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From: tomyee3@gmail.com (ProkaryoticCaspaseHomolog)
Newsgroups: sci.physics.relativity
Subject: Re: Weakness in the results of the three tests of GR shown in rhe lasr
 century,.
Date: Mon, 4 Nov 2024 01:57:21 +0000
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On Sun, 3 Nov 2024 22:30:01 +0000, J. J. Lodder wrote:

> It is a clockwork in which everything hangs together.
> Having some distances at some time to some nanoseconds correct
> means that you must have the whole system to comparable accuracies.
> (or the computations will go off)

The statement of yours which I questioned was "JPL tracks and computes
'everything' in the solar system, from probes to planets, to an
accuracy of about 10^-10."

Some objects in the solar system are tracked to far greater accuracy
than 10^-10. The position of Mars, for instance, is known to about
1-2 meters thanks to transponder data from the Mars orbiters and
landers on the surface, implying positional accuracies on the order
of 10^-12. On the other hand, many objects in the solar system are
tracked to _far lower accuracy_. I imagine that most of the tracked
objects in the Minor Planet Center database have orbits known to
10^-8 or worse. Every year, hundreds to thousands of asteroids are
"lost" because of ill-determined orbits. Furthermore, the orbits of
many of these minor objects do not follow your "clockwork" paradigm
very closely at all, due to non-gravitational forces. For example,
have you heard of the Yarkovsky effect, which is the result of
anisotropic emission of thermal photons from rotating bodies?
https://en.wikipedia.org/wiki/Yarkovsky_effect
There is also solar radiation pressure, outgassing, occasional
collisions, etc.

The other point that I made was that the meaning of "10^-10 accuracy"
is rather ambiguous. For instance, since it has not been too many
years since the last Venus orbiters and Venus flybys, the current
positional accuracy of Venus may be known to the 10^-10 level. Does
that mean that the longitude of perihelion is known to 10^-10? Of
course not! The orbit of Venus has extremely low eccentricity, which
makes it difficult to determine this value. So the longitude of
perihelion is known to only a few tenths of a degree. That is what
I meant when I wrote that the accuracy depends on "what specific
parameters one is discussing".