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# Galilean relativity, or is there such thing as absolute motion?

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2 hours ago, OceanBreeze said:

It will slow down until it reaches equilibrium with the wind force and the resistance forces (rolling resistance being the chief resistance force).

OK.   If the air was blowing from the right end of the tunnel towards the left, you are predicting the cart will move to the left slower than the air, so slower than 10mph (steady-state).

Now suppose we turn off the fans and turn on the treadmill belt with the belt moving at 10mph.  The belt is moving from the left towards the right.  Instead of running the cart up to 10mph and then releasing it, the arm holds the cart in place (at rest with respect to the air) and then lets it go.  This is the scenario in the youtube video I linked to above.  Do you agree that the cart will accelerate and advance up the belt - to the left - at some non-zero steady-state speed?  (This is just as shown in the video I linked to above.)

If you agree with that, note that after a trivial Galilean transform (to a frame moving at 10mph with respect to the original frame) the air and belt velocities are identical in the two scenarios, as is the initial condition (cart at rest with respect to the air) - but you are predicting a different outcome for the forces and motion of the cart from the same initial condition.  If I take your prediction for the fan-driven case and transform so the air is at rest and the belt moves at 10mph from left to right, your prediction is a cart that moves to the right, losing ground against the belt.  On the other hand the video shows a cart moving to the left, up the belt.  How then is your prediction consistent with Galilean invariance?

The only real difference between these two experiments is what is ultimately creating the relative velocity between the air and belt (it's a fan in the first case and a treadmill belt motor in the second).  How is the cart supposed to know about that, when the air and belt (the two things it interacts with) behave identically after the Galilean transform?

Edited by truthseeker

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ECM;

The original ?
There is an unstated fact beginning with human methods of measurement.All measurement is relative to an arbitrarily defined standard, which is chosen for convenience.When Einstein developed Special Relativity, he chose the simplest state of motion, constant velocity, considering only speed and direction. In his 1905 paper, he used a common example of em induction, requiring only a relative motion of coil and magnet.

1. Consider an airplane parked on the ground. Passengers Ann and Bob sit on opposite sides of the aisle. Ann tosses an object b at speed u, across the aisle to Bob.

2. The airplane leaves the ground, ascends to a specific altitude and constant velocity v.With the same seating arrangement, Ann tosses an object b at speed u, across the aisle to Bob.In both cases, the motion of b is the same within the plane.The plane imparts v to all elements of the plane, including the passengers and object bAll elements are moving parallel in the same direction, thus there is no motion to detect within the plane. The physics within the moving plane is the same as on the ground.

Newton's definition of 'rest' is flawed. There is no um for rest. 'Rest' is the absence of motion, just as 'darkness' is the absence of 'light'. Rest is a special case of motion when multiple objects have the same velocity, they are at 'relative rest'. Thus they can be moving at high speed and still be at rest, without contradiction.

The 'new and improved' ?
[quote]
A rolling wheel puts down a contact patch and normally must move by bringing that contact patch back and laying down another, in a continuous manner. It seems to me that on the treadmill belt, the belt will bring the contact patch back for the wheel, reducing the work done by the wheel in rolling. Indeed, this is how the belt forces the wheel to roll at all![/quote]

The wheel is not powered. The conveyor motor is doing the work. The belt applies a torque to the wheel and it rotates in place.

A few observations.

Assuming a mobile transporter with wheels (cart) sitting on a hard surface, gravity accelerates the cart, slightly deforming the wheel surface contact to a small flat spot.Traction depends on weight and a deformable tire. We have Amish communities nearby who use horse driven buggies with wheels capped with a metal rim to reduce wear.In this case the wheels are not designed for traction, but act as bearings to minimize friction.A typical conveyor belt is supported by a rigid surface underneath, and does not flex.

If the air surrounding the conveyor is still at startup, it should remain as such at operating speed. Air pressure at ground level results in an insignificant dragging of tiny amounts at the belt surface.

Just wanted to show some of the complexity of wheel experiments.

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On 1/26/2022 at 11:47 AM, OceanBreeze said:

The only part of the belt that matters to the cart is where the wheels touch the belt

Nope.  If you had tank treads, or even just a linear induction motor floating over the belt, you could still harvest energy - as long as there's that difference there.  The "little arcs" matter not at all; that's just a detail of how wheels work and not required for energy transfer.

