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

[humber]

Occam's Razor^WP: "All other things being equal, the simplest solution is the best." (One English version.)

My question: what is the simplest explanation for the fact that thousands of posts seem to have barely narrowed the gap between humber's view of the validity of the treadmill (in particular) but physics in general, and the more or less common view of most or all others posting here? Part 2: what is the best way to proceed from here?

In no particular order, some possible candidates (where "we" means more or less all recent posters here except humber, I hope that's not presuming too much, and sorry humb, you're in a category all on your own again):

1. We are all wrong. That is, we're not deliberately colluding but somehow have all "independently" come to the same incorrect understanding (or slight variations on it). Possibly there are rogue textbooks out there and we're all part a group that has been infected with wrong ideas while Humber has managed to avoid that fate.

2. Humber genuinely has great difficulty with concepts like "relativity" and/or "directions", positive versus negative... I don't know exactly what it seems to be something of that general nature. So he's genuine in his beliefs but just terribly misguided in some way. Perhaps he had a good understanding once but that has mostly gone now.

3. Humber knows a lot more than he lets on, but for some reason is playing the role of... well... the person we all "see". In other words it's all basically a big game to him. He understands, but pretends not to in some critical areas, and deliberately evades answering questions that would expose him or end the game before he's good and ready.

4. We (all except Humber) are colluding in some fashion and trying to confuse Humber with our essentially common (but incorrect) story. We arrange to make the same mistakes, or follow the lead of whoever has the best story going, etc.

5. There are at least two different "games" being played. We're essentially using Newtonian mechanics and arguing in terms of the usual idealised "models" found in textbooks and so on, while humber might believe he is "more correct" when he "denies" things (usually without explanation) by internally justifying himself on the basis of any sloppiness or ambiguity he find's in the questions or scenarios put to him and whatever other ideas or knowledge he may be working from. So we're just basically not talking about the same things...

Any other ideas?

If the truth is #3 or #4 from my list then this may continue for as long as someone is alive and not bored to tears by the whole thing. #5 is almost as bad if true. Of course I "know" that #1 and #4 aren't really true but I'm trying to be even-handed here and perhaps Humber really thinks one of those is the explanation. #2 is presumably the reason that many of the "we" are still here, although if you see #3 as true then I guess you could still be here for entertainment or other purposes...

Occam.s Razor does not work that way, but the fact is, the treadmill is invalid.

 

[Clive]

SIMILARLY, a boudary layer on the treadmill which is travelling RIGHT to LEFT wrt to the ground, but slower than the belt (ALL of which you admit is the case) is travelling LEFT to RIGHT wrt an observer travelling on the belt.

RossFW, this is wrong because of your ignorence and lack of intuition.

Why??? The reason is that the observer travelling on the belt is standing on his head on the far side of the belt from where the first observer is and is facing in the same direction as the first observer. (That might be CW. I'm not sure.) But anyway, the head-standing observer now needs to use a mirror to how the boundary layer affects his hair and in the mirror he will still see RIGHT to LEFT. (After falling over he decides to sit on belt on the same side again facing back across the belt towards the first observer and he still sees the boundary layer moving RIGHT to LEFT so he knows for sure now!

After that he did some sums... but that will be another story.

 

[humber]

Lets see how Humber refutes this analogy (I'll even take him off ignore, temporarily):-

Humber,

Lets say you are sitting sideways in a car, facing it's RIGHT side. The general traffic flow is from your RIGHT to your LEFT wrt the ground.

You overtake a slower vehicle to it's LEFT (your RIGHT) side. From your point of view, the car start out on YOUR LEFT, passes in FRONT of you, then ends up on YOUR RIGHT.

SO, even though the car you passed is travelling RIGHT to LEFT wrt the surface, it is travelling LEFT to RIGHT wrt to you.


SIMILARLY, a boudary layer on the treadmill which is travelling RIGHT to LEFT wrt to the ground, but slower than the belt (ALL of which you admit is the case) is travelling LEFT to RIGHT wrt an observer travelling on the belt.

I know this is wrong because of my ignorence and lack of intuition, but please tell me why??

