Merged DDWFTTW in a “Real” Wind

[windgrins]

The GPS in question and the errors in direction at rest.

I believe with today's best commercial GPS, static navigation errors due to slow speeds are only significant under 1 mph. Even at a decent walking speed, the dynamic navigation is very accurate, so this should not have been a problem with the cart slowing down, in my opinion.

http://www.internationalskeptics.com/forums/attachment.php?attachmentid=22144&d=1305219854

Profpangloss is correct for speeds below about 2mph for the GPS and so is Drewid when he says "at very low speeds obviously." (the GPS will have large errors in heading.)

To put a finer point on it:

If one uses the data supplied by the chart Humber provided above and below, it is clear that the GPS generating that data was giving position errors less than 2 inches for the data set provided over a 1 sec period (assuming this was the sampling rate.). This is easily computed from the speed column. From this information, it can be gleaned that the relative accuracy of this GPS is very high. Computationally, this implies the worst case heading errors to be less than 7 degrees at motion greater than 1mph and less than 3.5 degrees with speeds greater than 2mph. As the speeds increase, the heading errors decrease as the noise in the position measurements become a smaller percentage of the change in position. For a fixed position of the receiver, the receiver will generate random headings with these being completely meaningless.

Not understanding this issue with GPSs at a standstill, which anyone who has ever used one for precision navigation or surveying does, As usual, brings into question, Humber's posturing as a measurement expert. It never even seemed to dawn on him what the other poster's were discussing in this regards.

I think we can expect the trend to continue that Humber will continue to claim expertise in areas he has demonstrated he knows little about:

Physics
Electronics
Aerodynamics
Measurement Expertise including error analysis
Navigation
Sailing vehicles
Airplanes
Space Technology
The meaning of words in coherent sentences
Coherent sentences.

So far, we've not seen any area that Humber seems to know much about at all. His analyses so far have all been nonsensical and I expect this to continue.

Regards,

WindGrins

 

[humber]

So far, we've not seen any area that Humber seems to know much about at all. His analyses so far have all been nonsensical and I expect this to continue.

Regards,

WindGrins[qimg]http://www.internationalskeptics.com/forums/imagehosting/thum_488654dce775dd8294.png[/qimg]

It's just one of many measurement errors.

The remaining and entirely untouched NALSA data which says the wind changes from + 50 to -50 degrees during a ddw trial, is not affected by the lax attention to detail, that corrupts the data, and makes continuous plotting difficult.

Moreover, the method used to derive the GPS direction from the usual and expected stationary scatter, goes out of its way to make things worse.
The GPS outputs 1 sample/sec, but the logger take 5samples/sec so 5 consecutive and identical readings, but there is a change in angle for each of those 5 samples, as my data you posted shows.
ETA: each line is 0.2s apart.

 

[jduffy77]

Heh, as to your analogy, wouldn't they at least have to explain why below zero temperatures were required in the first place?

So you are saying that you don't understand, or need explanation as to why ddw is needed to establish a ddwfttw record? How can you think that makes sense? You need to explain that more.

I have tried to help you many times now and it seems like I am just making things worse. When you string words that you don't understand together it makes you sound silly but at least it is less clear how ignorant of the subject matter you actually are.

And no offence taken wrt my childlike stringing of words btw. I play to my audience.

If you are saying that your audience is less informed on the BB cart then you are then you are going about it the wrong way. I don't really think you are more informed than anyone here, but if you believe that, rather then emulating a child and using words which you believe the other children won't understand why don't you try explaining and supporting your positions more clearly.

 

[profpangloss]

Not energy, at least not any important amount, just momentum.

You cannot choose absolutely any frame of reference that you like, if you want to use Newton's laws of motion in their usual form. You can choose any inertial frame of reference.

You can choose a frame of reference in which the Earth is initially stationary, but if the Earth's momentum changes, as it will in response to forces on the Earth, you cannot choose a frame of reference in which the Earth remains stationary, because that frame of reference is not inertial.

Conservation of momentum does not hold in non-inertial frames of reference.

As Subduction Zone pointed out, your argument would imply, not only that the Blackbird cannot work, but also that no car can work. When a car accelerates, its momentum changes. Where is the corresponding oppositely-directed change, to satisfy conservation of momentum? It is in fact in the momentum of the Earth, massive though it is. Its large mass implies a small velocity change, but not a small momentum change. The change in momentum of the Earth equals the change in momentum of the car, just in the opposite direction.

Also see this post of mine, which perhaps you missed in all the irrelevancy that goes on in this thread.

You are just totally wrong here! I can choose any reference frame I want, and I chose the frame where the earth is stationary. The laws of conservation of momentum and conservation of energy must hold true in that frame, as they must hold true in any reference frame. The earth CANNOT have momentum in this frame because it is stationary! Nothing can be clearer than that! The earth has no initial velocity and NO velocity change. Your argument is entirely incorrect.