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I'll add that "how does it work" is a separate question from "what does it do?" There may or may not be viable discussion in the scientific investigation of "how does it work," (I personally think the face-value explanations given by Veritasium/Drela/Cavallaro explain it correctly, but could there be something in the vibrating wheels/vibrating treadmill? Who knows. But I'm pretty sure the desert floor wasn't vibrating in those 2 videos) but such discussion will never be viable until the basic facts of its motion are laid down and agreed on. If we can't simply agree on the relative speed of 3 objects, how can we possibly go on to trickier details of the causes behind them? It'd be like trying to do calculus before we can agree on 2+2.

@OceanBreezeSo after your whole participation in the thread, to try to get a gauge in exactly what your position is on the matter, let me ask you (the "what does it do" question): can a propcart

- accelerate to a speed higher than wind speed

- sustain a speed higher than wind speed

- sustain a nonzero speed if the wind is removed?

- you've stated that the presence of air is required. Can this air be moving at the same velocity as the surface (i.e. be stationary relative to the surface) or does it have to be moving relative to the surface, in order for the propcart to work?

Edited by EfisCompMon
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Moderator Note: I see the sh1t posts have not stopped even after a warning was given. They have cropped up not only in this thread, but others as well. Stronger moderation actions are now called for. Both Jeffrey's Tubes8 and his sock Auto, will have their posting privileges suspended for a period of not less than 2 months. I don't like taking this action, but after repeated warnings, it is the only action left to take.

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23 hours ago, billvon said:

Nope.  If you had tank treads, or even just a linear induction motor floating over the belt, you could still harvest energy - as long as there's that difference there.  The "little arcs" matter not at all; that's just a detail of how wheels work and not required for energy transfer.

But you don't have tank threads or an induction motor floating over the belt. The interface between the belt and the wheels is what you have, and energy is transferred to the wheels by the belt forming small arcs at the bottom of the wheels, where a differential force is developed. I suggest you read up on how belt drives work.

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2 minutes ago, OceanBreeze said:

The interface between the belt and the wheels is what you have, and energy is transferred to the wheels by the belt forming small arcs at the bottom of the wheels, where a differential force is developed. I suggest you read up on how belt drives work.

Does this work any differently if the ground surface is moving and vehicle stationary, vs. ground surface stationary and vehicle is moving?

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On 1/28/2022 at 1:27 AM, sluggo said:

ECM;

The original ?
There is an unstated fact beginning with human methods of measurement.All measurement is relative to an arbitrarily defined standard, which is chosen for convenience.When Einstein developed Special Relativity, he chose the simplest state of motion, constant velocity, considering only speed and direction. In his 1905 paper, he used a common example of em induction, requiring only a relative motion of coil and magnet.

1. Consider an airplane parked on the ground. Passengers Ann and Bob sit on opposite sides of the aisle. Ann tosses an object b at speed u, across the aisle to Bob.

2. The airplane leaves the ground, ascends to a specific altitude and constant velocity v.With the same seating arrangement, Ann tosses an object b at speed u, across the aisle to Bob.In both cases, the motion of b is the same within the plane.The plane imparts v to all elements of the plane, including the passengers and object bAll elements are moving parallel in the same direction, thus there is no motion to detect within the plane. The physics within the moving plane is the same as on the ground.

Newton's definition of 'rest' is flawed. There is no um for rest. 'Rest' is the absence of motion, just as 'darkness' is the absence of 'light'. Rest is a special case of motion when multiple objects have the same velocity, they are at 'relative rest'. Thus they can be moving at high speed and still be at rest, without contradiction.

The 'new and improved' ?
[quote]
A rolling wheel puts down a contact patch and normally must move by bringing that contact patch back and laying down another, in a continuous manner. It seems to me that on the treadmill belt, the belt will bring the contact patch back for the wheel, reducing the work done by the wheel in rolling. Indeed, this is how the belt forces the wheel to roll at all![/quote]

The wheel is not powered. The conveyor motor is doing the work. The belt applies a torque to the wheel and it rotates in place.

A few observations.

Assuming a mobile transporter with wheels (cart) sitting on a hard surface, gravity accelerates the cart, slightly deforming the wheel surface contact to a small flat spot.Traction depends on weight and a deformable tire. We have Amish communities nearby who use horse driven buggies with wheels capped with a metal rim to reduce wear.In this case the wheels are not designed for traction, but act as bearings to minimize friction.A typical conveyor belt is supported by a rigid surface underneath, and does not flex.

If the air surrounding the conveyor is still at startup, it should remain as such at operating speed. Air pressure at ground level results in an insignificant dragging of tiny amounts at the belt surface.

