Question on forces acting on an aircraft in climb
CPB,
You make sense, but there are still loose ends.
If you won't define Gravity as an acceleration, what is your understanding of what causes it?
What little understanding I have of general relativity talks of gravity a being a curveture of space-time, which governs the motion of inertial objects.
In other words,it talks exclusivley about acceleration, not force. Force is a consequence of the mass of the object and the acceleration due to the space-time curveture.
Thus, the response to "Why do you have weight when not accelerating" is that you ARE accelerating in curved spacetime. You consider us inertial while on the ground. GR considers us inertial while in free-fall, but NON inertial when on the ground.
Newtons laws can be used to calculate the effects of forces very accuratley, and in Newtonian physics, there can be no acceleration without force. What Newton does NOT do is explain WHY gravity does what it does. GR does, and it does indeed tret gravity AS an acceleration, rather than just a CAUSE of acceleration.
You make sense, but there are still loose ends.
If you won't define Gravity as an acceleration, what is your understanding of what causes it?
What little understanding I have of general relativity talks of gravity a being a curveture of space-time, which governs the motion of inertial objects.
In other words,it talks exclusivley about acceleration, not force. Force is a consequence of the mass of the object and the acceleration due to the space-time curveture.
Thus, the response to "Why do you have weight when not accelerating" is that you ARE accelerating in curved spacetime. You consider us inertial while on the ground. GR considers us inertial while in free-fall, but NON inertial when on the ground.
Newtons laws can be used to calculate the effects of forces very accuratley, and in Newtonian physics, there can be no acceleration without force. What Newton does NOT do is explain WHY gravity does what it does. GR does, and it does indeed tret gravity AS an acceleration, rather than just a CAUSE of acceleration.
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As far as I'm concerned, being an individual that experiences life in a relatively weak gravity field whilst never moving more than a tiny fraction of C relative to anything that is of interest to me , I do NOT see the need to invoke GR when dealing with every day mechanics.
Accordingly, Newtonian physics is perfectly adequate for teaching PofF. Introducing more advanced physics simply adds confusion to a student cohort who often have only the most tenuous grasp of maths and physics.
So, yes, there are loose ends. But GR has loose ends as well. Where do we go next? Einsteins fields equations before first solo? Unified field theory before ATPL?
Physics is like a tool box. You use the right tool for the right job. In this case, newtonian physics is the right tool for analysing forces in climb, descent and turning.
Why do you want to invoke GR when by your own admission you have little understanding of it? (That's a rhetorical question by the way... it means don't).
Now, fascinating as its been, I am done with this thread. Its become very circular and tending to drift well off topic.
regards,
pb
Accordingly, Newtonian physics is perfectly adequate for teaching PofF. Introducing more advanced physics simply adds confusion to a student cohort who often have only the most tenuous grasp of maths and physics.
So, yes, there are loose ends. But GR has loose ends as well. Where do we go next? Einsteins fields equations before first solo? Unified field theory before ATPL?
Physics is like a tool box. You use the right tool for the right job. In this case, newtonian physics is the right tool for analysing forces in climb, descent and turning.
Why do you want to invoke GR when by your own admission you have little understanding of it? (That's a rhetorical question by the way... it means don't).
Now, fascinating as its been, I am done with this thread. Its become very circular and tending to drift well off topic.
regards,
pb
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Capt PB
Er. Interesting but not very convincing, since the atmosphere of Mars is 1 % of that of earth and is mostly carbon dioxide.
Wizofoz
Not quite. Gravity or the gravitational constant (with a big G) is a weak force which exerts an attraction on all objects near and far. Gravity (little g) is the acceleration imparted to objects on or near the surface. Gravitational acceleration is the force or acceleration on an object caused by Gravity.
