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Originally Posted by papageno
Halley's comet's orbit has not been observed only in the last nine years, but it has been observed for centuries.
If you actually understood anything about celestial mechanics, you would know that the "anomalies" would add up.
Halley predicted the orbital period over three hundred years ago, predictions that still works accurate to the month.
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If Haley's comet's outer orbit is a couple of arc seconds outside of the Newtonian prediction now, it has ALWAYS be off a few arc seconds in the outer orbit, and how could anyone possibly know that? Every time it ventures near the sun, the orbital clock is reset by the varying effects of the solar wind.
Halley accurately predicted how Saturn and Jupiter would effect the comet, (So I have read), but the perturbations were based upon the Newtonian Masses of Saturn and Jupiter - Since Newton incorrectly predict the mass of these planets, the 2 & 3rd order perturbations upon the orbit of the comet also under-predict the mass of the comet.
This is why Deep Impact is so important: If the comet is much more dense than a 'dirty snowball' should be, if the predictions for the mass of the comet are based at all upon the orbit (and I don't know if they are), these predictions will be wrong.
It also means the theory for the formation of the solar system that predicts the outer planets are much less massive than the inner planets is not confirmed by the density of the 'left over' matter making up the comets.
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Originally Posted by papageno
By the way, the Pioneer anomaly does not support a continuous variation of G.
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Yes and No. The unmodeled acceleration is only obvious at distances where the solar wind cannot be used in the modeling.
If one assumes that the portion of the solar wind curve that does not attenuate as a 1/r^2 function is part of the anomalous acceleration, the magnitude of this fraction is, as best as I can tell, is greater than the variation in the 'linear' protion of acceleration.
I am assuming the 'space wave' function attenuates as a function of 1/(r-ro) where ro is the effective radius of the sun and r>r0. So when the probes were closest to the sun, and the rate of change in "G" the greatest, it is completely masked by the solar wind. At greater distances, the differences in the fractional accelerations at (1/20...1/21...1/22.......1/28 au) are small.
In addition, I am assuming that the speed of light is increasing at approximately the same rate of change as the probes are accelerating (and for the same reason), so this cuts the observed rate of change in half. (1/40...1/42...ect.) Pioneer probe distances are based upon two-way ranging data.
Finally, if you look at the raw data, there is a roughly periodic function in the 'unmodeled residuals'. It would be interesting to try to model this, correlating it with the path of the Doppler signal both to and from the probes, and determine if these periodic functions are consistant with varying the speed of light as it passes near the sun, and possibly even Jupiter and Saturn.