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Mystery Force Affecting Probes
imipak writes: "The BBC reports that after exchaustive investigations, NASA scientists have run out of possible explanations for the mysterious tiny course deflections experienced by the Pioneer and Voyager spacecraft as they head out of the solar system towards the heliopause. Could it be that there's something wrong with our theory of gravity? (Well, yes, we already know that...) or could it be Oort Cloud objects? The tenth planet? Informed comment, please!"
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Hurrah! Please explain it for me, guys. I have a friend at NASA who would really like to know.
If they're slowing as they get very far from the Sun, that seems to imply that the force of gravity is not dropping of quite as fast as 1/r^2.
The problem is, as the article points out, we would have seen the effects of this on the orbits of the planets if this was the case.
I'm personally wondering about drift in the probes' radio sources throwing off the doppler measurements, but if this was happening they should have caught it already (you can directly measure the probes' positions by measuring the round-trip signal times to them at a few different imes during the year).
My (recently deceased) dad is on that paper.. he believed that it was most probably (b) (outgassing of some sort, possibly a malfunction/weakness common to both pioneer probes). No real evidence of that of course, and a "mysterious" force is more publishable ;) Still it is very spooky.
(g) and (h) were (in his opinion) the least likely.
Note that the paper was actually first released in April, and just revised today.
Could it be that there's just more mass in the solar system than we think? Wait, hear me out. I'm not talking about Planet X or a bloated G, I'm talking about ambient stellar gas.
Here's the deal: On the Earth, the gravitatinal forces acting on you at the surface all sum out to equal to the forces that would be exerted by a point source with the Earth's mass and a distance r, the diameter of the Earth. Though that ocean to your left and that continent to your right pull you in opposite directions, and the ground under your feet is pulling harder than the ground in China (um, unless you're in China, in which case, 'hi'), but it all sums out exactly right to a point mass at radius r.
Now, take that example and pose it to the solar system. Forget about the forc of solar wind blowing, and realize that all that wind has mass, and exists everywhere. It's pretty thin, but it's a lot thicker than the four hydrogen atoms per cubic meter in deep interstellar space. All that stuff, wispy as it is, has mass, and even though most of it is so godawful far away, the net gravitational effect of all of it is as if there were an additional point source inside the sun, with the mass of all the stray gasses and particles inside the huge sphere that has the sun as the center and the space probe on the outer surface.
What makes the math even more wonky is that, assuming a roughly even distribution of gas as inversely proportional (or inverse square, or even constant, doesn't matter in this case as long as it's uniform by uniform radius) to the distance form the sun, then the farther out the probe goes, the more mass there is behind it, and the farther back the point source goes.
If the density were uniform (it's not) then the effect of this force would actually increase as the probe got further away. As it is, it may be a constant force. For conceptualization's sake, if you had a well to the center of the earth and went to the bottom (forget magma, use the moon if it makes you feel better) you'd be weightless. Go halfway up, and you'd have a force of one-half g. Go to the surface and you are being pulled with a stronger force than you were when you were closer to the center.
Anyhow, HTML's bad for math, but I just wanted to get the idea out there. I don't have enough info on particulate density over the scope of the solar system and beyond to make any educated numbers anyhow. Hopefully someone out there does.
Kevin Fox
--
Kevin Fox
--Fermat
An early theory of gravity said it pushed in all directions at the same time but things with mass blocked it slightly. The attraction force is simply the delta of pushes from two sides not being equal. This was thrown out because things in space would slow down over time. However...
it appears that things do slow down over time. The deep space probes are not the only ones showing this. The gps sats are doing it and this is one of the problmes that gravity probe B is suppoed to help solve. I guess it means we have a wrong view of what keeps up stuck on this world.
I'm not sure what planet you're on because you seem to be trying to write an anti-science diatribe and yet much of what you say is no different from the view of a scientist.
---- SIGFPE
Check out the JPL final paper on this.
:
Possibles are
(a) Heat Ejection (b) Gas Leak (c) Clock Drift (d) Anomalous objects (pretty dead, despite BBC giving prominence) (e) modifications to gravity (f) solar radiation pressure (g) systematics of observations (h) antenna radiation pressure
Let the armchair speculation begin. (But remember to read the paper to check your answers!) Have Fun!
Mode (3) smart-aleck mode. Press * to return to main menu.
While this news report is very likely just a measurement error, we must be reminded that the last time we discovered an error in a celestial body's trajectory we reinvented the notion of the universe.
One of the big open questions of the day is: What is the shape of the universe? Euclidean, hyperbolic, a torus--we aren't sure. It is thought that each of these geometries would profoundly affect an object moving across the universe in a different way. These NASA probes could in a sense be the moving laboratory that we need to understand what exactly our universe looks like.
Robert
http://wso.williams.edu/~rmcgehee