Just wanted to show some of the complexity of wheel experiments.

quote]
A rolling wheel puts down a contact patch and normally must move by bringing that contact patch back and laying down another, in a continuous manner. It seems to me that on the treadmill belt, the belt will bring the contact patch back for the wheel, reducing the work done by the wheel in rolling. Indeed, this is how the belt forces the wheel to roll at all![/quote]

This is exactly right. The treadmill belt must develop a torque ( a differential force) to turn the wheel. To do that, the belt must flex. Read up on how a belt drives a wheel. It cannot develop a differential force with point contact. Point contact result is sliding only.

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13 minutes ago, EfisCompMon said:

Does this work any differently if the ground surface is moving and vehicle stationary, vs. ground surface stationary and vehicle is moving?

The ground surface never moves! When you change reference frames, you do not change the physical reality! You only observe the same experiment from a different frame of reference. You and some others seem to think the observer can change the experiment by changing the reference frame!

On the ground, the wheel must roll, that is, it must deform into a contact patch, as I described earlier. You will be surprised at how much energy is lost to heat and deformation! Thai is why F1 racers need to change their tires often during a race.

When the vehicle is moving, this deformation must occur otherwise the wheel cannot roll! If you observe this same situation from a frame where the vehicle  is at rest, and the ground appears to be moving, you will see this same deformation. It cannot be any different or this would be a very strange world indeed!

Edited by OceanBreeze
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12 minutes ago, OceanBreeze said:

The ground surface never moves! When you change reference frames, you do not change the physical reality!

So your answer to the title of the thread is that yes there is such thing as absolute motion (or, in this case, absolute rest)?

Quote

You only observe the same experiment from a different frame of reference. You and some others seem to think the observer can change the experiment by changing the reference frame!

Well kind of yes by changing reference frame, you are changing which v's = 0, and which v's = something else. But Galilean Relativity also means that as long as you've accurately kept track of which v's did what, the experiment has not changed (however calculating it, might have become more or less cumbersome).

I know you've expressed some irritation at people telling you what Galilean Relativity entails, but you also keep making statements that contradict it. In this case, the statement that the ground never moves; and the reality is that it moves in every frame of reference except one. (Also strange, in a thread with multiple videos in a frame of reference where the ground moves).

Quote

On the ground, the wheel must roll, that is, it must deform into a contact patch, as I described earlier. You will be surprised at how much energy is lost to heat and deformation! Thai is why F1 racers need to change their tires often during a race.

When the vehicle is moving, this deformation must occur otherwise the wheel cannot roll! If you observe this same situation from a frame where the vehicle  is at rest, and the ground appears to be moving, you will see this same deformation. It cannot be any different or this would be a very strange world indeed!

OK so a higher contact area passes more friction, meaning more tangential force, meaning more torque without slipping. Completely agreed. What is the bearing of this on the possibility of DDWFTTW on the desert floor and/or a treadmill?

Edited by EfisCompMon
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5 hours ago, EfisCompMon said:

I'll add that "how does it work" is a separate question from "what does it do?" There may or may not be viable discussion in the scientific investigation of "how does it work," (I personally think the face-value explanations given by Veritasium/Drela/Cavallaro explain it correctly, but could there be something in the vibrating wheels/vibrating treadmill? Who knows. But I'm pretty sure the desert floor wasn't vibrating in those 2 videos) but such discussion will never be viable until the basic facts of its motion are laid down and agreed on. If we can't simply agree on the relative speed of 3 objects, how can we possibly go on to trickier details of the causes behind them? It'd be like trying to do calculus before we can agree on 2+2.

@OceanBreezeSo after your whole participation in the thread, to try to get a gauge in exactly what your position is on the matter, let me ask you (the "what does it do" question): can a propcart

- accelerate to a speed higher than wind speed

- sustain a speed higher than wind speed

- sustain a nonzero speed if the wind is removed?

- you've stated that the presence of air is required. Can this air be moving at the same velocity as the surface (i.e. be stationary relative to the surface) or does it have to be moving relative to the surface, in order for the propcart to work?

I consider some of your questions to be silly but I will answer them anyway:

1) Can a propcart accelerate to a speed higher than wind speed? It is possible for the cart to get ahead of the average wind speed in a variable wind. If the wind speed should drop suddenly, the cart cannot respond immediately, and for a few seconds it will exceed the local wind speed. That is when you may see the streamers flip backwards. But this is only a transient condition. The cart will start to slow if the wind does not pick up again. Once the wind picks up, the cart will be below wind speed. It can also exceed windspeed if it does not follow a direct down wind path.

