My best guess is that the winds have changed from NW and are now Southerly winds at 15 (bunch of zeros) to 20 (many more zeros) mph creating the drag.
ANOMALOUS GRAVITATIONAL FORCE? A discussion of this phenomenon appears in the 4 October 1999 issue of Newsweek magazine (See also the December 1998 issue of Scientific American.) The mystery of the tiny unexplained acceleration towards the sun in the motion of the Pioneer 10, Pioneer 11 and Ulysses spacecraft remains unexplained. A team of planetary scientists and physicists led by John Anderson (Pioneer 10 Principal Investigator for Celestial Mechanics) has identified a tiny unexplained acceleration towards the sun in the motion of the Pioneer 10, Pioneer 11, and Ulysses spacecraft. The anomalous acceleration - about 10 billion times smaller than the acceleration we feel from Earth's gravitational pull - was identified after detailed analyses of radio data from the spacecraft. A variety of possible causes were considered including: perturbations from the gravitational attraction of planets and smaller bodies in the solar system; radiation pressure, the tiny transfer of momentum when photons impact the spacecraft; general relativity; interactions between the solar wind and the spacecraft; possible corruption to the radio Doppler data; wobbles and other changes in Earth's rotation; outgassing or thermal radiation from the spacecraft; and the possible influence of non-ordinary or dark matter. After exhausting the list of explanations deemed most plausible, the researchers examined possible modification to the force of gravity as explained by Newton's law with the sun being the dominant gravitational force. "Clearly, more analysis, observation, and theoretical work are called for," the researchers concluded. The scientists expect the explanation when found will involve conventional physics.Pioneer 10 will continue into interstellar space, heading generally for the red star Aldebaran, which forms the eye of Taurus (The Bull). Aldebaran is about 68 light years away and it will take Pioneer over 2 million years to reach it.
Heck, it could be something like time-dilation affecting the instruments or just the awful cold of deep space throwing the computer out of whack. They don't have radar bouncing off this little gizmo, they just try to triangulate on it with radio dishes. They find an error in it's calculated position so tiny it amounts to 6 mph in a century, so it's out of position by a couple thousand miles or less, out of a billion and a half! Their radio dishes might be in error by that much...
Whatever is causing it, a little humble pie is good for these guys.
I don't know.
I always had a gut feel that calculations which relied on the speed of light or square of the distance worked fine while we were able only to apply them to terrestrial situations. Now that we're getting into bigger numbers, maybe we'll discover it's really only .99999999999 times the square of the distance.
I need to conduct further experiments to fully validate this force. Cheers!!!!
second guess, totally different. correct conclusions, reason for slow down is from the presence of onboard radio transmitters, the propogation itself, they are somehow tied in with gravity.
/layman's guesses
I sincerely doubt that any physicist or astronomer knows the exact value of the gravitational constant out to 10 decimal places.
They also don't know the exact mass of the spacecraft - there may be residual fuel onboard that wasn't used but isn't accounted for in the mass calculation.
Maybe there is something subtle we don't know yet about light, gravity, and space. This is exciting news, we may be on the brink of a new understanding of where we live.
This data will have to be watched for a long while! Perhaps a deep space interferometry experiment or long paseline ring laser gyro would shed some (delayed) light on the "matter".
"Based on 50 years of accumulated observations of the motions of galaxies and the expansion of the universe, most astronomers believe that as much as 90 percent of the stuff constituting the universe may be objects or particles that cannot be seen. In other words, most of the universe's matter does not radiate--it provides no glow that we can detect in the electromagnetic spectrum.
"First posited some 60 years ago by astronomer Fritz Zwicky, this so-called missing matter was believed to reside within clusters of galaxies. Nowadays we prefer to call the missing mass 'dark matter,' for it is the light, not the matter, that is missing."
Perhaps the answer to that mysterious force lies HERE.
My best guess is that the winds have changed from NW and are now Southerly winds at 15 (bunch of zeros) to 20 (many more zeros) mph creating the drag.
How did Voyager get farther out? Was it launched at a higher rate of speed, or did Pioneer 10 spend more time orbiting planets, or what?
Well, duh (as the old joke goes), if that's the case - go at night.