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Pioneer Anomaly Solved
First time accepted submitter gstrickler writes "After years of work recovering and analyzing old mission data and vehicle schematics, a just published analysis(Pdf) provides strong evidence for anisotropic thermal radiation being the source of the slowing of the Pioneer 10 and 11 spacecraft. The theory isn't new, but the recovered data and new analysis provide solid evidence that at least 80% of the deceleration is accounted for by anisotropic thermal radiation. Members of The Planetary Society were instrumental in recovering the data and helping fund the analysis. The lesson is, in space, it matters what direction your heat radiating surfaces point."
Sorry to self-correct - acceleration is a vector, it has both magnitude and direction. By summing all of the acceleration vectors, you get a resultant which determines the rate of change of your velocity.
Is it just my observation, or are there way too many stupid people in the world?
its accelerating backwards... ie, it's effectively got its "engine" (ie the heat radiating surface) pointing in the direction its heading, and this is slowing it down. I guess its still got a lot of velocity, but this is being reduced by the lack of anything pushing it in the right direction.
In other words, in space, your hot arse is a form of propulsion!
Does this discovery have a relationship (however distant or inefficient) to Nuclear Lightbulb or Nuclear Photonic propulsion? https://en.wikipedia.org/wiki/Nuclear_lightbulb
The lesson is, in space, it matters what direction your heat radiating surfaces point.
It matters in bed too.
It must have been something you assimilated. . . .
A portuguese aeronautics engineering student from Instituto Superior Técnico already figured this out way back in 2009 in his masters thesis, available here.
Slashdot, fix your code or at least hire someone who is competent at it to do it for you.
Well actually, if they'd anticipated this and pointed the heat dissipating surfaces to the rear, Pioneer would be going faster.
I'm not sure they'd have done anything... the effect is so small, completely irrelevant for the main part of the missions, and they might have other reasons for orienting the craft a certain way -- maybe to maximize cooling. As a rule the side that emits the most photons would also be absorbing the most from the sun. I realize the situation could be more complicated than this; if it was simple the result would have been calculated a long time ago.
What I'm wondering is how many people will remove this from their "these handful of unexplained results in not fully understood circumstances mean all of physics are wrong (and my pet theory is right)" lists?
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Will this effect be powerful enough to ever cause it to stop, turn around and come home? And when it does so, how much strife will it cause to Spock and Kirk?
Could one compromise and put the radiators perpendicular to the direction of the sun (and travel?) eg, not on the front or back, but on the sides? Provided you did so equally, any force resulting in their radiation should cancel itself out.
For large sets, this will be our guide even unto death, for the LORD will work for each type of data it is applied to...
[...]and they might have other reasons for orienting the craft a certain way -- maybe to maximize cooling.
One end of the spacecraft is a big-ass radio dish, and the orientation is determined by pointing that dish at the Earth so that we can communicate with it.
Does it have mass?
In a sense yes. Radiation and all other forms of energy have relativistic mass, as in the m in E=mc^2, as in things that have more energy (moving objects, high-energy states of atoms and molecules, systems in general) have more mass as it applies to inertia and gravity.
Heat radiation as in (mostly infrared) photons don't have rest mass. That's the m0 in E = root(pc^2 + m0^2*c^4). So they don't have mass in the sense of matter as you usually think of it. But it turns out the way you usually think of mass is not equivalent to matter. Even though the usual way you think about it is that they are.
Hope that clears things up. :)
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Am I arrogant for saying "wasn't this obvious?"
Not really as long as you realize that some things seem obvious once you know they're true... Or as long as you just mean "obvious possibility".
It's not like they didn't know that if there was a favored direction for the emission of radiation that this would affect the velocity of an object. The concept of a photon drive existed for decades before the Voyagers were launched. It's just that it was though that whatever net force there was would be essentially zero. Assume a uniform, spherical Voyager craft...
This has been a long-standing possible, and then probable, explanation for the anomaly. Seems to have taken quite a bit of effort to figure out what the actual value of the force would be with sufficient precision. I remember what seems like a long time ago an article posted to /. about someone calculating the effect of heat radiation using Phong shading, the 3D graphics technique, as an approximation and got pretty good agreement.
Going all the way to a complete finite element analysis, using multiple methods to come up with the coefficients for the model, and getting a result that leaves only a noise-level signal is pretty impressive. And not what I'd call obvious.
So despite maybe feeling like it, it's not exactly a case of research by the Maximegalon Institute of Slowly and Painfully Working Out the Surprisingly Obvious.
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I thought that E=mc^2 meant that E could me converted to M not that all it was both energy and mass at the same time.
So did I! But it's not a conversion, it's an equivalence! Energy and mass -- relativistic mass, the quantity that informs our notions of gravity, weight, and inertia -- are really, always, the same thing just in different units. If there's more energy in a system, then it weighs more on a scale. Water weighs less than two hydrogen and one oxygen because it's at a lower energy state. This of course includes the energy that is in the form of rest mass.
Rest mass is a form of energy. It can be converted into other forms of energy at a rate equal to m0*c^2. Energy and relativistic mass are always related by the equation E=mc^2.
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The "speed" of the Pioneer craft is usually referenced to the Sun and it's orbit