2) Can a propcart sustain a speed higher than windspeed (direct down wind) NO.

3) Nonsensical question! With no wind (and no treadmill) the cart isn't going anywhere.

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6 minutes ago, OceanBreeze said:

I consider some of your questions to be silly but I will answer them anyway:

1) Can a propcart accelerate to a speed higher than wind speed? It is possible for the cart to get ahead of the average wind speed in a variable wind. If the wind speed should drop suddenly, the cart cannot respond immediately, and for a few seconds it will exceed the local wind speed. That is when you may see the streamers flip backwards. But this is only a transient condition. The cart will start to slow if the wind does not pick up again. Once the wind picks up, the cart will be below wind speed. It can also exceed windspeed if it does not follow a direct down wind path.

2) Can a propcart sustain a speed higher than windspeed (direct down wind) NO.

Are these statements consistent with the data gathered during Blackbird's record run? Is any such slowing-down tendency present, once it went above the average wind speed?

Quote

3) Nonsensical question! With no wind (and no treadmill) the cart isn't going anywhere.

Well, it is a vey easily-answered question, but I wouldn't say nonsensical. And you will have to humor me with it, after you've said multiple times things like "the treadmill cart has nothing to do with wind or wind energy." Do you still stand by that? You've since stated that the presence of air is necessary. Is the presence of relative motion between the air and the surface (aka wind), also necessary?

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5 minutes ago, EfisCompMon said:

So your answer to the title of the thread is that yes there is such thing as absolute motion (or, in this case, absolute rest)?

How the hell do you come to this conclusion? A word to the wise, do not put words in my mouth or attribute any statement to me that I have not made.

Quote

Well kind of yes by changing reference frame, you are changing which v's = 0, and which v's = something else. But Galilean Relativity also means that as long as you've accurately kept track of which v's did what, the experiment has not changed (however calculating it, might have become more or less cumbersome).

Sure, relative velocities change but anything physical going on does not and cannot be seen to be different based on reference frame choice. Stop changing the goal posts! You were asking about the physics of the rolling wheel. It cannot be any different based on the choice of reference frames.

Quote

I know you've expressed some irritation at people telling you what Galilean Relativity entails, but you also keep making statements that contradict it. In this case, the statement that the ground never moves; and the reality is that it moves in every frame of reference except one. (Also strange, in a thread with multiple videos in a frame of reference where the ground moves).

The ground never moves! You only see it appear to move in different frames of reference. Here on Earth, the ground is considered to be stationary and is used as a stationary reference. For these experiments with the cart, it would be insane to think the ground actually moves. For a satellite in space or an observer on the moon, it may be useful to consider that Earth is moving through space at a high velocity. But for experiments on the ground, it is the sane approach to consider the ground as a stationary reference and nearly inertial. Yes, I do indeed understand Galilean relativity but I don't carry it to ridiculous extremes to try to prove a point about a ridiculous claim of ddw.

Quote

OK so a higher contact area passes more friction, meaning more tangential force, meaning more torque without slipping. Completely agreed. What is the bearing of this on the possibility of DDWFTTW on the desert floor and/or a treadmill?

For one thing, The 450 kg cart will lose a lot of energy rolling those tires across the desert floor. The 200 gram cart on the treadmill, where the tires are spun by the belt, it is the belt that deforms and any power loss is quickly made up for by a constant velocity belt. The cart loses little or no energy in the tires. Again, you are trying to compare two very different experiments and you still do not understand that Galilean relativity applies only to one and the same experiment as seen from different frames of reference. You and many others have been fooled by this claim and it will take you some time to realize how wrong you are and deprogram your mind back to reality.

This is whay I do not want this on this forum! It has been discussed for 12 years on other forums and still without a scientific evidence that is non-controversial. It is just an endless Internet pissing contest and I will be closing this thread soon.

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14 minutes ago, EfisCompMon said:

Are these statements consistent with the data gathered during Blackbird's record run? Is any such slowing-down tendency present, once it went above the average wind speed?

Well, it is a vey easily-answered question, but I wouldn't say nonsensical. And you will have to humor me with it, after you've said multiple times things like "the treadmill cart has nothing to do with wind or wind energy." Do you still stand by that? You've since stated that the presence of air is necessary. Is the presence of relative motion between the air and the surface (aka wind), also necessary?

Now you have taken this into banned territory. I warned about that.

This forum is under no obligation to host a discussion on the "blackbird" which I am convinced is crackpottery. so, thread is closed.