Split Thread The validity of classical physics (split from: DWFTTW)

[jjcote]

I asked a week or so ago what question I should ask Mark. I proposed some wording, and you replied, "Yes, that sort of thing". You had your chance to bring up your whacko clauses at that point. If the question was too vague, Mark would have asked me to clarify. Now that he has given a straightforward answer, you respond with all kinds of bizarre caveats that make sense only in the humberverse.

You objections make it clear that you have a complete lack of understanding of the basic concept behind the treadmill. The treadmill is not supposed to be dragging air along with it (although if it did, it would be an even better match to outdoors, because it would be mimicking the wind gradient). If there is no wind (relative to the floor) at propeller height, then that's exactly what it's supposed to be doing. Your comments about the balloon having forward drag when moving at less than windspeed show a similar total failure of comprehension. It's clear that the aircraft carrier discussion would be a waste of time, as you are not willing to actually think, and everybody else who is listening (except humb, I guess) already understands how things work in the real universe.

If you contact Mark, try not to be too much of a pest. But I'm sure he's used to fielding queries from crackpots; we used to get them back when we were working on the Daedalus HPAs.

See ya. (or not.)

 

[Subduction Zone]

once again humber illustrates clearly that he does not understand what is going on with the treadmill. First off there is this little gem:

"You did no make it clear that the cart is stationary w.r.t .the belt. This may lead Dr Drela to think that you meant that the cart actually moves with the belt. I have said that case is valid."

Actually the cart is moving with respect to the belt. If it was stationary with respect to the belt it would shoot off the end as the belt rotated.

And he also gets this backwards and wrong:

"(1) Point one is an outright failure. The belt does not produce a wind of uniform height. This too I have claimed. Video #7 demonstrates that the air flow is only significant just above the belt, but not at propellor height."

The apparent wind would be lowest just above the belt.

As for c above, that the cart was balancing, that was only one case where they purposefully slowed the treadmill and tipped it up to keep the cart from advancing. When the treadmill was running at 10 mph the cart continually advanced down the belt indicating a speed faster than the 10 mph tailwind. Lets go on a. does not really matter. b. friction is assumed to be enough to prevent slippage since none was evident and if present would harm the carts chances of success, since it succeeded there was no slippage. d. It is obvious to everyone but humber that this is what they were testing for. e. doe not matter. f. does not matter and not true, the cart advanced down the treadmill except for one case where they (once again) purposefully lowered the power of the treadmill (wind) so that they could achieve a steady state case. g. hey there is no g, maybe he would have been right on this one but I doubt it.

 

[spork]

They are the same if the real wind is uniform with height.
In reality there is a wind gradient, which the treadmill test can't duplicate properly. But the treadmill test can certainly validate the theoretical models, which assume there's no wind gradient to begin with.

Clearly Mark considers the treadmill as valid. However this is an unfortunate reply. I'm going to do something I never expected to do - I'm going to disagree with one of his points. And I'm nearly certain Drela would agree with this given about 2 seconds of thought.

The difference is NOT one of treadmill vs. ground. It's a difference of size. There IS a gradient above our treadmill as demonstrated in one of our videos. Gradient develops with distance. If I put a tall table in an open space and conducted my experiment on that table in a tailwind, it would also have minimal gradient. If I make my treadmill very long it will develop more gradient.

Moving ground and still air is IDENTICAL to moving air over still ground. The difference Drela notes is only one of scale.

JJ, I don't want to ask you to bother Mark if you think it's unnecessary, but I'd love to have a quote from him on this matter. I'm confident we're on the same page, but I think he leaves a crack open for all those sceptics that claim the treadmill is not valid.



Oh - yeah, again I don't have time to address humber point by point, but I'll just say half of what he has said is wrong and the other half are lies. Good enough?

 

[humber]

An alternate suggestion...
1. has a grandiose sense of self-importance (e.g. exaggerates achievements and talents, expects to be recognized as superior without commensurate achievements) (SCORE)

I am a doer. I usually have several projects on the go. I like adventure and risky sports. You are a tourist.

