"Mysteriously, five spacecraft that flew past the Earth have each
displayed unexpected anomalies in their motions.

These newfound enigmas join the so-called "Pioneer anomaly" as hints
that unexplained forces may appear to act on spacecraft.

A decade ago, after rigorous analyses, anomalies were seen with the
identical Pioneer 10 and 11 spacecraft as they hurtled out of the solar
system. Both seemed to experience a tiny but unexplained constant
acceleration toward the sun.

A host of explanations have been bandied about for the Pioneer anomaly.
At times these are rooted in conventional science — perhaps leaks from
the spacecraft have affected their trajectories. At times these are
rooted in more speculative physics — maybe the law of gravity itself
needs to be modified.

Greysky

http://talk.guardian.co.uk/WebX/.7760665c...@810.BdfPaIxwNMl@

NASA Baffled by Unexplained Force Acting on Space Probes  You are
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Started by tobygr at 08:15am Mar 2, 2008 GMT

http://www.space.com/scienceastronomy/080229-spacecraft-anomaly.html

"Mysteriously, five spacecraft that flew past the Earth have each
displayed unexpected anomalies in their motions.

These newfound enigmas join the so-called "Pioneer anomaly" as hints
that unexplained forces may appear to act on spacecraft.

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tobygr - 08:17am Mar 2, 2008 GMT (#1 of 11)
""I am feeling both humble and perplexed by this," said Anderson, who
is now working as a retiree. "There is something very strange going on
with spacecraft motions. We have no convincing explanation for either
the Pioneer anomaly or the flyby anomaly."

In the one probe the researchers did not confirm a noticeable anomaly
with, MESSENGER, the spacecraft approached the Earth at about latitude
31 degrees north and receded from the Earth at about latitude 32
degrees south. "This near-perfect symmetry about the equator seemed to
result in a very small velocity change, in contrast to the five other
flybys," Anderson explained -- so small no anomaly could be confirmed.

The five other flybys involved flights whose incoming and outgoing
trajectories were asymmetrical with each other in terms of their
orientation with Earth's equator.

For instance, the NEAR mission approached Earth at about latitude 20
south and receded from the planet at about latitude 72 south. The
spacecraft then seemed to fly 13 millimeters per second faster than
expected. While this is just one-millionth of that probe's total
velocity, the precision of the velocity measurements was 0.1
millimeters per second, carried out as they were using radio waves
bounced off the craft. This suggests the anomaly seen is real -- and
one needing an explanation.

The fact this effect seems most evident with flybys most asymmetrical
with respect to Earth's equator "suggests that the anomaly is related
to Earth's rotation," Anderson said.

As to whether these new anomalies are linked with the Pioneer anomaly,
"I would be very surprised if we have discovered two independent
spacecraft anomalies," Anderson told SPACE.com. "I suspect they are
connected, but I really do not know."

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pgboys - 08:45am Mar 2, 2008 GMT (#2 of 11)
I saw an Horizon once that seemed to suggest that (crudely) "spinning
objects slow time".

Proper scientists had even got funding to build something that should
send information back in time (at least back to the point when it was
turned on), allowing the future to communicate with the past.

--------------------------------------------------------------------------- -----
ironE - 08:52am Mar 2, 2008 GMT (#3 of 11)
Could this not be related to some kind of small possible variation in
the relative ambient gravitation, as a body approaches the equatorial
zone? Or is the gravitational "pull" perfectly constant across all
latitudes?

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coshipi - 09:05am Mar 2, 2008 GMT (#4 of 11)
pgboys

That's a consequence of General Relativity. The funding wasn't to
build something that could send information back in time, but to
investigate the theory in sufficient detail to determine whether such
a device was in principle possible. Last I heard the state of play was
"we're not sure yet, but probably not".

I presume that NASA's calculations allow for General Relativity not
just Special Relativity.

ironE

Variations in the gravity of the Earth, both with latitude and in a
complicated pattern caused by the mass distribution (mainly to do with
differences between oceanic and continental crust, and incomplete post-
glacial isostatic recovery) are well known. Again, if NASA haven't
included this in their calculations I'd be very surprised.

--------------------------------------------------------------------------- -----
MalcolmMcm - 09:41am Mar 2, 2008 GMT (#5 of 11)
Hmm.. if the 'brane theory idea that the relative weakness of gravity
is down to "leakage" in some gravity-only dimension holds water you
might expect some deviation from inverse square at short ranges, which
would be invisible at the solar system level.

I wonder if anyone's looked for a gravition vs. distance curve that
would account for such anomilies e.g. a small inverse cube component.

--------------------------------------------------------------------------- -----
ironE - 09:50am Mar 2, 2008 GMT (#6 of 11)
Earth does have her quirks, though, the ones mentioned above as well
as the dense, spinning core inside a likewise rotating mantle - there
must be massive energy discharge associated, which perhaps hasn't
fully been brought to light because until these probes flew by there
hadn't been a 'detection system' capable of picking up the small
variations - now, with this effect on objects travelling very long
paths, the math is revealing such a (possible) rotatio-gravitational
anomaly?!

Of course that's pure conjecture based on very sparse information...

I suppose there'll be sleepless nights for a good many astrophysicists
until this one's sorted out

--------------------------------------------------------------------------- -----
pgboys - 10:05am Mar 2, 2008 GMT (#7 of 11)
Ah, cheers coshipi - I hoped I hadn't just imagined it.

--------------------------------------------------------------------------- -----
aegian - 11:29am Mar 2, 2008 GMT (#8 of 11)
It must be frustrating that the anomaly is so small. Any smaller and
it wouldn't be there. Much bigger and we'd be looking for something
that accounts for it with more confidence. It's like Yossarian not
quite having jaundice at the start of Catch-22...

--------------------------------------------------------------------------- -----
ironE - 11:36am Mar 2, 2008 GMT (#9 of 11)
Did he exhibit a wobble as well?

--------------------------------------------------------------------------- -----
coshipi - 03:36pm Mar 2, 2008 GMT (#10 of 11)
ironE

The difference in spin rates between the mantle and the core is
extremely small - you're looking at a whole Earth angular velocity of
~2pi/day, with a difference between core and mantle of the order
(0.000 000 000 01)/day. (That was ten to the minus eleven.) I don't
think this is going to account for anything like as big an anomaly as
they're seeing.

Much more significant would be an error in our estimates of the
variation of the Earth's density with distance from the centre, and
such an error is possible. Our estimate of the mass of the Earth is
based on celestial mechanics, so any error in that cancels itself out
when you're doing celestial mechanics - but any error in our estimate
of the radial variation of density on General Relativistic effects
doesn't cancel itself out in the same way. And we don't have any very
good method of estimating the density of the mantle and core as a
function of radius. All our information about the mantle and core is
derived from propagation of seismic waves, and we don't know enough
about the properties of matter at the temperatures and pressures
inside the Earth to work anything out very accurately. Even the
temperature and pressure estimates could be quite a long way out.

--------------------------------------------------------------------------- -----
CaptPugwash - 05:46pm Mar 2, 2008 GMT (#11 of 11)

-Honest John

BUAHAHAHAHAHAHAHAHAHAHAHAHAHA!

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