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Uh-Oh.

Bernouilli's principle states, or rather observes, that the pressure 
in a moving fluid is lower than the pressure in a standing 
fluid.  This is hard to believe at first glance, but I use the 
analogy of cars on a freeway:  when they are moving fast, the 
distance between them is larger (low pressure), when they are in a 
traffic jam, the "car-fluid pressure" is high.

So much to Bernouilli.

The only ONLY way to get anything to fly is by making the air 
pressure below the object higher than the air pressure above the 
object.  It has nothing to do with wing SHAPE -- the wing shape can 
help make flying more efficient, but it is not decisive in whether a 
thing will fly.  Check out some pieces of trash one day on a windy day.

So:  you set up a pressure differential above and below a plane 
wing.  You do this by moving the plane through the air at very high 
speeds so that the air gets shoved up under the forward part of the 
wing.  The wing blocks (part of) the air from flowing behind 
it:  So  you have high pressure below and low pressure behind.


SO.... it turns out (it is a CONSEQUENCE, not a cause!!!) that the 
air particles below the wing are slower than the air particles above the wing.


Still don't believe this?:  a terrible, common "explanation" of 
flight  is that because the wing is shaped the way it is, the air 
above the wing has a longer distance to travel than the air below the 
wing.  So it moves faster to keep up.

WHAT????  How does air know how far it has to go?  And ... why does 
it need to keep up with the other air????

Bernouilli is OK, but it doesn't make planes fly.  Flying planes make 
Bernouilli.



But what do I know?  I'm just a chemist.

Natasha

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