2. is preoccupied with fantasies of unlimited success, power, brilliance, beauty, or ideal love (SCORE)

Armchair Oprah, and rather flawed. I am a pragmatist, not an idealist.

3. believes that he or she is 'special' and 'unique' and can only be understood by, or should associate with, other special or high-status people (or institutions) (SCORE)

If you mean that I am accustomed to a higher level of discourse and presumed knowledge, yes.

4. requires excessive admiration (?)

Unlike this vainglorious piffle.

5. has a sense of entitlement, i.e., unreasonable expectations of especially favorable treatment or automatic compliance with his or her expectations (SCORE)

Doesn't look like it to me. I am persistent, and not at all bothered by your insults, but you are.

6. is interpersonally exploitative, i.e., takes advantage of others to achieve his or her own ends (?)

You seem unsure. Let me help you. Where have I taken the reputation of others to my advantage, and who has?

7. lacks empathy: is unwilling to recognize or identify with the feelings and needs of others (?)

Wow, Dr Huh, you really are covering all bases. Sociopath too.

8. is often envious of others or believes that others are envious of him or her (?)

I have track record you are unlikely to match, my friend. Like saving face over apologies, envy does not interest me.

9. shows arrogant, haughty behaviors or attitudes (SCORE)

Yes. I do not suffer fools gladly. Nobody who is polite or rational, yet poses an opposite view, is subject to this. You are.

The above are diagnostic criteria for a narcissistic personality disorder. A narcissistic personality disorder as defined by the DSM is characterized by a pervasive pattern of grandiosity (in fantasy or behavior), need for admiration, and lack of empathy, beginning by early adulthood and present in a variety of contexts, as indicated by five (or more) of the above.

What a monument to idiocy you really are. I do call people like Spork idiots.
But Spork does do things. He parachutes and so forth and takes interest in what he sees as right.
You are different. You are not wrong, nor stubborn about your views, but simply a partly-educated dunce.

As this may be seen as attacking the arguer I insist on saying that the text above in no way supports the argument that humber is wrong and others are right. I am making an argument that states that humbers writings match the symptoms of a narcissistic personality disorder. This is not polite of me, but what the heck. I just thought, looking at some scientific texts on psychology, that this really is an interesting subject as itself.

But you do it anyway. If I insult you, it is deliberate, that I have made explicit. However, rules prevent me from expressing my real feelings. You do not even have the courage of you convictions.

 

[Tunny]

No, they are not correct it seems. The mass and shape do affect the outcome, yet it would seem odd that all objects can jump from being almost stationary, to being able to accelerate to waterspeed.

Can anyone parse what he's saying here? Is he really amazed at the concept of motion? One might just as well find it odd that a stationary object released at a height can miraculously accelerate to terminal velocity. (Hint: In both cases, there is a force being applied to the object. Further hint: You tend to find that whenever there is acceleration.)

I find it difficult to understand what makes the difference.

What difference? I'm not following you. The text you were directly responding to described exactly how more massive and/or streamlined objects will accelerate at a lesser rate than less massive and/or less streamlined ones.

Surely, the force must be graduated, and that will certainly mean the some objects will simply not have enough time to accelerate. A very heavy object, driven my a small force may take weeks to reach windpeed, or perhaps years.

Well, an aircraft carrier, which is about the most massive/streamlined real-world example I can come up with, and therefore about the worst-case real-world example in terms of being affected by the current, probably doesn't take more than some reasonable number of minutes (perhaps hours) to reach waterspeed (which I think is what you meant). Perhaps someone with shipping experience could comment. In any case, taking your argument to extremes doesn't help your case at all -- it merely continues to confirm what everyone else is saying. Even supertankers have to account for current flows in their navigation.

Also, it seems that there is a minimum amount of force required to move any object at all. How do yo explain that?

