On May 8, 7:10 pm, dlzc wrote:
Dear Albertito:

On May 8, 10:27 am, Albertito wrote:

On May 8, 5:46 wrote:
...
The Earth Sun barycenter is well inside the Sun,
to the tune of a few hundred meters (I think).
The acceleration the Pioneer spacecraft is
experiencing would have consumed that distance
by now.

Yes, I take the signs right. My original post was
just the hypothesis of anomalous gravitational
Doppler shifts. Of course, we still don't know the
cause of Pioneer anomaly.

Right.

Maybe, it is only systematics. But, there is a
possibility of new physics.

Not really, or at least not on something that is not discerning of
"object size". Because the velocities are not terribly different that
are already experienced by comets and such... which also don't undergo
the "anomalous" effects.

If the cause is gravitational, then we have an
interesting issue here. The possibility of
anomalous gravitational shifts shouldn't be rule
out.

*Have* to be. Other objects don't show this acceleration.

Now remember, we "saw" the Pioneer spacecraft
getting anomalously *closer*, not further. Did
you get your signs right in the initial post?

That would be only apparent *closer*, not real,

But it would be closer *at both ends*. Largely, the acceleration was
detected by "round trip time of flight". Earth gets closer too.

if the cause is *anomalous* gravitational shifts.

Really unlikely as I said, since comets and planets are not affected.
But hey...

David A. Smith

All objects that seem to show the Pioneer anomaly
have something in common: they all are escaping
the solar system with hyperbolic trajectories. Planets,
asteroids, satellites and comets in the solar system
exhibit elliptical orbits, so they do not show the Pioneer
anomaly. They are not actually escaping the solar system.
When an object escapes any gravitational system, it
transfers momentum to the system. When an object
enters into (it's being trapped by) a gravitational system,
it gains momentum from the system. These transactions
of momenta for object escaping or entering into gravitational
systems seem not to be very well accounted for by GR or
by Newtonian gravity. This physics must be better understood.
But until then, anomalous gravitational Doppler shifts shouldn't
be ruled out as a possible explanation of the Pioneer anomaly
and other 'graviational' anomalies observed in the solar system.