Cars traveling this way do not move backwards w.r.t each other. This is evidenced by the wheel rotation.w.r.t the road. All axles move forward w.r.t the road. That is the only way one car can travel backwards w.r.t another. The belt flow is actually flowing backwards, as the paddles demonstrates, not just slower, as in these examples.
Glad to be of help, again. You are now slightly less ignorant.

 

[humber]

RossFW, this is wrong because of your ignorence and lack of intuition.

Why??? The reason is that the observer travelling on the belt is standing on his head on the far side of the belt from where the first observer is and is facing in the same direction as the first observer. (That might be CW. I'm not sure.) But anyway, the head-standing observer now needs to use a mirror to how the boundary layer affects his hair and in the mirror he will still see RIGHT to LEFT. (After falling over he decides to sit on belt on the same side again facing back across the belt towards the first observer and he still sees the boundary layer moving RIGHT to LEFT so he knows for sure now!

After that he did some sums... but that will be another story.

Still, there is the matter of the boundary flow to consider. Your last attempt failed, so you need to try again.

 

[RossFW]

Cars traveling this way do not move backwards w.r.t each other.

OH.........FOR............GODS.......SAKE

So a car that starts on you left and ends up on your right is NOT travelling from your left to your right WRT you.

Yes I am less ignorant.

I began to think you had some clue about relative motion.

You don't.

Thanks for clearing that up......

 

[CORed]

Occam's Razor^WP: "All other things being equal, the simplest solution is the best." (One English version.)

My question: what is the simplest explanation for the fact that thousands of posts seem to have barely narrowed the gap between humber's view of the validity of the treadmill (in particular) but physics in general, and the more or less common view of most or all others posting here? Part 2: what is the best way to proceed from here?

In no particular order, some possible candidates (where "we" means more or less all recent posters here except humber, I hope that's not presuming too much, and sorry humb, you're in a category all on your own again):

1. We are all wrong. That is, we're not deliberately colluding but somehow have all "independently" come to the same incorrect understanding (or slight variations on it). Possibly there are rogue textbooks out there and we're all part a group that has been infected with wrong ideas while Humber has managed to avoid that fate.

I'm going to rule this one out. If it's correct, I wasted a lot of time in school. If Newtonian Physics is wrong (except as modified by relativity and quantum mechanics) then all the other science I learned is wrong too.

2. Humber genuinely has great difficulty with concepts like "relativity" and/or "directions", positive versus negative... I don't know exactly what it seems to be something of that general nature. So he's genuine in his beliefs but just terribly misguided in some way. Perhaps he had a good understanding once but that has mostly gone now.

A strong possibility, and yet it's kind of hard to believe he could be so wrong, so consistently, about so many things.

3. Humber knows a lot more than he lets on, but for some reason is playing the role of... well... the person we all "see". In other words it's all basically a big game to him. He understands, but pretends not to in some critical areas, and deliberately evades answering questions that would expose him or end the game before he's good and ready.

Another strong possibility, but if Humber is playing a game with us, his persistence is remarkable.

4. We (all except Humber) are colluding in some fashion and trying to confuse Humber with our essentially common (but incorrect) story. We arrange to make the same mistakes, or follow the lead of whoever has the best story going, etc.

Well, I know I'm not colluding, but maybe the rest of you are and have me fooled and Humber is the one voice of truth and reason .... No, that can't be right.

5. There are at least two different "games" being played. We're essentially using Newtonian mechanics and arguing in terms of the usual idealised "models" found in textbooks and so on, while humber might believe he is "more correct" when he "denies" things (usually without explanation) by internally justifying himself on the basis of any sloppiness or ambiguity he find's in the questions or scenarios put to him and whatever other ideas or knowledge he may be working from. So we're just basically not talking about the same things...

I think this is at least part of the picture. I think Humber sees pure Newtonian mecanics as something that doesn't really apply to "real world" .

Any other ideas?