 

[jduffy77]

You are just totally wrong here! I can choose any reference frame I want, and I chose the frame where the earth is stationary. The laws of conservation of momentum and conservation of energy must hold true in that frame, as they must hold true in any reference frame. The earth CANNOT have momentum in this frame because it is stationary! Nothing can be clearer than that! The earth has no initial velocity and NO velocity change. Your argument is entirely incorrect.

As I have said before the most hilarious thing about pranggloss is that some of the clearest proof that the cart works is his own math. All anyone needs to do is separate it from his prose and correct a couple of obvious mistakes.

 

[humber]

Not as hilarious as the trial crap-shoot. Just keep plugging away with a pile of junk, until that gusty 100 degree wind just happens to force the wind vane to read 10 degrees.

 

[profpangloss]

As I have said before the most hilarious thing about pranggloss is that some of the clearest proof that the cart works is his own math. All anyone needs to do is separate it from his prose and correct a couple of obvious mistakes.

I think it is hilarious that you, and other cart supporters, do not even understand that in the frame where the earth is the stationary reference, the earth cannot have momentum! That is hilarious and sad at the same time, but it is indicative of the level of technical understanding that would allow for a belief in a cart that can go ddwfttw.

 

[jduffy77]

You are just totally wrong here! I can choose any reference frame I want, and I chose the frame where the earth is stationary. The laws of conservation of momentum and conservation of energy must hold true in that frame, as they must hold true in any reference frame.

Correct. Unlike Humber pranggloss usually gets most things right and then buries an error or two in his long drawn out "analysis". It is true that he can choose any reference frame he wants. What he hasn't done yet is an analysis where he sticks to the same frame throughout the entire analysis while at the same time correctly considering the KE of all parts of the system.

 

[Michael C]

You are just totally wrong here! I can choose any reference frame I want, and I chose the frame where the earth is stationary. The laws of conservation of momentum and conservation of energy must hold true in that frame, as they must hold true in any reference frame. The earth CANNOT have momentum in this frame because it is stationary! Nothing can be clearer than that! The earth has no initial velocity and NO velocity change. Your argument is entirely incorrect.

The velocity of the Earth does indeed change, even though the change in velocity will be much too small for us to measure. See for instance this page on the conservation of momentum:

"A good example of this is a ball that is dropped from a height. If we are considering the ball alone, then the momentum is m_bv_b before the ball collides and -m_bv_b when the ball hits the Earth. The change in momentum is 2m_bv_b not zero. It appears to gain momentum from nowhere. However, we need to consider the change in momentum of the Earth. It moves with a velocity v_E after the collision. The conservation of momentum, m_bv_b + m_E.0 = m_b(-v)_b+m_Ev_E. The Earth has to gain the same momentum as the ball but because the mass of the Earth is so large, the movement is unmeasurable."​

 

[profpangloss]

The velocity of the Earth does indeed change, even though the change in velocity will be much too small for us to measure. See for instance this page on the conservation of momentum:

"A good example of this is a ball that is dropped from a height. If we are considering the ball alone, then the momentum is m_bv_b before the ball collides and -m_bv_b when the ball hits the Earth. The change in momentum is 2m_bv_b not zero. It appears to gain momentum from nowhere. However, we need to consider the change in momentum of the Earth. It moves with a velocity v_E after the collision. The conservation of momentum, m_bv_b + m_E.0 = m_b(-v)_b+m_Ev_E. The Earth has to gain the same momentum as the ball but because the mass of the Earth is so large, the movement is unmeasurable."​

The velocity of the earth does NOT change in the frame of reference where the earth is stationary! Can you really fail to understand that?

 

[jduffy77]

The velocity of the earth does NOT change in the frame of reference where the earth is stationary! Can you really fail to understand that?

Can you really fail to understand that the frame of reference chosen defines the KE of other parts of the system?

 

[windgrins]

Sorry, despite your protests, you are wrong.

You are just totally wrong here! I can choose any reference frame I want, and I chose the frame where the earth is stationary. The laws of conservation of momentum and conservation of energy must hold true in that frame, as they must hold true in any reference frame. The earth CANNOT have momentum in this frame because it is stationary! Nothing can be clearer than that! The earth has no initial velocity and NO velocity change. Your argument is entirely incorrect.

Sorry,

Your argument doesn't hold water. First of all, you can't just "choose any frame I want." It has to be an Inertial frame of reference. If you choose an Inertial Reference Frame that is initially indexed to the earth then the Inertial Reference Frame continues Inertially whether the earth moves or not. The earth is moved all the time by rotation and in its orbit about the sun and gravitational influence by the moon and also by major events such as earthquakes but the inertial frame can't be allowed to track these changes or otherwise it isn't an "IRF" in the strict sense of the term.

