Return to Answer

I would like to post a comment, but as I do not have enough "reputation" score to do so, here is my complement to @asdflex's comment.

As you probably know, motion is always defined relative to a reference (the point you define as fix in YOUR convention, plus the 3 orthogonal Cartesian axis in 3D space of YOUR CHOOSING). By definition then, your description of motion would be meaningless if you leave ambiguous your conventions.

Now, to address your question specifically:

It looks like your video is made with the type of reference called Celestial Reference Frame. There is an internationally agreed one called the ICRF. As an introduction to this concept you can look at this paper: The Next Generation Celestial Reference Frame by M. Johnson et al (https://arxiv.org/pdf/1903.11145.pdf). Below is an extract of the intro: "It is only by using this inertial reference frame that we are able to disentangle our observations of the motions of celestial objects from our own complex path around our star, and its path through the galaxy, ..."

Your next drawing seems to designate the Sun as the center of the reference frame. Note that you still have to specify the 3 axis to have a fully-defined reference. And here you have the choice between many possibilities (cf this link https://www.mssl.ucl.ac.uk/grid/iau/extra/local_copy/SP_coords/heliosys.htm).

Note that people also use ECI (Earth-Centered Inertial) and ECEF (Earth-Centered-Earth-Fixed) references. Let's use these to illustrate the difference that the selection of the reference can make to the description of motions. When we say that a satellite is in geostationary orbit, implicitly we refer to the ECEF. The said satellite appears at rest compared to an observer on Earth, who feels that he is at rest also, because he is moving together with the rotating reference. Now, if we use instead the direction of a star to tie the X-axis with (this is the only difference between ECI and ECEF), then the motion of our geostationary satellite is a closed circle, not a fix point.

The bottom line is that, people choose a reference frame to describe a motion, in the way that is most convenient to them. There is nothing absolute, there is nothing we "neglect" in a given selection. As long as two reference systems are fully defined, a trajectory in one can be mathematically translated into the other. In other words, we don't loose the power of prediction of a motion when choosing a reference frame.

I would like to post a comment, but as I do not have enough "reputation" score to do so, here is my complement to @asdflex's comment.

As you probably know, motion is always defined relative to a reference (the point you define as fix in YOUR convention, plus the 3 orthogonal Cartesian axis in 3D space of YOUR CHOOSING). By definition then, your description of motion would be meaningless if you leave ambiguous your conventions.

Now, to address your question specifically:

It looks like your video is made with the type of reference called Celestial Reference Frame. There is an internationally agreed one called the ICRF. As an introduction to this concept you can look at this paper: The Next Generation Celestial Reference Frame by M. Johnson et al. Below is an extract of the intro:

It is only by using this inertial reference frame that we are able to disentangle our observations of the motions of celestial objects from our own complex path around our star, and its path through the galaxy, [...]

Your next drawing seems to designate the Sun as the center of the reference frame. Note that you still have to specify the 3 axis to have a fully-defined reference and here you have the choice between many possibilities (cf this link).

Note that people also use ECI (Earth-Centered Inertial) and ECEF (Earth-Centered-Earth-Fixed) references. Let's use these to illustrate the difference that the selection of the reference can make to the description of motions. When we say that a satellite is in geostationary orbit, implicitly we refer to the ECEF. The said satellite appears at rest compared to an observer on Earth, who feels that he is at rest also, because he is moving together with the rotating reference. Now, if we use instead the direction of a star to tie the X-axis with (this is the only difference between ECI and ECEF), then the motion of our geostationary satellite is a closed circle, not a fix point.

The bottom line is that, people choose a reference frame to describe a motion, in the way that is most convenient to them. There is nothing absolute, there is nothing we "neglect" in a given selection. As long as two reference systems are fully defined, a trajectory in one can be mathematically translated into the other. In other words, we don't loose the power of prediction of a motion when choosing a reference frame.

I would like to post a comment, but as I do not have enough "reputation" score to do so, here is my complement to @asdflex's comment.

As you probably know, motion is always defined relative to a reference (the point you define as fix in YOUR convention, plus the 3 orthogonal Cartesian axis in 3D space of YOUR CHOOSING). By definition then, your description of motion would be meaningless if you leave ambiguous your conventions.

Now, to address your question specifically:

It looks like your video is made with the type of reference called Celestial Reference Frame. There is an internationally agreed one called the ICRF. As an introduction to this concept you can look at this paper: The Next Generation Celestial Reference Frame by M. Johnson et al (https://arxiv.org/pdf/1903.11145.pdf). Below is an extract of the intro: "It is only by using this inertial reference frame that we are able to disentangle our observations of the motions of celestial objects from our own complex path around our star, and its path through the galaxy, ..."

