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Newsgroups: sci.physics.relativity
Subject: Re: The Shapiro's experiment HOAX. A 1968 TIME article.
From: nospam@de-ster.demon.nl (J. J. Lodder)
Reply-To: jjlxa31@xs4all.nl (J. J. Lodder)
Date: Sun, 20 Oct 2024 11:27:10 +0200
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rhertz <hertz778@gmail.com> wrote:

> On Sat, 19 Oct 2024 19:42:59 +0000, J. J. Lodder wrote:
> 
> <snip>
> 
> > [snip irelevancies about history space travel, yes we all know]
> >
> > And back to the point:
> > You whine about a popularised account of Shapiro's radar measurements
> > of planetary distances. (and relativistic delays that were a by-product)
> > All this from almost 60 years ago.
> >
> > It has completely escaped your notice that in the meantime
> > measurements in the solar system have increased more than a thousandfold
> > in accuracy,
> > (by using transponders in interplanetary probes instead of radar echos)
> > and that Shapiro delays are nowadays taken into account
> > as a routine correction that needs to be applied
> > to get interplanetary distances and hence navigation right.
> >
> > In other words, it is no longer an issue of science,
> > it is routine engineering, (at places like JPL)
> >
> > Jan
> 
> I insist that you are an ignorant idiot pretending to know something
> about radio/laser communications.
> 
> You are the one who started this by asserting that passive reflections
> of EM radiation decay with 1/r?, and not the usual 1/r?. This stupidity
> alone is enough to disqualify you for any further discussion about EM
> propagation in outer space. Any RF/laser engineering expert would put
> you on the "IGNORE LIST", just for being such a donkey.

I should have expressed myself more carefully there.
Meant was of course an extra factor 4 for twice the distance.

> I have to remark a couple of things:
> 
> 1. If you are a woman, I apologize. I only call names to men. Even more,
>    I withdraw my comments about your stupidity and ignorance, and let
>    you to chose what you are. Of course that you're not a connoisseur on
>    these subjects.

My my, a Frenchie pretending to be a gentleman.
 
> 2. You didn't let me know which are your academical degrees. Let me
>    know, as it would help a lot to understand some biases of your
>    thoughts.

Three doctorates and two Nobel prizes, just like you.

> 3. You keep insisting with transponders and their importance, as if I
>    had written anything about them. On the contrary, I showed to you
>    that transponders are essential in space (and earthly) travels.

You were obviousy ignorant of the importance of them
in the context of precise space navigation.

> 4. It makes me sad your ignorance about what is required for space
>    travel's guidance. It seems that you didn't read a single word of
>    what I wrote on this matter.

I did, it is nonsense.

> 5. Shapiro's delay is IRRELEVANT in space travel. Completely useless.
>    Any space flight is computed IN REAL TIME with many sophisticated
>    optical and EM based techniques, like triangulations with WELL KNOWN
>    trajectories of selected celestial bodies (planets, moons, asteroids)
>    plus the traditional guidance by well known fixed stars.

Those 'sophisticated optical and EM based techniques'
do need relativistic corrections.
(at the present level of accuracy)

>    There is no 3D celestial GPS to be used in space flights. A link
>    with Earth stations are UNIDIMENSIONAL in a 3D space.

It is necessary to do a complete integration
involving the whole solar system to know where everything is.
(to a hundred meters or so, limited mainly by asteroid noise)
This is of course an expert job. (for JPL for example)
It requires a lot of computational power.

The accuracy has increased to the point where it becomes necessary
to give the AU a defined value, because the motions of the Earth are to
erratic to serve as a base for it.

Back to the point: Once you arrive at accuracies measured in nanoseconds
the Shapiro delay becomes a correction to be applied routinely,

Jan

-- 
1 astronomical unit         = 149 597 870 700 metres (exactly) 
Best measurement before was = 149 597 870 691(6)
Yes, positions objects in the solar system are noways known
to a few meters, or some tens of nanoseconds.