I think it's a combination of #2 and #5, with maybe a bit of #3 thrown in. I think Humber has had some training in physics, but doesn't fully understand it, or, perhaps more to the point, doesn't really believe it, as it conflicts with some of his preconceptions. I think he genuinely has a problem with frames of reference other than the ground, or at least thinks that they are not useful to solving real world problems. I think he genuinely thinks the treadmill tests are not valid, even though he can't really quite work out why. I think he has come up with a view of the world that is a mixture of Newtonian mechanics as he misunderstands them and the "classic" earth-centered view that he probably worked out before he had whatever physics training he may have had. I think it works for him most of the time, until something like the DDWFTW cart on the treadmill comes along that doesn't fit his world view, and he decides it's wrong and backwards. This is more 2 than 5, but I think Humber has a practical view of physics that mostly works for him, even if a lot of the theory is wrong, or not really developed at all. After all, in the "real world", at least on the surface of a planet, you really do need to expend energy, and exert force, to keep things in motion. Now we all know that's because of friction and drag, and that if you could get rid of those factors, objects in motion really would stay in motion, as they do in space, but I think Humber, on the intuitive level thinks that if you stop pushing something, it stops moving.

I also think there is a bit of #3 thrown in. While I think Humber's belief that the DDWFTW cart and the treadmill tests are invalid are real, I think he likes to play the fool (only sometimes he only thinks he's playing), and he likes to get us all worked up, and he doesn't like to get pinned down, because when he does, we tear into him for his mistakes, and he definitely doesn't like to admit he's wrong, even when he knows he is.

Well, here I am trying to psychoanalyze someone based on a bunch of internet posts, so it's very likely that I'm completely wrong. But, this is the best I can come up with.

If the truth is #3 or #4 from my list then this may continue for as long as someone is alive and not bored to tears by the whole thing. #5 is almost as bad if true. Of course I "know" that #1 and #4 aren't really true but I'm trying to be even-handed here and perhaps Humber really thinks one of those is the explanation. #2 is presumably the reason that many of the "we" are still here, although if you see #3 as true then I guess you could still be here for entertainment or other purposes...

I think Humber very likely thinks #1 or #4 is true.

 

[Dan O.]

I'll even take him off ignore, temporarily

No Ross, look away! You're not old enough to handle such truths. It's going to stunt your growth and make you go blind.

 

[Dan O.]

I think humber was initially wrong and honestly tried to defend his position. Eventually he began to realize that his position was incorrect though still doesn't realize how it is incorrect. To try and cover up his mistake, he is now taking the position of a troll that disagrees with everything but won't give a straight answer because that might accidentally get something right and blow his cover story.

 

[CORed]

Like I said, a little arithmetic

with one incorrect value and one reversed sign

proves that your claim is impossible.

This is the kind arithmetic that makes bridges fall down.

 

[mender]

Clive, I agree with CORed's summation.

Another of humbre's problems is that he doesn't specify which observer's view he's using to answer a particular question. In most cases, I read his answers with the assumption that he is still using the ground as a reference, regardless of what he starts off saying. That's the only point of view that he considers valid.

Humbre, the cart works worse when it is in the boundary layer. It needs to have "clean" air to use or the performance drops off (tested!). The reason is that it depends on the speed difference between the ground and the air to function properly. In the boundary layer, some of that speed difference is missing.

 

[humber]

Lets see how Humber refutes this analogy (I'll even take him off ignore, temporarily):-

Humber,

Lets say you are sitting sideways in a car, facing it's RIGHT side. The general traffic flow is from your RIGHT to your LEFT wrt the ground.

It can be perhaps 10kph

You overtake a slower vehicle to it's LEFT (your RIGHT) side. From your point of view, the car start out on YOUR LEFT, passes in FRONT of you, then ends up on YOUR RIGHT.

that car is traveling at say 8kph.

SO, even though the car you passed is travelling RIGHT to LEFT wrt the surface, it is travelling LEFT to RIGHT wrt to you.

I am traveling 2km faster than the other vehicle.

SIMILARLY, a boudary layer on the treadmill which is travelling RIGHT to LEFT wrt to the ground, but slower than the belt (ALL of which you admit is the case) is travelling LEFT to RIGHT wrt an observer travelling on the belt.

