Wizofoz,
Craving indulgence from those (I am sure most discussants) who don't really see what this has to do with aviation, here is my rational reconstruction of part of the debate.
You suggested that (paraphrasing) there is no causality between force and acceleration because of the symmetry, namely they are related by an equation
(at this point, we were discussing Newtonian dynamics).
I said that causality is an asymmetric notion and equations obviously not, so that one cannot argue about what causes what just using equations.
You said that indeed one can: since you couldn't extract a notion of cause from the equations, it meant there was no such notion at work.
I said that was an operationalist argument (it is) and said operationalism has been discredited (it has). I didn't say how, and I don't think this is the place to discuss such philosophies of science.
I haven't been involved in any of the discussion about "Real Weight" and "Apparent Weight".
Your correspondent doesn't apparently know what operationalism is, but believes that the EEP is well established (let me provide a link to
Clifford Will's 2001 survey ) and thinks this establishes operationalism (whatever he thinks it might be) as equally well-confirmed.
The logic behind these views escapes me. You take a phenomenological theory (such as Newtonian dynamics or GR), say it has been well-confirmed (which it has) and use this to say that nothing not mentioned by the theory has any reality.
Quite apart from the operationalist twist you gave your justification, this kind of argument cannot be right. GR is well-confirmed. Brans-Dicke is also well-confirmed (mostly by the same tests) but differs from GR in certain conceptual respects. It is not actually known at this point which is preferable. You could use the argument style to say nothing not mentioned by Brans-Dicke has any reality (if you believed in that) as well as use it to say nothing not mentioned by GR has any reality (if you believe GR). Now you would have turned a discussion about which phenomenology agrees better with measurement (GR or B-D) into an argument about what things exist!
Similarly, the Standard Model is well-confirmed. It is also, by almost unanimous opinion, wrong. If you followed your argument scheme and said that nothing not mentioned in the Standard Model has any reality, I imagine you would be roundly contradicted by almost all particle physicists (certainly by almost all I know, including the one I helped hire), who know that there is more stuff that the Standard Model doesn't cope with but they don't know what it is.
I don't see that you have established that an assertion, that forces cause acceleration rather than acceleration causing forces, has no meaning. (Your physicist correspondent didn't offer a comment about that, I guess because you didn't ask.) Second, I don't think you can reasonably make ontological decisions on the basis of a phenomenological theory.
I am happy to stop here.
I am not sure anyone can win the "Apparent Weight" versus "Real Weight" debate. You would deny any distinction, say by appeal to an equivalence principle. I imagine you think that those who think they are distinct are appealing to a privileged frame, and I think they would agree they are. You would say, I imagine, "no frame can be privileged". They would say "here, I just privileged
this one". It is not obvious to me that one view is to be preferred over the other.
PBL