Classical Acceleration is the change in velocity over time, and is caused by the result of the total of the forces acting on a body of constant mass.[Newton a=F/m]. But there are several types of acceleration – proper acceleration, coordinate acceleration, uniform acceleration, Euler acceleration etc. And just to make life more interesting, we are in a rotating reference frame and subject to 2 or 3 pseudo or fictitious forces.
Wizofoz
The relevant bit in GR is the Einstein Field Equations where the use of Euclidian geometry is eschewed in favour of Gaussian coordinates to allow accurate curvature calculations. It has been my understanding, possibly imperfect, that it is the need to preserve the equivalence principal that gives rise to discussion of acceleration. Other than that, Einstein treats gravity as a force, as can be seen from the following quotes:
“We must note carefully that the possibility of this mode of interpretation rests on the fundamental property of the gravitational field of giving all bodies the same acceleration, or, what comes to the same thing, on the law of the equality of inertial and gravitational mass.”
And
“Bodies which are moving under the sole influence of a gravitational field receive an acceleration, which does not in the least depend either on the material...”
(source: A Einstein , 1920, Relativity: the Special and General Theory, Chapter 19)
Fortunately, one does not need to be au fait with all of this to fly. The OP’s question can be satisfactorily answered by referring to page 3-19 of the FAA’s ‘Pilot’s Encyclopaedia of Aeronautical Knowledge’ has a section on ‘Forces in Climbs’.
Pilot's Encyclopedia of Aeronautical ... - Google Books
how does that sound
Wizofoz
Basically I'm saying this:-
You define weight as being due to gravity and "Apparent" weight as being due to acceleration.
But gravity IS an acceleration. ALL the force being felt by the aircraft is due to acceleration, and there is no need to divide the too into different "Types" of force.
You define weight as being due to gravity and "Apparent" weight as being due to acceleration.
But gravity IS an acceleration. ALL the force being felt by the aircraft is due to acceleration, and there is no need to divide the too into different "Types" of force.
Classical Acceleration is the change in velocity over time, and is caused by the result of the total of the forces acting on a body of constant mass.[Newton a=F/m]. But there are several types of acceleration – proper acceleration, coordinate acceleration, uniform acceleration, Euler acceleration etc. And just to make life more interesting, we are in a rotating reference frame and subject to 2 or 3 pseudo or fictitious forces.
Wizofoz
Newtons laws can be used to calculate the effects of forces very accuratley, and in Newtonian physics, there can be no acceleration without force. What Newton does NOT do is explain WHY gravity does what it does. GR does, and it does indeed tret gravity AS an acceleration, rather than just a CAUSE of acceleration.
“We must note carefully that the possibility of this mode of interpretation rests on the fundamental property of the gravitational field of giving all bodies the same acceleration, or, what comes to the same thing, on the law of the equality of inertial and gravitational mass.”
And
“Bodies which are moving under the sole influence of a gravitational field receive an acceleration, which does not in the least depend either on the material...”
(source: A Einstein , 1920, Relativity: the Special and General Theory, Chapter 19)
Fortunately, one does not need to be au fait with all of this to fly. The OP’s question can be satisfactorily answered by referring to page 3-19 of the FAA’s ‘Pilot’s Encyclopaedia of Aeronautical Knowledge’ has a section on ‘Forces in Climbs’.
Pilot's Encyclopedia of Aeronautical ... - Google Books
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One can argue all one likes about what causes what, but if one uses as an example a primarily phenomenological theory, such as GR, then one is going to find it hard to answer questions about causes. Phenomenological theories describe what happens, and like Newtonian dynamics or GR tie disparate phenomena together elegantly. But they have little or nothing to say about causes.
I pointed this out before, but it didn't seem to resonate. I take it no one (else) discussing here is familiar with the literature on causation.
I looked for deeper grounds behind Wizofoz's argument about forces and mass-accelerations being the same thing. So far I have understood little more than a simple assertion of the phenomenology (with which no one at this point 350 years later can really disagree), coupled with a strong dose of operationalism to say there is nothing more than that. It beats me how one can, after embracing an argument which says they don't exist, still try to argue about causes. But then, this is PPRuNe.
