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Newsgroups: sci.physics.relativity
Subject: Re: Weakness in the results of the three tests of GR shown in rhe lasr century,.
From: nospam@de-ster.demon.nl (J. J. Lodder)
Reply-To: jjlxa31@xs4all.nl (J. J. Lodder)
Date: Tue, 5 Nov 2024 14:19:35 +0100
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ProkaryoticCaspaseHomolog <tomyee3@gmail.com> wrote:

> 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.

Certainly, 10^-10 is merely a typical accuracy.
But your excessive snipping has removed the context,
and hence the point.
(which was rh's complete ignorance of the state of the art
 with his claim that Mercury's precession
 cannot be calculated to sufficient accuracy)

> Every year, hundreds to thousands of asteroids are
> "lost" because of ill-determined orbits.

Yes, but that contributes only to the asteroid noise,
which is small anyway.

> 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?

Barely detectable, and completely irrelevant
for the calculation of anything else.

> 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.

See above.

> 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".

Disingeneous, to put it mildly.
The age when planetary calculations were done
by perturbing instantaneous orbital elements is long past.
Nowadays JPL and friends just do direct integrations.

And yes, if you try to parametrise the results in unsuitable ways
the parameters may be inaccurate.
This is completely irrelevant for knowing where Venus actually is,

Jan