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The McMinnville case
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Larry
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PostPosted: 03/28/2013, 10:30 pm    Post subject: The McMinnville case Reply with quote

Haraka wrote:
 
“…The motion of the disc is certainly probably going to be irregular and five variables ( not including possible  "bounce" as you noted on the wire) doesn't help.  This I think makes a resolution virtually impossible. …”
 
I’m not sure what you mean by ‘resolution’.  If you mean that the behavior of the system would be ‘virtually impossible’ to predict, I don’t agree.  There are any number of computer programs (i.e., MATLAB) that could be used to simulate the equations of motion of this kind of system.  However, I think it would actually be easier and more definitive to simply make up a model and hang it on a wire and watch what happens when the wind blows on it.  After all, that is what the hoax hypothesis claims happened.  Paul Trent was living in a time and location when he did not have many resources to create a hoax.  If he hoaxed the photos with a small model, the model had to either be a manufactured object that he would have had access to or had to be model that he made up for the purpose.
 
If you mean that it would be ‘virtually impossible’ to draw any conclusions from such a simulation, I don’t agree with that either.  If the model is capable of behaving as the IPACO analysis proposes it did, then that result should be quite evident.  If the model behaves as I think it will, then that would be fairly strong evidence to refute the IPACO explanation. 
 
“…I'm more used to centre of gravity ( C of G ) as a term  and presume that is equivalent to your Centre of Mass.”
 
Yes, they refer to the same point.
 
“…Aerodynamically  of course the centre of pressure ( C of P)  typically moves forwards against the direction of airflow as the  the  Angle of Attack  ( Alpha) increases, right up to the stall of the airfoil at around 15 deg.”
 
Well, it’s not really accurate to think of the CP as moving forward in proportion to Alpha. As soon as the airfoil is generating lift due to circulation, then that lift vector shows up instantaneously at the ¼ chord.  The airfoil can generate lift EITHER because it has intrinsic camber (as the Trent UFO shape does) OR because it is experiencing a positive angle of attack, or from BOTH sources simultaneously. 
 
However, it is true that the MAGNITUDE of the lift vector will increase as Alpha increases--up to the point of stall.  Once the airfoil has fully stalled and it is no longer generating stable lift, then the CP moves back towards the ½ chord position. 
 
“…Increasing Alpha  invokes a consequent  increase in the Coefficient of Drag…”
 
Yes, you are right.
 
“… ( probably adding both to "r" and "s" components in this case)…”
 
It would add directly to the ‘r’ component in all cases because the drag force is always in the downwind direction.  It would add to the ‘s’ component if and only if the ‘b’ angle is non-zero.  A non-zero  ‘b’ angle is necessary in order to create a component of lift that is in the ‘r’ plane.
 
 “…which again suddenly drops  as the disc stalls ( C of P moving rapidly  aft) , building up again as it recovers and adding to the overall oscillatory interaction. …”
 
Yes, I think that’s right.
 
“… The subtended angle of the diameter of the supposed line  when considered in relation to the size and irregularity of the film grain will probably  defeat any digital resampling and analysis. Certainly sub-pixel features spatially (especially linear ones) can be pulled out by post processing, indeed the human visual system does it rather well as Francois has indicated. To me, in this example, "absence of evidence is not necessarily evidence of absence" will probably remain the verdict regarding the probable  suspension line.”
 
I agree that absence of evidence is not evidence of absence, UNLESS one can show from independent computation, analysis, or simulation that evidence would have been detected if it had been present.  This kind of argument is used in science, all the time.  As far as I can tell, that computation, analysis, or simulation has not been produced in the Trent photo case, but I’m not sure that anyone has tried to do so in a systematic, comprehensive, and definitive manner.  Given the significance of the case, I would think that would be a fairly important effort to undertake.  I would like to see a rigorous, peer-reviewed quantitative discussion by an expert that predicts exactly what one would expect to see (for strings of different sizes and illuminations) using different detection algorithms and then compare that to what is actually observed in the Trent photos.
 
Again, I would think that this could be helped by building a simple model and photographing it under the same conditions as the Trent photos.
 
