"Pioneer anomalous acceleration" and Cassini

"Jim Greenfield" bravely wrote to "All" (04 Nov 03 23:57:09)
--- on the heady topic of " "Pioneer anomalous acceleration" and Cassini"

JG From: (Jim Greenfield)
The question was settled years ago. There *is* definitive anomalous
acceleration in pioneer and the voyagers. No theoretical explanation has
yet been settled on.

JG Finally gathered the courage to tentatively suggest that when photons
JG are emmitted, they give a 'recoil' against the source. If radiation
JG from within the craft is directed in a particular direction, a thrust
JG might occur. (I thought that this would be so insignificant as to be
JG immesurable and undetectable, but maybe not)
JG What would happen to a high-power laser carefully suspended- any
JG chance of detecting an observable thrust counter to beam direction???

Saying a photon is "emitted" is a bit of a misnomer. I'd rather say a
photon is released or let go. The momentum recoil is in the photon.
That momentum is what results in radiation pressure on the receiving
end. A photon is not so much emitted as the rest of the universe leaves
it behind in time since after all the photon sees zero time elapsed.
Anyways for whatever it's worth, photons interact with spacetime and in
a sense it is spacetime that moves not the photon. The photon is just a
little bit of history or information left behind and telling what the
universe was doing at that instant.

.... "Time is what clocks measure..." -- Albert Einstein

Jim Greenfield wrote in message
om...
"greywolf42" wrote in message
...
Jonathan Silverlight
wrote
in message ...


There's an article in the current issue of Nature that seems relevant
to
the Pioneer anomalous acceleration question ("A test of general
relativity using radio links with the Cassini spacecraft" B Bertotti,
L
Iess and P Tortora, Nature vol 425. No. 6956 p. 374,
doi:10.1038/nature01997)
AFAICS they have accurately modelled emission from the RTGs and they
don't see any unexplained acceleration.

They haven't looked for anomalous acceleration with this experiment.
The
referenced experiment measures the time-delay of the signal in a
gravitational field. Nothing more.

Does that mean the question is settled, or isn't their measurement
sufficiently sensitive?

The question was settled years ago. There *is* definitive anomalous
acceleration in pioneer and the voyagers. No theoretical explanation
has
yet been settled on.

Finally gathered the courage to tentatively suggest that when photons
are emmitted, they give a 'recoil' against the source. If radiation
from within the craft is directed in a particular direction, a thrust
might occur. (I thought that this would be so insignificant as to be
immesurable and undetectable, but maybe not)
What would happen to a high-power laser carefully suspended- any
chance of detecting an observable thrust counter to beam direction???

Such recoil can indeed be measured over such long distances, when no other
significant forces are expected -- such as in interplanetary space.
However, the contribution from this source has been carefully modeled.
They've tried many variations and over the past 20 years. No "standard"
theory can account for the observations.
--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail}

In message , George Dishman
writes

The data from Pioneer is sent back by radio. The power is
nominally 8W, a little more than a mobile phone. The radiation
pressure from the beam is about 13% of the magnitude of the
anomaly but the beam pushes the craft away from the Earth while
the anomaly is an acceleration towards the Earth. This is why
asymmetric thermal radiation from the RTGs was looked at as a
possible explanation, they emit a couple of kW altogether. The
trouble was that nobody could figure out how to explain the
asymmetry.

Doesn't Ned Wright claim otherwise? You only need 60 watts to produce
the effect. And Bertotti et al. state that solar radiation pressure on
Cassini is about an order of magnitude less than the RTGs thermal
thrust, and quote a figure of 175 watts for the solar power. OTOH,
Cassini has 20 x the mass of Pioneer.
--
Rabbit arithmetic - 1 plus 1 equals 10
Remove spam and invalid from address to reply.

In message , greywolf42
writes
Jonathan Silverlight wrote
in message ...

Then why are you attempting to claim results other than what the paper and
observations were about?

In my original question, I simply asked if the Bertotti paper shed any
light on the Pioneer anomaly, given that it reports much more accurate
figures and shows no unusual residual effect.


I don't know if the solar opposition experiment has been published, but
the point is that Bertotti et al.

Horsefeathers. The reference under discussion was Anderson and Lau -- not
Bertotti. And the difficulty of modelling the emission is not physically
different for Bertotti than four Anderson and Lau.


Both groups consider that most of the acceleration comes from thermal
emission, but Bertotti et al. say most of the RTG emission from Cassini
is isotropic. There is still a substantial net thrust. Has Anderson
answered Ned Wright's argument that the anomaly can be explained by
anisotropy of the emission? http://arxiv.org/abs/gr-qc/0107092

quote a figure for the acceleration
from the RTGs of 3 x 10^-9 m s^-2, with an error of 9 x 10^-11 m s^-2.
That error is about "an order of magnitude" less than the Pioneer
effect.

Not according to Anderson and Lau.