No, of course not.
All vehicles are traveling in the same direction w.r.t the road, so none are traveling backwards, from any car's perspective. They may look that way, but they are not.
Both cars have the common reference of the road, that is how they move, so the difference in velocities is the difference between the two referred to the road, not to each other .
You can make one suddenly zero, in which the slower car moves right to left at 8kph. (you know, like over-taking...) If that same car were actually going backwards, w.r.t that other car, then it would move away at 2kph left to right.
There you go. Ground related vehicles are "a bit of a problem" for ides of relative motion.

 

[mender]

All vehicles are traveling in the same direction w.r.t the road, so none are traveling backwards, from any car's perspective. They may look that way, but they are not.
Both cars have the common reference of the road, that is how they move, so the difference in velocities is the difference between the two referred to the road, not to each other .
You can make one suddenly zero, in which the slower car moves right to left at 8kph. (you know, like over-taking...) If that same car were actually going backwards, w.r.t that other car, then it would move away at 2kph left to right.
There you go. Ground related vehicles are "a bit of a problem" for ides of relative motion.

See, I was right, humbre always takes the ground's point of view as the only valid one. He just can't understand how anyone could think differently.

Everything has the common reference of the ground, unless you're out in space, in which case gravity no longer attracts the mass that becomes the weight to provide the friction to supply the force which can't accelerate the cart, so the treadmill is invalid.

Hey, humbre, speaking of space, two spaceships are out in space and they are at rest with each other and are pointing in the same direction. One of them fires their thrusters and starts to move. Who is moving backwards? Who gets to decide?

Or:

Two cars are side by side in a parking lot, one driving forward and the other backing up, both heading to the same corner of the parking lot. The car backing up is moving faster toward that spot than the car driving forward. Is the car backing up moving forward faster than the car moving forward, or is the car moving forward moving faster than the car backing up?

 

[Brian-M]

No, you are missing one step. Arithmetic shows the error. See below.


The cart's direction, like the wind's, is positive and moving left to right.
The flow is 4m/s slower than the wind, but moving right to left.
Hence -6m/s w.r.t the cart.
6m/s right to left. Check

But you stated in your original post that this was a windspeed cart. This means that cart speed and windspeed is the same thing. If the "flow" if 4m/s slower then the wind then it is also 4m/s slower than the cart. You don't even need to do any math to figure this out... the information is there right from the start.

If the "flow" is moving 4m/s slower than the wind then it's velocity is -4m/s relative to the wind. Since cart speed is wind-speed, then it's also moving at -4m/s relative to the cart.

 

[humber]

Clive, I agree with CORed's summation.

Another of humbre's problems is that he doesn't specify which observer's view he's using to answer a particular question. In most cases, I read his answers with the assumption that he is still using the ground as a reference, regardless of what he starts off saying. That's the only point of view that he considers valid.

Humbre, the cart works worse when it is in the boundary layer. It needs to have "clean" air to use or the performance drops off (tested!). The reason is that it depends on the speed difference between the ground and the air to function properly. In the boundary layer, some of that speed difference is missing.

If the boundary layer comes only from the action of the cart, then it works. That is, there is boundary generated by moving back with the belt, ( motion generated flow) but then there could be no boundary flow at windspeed. The boundary flow at windspeed, is actually a result of the belt-generated flow. Taken separately, they work if you decide which reference to use. However, when standing on the belt and moving with it, belt-generated flow opposes the motion-generated flow. They cannot balance against the main wind, to produce the constant value of the real wind. The paddle demonstrates this.

 

[Clive]

That is correct, Clive,

Cool. I got a tick from Humber! I will treasure this. Is there a T-shirt I can buy?

...but it is independent of veloicty.

Already I'm not sure what you're trying to say. What is independent of which velocity? I calculated the difference between two velocities and you said that was correct.