It's called friction. Perhaps you've heard of it? If the force holding something in place is greater than the force applied to it, it won't move. Absent friction or other external effects, even something as massive as the International Space Station will respond to tiny rocket impulses, accelerating at a rate that, what do you know, precisely matches the force divided by the mass. You could even express it in a formula...

Tunny

 

[humber]

If you contact Mark, try not to be too much of a pest. But I'm sure he's used to fielding queries from crackpots; we used to get them back when we were working on the Daedalus HPAs.

See ya. (or not.)

You mean when I contact him. I will mention why.

 

[sol invictus]

I do not suffer fools gladly.

You must never be glad, then...

 

[sol invictus]

The difference is NOT one of treadmill vs. ground. It's a difference of size. There IS a gradient above our treadmill as demonstrated in one of our videos. Gradient develops with distance. If I put a tall table in an open space and conducted my experiment on that table in a tailwind, it would also have minimal gradient. If I make my treadmill very long it will develop more gradient.

Yes, you're correct of course. But I think that's what he meant - he probably had in mind a small treadmill.

Anyway if we're going to worry about that we should also distinguish between "real" wind outside which could be gusty, turbulent, etc., wind near the ground versus on a table as you mentioned, wind in a wind tunnel which will have somewhat different characteristics, etc. None of that matters, because this cart is robust enough not to be significantly affected by minor variations like that.

 

[humber]

once again humber illustrates clearly that he does not understand what is going on with the treadmill. First off there is this little gem:

"You did no make it clear that the cart is stationary w.r.t .the belt. This may lead Dr Drela to think that you meant that the cart actually moves with the belt. I have said that case is valid."

Actually the cart is moving with respect to the belt. If it was stationary with respect to the belt it would shoot off the end as the belt rotated.

Yes. That is correct. It is stationary w.r.t ,the ground, and so the air. Fischer, and I think Lancaster, used models that were pulled through the air.
That is the difference. Moving air mass. I need not answer the remainder, because that is game over.

And he also gets this backwards and wrong:
"(1) Point one is an outright failure. The belt does not produce a wind of uniform height. This too I have claimed. Video #7 demonstrates that the air flow is only significant just above the belt, but not at propellor height."
The apparent wind would be lowest just above the belt.

That is also correct. It does not produce a flow at propeller height. That is the problem, there is no moving windmass around the propellor. You did not comment on the fact that even that wind is going the wrong way.

As for c above, that the cart was balancing, that was only one case where they purposefully slowed the treadmill and tipped it up to keep the cart from advancing. When the treadmill was running at 10 mph the cart continually advanced down the belt indicating a speed faster than the 10 mph tailwind.

No you are putting words in Dr Drela's mouth when you say 'tailwind'. He is talking about the flow generated by the belt. The cart slips on the belt. Carefully observe video #7. It goes backwards. Take a look at the fork video. The cart continues to move backwards, even after the force is removed. Even if you say it is slowing, rather than going backwards, do you think an impulsive force can do that in the real world?

Lets go on a. does not really matter.

It is the point.

b. friction is assumed to be enough to prevent slippage since none was evident and if present would harm the carts chances of success, since it succeeded there was no slippage.

Bad logic. You suggest failure of your outcome as the only option. Also, slippage is there, bu not necessary to the cause.

d. It is obvious to everyone but humber that this is what they were testing for.

So you say. A test that cannot be falsified, has no truly valid outcome.

e. doe not matter.

Absurdities do matter. That is why there is the objection. You pass too glibly over that. There are conrtradictions between belt and ground views. That also invalidates the model.

f. does not matter and not true, the cart advanced down the treadmill except for one case where they (once again) purposefully lowered the power of the treadmill (wind) so that they could achieve a steady state case.

No, the friction was simply outside the balance limits.

You have made points about questions that were not asked. The one solid reply that we have, shows that the treadmill fails. That failure is not trivial, and invalidtes the treadmill.