I am by nature an empiricist and I am not nihilistic.  That means I subscribe to the metaphysical belief that real knowledge can be had by means of direct experimentation.  “Tis better to light a single candle than to curse the darkness.”


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elevenaugust
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PostPosted: 03/29/2013, 12:23 am    Post subject: The McMinnville case Reply with quote

Larry wrote:

As far as I can tell, that computation, analysis, or simulation has not been produced in the Trent photo case, but I’m not sure that anyone has tried to do so in a systematic, comprehensive, and definitive manner.  Given the significance of the case, I would think that would be a fairly important effort to undertake.  I would like to see a rigorous, peer-reviewed quantitative discussion by an expert that predicts exactly what one would expect to see (for strings of different sizes and illuminations) using different detection algorithms and then compare that to what is actually observed in the Trent photos.
 
Again, I would think that this could be helped by building a simple model and photographing it under the same conditions as the Trent photos.
 

Yes, that's what I would like to do, but the first problem here is to find the same (working, of course) camera model. An old Roamer I in working conditions is not that easy to find nowadays...

Quote:
If you mean that it would be ‘virtually impossible’ to draw any conclusions from such a simulation, I don’t agree with that either.  If the model is capable of behaving as the IPACO analysis proposes it did, then that result should be quite evident.  If the model behaves as I think it will, then that would be fairly strong evidence to refute the IPACO explanation.


Well, there are so many unknown and variable parameters (weight of the model, wind direction and speed [let alone swirling wind]) that the possibilities to find, after sufficient tries, the same configuration as those that can be seen in the photos, considerably increase IMO.


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Haraka
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PostPosted: 03/29/2013, 07:55 am    Post subject: The McMinnville case Reply with quote

 We  don't know the actual  shape of the model either, only what it looks like in poor images from  two perspectives. In addition we have no knowledge of its mass and mass distribution, nor even are we certain of its point or conditions of suspension .
The CP will  move forward as alpha increases( up to 15 deg), tending to accelerate the pitch up  and the relationship of that to the fixed CofG ( wherever that is ) will greatly affect the overall pitching behaviour of the disc. Furthermore,  the suspension wire could be  attached to restrict  pitch in one axis ( e.g. if by a transverse pin) . The fact that the wire is assumed taught  in no way invalidates the IPACO analysis which is of a dynamic system taken at two points in time.  In addition, the vertical "lift" component at the resolved CP is only one vector :there is a forward component as well which will also alter the behaviour of the disc: the characteristics of this will depend on the aerodynamic profile  of the section.
I would suggest therefore, that any attempt to replicate  the dynamic characteristics of a system of which so many significant components are unknown as a means to possibly suggest resolution  of the problem, would be heavily criticised as being probably unrepresentative of what is going on.


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Larry
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PostPosted: 04/03/2013, 03:59 am    Post subject: The McMinnville case Reply with quote

Haraka wrote:
 
“…Well, there are so many unknown and variable parameters (weight of the model, wind direction and speed [let alone swirling wind]) that the possibilities to find, after sufficient tries, the same configuration as those that can be seen in the photos, considerably increase IMO…”
 
You’ve got the logic exactly backwards.
 
The kinematic analysis done so far shows that the relative motion of the object between the two photos was quite simply explained by a pendulum with a length of about 2.6 ft having swung about 17 degrees almost directly away from the camera together with the model having tilted forward about 8 degrees around one of its body-fixed axes.   This is based on the assumption that the object has a circular planform—an approximation which I accept.
 
The other stated assumption was that the model was hanging from a slender thread that is below the limit of resolution of the camera.  As I showed above, the assumption of using a single thread leads to 5 Degrees of Freedom in the dynamic model.  From statistical mechanics, it follows that as the number of DOF of a system increases, the probability of the system assuming any one particular configuration from among all the possible configurations decreases exponentially, with the number of DOF.  In MM1, only 2 DOF have taken on non-zero values; in MM2 the same 2 DOF have taken on different numerical values, but no other DOF have been excited.  If there were 3 additional DOF available to be excited in the time interval between MM1 and MM2, the probability that they would NOT have been excited is vanishingly small.  From this I conclude that we are NOT seeing a model suspended on a single thread.
 