Could someone check my arithmetic? Anderson et al. use cm s^-2 rather
than meters - I don't know why - and their figure of -26.7 x 10^-8 cm
s^2 can be compared directly with the original Pioneer anomaly of 8 x
10^-8 cm s^2. They quote an error of 1.1 x 10^-8 cm s^2, which is about
the same as Bertotti et al. and is comfortably less than the "effect".
If that figure is actually wrong - inaccurate, as opposed to being
imprecise - wouldn't it show up in the residuals? That's what prompted
my original post, and I haven't seen a reply showing it wouldn't.


Anderson et al. quote a figure for a_r (the radial acceleration, mostly
due to the RTGs) of -26.7 x 10^-8 cm s^-2, which is essentially the same
when you convert.

Yes. And Anderson and Lau mention that "the uncertainty in the thermal
model overwhelms any plausible application of the Pioneer anomaly to
Cassini."

As Volker Hetzer says, there's a contradiction between the statements
that "the result is not anomalous" and "the uncertainty in the thermal
model overwhelms any plausible application of the Pioneer anomaly to
Cassini". The new measurements are much more accurate than the Pioneer
ones (compare the residuals) and the Pioneer effect doesn't appear.

How are they more accurate? According to Anderson, the measurements
of 'anomalous accelerations' would are 10 times less precise than the gross
effect measured to 2 sig figs on Pioneer. Due to "the uncertainty in the
thermal model" of Cassini.

I don't see how you get that figure. Anderson et al. say "Finally, the
error in ar from 27 days of Cassini Doppler data is about two times
better than the result from 11 years of Pioneer 10 Doppler data "
I think that's pessimistic; they are now getting Doppler residuals of
microns per second.
--
Rabbit arithmetic - 1 plus 1 equals 10
Remove spam and invalid from address to reply.

"Jonathan Silverlight" wrote
in message ...
In message , George Dishman
writes

The data from Pioneer is sent back by radio. The power is
nominally 8W, a little more than a mobile phone. The radiation
pressure from the beam is about 13% of the magnitude of the
anomaly but the beam pushes the craft away from the Earth while
the anomaly is an acceleration towards the Earth. This is why
asymmetric thermal radiation from the RTGs was looked at as a
possible explanation, they emit a couple of kW altogether. The
trouble was that nobody could figure out how to explain the
asymmetry.

Doesn't Ned Wright claim otherwise? You only need 60 watts to produce
the effect.

Yes. 8W is about 13% of Anderson's figure of 63W.

The RTGs produce about 2070W of heat so if that was
split 1003W towards the Sun and 1067W away from it,
that could explain the effect.

And Bertotti et al. state that solar radiation pressure on
Cassini is about an order of magnitude less than the RTGs thermal
thrust, and quote a figure of 175 watts for the solar power. OTOH,
Cassini has 20 x the mass of Pioneer.

I haven't had a chance to look at that paper yet.
Is it available on-line without a subscription?

George

"Asimov" wrote in message . ..
"Jim Greenfield" bravely wrote to "All" (04 Nov 03 23:57:09)
--- on the heady topic of " "Pioneer anomalous acceleration" and Cassini"

JG From: (Jim Greenfield)
The question was settled years ago. There *is* definitive anomalous
acceleration in pioneer and the voyagers. No theoretical explanation has
yet been settled on.

JG Finally gathered the courage to tentatively suggest that when photons
JG are emmitted, they give a 'recoil' against the source. If radiation
JG from within the craft is directed in a particular direction, a thrust
JG might occur. (I thought that this would be so insignificant as to be
JG immesurable and undetectable, but maybe not)
JG What would happen to a high-power laser carefully suspended- any
JG chance of detecting an observable thrust counter to beam direction???

Saying a photon is "emitted" is a bit of a misnomer. I'd rather say a
photon is released or let go. The momentum recoil is in the photon.
That momentum is what results in radiation pressure on the receiving
end. A photon is not so much emitted as the rest of the universe leaves
it behind in time since after all the photon sees zero time elapsed.
Anyways for whatever it's worth, photons interact with spacetime and in
a sense it is spacetime that moves not the photon. The photon is just a
little bit of history or information left behind and telling what the
universe was doing at that instant.

I am not interested in the photon after it leaves its source, but in
its EFFECT on that source- as in the recoil of my rifle against my
shoulder.
George and Lupus seem to think there is a counter-push on the source
caused by beam emmission, but you claim all energy is retained in the
photon (correct?)

Jim G

"Jim Greenfield" wrote in message
om...
"Asimov" wrote
in message . ..
"Jim Greenfield" bravely wrote to "All" (04 Nov 03 23:57:09)
--- on the heady topic of " "Pioneer anomalous
acceleration" and Cassini"

JG From: (Jim Greenfield)
The question was settled years ago. There *is* definitive
anomalous
acceleration in pioneer and the voyagers. No theoretical
explanation has
yet been settled on.


There is a new article Nov 3 by Anderson et al with a mundane
explanation no new force or planet etc.
I dont know how this fits in with the speculations on the
properties of photons being discussed. Perhaps light is not
something carried by a photon or a wave or a probablistic photon
or something even more abstract and mysterious. Perhaps light is
the cumulative effect of instantaneous forces at a distance with
a delay of r/c for rc and 1 second for rc. See
www.bestweb.net/~sansbury


JG Finally gathered the courage to tentatively suggest that
when photons
JG are emmitted, they give a 'recoil' against the source.
If radiation
JG from within the craft is directed in a particular
direction, a thrust
JG might occur. (I thought that this would be so
insignificant as to be
JG immesurable and undetectable, but maybe not)
JG What would happen to a high-power laser carefully
suspended- any
JG chance of detecting an observable thrust counter to beam
direction???

