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delta3
13th Jun 2005, 08:55
During many passionate discussion in this forum, communication between participants was at the least difficult. Perhaps this is due to the fact that they were using different simplified rules of thumb in their reasoning.

In science one tries to start from 'universally' valid rules and build models on top of them. These models most of the time consists of coupled subsystems that influence each other in complex ways. Once in a while science discovers that the universality of the rules is questionned. For instance relativity questioned Euclidean models. Compressable flow versus incompressable models. But by adding reasanable restriction science was able to revalidate the rules and models, be it that this process took decades even centuries.

Once the models are build their behaviour can be checked in certain area's of operations or along certain scenario's. This is also part of the validation of the models versus the real world, and concerns variables that can be measured with the present technology. This may lead to a number of rules of thumb that are more easy to remember. These rules of thumb do not have the same universality as the underlying rules. Applying them inappropriately can lead to what we see in the discussions here.

On the other hand these rules of thumb are not only handy, but may be necessary to make things practical and manageable. We are for instance not using a thermodynamical onlime model to manange the engine inflight, but base decisions on some Temperature and pressuer gauges.

These rules of thumb may however not always be appropriate to base scientific reasoning on. So once in a while it may be necessary to take several steps backward, dig deeper and wider before coming up with explanations. This may take a person months or years.

This is my opinion on what (Nick's) myths are about : they should stimulate the digging and one should not expect to find immediate answers, certainly if starting off with rules of thumb.

Delta3

NickLappos
13th Jun 2005, 14:48
delta3,
Nice summary of the problem, but I would characterize the issue as less of "rule of thumb" and more of "described model" where a rule of thumb is a calculation simplification (6 knots per thousand for Vne, or 2 degrees per thousand for OAT lapse), and the model is like "what happens in VRS or IGE."

I am reminded of the scene in the movie "The Sand Pebbles" where Steve McQueen describes the ship's steam plant to an astute chinese engineer, using a dragon as the steam and saying the the main stop steam valve kills the dragon. The explanation model we chose is determined by the sophistication of the student and the communication barrier that exists (language, or technical background, for examples).

I do not advocate models that state pure mathematics (except as proof of the proposed model) because the math is not an intuitive model for most people. I also do not believe the use of incorrect physical explanations is advisable ("IGE goes OGE when the bubble is too far away", or "VRS involves rotor stall") because this is simply wrong, and potentially misleading.

I think the model we use should have reasonable correlation to the actual case. I am reminded of one of my favorite quotes, “If you can't make it clear, you don't understand it yourself.” A true master explains in a valid way, without confusing his student. Think of Einstein's classic book "On Relativity." I think we owe it to our students to understand the condition well enough to explain it without inventing new physics.

Dave_Jackson
13th Jun 2005, 19:03
To develop upon Nick's excellent 'Sand Pebbles story' about the relevance of levels of understanding,
the following is spewed out . :yuk:


The sciences are anchored in mathematics.
Mathematics is anchored in the concept of one. (unity).
Unity is a manmade construct.
Therefore the sciences are nothing more that a manmade means of communicating manmade realities.


All of the above is anchored in philosophy.
If all these anchors are weighing you down ~ consider taking up the following new belief system.

The Irrefutable Theocracy (TIT)

The theory of TIT;

TIT is based on the concept that the world of a newborn is its mother, and specifically her breast. When weaned, the infant searches for replacement beliefs. This is where religions and governments step in with their specific constructs of ideology and faith.

The commandments of TIT;

1/ There is no 'Meaning of Life'.
2/ There is no reason for any more commandments.


All IMHO :E

Now the helicopter should look very simple. :D

delta3
13th Jun 2005, 22:17
It got to be an elephant mistaking the Mount Everest for a breast

Delta3