PBL
I pointed this out before, but it didn't seem to resonate. I take it no one (else) discussing here is familiar with the literature on causation.
I looked for deeper grounds behind Wizofoz's argument about forces and mass-accelerations being the same thing. So far I have understood little more than a simple assertion of the phenomenology (with which no one at this point 350 years later can really disagree), coupled with a strong dose of operationalism to say there is nothing more than that. It beats me how one can, after embracing an argument which says they don't exist, still try to argue about causes. But then, this is PPRuNe.
PBL
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PBL
Yes, I noticed, and also noticed that the philosophy of physics appears to have been banned by Wizofoz. I am aware of some of the literature on determinism/causation.
I pointed this out before, but it didn't seem to resonate. I take it no one (else) discussing here is familiar with the literature on causation.
Well at least I kept the conversation lively!
Thanks to all, I have learned a lot from the discussion.
I didn't want to cede my position simply as a surrender to authority. Those who have posted here obviously have a greater education in physics than I, but unless you could explain it to me, I didn't want to just say "I guess you were right".
Yes I understand (and always have) that part of the forces an aircraft experiences are due to gravity and (lets see if I can phrase this to CPBs satisfaction), when acted upon by an additional force, the aircraft will undergo an acceleration. the pilot will then feel a force in the opposite direction, and the sum of the two are the "Apparent weight".
But unless you can explain what gravity IS, not just what it DOES, and if you conceed that you can't objectivley MEASURE (as opposed to OBSERVE) which force is which, I didn't necessarily agree that they can be seperated into different catagories. If this is operationalism, then I'm not prepared to abandon operationalism as being valid at least in the study of purely physical phenomena, and I don't think the literature PBL cited says I have to.
Thanks to all, I have learned a lot from the discussion.
I didn't want to cede my position simply as a surrender to authority. Those who have posted here obviously have a greater education in physics than I, but unless you could explain it to me, I didn't want to just say "I guess you were right".
Yes I understand (and always have) that part of the forces an aircraft experiences are due to gravity and (lets see if I can phrase this to CPBs satisfaction), when acted upon by an additional force, the aircraft will undergo an acceleration. the pilot will then feel a force in the opposite direction, and the sum of the two are the "Apparent weight".
But unless you can explain what gravity IS, not just what it DOES, and if you conceed that you can't objectivley MEASURE (as opposed to OBSERVE) which force is which, I didn't necessarily agree that they can be seperated into different catagories. If this is operationalism, then I'm not prepared to abandon operationalism as being valid at least in the study of purely physical phenomena, and I don't think the literature PBL cited says I have to.
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Wizofoz
Fair enough. Concerning
there is much to choose from, e.g. http://www.imsc.res.in/~iagrg/IagrgSite/Activities/IagrgMeetings/25th_Iagrg/VRtalk.pdf
or http://arxiv.org/abs/1001.0785
and many others besides.
Fair enough. Concerning
what gravity IS, not just what it DOES,
or http://arxiv.org/abs/1001.0785
and many others besides.
Classical mechanics is for 'everyday stuff'
Relativistic mechanics is for things going very very fast
Quantum mechanics is for very small things---it's not too tough... just the same seven postulates repeated endlessly
For spectroscopic work the relativistic and quantum mechanics are both important...and that's a very nasty topic:
Einstein's time dilation theory was proven using an two atomic clocks and a DC-8...the moving one slowed a bit---
according to the correspondence principle QM will converge to suit the classical case
All measuring devices introduce a perturbation in the system... a thermometer or electric metering transformer,..flowmeter.... for example...thereby altering the system and creates a definite inaccuracy...albeit infinitesimal is most cases...an NOTHING CAN BE DONE ABOUT IT
Lastly wrt to momentum and position there is no limit, to accuracy of measurement only if one of those variables is zero [i.e not moving],..if not, then it is impossible to measure either quantity with an accuracy greater than h/2pi...now ..
and lastly
they have some guys already working on the final unknowns in theoretical and experimental physics...I know one...
