I Astronomy in a Simple Solar System

[PeterDonis]

your initial definition of Orbit is so far from normal experience

No, it isn't. I am using the same definition you are using: the "shape" of the orbit in space is its shape in whatever frame has been chosen. The problem is that the frame you are implicitly using does not even exist; it can't be constructed. See further comments below.

You and I know that the Moon is sometimes nearer and sometimes further away from the Sun but that it always 'goes the same way' around the Earth.

No, we do not "know" that; that is my point. What you are doing here is taking a claim which is perfectly valid if we only consider the Earth and the Moon, and assuming that you can just stick the Sun into your analysis without changing anything except adding an orbit for the Sun. But you can't. To do that, you would have to be able to take the Earth-centered inertial frame that you are implicitly using to describe the Moon's orbit about the Earth, and extend it over a large enough region of spacetime to include the Sun for a long enough time period (at least one month). And you cannot do that; no such frame can be constructed. That is what I have been saying, and neither you nor anyone else has refuted it.

As far as Earth people are concerned, the Orbit of the Moon around the Earth would not change substantially, were the Sun to disappear.

This is another claim that you cannot make without having a frame that can cover a large enough region of spacetime to make the comparison you are making. And no such frame exists.

The geometry of its path through space can be interpreted in many different ways

It is true that the geometry of any object's spatial trajectory is frame-dependent. But that still requires that whatever frame you are using must exist and must include all of the objects you are using in your analysis. And the frame you are implicitly using to make your claims does not exist, because no frame can be constructed that includes the Earth, Moon, and Sun and has the properties you are assuming.

You have a model that is, perhaps, self consistent

And you don't. That's my point. You think you do, but you are wrong, because you are just waving your hands instead of actually doing the math.

 

[PeterDonis]

Thread closed for moderation.

 

[berkeman]

After a Mentor discussion, the thread will remain closed. Thank you everybody for your contributions.