To make things simple, lets assume the speed of light is 100 m/s and both the spaceships are travelling at 60 m/s towards each other (relative to a person at rest). But, since they are travelling at high speeds, adding up 60+60 to get 120 doesn't work because spaceship A won't measure the speed of spaceship B to be 60m/s because they are in a different inertial frame compared to the person at rest and will make different measurements. Relativistic equations have to be used in this case to determine what the observer in spaceship A will measure. The equation used is v = v0*sqrt(1-v^2/c^2) So spaceship A will measure the speed of spaceship B to be 60*sqrt(1-v^2/c^2) = 60*sqrt(1-60^2/100^2) = 60*0.8 = 48m/s So that means relative to spaceship A, spaceship B will be travelling at 60 + 48 = 98 m/s.. still less than the speed of light.
No they aren't, and I don't know where people get this idea.
In special relativity, there is a factor called "beta" which is used to calculate time dilation, spacial contraction, relativistic momentum, etc. It's defined like this:
beta = 1 / sqrt(1 - v^2/c^2)
Where v is your velocity as measured w.r.t. some chosen reference frame.
Now, think about time travel. This would be equivalent to a negative time dilation factor (time moving "backwards"). In other words, a negative beta. People seem to just assume that, if v > c, then beta is negative. But it isn't.
If v > c, then the term (1 - v^2/c^2) is negative. What's the square root of a negative number? It's imaginary. So, if you move faster than light, the beta factor becomes imaginary. You aren't moving backward in time -- you are moving in imaginary time.
To sum up, traveling faster than light doesn't make you go backward in time. It's a meaningless concept. Unless, of course, you are willing to accept the existence of "imaginary time."
oops.. I should have done 48+48 = 96 since both objects are at reletivistic speeds. Sorry about that.
No. While a direct measurement of the speed of gravity will have to await the detection of gravitational waves by LIGO or a similar experiment, the speed of gravity has already been measured indirectly, and found to equal the speed of light, to within a few percent accuracy. This experiment, for which the 1993 Nobel Prize in physics was awarded to Taylor and Hulse, measured the rate at which the orbits of two neutron stars were inspiralling due to loss of energy from gravitational waves -- that rate depending sensitively on the speed of those waves. See also this FAQ.
No, they're traveling apart at (0.75+0.75)/(1+0.75*0.75) = 0.96*c. See this FAQ.
Not relativity per se, but ordinary mechanics: the push would propagate along the rod as a "kink", at a speed equal to the speed of sound in the medium the rod is made of. See this FAQ.
While that would make a nice and simple explanation, I think that this paper is flawed, since it does not take into account the different density of the kuiper belt in the directions the Pioneers are headed. The kuiper belt is most concentrated around the ecliptic (the plane the planets are moving in as well), and Pioneer 10 is more or less within that plane, while Pioneer 11 is about 17 degrees above it, which should make a difference. Oh, and they got the mass of the spacecraft wrong, it's 258kg without fuel (some should be left), and they're assuming 241kg. Their speculation about dust particles is not very credible, as the pioneers would not survive many of those breaking them down at the observed rate.
It is standardly accepted math that a divide-by-zero is absurd but the following is true:
Given the numbers n,m, then for any value of n, as m approaches zero, n/m approaches infinity. As such, this is strictly speaking an asymptopic problem, but it is reasonable to say that a zero volume object with a non-zero mass has functionally infinite density.
"Stumble before you crawl"
You're forgetting the fact that both times and distances change, depending on who's doing the measuring.
In C's frame, after 3.333 ms (as measured by C's clock), the distance between A and C is 750 km, and likewise for B (as measured by C's meter sticks). The total distance between A and B is 1500 km (as measured by C's meter sticks).
In A's frame, after 3.333 ms (as measured by A's clock), the total distance between A and B is 960 km (as measured by A's meter sticks).
In B's frame, after 3.333 ms (as measured by B's clock), the total distance between A and B is 960 km (as measured by B's meter sticks).
Yes, we have detected dark matter. I agree that the galactic rotation curves, etc., are indirect "detections" only, but gravitational lensing is pretty damn direct. Light rays from distant objects are being bent by some large, dark, gravitational masses. These masses, particularly in galaxy clusters, have been mapped out and show differences from the the galaxy distribution themselves.
I agree with your other statements at some level, even taking to account the lensing results.
Professor of Astronomy, Author of Spider Star & Star Dragon (Tor)
Time is an illusion. Lunchtime doubly so.
Tell that to the neutrino guys I've worked with.
Neutrinos have non-zero rest mass, and hence are known and detectable dark matter. (It's worth noting, though, that they're "hot" dark matter, and "cold" dark matter is more like what you're complaining about. Neutrinos also only account for maybe 20% of the needed dark matter.)
It's not a "Wild Ass Guess", Hulse and Taylor won the Nobel in 1993 for their discovery of a binary pulsar system which is slowing down precisely as predicted by general relativity - because the gravitational waves being emitted are carrying off energy. See here.
(Yes, I know you mean ripples in spacetime. But it's pretty clear that the other poster thought you meant gravitational waves, and that's what the Hawking quote was about, too.)
The real Captain Avatar is a fictional character, so I suppose he doesn't mind if I impersonate him.