 

[humber]

double post

 

[humber]

Clearly Mark considers the treadmill as valid. However this is an unfortunate reply. I'm going to do something I never expected to do - I'm going to disagree with one of his points. And I'm nearly certain Drela would agree with this given about 2 seconds of thought.

Why don't you ask him, rather than speak for him?

The difference is NOT one of treadmill vs. ground. It's a difference of size. There IS a gradient above our treadmill as demonstrated in one of our videos. Gradient develops with distance. If I put a tall table in an open space and conducted my experiment on that table in a tailwind, it would also have minimal gradient. If I make my treadmill very long it will develop more gradient.

The gradient does not reach the propellor with any significance. The toilet paper shows that gradient to rapidly diminish, and to be going the wrong way. As Drela noted, the airmass is the equivalent, not merely the velocity. That is a major failure, that has been repeatedly pointed out, not only by me, but many others.

Moving ground and still air is IDENTICAL to moving air over still ground. The difference Drela notes is only one of scale.

Under the correct circumstances, the first point is true, but not for the treadmill.
Yes, scale. The flow is too small, and in the wrong direction.

JJ, I don't want to ask you to bother Mark if you think it's unnecessary, but I'd love to have a quote from him on this matter. I'm confident we're on the same page, but I think he leaves a crack open for all those sceptics that claim the treadmill is not valid.

I think that he may be bothered more by having his name giving credence to the treadmill. I will ask if jjcote does not.

Oh - yeah, again I don't have time to address humber point by point, but I'll just say half of what he has said is wrong and the other half are lies. Good enough?

No, half-truths are not enough.

 

[jjcote]

Clearly Mark considers the treadmill as valid. However this is an unfortunate reply. I'm going to do something I never expected to do - I'm going to disagree with one of his points. And I'm nearly certain Drela would agree with this given about 2 seconds of thought.

The difference is NOT one of treadmill vs. ground. It's a difference of size. There IS a gradient above our treadmill as demonstrated in one of our videos. Gradient develops with distance. If I put a tall table in an open space and conducted my experiment on that table in a tailwind, it would also have minimal gradient. If I make my treadmill very long it will develop more gradient.

I don't think you're really disagreeing. The way I read this, the air near the surface is going to "stick" to the surface, and you'll get a gradient as you move away from it. The problem with is that with the treadmill, the fact that the belt is small compared to the test apparatus (the cart) means that the gradient will be attenuated by the fact that the air in the rest of the room doesn't exhibit the gradient (the air resists "piling up" at the back of the treadmill). If the treadmill were longer (and ideally also wider), it would behave more like the open ground in this regard. It is true that this effect helps the cart on the treadmill, although a full-size cart is less susceptible to it, since the prop is up away from the ground. Tiny carts are always going to be adversely affected by this when outdoors.

Nevertheless, the windspeed should be measured where the prop is. In an outdoor test, you wouldn't measure the wind at 2 m elevation and require the cart to beat it that speed if the cart is only 30 cm tall.

What the treadmill mimics exactly is a cart outdoors that is sitting in a hole cut in a giant sheet of paper that is lying on the ground. Some unseen hand slides the paper along the ground at the speed of the wind, but the cart never touches the paper (doing so would be equivalent to falling off the treadmill). That sheet of paper would cause there to be no gradient.

This is a minor effect, and as Mark says, the theoretical analysis ignores it anyway.

 

[humber]

You must never be glad, then...

That the best you can do? A parroted reply. Oh, wait...

Yes, you're correct of course. But I think that's what he meant - he probably had in mind a small treadmill.

Dr Drela;
"They are the same if the real wind is uniform with height.
In reality there is a wind gradient, which the treadmill test can't duplicate properly. But the treadmill test can certainly validate the theoretical models, which assume there's no wind gradient to begin with."

