Seriously, folks, besides the fun reasons, these are the rational possibilities:[ol][]The measurement/observation/calculation is faulty[]There is a gravitationally influential body or force that we have not yet discovered or detected that accounts for it, possibly invisible until now[][]All possible factors have not been taken into account (someone forgot to carry the 1 or add the micrometeorites)The laws of physics as we know them do not work in such an environment without some compensation, in the same way that Newton’s laws were modified by Einstein and Einstein’s by Big Bang Theories.[/ol]
Probably just the normal delays one encounters whilst the work on the Hyperspace bypass is underway. As I understand it they should be finishing up the demolition work fairly soon.
Perfect combination of post and post number! <golf clap!>
The hubble zoomed into the Pioneer 10 with it’s high powered camera, and noted that it’s left blinker was stuck on.
If it happened only to Pioneer 10 & 11, then I would suspect a misunderstanding or misinterpretation of the results. Did NASA claim that Voyager 1 & 2 were showing the same anomaly?
Bump.
A partial explanation of the anomaly.
This link was at the bottom of your “partial explanation.”
Alcoholism and Genetics; and Why Aren’t the Pioneer Spacecraft Where They Should Be?
Gee, is that what explains the rest?
Not necessarily, I think. The article just says each year, the satellite is off by 5000 km short of projections. If projections are made yearly (I don’t know how they are made, since the article doesn’t explain it), it would stand to reason that the calculated velocity is getting a little slower every time, and projections made with the newly calculated (and slower) velocity still end up being off by 5000 km after a year is passed. So, even plugging in the new velocity year after year, projections are ending up short, suggesting that the spacecraft, in fact, is slowing down.
But, like I said, I don’t know how they make these projections, or anything.
As I’ve said before, theoretical physics are theoretical. The “Laws” we have are, all humor aside, simply suggestions. There’s more to this universe than what we can see and we are a damn sight away from understanding all of it. Not every…
Wait…
Slowing down you say? Isn’t velocity and time and acceleration / deceleration and such pretty well understood by now?
Hmm… Nossir, I don’t like it.
Now get off my lawn and take your space junk with you.
This passage seems to be glossing over the details. Does this imply that the heat radiating to space slowed down the probe? I guess in the form of infrared radiation? Would that have reactive force in the Newtonian sense, like rocket fuel? Do IR photons have mass? Why would the heat have a directional component (and thus slow down the craft), wouldn’t it radiate equally in all directions? Or is that affected by the shape of the craft somehow?
Sailboat
The probe is not slowing down. The solar system is speeding up. We already have two other galaxies headed on a collision course with the Milky Way. Evidently there is an even larger one on the other side of the probe.
Photons (e.g., IR) do not have mass, but they do have momentum, but whether or not it would cause the acceleration (which can be plus or minus), I don’t know. I do recall reading years ago that the amount of “solar” pressure (absorbed) on a football field at noon was equivalent of a small feather (Wikipedia claims a pressure of 4.6 microPascals or by my calculations the force equivalent of 2 grams x 1g per football size area). So, if one can assumes that S/C is emanating IR radiation from one spot which is greater than the rest of the S/C, it would have a cumulative impact over time. Since we’re talking decades, I calculated that the total decelerating force would be about 1e-11 m/sec-2, or about 1 trillionth of a “g”. The mass of Pioneer 10/11 is 258 kg (dry; but with fuel it becomes heavier so the deceleration will be less than indicated below), so a little math tells us that we get a force of about 2.5e-09 Newtons. We’ll assume that the force for IR is only 10% of full daylight and guess that amount of infrared is about 10 Watts, gives us get roughly 4.6 nanoPascals emissive power. And lets assume that we’ve got only a square foot of hot spot. That drops it down to roughly 500 picoPascals. Using F=ma, we get the following number: approximately 2e-12 m/sec-2. So with this half-assed math calculation, it is within the realm of possibility. Or a very lucky guess. Dopers feel free to pillar my assumptions (which are vastly oversimplified).
With respect to heat radiating away from the spacecraft in an isotropic fashion, no. Satellites have insulating and radiative surfaces depending on the thermal requirements which are affected by the kind of power source, the distance from the sun, the amount of internal power dissipation, etc. Having worked on S/C, I know we used materials that can reflect visible light and IR, or visa versa and reflect visible light, but absorb IR, and visa versa. I would assume that backend of Pioneer 10/11 is well insulated to keep the IR in as a result of pointing into the blackness of space (and hence, cold), while the front end pointing approximately to the sun would use less insulation–the antenna, you’ll note, was painted white to keep it from heating up and warping which would affect the gain; it also serves as a radiation shield.
My specialty is testing S/C, not thermal engineering, so take my above explanation with a grain of salt.
Ever since Scotty died the drive has been going to hell. And before that, he’d blimped up so much that beaming him up was taking twice the predicted energy.
…or they just discovered that tractor beams can be employed while a cloaking device is engaged. 