I say that the difference in speed (velocity to be more precise) between that of the free air stream well above the surface and that in the "boundary layer" at some fixed height above the surface will be constant (or close enough for our purposes). Same speed, same direction, and your "paddle" will always be turning in the same direction as the "wind" at the top. (CW in the usual orientation we have been using.) This is true for "real wind" over road and "induced wind" (if that's reasonable term) over the treadmill surface (for a large enough treadmill, same surface characteristics, blah, blah, blah).

At windpeed, I can say that the wind velocity of w,r,t wind is "windspeed" that is 0.
This means that the boundary is still moving forward, bit not at windspeed, so that is 2km/hr in "treadmill" terms. However, the actual differential of wind and flow, remains at 8km/hr.

If you want to say the speed of the air (high above the surface) is 0 km/hr, then that is okay but you are now using a "datum" (frame of reference) that is moving along with that air which is moving above the road). In other words, we might imagine that a particular molecule of O₂ is basically sitting at the origin (0,0,0) of our coordinate system all the time. But that means we have to measure all displacements and velocities from that very same frame of reference. In other words, the road is now moving at -10km/hr (using negative for "to the left" and we're observing from out to the side) and the boundary layer is moving at -8 km/hr (which you will note is still 2 km/hr faster than the road. This is all looking at "real wind" over a road. No treadmill in sight, but look, we get the same values as for the treadmill when using a frame of reference at rest w.r.t. the air well above the boundary layer.

I don't know what you mean when you say '... so that is 2km/hr in treadmill terms"'. What exactly is "in treadmill terms" meant to tell me? On the treadmill, if you use your anemometer to measure the flow you will again see it is 2km/hr RELATIVE to the belt. The belt is moving to the left (in the room) under "still air". It drags the lower parts of that air mass along with it (but not quite as fast unless perhaps it's right beside the belt). So it still moving "left" (w.r.t. room) but only at 8 km/hr. The belt is moving left at 10 km/hr. the boundary layer is moving left at 8km/hr, which is 2 km/hr "up the belt". Fix your anemometer to the belt and at the appropriate height and you will find it reads 2km/hr!

To repeat something important: the belt drags the very lowest parts of the air mass along with it at (let's say) the exact same speed that the belt is moving. (So zero difference in speed at that lowest level, and exactly the same on the road.) Just above that the air is dragged along by the belt at a slightly lower rate - the air is "slipping behind" the belt (small speed difference), and the amount of "slipping behind" increases with height above the belt until eventually there is effectively no effect and the air doesn't move. This varies by height in the same way for similar surfaces moving at some fixed speed relative to the air mass well above. Whether it's the air moving over the road, or a belt moving under the air the "profile" of that gradient is the same. You'd do well to view it from the surface (zero difference) building up with height above the surface, and building at the same rate over the "road" and the "belt".

No. Only by swapping methods. The equivalent for the real wind is +2km/hr. It still moves forward, but slower. It does not move away from the cart as it does on the belt.

I am trying really hard right now to follow your train of thought Humber. You have a tiny window of opportunity here! Don't waste it. If you truly have communicable information inside your head, then now is the time to lay it out in a way that others can digest and absorb. What you've been doing isn't working at all well. Try to think of some different approaches. Nice clear diagrams would help. It's no good just saying "no" over and over again.

Okay, so having said that...

I don't know what you mean by "swapping methods". I have tried to duplicate what appears to be your method to find the difference between free air flow and boundary layer flow. It was pretty simple I have to say. But you say I've done this incorrectly. So I think the ball is in your court now. You have to explain, teach, demonstrate in detail... if necessary go step by step and be prepared to answer any and all questions along the way until I (or perhaps other smarter cookies) can actually understand what your method(s) are.

In what sense do you mean "move away from the cart"? We're talking about a layer of air that covers the whole surface. If the cart is embedded in that flow then there'll be some parts of the flow that could be moving away and other parts moving towards the cart. If the cart is moving at the same velocity as the boundary layer then they will be at rest w.r.t. each other. I'm assuming you mean the cart moving at 10 km/hr over the surface but as I just said there is a whole layer of air moving relative to that cart. Maybe you were trying to say something about the direction of the flow?

SOS SOS SOS ... what the hell am I doing here!