So the posters are correct that if the earth is used to react against for momentum or energy purposes, the earth does move minutely wrt the initial (nearly )IRF. The earth itself has nothing to do with the IRF and you seem to confuse this fact. It is only a convenient index and only for most practical purposes is the earth "fixed"

So if you insist on doing your energy calculations precisely (which by the way is absurd) you must pick an IRF wrt to the far stars average motion. The earth is moving quite rapidly and rotating also in this frame.

Otherwise despite your machinations to the contrary, you are incorrect in saying:

You are just totally wrong here! I can choose any reference frame I want, and I chose the frame where the earth is stationary. The laws of conservation of momentum and conservation of energy must hold true in that frame, as they must hold true in any reference frame. The earth CANNOT have momentum in this frame because it is stationary! Nothing can be clearer than that! The earth has no initial velocity and NO velocity change. Your argument is entirely incorrect.

ETA:

Since three independent posters here point out the exact same error with no cross communication, you may want to think about your statement instead of being Humberlike and insisting you are correct, no matter what. All the posters are saying the same thing about your argument and point out the same fundamental error. An intelligent person would give pause to this.

Regards,

WindGrins

 

[profpangloss]

Can you really fail to understand that the frame of reference chosen defines the KE of other parts of the system?

Another enpty statement, just what I have come to expect from the cart supporters. The issue here is in the frame of reference where the earth is at rest, the earth cannot have momentum, since momentum is mass x velocity and the earth cannot have velocity since it is at rest. It also cannot have kinetic energy, since that is the energy of motion, and the earth is at rest. Have I spelled that out clearly enough now that we can move on, or do you still not understand it?

 

[Michael C]

The velocity of the earth does NOT change in the frame of reference where the earth is stationary! Can you really fail to understand that?

If the velocity of the Earth changes, it changes in any inertial frame. You can't have acceleration in one inertial frame and not in another!

We can indeed use the Earth to define an inertial frame in which the Earth is stationary at moment x, but if the velocity of the Earth changes after moment x, the Earth will no longer be stationary in the frame that we have defined.

 

[profpangloss]

Sorry,

Your argument doesn't hold water. First of all, you can't just "choose any frame I want." It has to be an Inertial frame of reference. If you choose an Inertial Reference Frame that is initially indexed to the earth then the Inertial Reference Frame continues Inertially whether the earth moves or not. The earth is moved all the time by rotation and in its orbit about the sun and gravitational influence by the moon and also by major events such as earthquakes but the inertial frame can't be allowed to track these changes or otherwise it isn't an "IRF" in the strict sense of the term.

So the posters are correct that if the earth is used to react against for momentum or energy purposes, the earth does move minutely wrt the initial (nearly )IRF. The earth itself has nothing to do with the IRF and you seem to confuse this fact. It is only a convenient index and only for most practical purposes is the earth "fixed"

So if you insist on doing your energy calculations precisely (which by the way is absurd) you must pick an IRF wrt to the far stars average motion. The earth is moving quite rapidly and rotating also in this frame.

Otherwise despite your machinations to the contrary, you are incorrect in saying:



Regards,

WindGrins

You are totally wrong!

 

[profpangloss]

If the velocity of the Earth changes, it changes in any inertial frame. You can't have acceleration in one inertial frame and not in another!

We can indeed use the Earth to define an inertial frame in which the Earth is stationary at moment x, but if the velocity of the Earth changes after moment x, the Earth will no longer be stationary in the frame that we have defined.

The point is, it does not change, it is always at rest by definition.

 

[Michael C]

The point is, it does not change, it is always at rest by definition.

If you define a frame where the Earth is always at rest, then that frame is not inertial.

 

[windgrins]

You clearly do not understand what an Inertial Reference Frame is.

Another enpty statement, just what I have come to expect from the cart supporters. The issue here is in the frame of reference where the earth is at rest, the earth cannot have momentum, since momentum is mass x velocity and the earth cannot have velocity since it is at rest. It also cannot have kinetic energy, since that is the energy of motion, and the earth is at rest. Have I spelled that out clearly enough now that we can move on, or do you still not understand it?

Nope. It's incorrect. You are making the error that the IRF is "tied" to the earth when it is initially only indexed to it. When the earth moves "non-inertially" it is no longer valid as the index. Inertial reference frames once defined have to move "inertially" in space and clearly can't be tied to accelerated objects. Otherwise they are not inertial reference frames.

Have Michael C and I spelled that out clearly enough now that we can move on, or do you still not understand it?

Regards,

WindGrins

 

[windgrins]

OK, explain why if you believe this!

You are totally wrong!

OK, explain why if you believe this!

WindGrins

 

[profpangloss]

If you define a frame where the Earth is always at rest, then that frame is not inertial.

Why wouldn't it be? The earth is at rest and there is wind and cart moving. They are all that is moving in that frame. Whatever momentum and energy they have must be conserved. It is that simple.