by Mark Bukovich

Created on: February 07, 2009   Last Updated: February 09, 2009

The sight of a sixty thousand pound hunk of metal rising into the air and jetting off over the horizon is indeed inspiring, almost magical. It is even more impressive to see a giant Boeing 747 take off or land in a high crosswind strafing toward the runway almost sideways. But what allows these large heavy machines to seemingly defy gravity? It is an intriguing question and one that inspired the author to pursue a degree in Aerospace Engineering.

Reading through other articles on this topic from magazines and the Internet, one may still be left asking, "But how does it lift? What really gets these ponderous birds off of the ground?" There are many incorrect explanations and many poorly explained correct ones. There are also some explanations that try to hold a middle ground, trying to explain difficult concepts with clever, easy to take in interpretations of difficult concepts. These attempts usually fail in that they still do not explain what really happens in the phenomenon called "lift". These articles usually state it is an aerodynamic force created by a difference in pressure. This is correct, but what causes this difference in pressure? For that matter, what is pressure? This article will attempt to answer these questions in an easy to understand fashion.

First one must understand what air actually is. Other explanations often tend to give air some kind of mystical status that somehow pulls or pushes on a wing or creates artificial wind or even a "pocket of air" on which the wing can rest. In reality, air is simply gas, a bunch of molecules moving about randomly. That's it, nothing more and nothing less.

What then is pressure? Pressure is simply air molecules bouncing into an object. When someone blows air into a balloon, what stretches it out? It is the multitude of air molecules forced into the balloon that bounce against the inside. It may seem silly at first; a little air molecule bouncing against something could hardly produce any kind of force. But when thousands upon thousands of air molecules are striking a surface, the effect multiplies drastically. What then does a higher pressure mean? It means that more air molecules are striking a surface with more force.

What does this have to do with airplanes and wings? One more thing must be understood first. To illustrate the next important concept, imagine a pipe with air flowing through it. Now imagine that at a certain point, the pipe narrows. Does the air flow at the same speed in the narrow section

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