Relativistic mechanics is for things going very very fast
Quantum mechanics is for very small things---it's not too tough... just the same seven postulates repeated endlessly
For spectroscopic work the relativistic and quantum mechanics are both important...and that's a very nasty topic:
Einstein's time dilation theory was proven using an two atomic clocks and a DC-8...the moving one slowed a bit---
according to the correspondence principle QM will converge to suit the classical case
All measuring devices introduce a perturbation in the system... a thermometer or electric metering transformer,..flowmeter.... for example...thereby altering the system and creates a definite inaccuracy...albeit infinitesimal is most cases...an NOTHING CAN BE DONE ABOUT IT
Lastly wrt to momentum and position there is no limit, to accuracy of measurement only if one of those variables is zero [i.e not moving],..if not, then it is impossible to measure either quantity with an accuracy greater than h/2pi...now ..
and lastly
they have some guys already working on the final unknowns in theoretical and experimental physics...I know one...
Last edited by Pugilistic Animus; 8th Jul 2010 at 21:21.
SPECIAL relativity deals with speeds approaching C
GENERAL relativity is applicable at any speed.
BTW PBL, how does your view on Operationalism fit with the concept of Equivalence, which is one of the cornerstones of GR?
GENERAL relativity is applicable at any speed.
BTW PBL, how does your view on Operationalism fit with the concept of Equivalence, which is one of the cornerstones of GR?
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Hi wizofoz,
I've enjoyed following your discussions over the last few days.
True - but Newtonian physics is a good approximation to GR and is much simpler to handle mathematically. GR can explain the advance of the perihelion of Mercury's orbit (1 degree per Century? something of that tiny magnitude)
Do we really need that sort of precision when discussing forces on an aircraft in the climb, or turning when pulling "delta g"? We know what earth's gravity feels like, so if we measure anything different - then it's due to some other acceleration.
I've enjoyed following your discussions over the last few days.
GENERAL relativity is applicable at any speed.
Do we really need that sort of precision when discussing forces on an aircraft in the climb, or turning when pulling "delta g"? We know what earth's gravity feels like, so if we measure anything different - then it's due to some other acceleration.
Hi rudder,
Have you considered that if you were in a fast elevator, accelerating towards the earth with an accelaration of 19.6m/s2, you'd be standing on the roof with no way of knowing that you weren't stationary, upright wrt the surface of the earth?
Or this- what AofA would an aircraft, flying inverted, have to achieve in order to show +1g on its g meter?
Have you considered that if you were in a fast elevator, accelerating towards the earth with an accelaration of 19.6m/s2, you'd be standing on the roof with no way of knowing that you weren't stationary, upright wrt the surface of the earth?
Or this- what AofA would an aircraft, flying inverted, have to achieve in order to show +1g on its g meter?
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Hi Wiz,
Yes I have considered these.
Unless the elevator lift shaft was infinitely long - I'd realise I was standing on the roof shortly after we hit planet earth and stopped. I've been standing in the present lift shaft for a lifetime and it doesn't hurt yet - so I guess I'm standing on the floor and it's stationary- but in earth's gravitational field.
The aircraft would have to pull 1G towards earth - so it will fly the same AofA as it would in level flight the normal way up (wheels towards earth).
Yes I have considered these.
Unless the elevator lift shaft was infinitely long - I'd realise I was standing on the roof shortly after we hit planet earth and stopped. I've been standing in the present lift shaft for a lifetime and it doesn't hurt yet - so I guess I'm standing on the floor and it's stationary- but in earth's gravitational field.
The aircraft would have to pull 1G towards earth - so it will fly the same AofA as it would in level flight the normal way up (wheels towards earth).
