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Readme contains wrong info #3998

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PiloniA opened this issue May 7, 2024 · 2 comments
Open

Readme contains wrong info #3998

PiloniA opened this issue May 7, 2024 · 2 comments

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@PiloniA
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PiloniA commented May 7, 2024

I am not sure if this is the right place for that issue:

In the Readme under Concepts-PlottingFrame (https://github.com/mockingbirdnest/Principia/wiki/Concepts#plotting-frame) in the 3rd paragraph it is stated:

"In addition, both the Sun and Earth rotate around you (or rather, the Moon) once every month."

This is not true. When you are standing on the moon, the earth seems to be on a fixed point (with a bit of wobble).
This is why we on earth always see the same side of the moon.
As a result also the graphic is wrong.

@PiloniA PiloniA changed the title Readme contains misleading info Readme contains wrong info May 7, 2024
@pleroy
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pleroy commented May 9, 2024

Wow, this has been around since 2016 and nobody noticed (or: nobody commented), egg on my face. Thanks for reporting.

I need to think a bit, because the goal of this document is to explain reference frames to beginners, so it needs to be simple enough. I'm concerned that the actual motion of the Earth seen from the Moon (a relatively small loop, due to nutation and to ellipticity) is going to be rather more difficult to explain and understand.

@PiloniA
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PiloniA commented May 9, 2024 via email

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