 

[humber]

See, I was right, humbre always takes the ground's point of view as the only valid one. He just can't understand how anyone could think differently.

Everything has the common reference of the ground, unless you're out in space, in which case gravity no longer attracts the mass that becomes the weight to provide the friction to supply the force which can't accelerate the cart, so the treadmill is invalid.

No, they have a forced common ground. That is how they move. Stopping one is not "taking a ground reference". OK, let's make it 0.5kph, rather than stopped, in which it is 7.5mph and 2.5kph if it were actually going backwards at 2kph. It's 7.7kph, so it is not going backwards.
You can do the same with forces, tying tow ropes between, to see who pulls who. Not the same thing at all. Any way acceleration would give the game away.

 

[spork]

I was on a flight all day, so I missed several pages. Yes, that's how fast this cancer is growing. But in trying to catch up, I think some things are becoming clear to me. First off, I think it's far beyond hopeless to think we're going to achieve any sort of understanding with humber (and I suspect we all know this). The notion of this reaching any sort of conclusion that's satisfying to either side seems beyond remote. I'm honestly at a loss. The more I think about this, the more I think we're "debating" someone we would avoid making eye contact with in person.

I'm trying to figure out how to say what I mean without attacking the person, but I fear it's coming out wrong. I guess what I mean to say is that when we can only see what someone posts on an internet forum, we assume things that we'd never assume if we met the person face to face. Consider this model and ask yourself whether it's consistent with everything that appears here... this member literally doesn't percieve the world as you and I do. I believe he has "experienced" some education, but I think it would be a mistake to call him "educated". I simply can't find a way to consolidate the combination of ignorance, arrogance, and persistence we see here, and ascribe it to someone that processes information like most other people do.

Thoughts?

 

[mender]

You can do the same with forces, tying tow ropes between, ....

No, you can't because a tether changes everything and invalidates the test. See, I was paying attention!

 

[humber]

Two identical cars approaching from opposite directions at equal speeds. When they pass, they will have zero velocity w.r.t each other, and zero KE.w.r.t each other For how long?
They are still running their engines at full power. Why?
Same for one car passing another. For how long does zero-land exist?
How fast would an object have to travel between those cars, to make use of that situation?

 

[Brian-M]

No, the flow is with the belt. That is negative. The premise of the treadmill is that the road/belt moves backwards w.r.t the cart. The tailwind is positive.

But you've gave the belt velocity as 10m/s in that post and the "flow" as being -6m/s... so according to your numbers, they're moving in opposite directions.

Can I assume that you left out the negative sign in front of the 10m/s by accident? And also left out the negative signs in front to your answers by accident too?

You can't just leave out the negative signs on half your negative numbers and still expect your math to make any sense to anyone else.


Here, let's start again with a wind-speed cart.

On The Road

Measured from the ground - Beside the road.
Boundary layer (at height X) is 4m/s slower than the wind.

Wind = 10m/s
Cart = Wind = 10m/s
Boundary Layer = Wind - 4m/s = 6m/s
Road = 0

To measure from the cart's perspective (or wind's perspective, which is the same thing as they are moving at the same velocity), subtract the cart's velocity (10m/s) from everything.

Wind = 10m/s - 10m/s = 0
Cart = 10m/s - 10m/s = 0
Boundary Layer = 6m/s -10m/s = -4m/s
Road = 0 - 10m/s = -10m/s


Now we try it on the treadmill

On The Treadmill
Measured from the ground - beside the treadmill
The boundary layer (at height Y) is still 4m/s slower than the wind.

Wind = 0
Cart = 0
Boundary Layer = Wind - 4m/s = -4m/s
Belt = -10m/s

Wait a sec... That's EXACTLY the same as on the road, from the cart's perspective!

Let's look at it from the belt's perspective by subtracting belt-speed from everything.

Wind = 0 - (-10m/s) = 10m/s
Cart = 0 - (-10m/s) = 10m/s
Boundary Layer = -4m/s - (-10m/s) - 6m/s
Belt = -10m/s - (-10m/s) = 0

Exactly the same as we start with on the road!

There is no difference.