<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[makis]
Your whole thinking is based on a fixed sun Tom. Attached with big bolts on a certain origin. Non-movable and if it is, magically powered to counter act any forces from the earth.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>
??? It is hard to follow you sometimes, Makis, so I may be trying to solve the wrong problem. But...
Step One - fix the Sun
The Sun is not bolted to the coordintate origin; rather, the origin is bolted to the Sun. As the Sun continues to move in whatever directions and with whatever accelerations it actually has (see note below), this coordinate system moves with it. We do this to make analysis of the Earth's motions <b>relative to the Sun</b> easier (because we no longer need to explicitly subtract the Sun's movements from the Earth's movements).
Step two - fix the Earth
Having done this (the first of several steps), we must now unbolt the origin of our coordinate system from the Sun and bolt it to the Earth. Now another analysis is performed, which determines the movement of the Sun <b>relative to the Earth</b>.
I think this might be what you are calling "magic", but of course it isn't.
NOTE - other masses can and do move the Sun. But they also move the Earth, and in general they are so far from both Earth and Sun that these additional motions are the same and cancel out. Jupiter is about the only significant mass that gets close enough (~4 AU at closest approach to Earth) to violate this conditon. But even so it causes only very minor deviations. (This does not seem to be playing a role in your disagreement.) In particular, Jupiter will accelerate the Earth slightly more than it accelerates the Sun when Jupiter is near closest approach to Earth.
Step Three - combine the partial results
The final step is to combine the results of the previous steps to get the whole answer, which is a predictive description of the moving Earth and the moving Sun relative to each other (or to their center-of-mass). This combination of results from the first two steps shows that the Sun makes a small orbit and the Earth makes a large orbit around their mutual center-of-mass; that each orbit takes one year; and that a line drawn between the centers-of-mass of each will always pass through their combined center-of-mass.
<BLOCKQUOTE id=quote><font size=2 face="Verdana, Arial, Helvetica" id=quote>quote:<hr height=1 noshade id=quote>[makis]
Disagreeing with someone does not mean I disrespect him. For me, TVF is a rare personality of immense intelligence. Very few people with his knowledge about cosmology and other subject matters can be found.<hr height=1 noshade id=quote></BLOCKQUOTE id=quote></font id=quote><font face="Verdana, Arial, Helvetica" size=2 id=quote>
It is not necessary to make an explicit disclaimer like this. We can tell from the tone of your voice and the words you choose what emotions you are expressing. At least most of the time - translation difficulties can sometimes make it hard to be sure. When in doubt we generally do NOT assume disrespect.
Having said this, I do still appreciate the gesture. I suspect others do, too.
Regards,
LB