Last edited by rudderrudderrat; 9th Jul 2010 at 09:58. Reason: extra text
Rudder,
Exactly so.
Point being, in neither case can you tell what is gravity and what is acceleration without referencing the planet. In both cases any physical interaction will be identical to being in 1g on (or not accelerating wrt) the Earth.
PBL seems to insist that because of causation, they are not the same thing.
I'm not saying he's wrong, but it does seem that that defies Equivalence, which is quite defiantly still a current concept in physics, being one of the principles of GR.
Exactly so.
Point being, in neither case can you tell what is gravity and what is acceleration without referencing the planet. In both cases any physical interaction will be identical to being in 1g on (or not accelerating wrt) the Earth.
PBL seems to insist that because of causation, they are not the same thing.
I'm not saying he's wrong, but it does seem that that defies Equivalence, which is quite defiantly still a current concept in physics, being one of the principles of GR.
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Hi Wiz,
Because we've all spent a lifetime experiencing what 1g feels like, measuring weights using spring balances, predicting the flight of tennis, squash, foot balls etc. - we reckon we can tell which acceleration is due to gravity. If we measure or notice a difference with respect to the reference frame of planet earth (e.g. looking out of the window or Artificial Horizon in IMC (same as lift shaft with no windows))- then it must be due to some other acceleration.
Because we've all spent a lifetime experiencing what 1g feels like, measuring weights using spring balances, predicting the flight of tennis, squash, foot balls etc. - we reckon we can tell which acceleration is due to gravity. If we measure or notice a difference with respect to the reference frame of planet earth (e.g. looking out of the window or Artificial Horizon in IMC (same as lift shaft with no windows))- then it must be due to some other acceleration.
Last edited by rudderrudderrat; 9th Jul 2010 at 11:03.
Rudder
Again completely true, but the Earth is not a priviledged frame of reference, and measurments made in any OTHER FofR are just as "Real".
Again completely true, but the Earth is not a priviledged frame of reference, and measurments made in any OTHER FofR are just as "Real".
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Originally Posted by Wizofoz
PBL, how does your view on Operationalism fit with the concept of Equivalence, which is one of the cornerstones of GR?
My view on Operationalism, which I take to be the view that concepts are to be identified with algorithms to measure them, is that it has been refuted in this form. The Stanford Encyclopedia author appears to think it can be rescued in some form.
My view on pure GR is that it is phenomenological, it describes. It doesn't assign causes. There are many equivalence principles you could be meaning; (a) that there is no difference between dynamics on the surface of the earth and dynamics inside a craft in free space which is accelerated at 1g by motors (b) that free fall in a gravitational field is independent of inertial mass; (c) ...... As far as I know, and that is not necessarily very far, (a) is refuted by tidal effects. GR in general appears still to be refuted by quantum theory (that is, it appears to be mutually incompatible and no one is prepared to give up quantum theory).
So what am I supposed to be "fit"ting? And does such a discussion fit at all on an aviation forum?
PBL
Insofar as Aviators are generally not dumb, and are usually interested in scientific discussions, sure, why not.
I in fact raised the issue on a more "Sciency" forum (JREF) and got replies which were interesting.
I'm not saying they refuted you, as it was me putting my interpretation on things you said, and I may well have mis-represented you and your arguments, but one poster (who I know to have a PhD in Physical Sciences) participateded in this exchange:-
me-
Sol Invictus (PhD dude):-
Me (Responding to a query)
Sol:-
So, firstly you can see that EVERYONE (including me) knows that at a practical level, invoking the Earth as a Frame of Reference makes sense in the real world, but also that from a purerly theoretical standpoint, operationalism appears to be alive and well.
The thread is here:-http://forums.randi.org/showthread.php?t=179962
If you'd like to read or participate in it.
I in fact raised the issue on a more "Sciency" forum (JREF) and got replies which were interesting.