However, Haraka also wrote:
 
“…nor even are we certain of its point or conditions of suspension…”
 
Which is a true statement, and got me to thinking about what kind of conditions of suspension might result in the motion we see in the two photos.
 
Basically, using 2 threads instead of 1 would do it.
 
Suppose that the model was actually hanging like a playground swing hangs—on two strings attached to two points on a diameter of the model.  Then, it would swing like a playground swing swings—the pendulum mode would be in a single plane of motion, and the model itself would be constrained to tilt around one of its body-fixed axes.  The plane of motion of the pendulum would be perpendicular to the axis of the support to which it was attached (the power wire, in this case).
 
What puzzled me was the fact that the plane of motion appears to have been coincidentally also the vertical plane that contains the camera LOS.  But, from the Maccabee diagram showing the plan view of the photography site, we can see that the camera sighting lines are virtually perpendicular to the lower power wire axis.  In other words, if you suspended a circular model with two threads (like the seat of a playground swing), tied the other two ends of the threads to the power wire about 1 disc diameter apart, and positioned yourself with a camera off the end of the swing arc, you would get the geometric arrangement implied by the two photos.  This method of suspension would suppress motion in exactly the 3 DOF that actually show no excitation.  You could then set the model in motion by “pushing the swing” (with a shovel handle or similar object) and be assured of having the model in the field of view, regardless of where the model was in its arc of motion. 
 
To me, the hoax hypothesis just took a quantum jump increase in probability.


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Haraka
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PostPosted: 04/03/2013, 06:15 am    Post subject: The McMinnville case Reply with quote

Unfortunately we don't see "motion in the two photos" .  What we see is the  condition of the system at two points in time ,not even knowing which came first.. How the model got from one condition to the other is problematical. It seems reasonable to infer that excitation by the relative airflow was quite  probably the main source of energy into the system. However we  have no clear idea of the vectors , the interaction between ( unknown)  aerodynamics and the rest of the ( postulated) suspension  mechanism or, indeed  how they might have been changing between the two conditions.  Certainly a simple single axis swinging may explain it , but amongst numerous others if the full dynamic situation is considered. 
Put it like this,  aerodynamically unstable lightweight structures, single point suspended in variable airflow conditions are unlikely to merely swing back and forth along one path.
Once you increase the number of anchorage points and thus begin limiting the degrees of freedom, then obviously the situation is different.
In this case the problem then of course continues to be a lack of photographic or other collateral evidence to support acceptance of such an hypothesis. 




P.S.
Haraka wrote: 
  
“…Well, there are so many unknown and variable parameters (weight of the model, wind direction and speed [let alone swirling wind]) that the possibilities to find, after sufficient tries, the same configuration as those that can be seen in the photos, considerably increase IMO…” 



Er, actually Larry ,Haraka didn't .... Okay


Last edited by Haraka on 12/14/2014, 06:03 pm; edited 2 times in total
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Haraka
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PostPosted: 08/06/2013, 10:42 am    Post subject: McMinnville Redux Reply with quote

 On  24th  March Larry was postulating linear pixel correlation as a possible methodology for finding suspension threads and asked :
 
Does anyone on the IPACO team have the knowledge, software, and/or ability to do this kind of analysis?  In my mind, this kind of analysis would be conclusive, one way or another.  If there is information about a vertical slender thread residing in the image, that would be definitive evidence of a small model

 
At that time such a capability was, in fact, one of those under testing within IPACO.  Using the McMinnville imagery as an example it was later demonstrated as  part of the Keynote address  at this year's international MUFON Conference in Las Vegas.
The probable existence of a suspension thread was indeed  shown by IPACO to be evident in the imagery.


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Haraka
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PostPosted: 12/02/2014, 02:45 pm    Post subject: The McMinnville case Reply with quote

The dust now having pretty much settled over the IPACO detection and analysis  of what is, conservatively , highly likely to be a suspension thread in one set of the McMinnville images, I have now put an Imagery Interpretation standpoint regarding these findings over on Geoff's Column on this site -  Back to McMinnville
  I have also put a small piece there on basic Radiometry, some  concepts of which were invoked by IPACO during the imagery analysis of the probable suspended small object .


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PostPosted: Today at 01:03 am    Post subject: The McMinnville case

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