He is making a comparison regarding the nature of the wind. If reproduction of the real gradient is not important, then models that do not rely on that gradient may be tested.
However, the expectation is of wind, the airmass, interacting with the model. The belt is not only the road, but the wind generator ( that is where the power comes from) so that laminar flow is the presumed wind.
It does not interact with the propeller, and is going the wrong way.
I also asked how does this generated headwind, become a tailwind at the propellor?
When I put this to you earlier, you ignored it. Now you must contradict Dr Drela.

Anyway if we're going to worry about that we should also distinguish between "real" wind outside which could be gusty, turbulent, etc., wind near the ground versus on a table as you mentioned, wind in a wind tunnel which will have somewhat different characteristics, etc.

So it is now not identical to real wind.

None of that matters, because this cart is robust enough not to be significantly affected by minor variations like that.

It can scarcely hold its own. I see that you are now backing away from zero wind velocity at windspeed, or that turbulence may indeed exist.

 

[Subduction Zone]

I am about to give up on humber, he is just to purposefully dense. I am beginning to think that the only proper way to argue with him is to set up a debate where each participant has their own dope slapper. Every time he issues a humberism he would receive a dope slap, to be fair the other members would have to have their own dope slappers to enforce a scientific view coming from them. We would probably also have to have a member of the medical profession to check humber occasionally for brain damage, though what test he could use would be problematic.

 

[spork]

I don't think you're really disagreeing. The way I read this, the air near the surface is going to "stick" to the surface...

I agree that you, me, and Mark see this the same way. The problem is that you can't talk about the difference between a treadmill and the ground. You can only talk about the difference in scale. If my treadmill were 100 miles long and a mile wide would any of these differences still exist? No.

This is a minor effect, and as Mark says, the theoretical analysis ignores it anyway.

But again, it's not a difference related to a moving ground under still air vs. moving air over stationary ground. I think we all agree on this - yes?

 

[sol invictus]

I agree that you, me, and Mark see this the same way. The problem is that you can't talk about the difference between a treadmill and the ground. You can only talk about the difference in scale. If my treadmill were 100 miles long and a mile wide would any of these differences still exist? No.

But again, it's not a difference related to a moving ground under still air vs. moving air over stationary ground. I think we all agree on this - yes?

The treadmill test is not exactly the same thing as the cart running downwind outside - obviously! That isn't the issue - the question all along has simply been whether or not the treadmill tests constitute sufficient evidence of the ability of the cart to run downwind faster than a steady wind. Drela's answer - and all of our answers - is yes, of course.

If you ask for more than that you're going to start getting tangled up. Just as an example, the wind seen by something moving along with the treadmill belt doesn't experience Coriolis force, unlike "normal" wind moving with respect to the earth's surface. Moreover it will tend to always move in the same direction (so long as the treadmill belt does). Of course that's totally irrelevant to this, but it's an example of a difference that would be there even if the treadmill covered the whole surface of the planet.

 

[humber]

Can anyone parse what he's saying here? Is he really amazed at the concept of motion? One might just as well find it odd that a stationary object released at a height can miraculously accelerate to terminal velocity. (Hint: In both cases, there is a force being applied to the object. Further hint: You tend to find that whenever there is acceleration.)

I know that. Why do you insist that I do not. Answer: It does not fit your model. Please let me know when the force of gravity disappears.

What difference? I'm not following you. The text you were directly responding to described exactly how more massive and/or streamlined objects will accelerate at a lesser rate than less massive and/or less streamlined ones.

OK, I will try to answer that, but first a question.
A physicist friend of mine once argued to his father, that if you push with your finger long enough upon an oil tanker, it will accelerate to a velocity of your choosing.
Correct or not?

Well, an aircraft carrier, which is about the most massive/streamlined real-world example I can come up with, and therefore about the worst-case real-world example in terms of being affected by the current, probably doesn't take more than some reasonable number of minutes (perhaps hours) to reach waterspeed (which I think is what you meant). Perhaps someone with shipping experience could comment. In any case, taking your argument to extremes doesn't help your case at all -- it merely continues to confirm what everyone else is saying. Even supertankers have to account for current flows in their navigation.