I'm not saying they refuted you, as it was me putting my interpretation on things you said, and I may well have mis-represented you and your arguments, but one poster (who I know to have a PhD in Physical Sciences) participateded in this exchange:-
me-
Hi guys,
I need some help from a physics Guru, even if it is to tell me I'm wrong so I can drop it.
On an Aviation forum, a discussion came up regarding the forces on an aircraft in a turn.
As you'd be aware, and aircraft in a 60deg Angle of Bank turn experiences 2g. People started refering to this as the Aircrafts "Apparent Weight".
I chimed in and said it was meaningless calling it "Apparent Weight" as it was indestiguishable from "Real" weght. Basically the the opposite force felt as a reault of the aircrafts acceleration was the same thing as that due to Gravity, so it was incorrect to label them as different things.
I got pretty soundly shouted down, and one posted invoked that I was using "Operationalsim" which was out-moded.
What are the physics heavy-weights opinions?
Thanks
I need some help from a physics Guru, even if it is to tell me I'm wrong so I can drop it.
On an Aviation forum, a discussion came up regarding the forces on an aircraft in a turn.
As you'd be aware, and aircraft in a 60deg Angle of Bank turn experiences 2g. People started refering to this as the Aircrafts "Apparent Weight".
I chimed in and said it was meaningless calling it "Apparent Weight" as it was indestiguishable from "Real" weght. Basically the the opposite force felt as a reault of the aircrafts acceleration was the same thing as that due to Gravity, so it was incorrect to label them as different things.
I got pretty soundly shouted down, and one posted invoked that I was using "Operationalsim" which was out-moded.
What are the physics heavy-weights opinions?
Thanks
There's a deep principle of physics - the equivalence principle - which says you're right. Inside a sufficiently small laboratory, you cannot tell whether you're in a gravitational field ("sufficiently small" means too small to measure tidal effects). If you feel an acceleration it could be because you're in a room or plane that's being supported against the force of gravity by the ground or air, or because the room or plane is accelerating in zero gravity due to something else (like an elevator cable or a banked turn), or some combination of the two as in your example.
Of course you could also just look out the window and observe you're flying over earth, and use your knowledge of its mass to determine which component of your weight is "real" and which is "apparent". But I suppose you consider that cheating.
ps - I'm not sure what "operationalism" is, but I think I believe in it.
Of course you could also just look out the window and observe you're flying over earth, and use your knowledge of its mass to determine which component of your weight is "real" and which is "apparent". But I suppose you consider that cheating.
ps - I'm not sure what "operationalism" is, but I think I believe in it.
Well, I copped a speil and a link to a philosophical document, and was told
"The view of science that quantities which you cannot discriminate with instruments are the same thing is about the only philosophy of physics which has been definitively discredited in the last hundred years. So it is rather inappropriate to try it on here, don't you think?"
I didn't understand what he meant...
"The view of science that quantities which you cannot discriminate with instruments are the same thing is about the only philosophy of physics which has been definitively discredited in the last hundred years. So it is rather inappropriate to try it on here, don't you think?"
I didn't understand what he meant...
Sol:-
Insofar as I can parse that, I disagree with it completely. The idea that the only real things are those we can (in principle) measure not only has not been discredited, it's one of the most powerful ideas around. It has repeatedly proven its worth over the last century (the equivalence principle being an excellent example).
The thread is here:-http://forums.randi.org/showthread.php?t=179962
If you'd like to read or participate in it.
SPECIAL relativity deals with speeds approaching C
GENERAL relativity is applicable at any speed.
GENERAL relativity is applicable at any speed.
For other activities since the system is so comparatively small against a massive and just too obvious reference [Earth] that use of GR reference frames would not increase the number of signifigant figures to be worth it, as stated...not an expert on it at all, but...you could try
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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
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
I am not sure anyone can win the "Apparent Weight" versus "Real Weight" debate.
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