Your next drawing seems to designate the Sun as the center of the reference frame. Note that you still have to specify the 3 axis to have a fully-defined reference. And here you have the choice between many possibilities (cf this link https://www.mssl.ucl.ac.uk/grid/iau/extra/local_copy/SP_coords/heliosys.htm).

Note that people also use ECI (Earth-Centered Inertial) and ECEF (Eart-Centered-Earth-Fixed) references.

I would like to post a comment, but as I do not have enough "reputation" score to do so, here is my complement to @asdflex's comment.

As you probably know, motion is always defined relative to a reference (the point you define as fix in YOUR convention, plus the 3 orthogonal Cartesian axis in 3D space of YOUR CHOOSING). By definition then, your description of motion would be meaningless if you leave ambiguous your conventions.

Now, to address your question specifically:

It looks like your video is made with the type of reference called Celestial Reference Frame. There is an internationally agreed one called the ICRF. As an introduction to this concept you can look at this paper: The Next Generation Celestial Reference Frame by M. Johnson et al (https://arxiv.org/pdf/1903.11145.pdf). Below is an extract of the intro: "It is only by using this inertial reference frame that we are able to disentangle our observations of the motions of celestial objects from our own complex path around our star, and its path through the galaxy, ..."

Your next drawing seems to designate the Sun as the center of the reference frame. Note that you still have to specify the 3 axis to have a fully-defined reference. And here you have the choice between many possibilities (cf this link https://www.mssl.ucl.ac.uk/grid/iau/extra/local_copy/SP_coords/heliosys.htm).

Note that people also use ECI (Earth-Centered Inertial) and ECEF (Earth-Centered-Earth-Fixed) references. Let's use these to illustrate the difference that the selection of the reference can make to the description of motions. When we say that a satellite is in geostationary orbit, implicitly we refer to the ECEF. The said satellite appears at rest compared to an observer on Earth, who feels that he is at rest also, because he is moving together with the rotating reference. Now, if we use instead the direction of a star to tie the X-axis with (this is the only difference between ECI and ECEF), then the motion of our geostationary satellite is a closed circle, not a fix point.

The bottom line is that, people choose a reference frame to describe a motion, in the way that is most convenient to them. There is nothing absolute, there is nothing we "neglect" in a given selection. As long as two reference systems are fully defined, a trajectory in one can be mathematically translated into the other. In other words, we don't loose the power of prediction of a motion when choosing a reference frame.

I would like to post a comment, but as I do not have enough "reputation" score to do so, here is my complement to @asdflex's comment.

As you probably know, motion is always defined relative to a reference (the point you define as fix in YOUR convention, plus the 3 orthogonal Cartesian axis in 3D space of YOUR CHOOSING). By definition then, your description of motion would be meaningless if you leave ambiguous your conventions.

Now, to address your question specifically:

It looks like that your video is made with the type of reference called Celestial Reference Frame. There is an internationally agreed one called the ICRF. As an introduction to this concept you can look at this paper: The Next Generation Celestial Reference Frame by M. Johnson et al (https://arxiv.org/pdf/1903.11145.pdf). Below is an extract of the intro: "It is only by using this inertial reference frame that we are able to disentangle our observations of the motions of celestial objects from our own complex path around our star, and its path through the galaxy, ..."

Your next drawing seems to designate the Sun as the center of the reference frame. Note that you still have to specify the 3 axis to have a fully-defined reference. And here you have the choice between many possibilities (cf this link https://www.mssl.ucl.ac.uk/grid/iau/extra/local_copy/SP_coords/heliosys.htm).

Note that people also use ECI (Earth-Centered Inertial) and ECEF (Eart-Centered-Earth-Fixed) references.

I would like to post a comment, but as I do not have enough "reputation" score to do so, here is my complement to @asdflex's comment.

As you probably know, motion is always defined relative to a reference (the point you define as fix in YOUR convention, plus the 3 orthogonal Cartesian axis in 3D space of YOUR CHOOSING). By definition then, your description of motion would be meaningless if you leave ambiguous your conventions.

Now, to address your question specifically:

It looks like your video is made with the type of reference called Celestial Reference Frame. There is an internationally agreed one called the ICRF. As an introduction to this concept you can look at this paper: The Next Generation Celestial Reference Frame by M. Johnson et al (https://arxiv.org/pdf/1903.11145.pdf). Below is an extract of the intro: "It is only by using this inertial reference frame that we are able to disentangle our observations of the motions of celestial objects from our own complex path around our star, and its path through the galaxy, ..."

Your next drawing seems to designate the Sun as the center of the reference frame. Note that you still have to specify the 3 axis to have a fully-defined reference. And here you have the choice between many possibilities (cf this link https://www.mssl.ucl.ac.uk/grid/iau/extra/local_copy/SP_coords/heliosys.htm).

Note that people also use ECI (Earth-Centered Inertial) and ECEF (Eart-Centered-Earth-Fixed) references.