They have engines. Interestingly, because of rising fuel costs, ships are now being modified for even lower drag. An estimated 10% saving. What do you say to that?

It's called friction. Perhaps you've heard of it?

If the force holding something in place is greater than the force applied to it, it won't move. Absent friction or other external effects, even something as massive as the International Space Station will respond to tiny rocket
impulses, accelerating at a rate that, what do you know, precisely matches the force divided by the mass. You could even express it in a formula...

Tunny

You are comparing kinematic transactions with the real world. Why is it that so many counter-examples are conducted in space?
When you accelerate a body in free space, you see only the case you describe. Forces are present, but are either notional or rockets.
This is baby physics.
What you fail to see, is that in the real world, there are always opposing forces, and the driving forces are complex. To avoid them, requires and artificial environment, and gravity is all but inescapable.
(please do not post a trivial exception)

 

[spork]

The treadmill test is not exactly the same thing as the cart running downwind outside - obviously!

Well we are getting into subtleties now. My claim is that surface moving under zero wind is identical to wind moving over a stationary surface. Yes if you decide one of those surfaces is the surface of the Earth (which happens NOT to represent an inertial frame) you'll run into problems.

If you ask for more than that you're going to start getting tangled up.

I think my statement above is 100% accurate. I'll be very surprised if you disagree with it.

 

[humber]

I agree that you, me, and Mark see this the same way. The problem is that you can't talk about the difference between a treadmill and the ground. You can only talk about the difference in scale. If my treadmill were 100 miles long and a mile wide would any of these differences still exist? No.

Yes, they would. Boundary conditions apply in three dimensions. The length of the treadmill is not an issue, nor was it mentioned, though the height was.
You certainly can talk about the difference between a treadmill and ground, especially when the belt is the road/ground, at the exclusion of a real or even relative ground.
Also, the belt is not only the road, but the wind's power source, so it must bet he generator. This makes a huge difference to the equivalence of the model.

But again, it's not a difference related to a moving ground under still air vs. moving air over stationary ground. I think we all agree on this - yes?

I don't think Drela does.

The treadmill test is not exactly the same thing as the cart running downwind outside - obviously! That isn't the issue - the question all along has simply been whether or not the treadmill tests constitute sufficient evidence of the ability of the cart to run downwind faster than a steady wind. Drela's answer - and all of our answers - is yes, of course.

Where 'not exactly' the same is not at all the same. He does not mention windspeed performance. Those are your words. You are both avoiding windmass.

If you ask for more than that you're going to start getting tangled up. Just as an example, the wind seen by something moving along with the treadmill belt doesn't experience Coriolis force, unlike "normal" wind moving with respect to the earth's surface.

Those you have previously rejected as insignificant, but there are effects of the treadmill wind not found in real wind, and significant effects of real wind, that are not found in treadmill wind. Airmass, being one of them.

Moreover it will tend to always move in the same direction (so long as the treadmill belt does). Of course that's totally irrelevant to this, but it's an example of a difference that would be there even if the treadmill covered the whole surface of the planet.

Belt generated wind flows in the wrong direction.

 

[jjcote]

I agree that you, me, and Mark see this the same way. The problem is that you can't talk about the difference between a treadmill and the ground. You can only talk about the difference in scale. If my treadmill were 100 miles long and a mile wide would any of these differences still exist? No.

I agree completely. Another way to do it would be to put the treadmill in the middle of a gym, and to surround it with a bunch more treadmills, all running the same direction. The airport people-mover conveyor, if can can manage to arrange to test on that, would be somewhat "better" than the home treadmill.

But again, it's not a difference related to a moving ground under still air vs. moving air over stationary ground. I think we all agree on this - yes?

Absolutely. (Depending on who you mean by "we all", of course.) How closely it matches the outdoors is simply a matter of how big the moving surface is compared to the cart, not whether it's the surface or the air that's "moving".