Saying a photon is "emitted" is a bit of a misnomer. I'd
rather say a
photon is released or let go. The momentum recoil is in the
photon.
That momentum is what results in radiation pressure on the
receiving
end. A photon is not so much emitted as the rest of the
universe leaves
it behind in time since after all the photon sees zero time
elapsed.
Anyways for whatever it's worth, photons interact with
spacetime and in
a sense it is spacetime that moves not the photon. The photon
is just a
little bit of history or information left behind and telling
what the
universe was doing at that instant.

I am not interested in the photon after it leaves its source,
but in
its EFFECT on that source- as in the recoil of my rifle against
my
shoulder.
George and Lupus seem to think there is a counter-push on the
source
caused by beam emmission, but you claim all energy is retained
in the
photon (correct?)

Jim G

"ralph sansbury" writes:

"Jim Greenfield" wrote in message
om...
"Asimov" wrote
in message . ..
"Jim Greenfield" bravely wrote to "All" (04 Nov 03 23:57:09)
--- on the heady topic of " "Pioneer anomalous
acceleration" and Cassini"

JG From: (Jim Greenfield)
The question was settled years ago. There *is* definitive
anomalous
acceleration in pioneer and the voyagers. No theoretical
explanation has
yet been settled on.


There is a new article Nov 3 by Anderson et al with a mundane
explanation no new force or planet etc.


Would you mind pointing me to the abstract/article? I couldn't find in neither
ads, nature nor arxive. I really would like to have a look at it.



--
Øystein Olsen, , http://folk.uio.no/oeysteio
Institute of Theoretical Astrophysics, http://www.astro.uio.no
University of Oslo, Norway

"Jim Greenfield" bravely wrote to "All" (05 Nov 03 21:28:55)
--- on the heady topic of " "Pioneer anomalous acceleration" and Cassini"

JG From: (Jim Greenfield)
JG Subject: "Pioneer anomalous acceleration" and Cassini
JG Organization: http://groups.google.com
JG Xref: aeinews sci.astro:7536

JG "Asimov" wrote in
JG message rg... "Jim
JG Greenfield" bravely wrote to "All" (04 Nov 03 23:57:09) --- on the
JG heady topic of " "Pioneer anomalous acceleration" and Cassini"
JG From: (Jim Greenfield)
The question was settled years ago. There *is* definitive anomalous
acceleration in pioneer and the voyagers. No theoretical explanation has
yet been settled on.

JG Finally gathered the courage to tentatively suggest that when photons
JG are emmitted, they give a 'recoil' against the source. If radiation
JG from within the craft is directed in a particular direction, a thrust
JG might occur. (I thought that this would be so insignificant as to be
JG immesurable and undetectable, but maybe not)
JG What would happen to a high-power laser carefully suspended- any
JG chance of detecting an observable thrust counter to beam direction???

Saying a photon is "emitted" is a bit of a misnomer. I'd rather say a
photon is released or let go. The momentum recoil is in the photon.
That momentum is what results in radiation pressure on the receiving
end. A photon is not so much emitted as the rest of the universe leaves
it behind in time since after all the photon sees zero time elapsed.
Anyways for whatever it's worth, photons interact with spacetime and in
a sense it is spacetime that moves not the photon. The photon is just a
little bit of history or information left behind and telling what the
universe was doing at that instant.

JG I am not interested in the photon after it leaves its source, but in
JG its EFFECT on that source- as in the recoil of my rifle against my
JG shoulder.
JG George and Lupus seem to think there is a counter-push on the source
JG caused by beam emmission, but you claim all energy is retained in the
JG photon (correct?)

If there was a recoil then a source such as an electron would be losing
or gaining mass simply by a change in temperature. This hasn't been
reported yet.

"Oeystein Olsen" wrote in message
...
"ralph sansbury" writes:

"Jim Greenfield" wrote in message
om...
"Asimov"
wrote
in message
. ..
"Jim Greenfield" bravely wrote to "All" (04 Nov 03
23:57:09)
--- on the heady topic of " "Pioneer anomalous
acceleration" and Cassini"

JG From: (Jim Greenfield)
The question was settled years ago. There *is*
definitive
anomalous
acceleration in pioneer and the voyagers. No
theoretical
explanation has
yet been settled on.


There is a new article Nov 3 by Anderson et al with a
mundane
explanation no new force or planet etc.


Would you mind pointing me to the abstract/article? I couldn't
find in neither
ads, nature nor arxive. I really would like to have a look at
it.
I saw something on Google the other day with the Nov 3 date
and the Kuiper belt object explanation but maybe it was an older
paper as I couldn't find it again today.



--
Øystein Olsen, ,
http://folk.uio.no/oeysteio
Institute of Theoretical Astrophysics, http://www.astro.uio.no
University of Oslo, Norway