In aerodynamics, the boundary layer is the layer of air just above the wing. The air that is in contact with the wing, counter-intuitively enough, remains pretty much immobile during flight; which means dust on the wing would not be swept away. The next layer up of air molecules has some velocity; the next layer up yet more velocity; and so forth, until the air molecules are far enough from the wing that they are not disrupted by the passage of the aircraft, and move backwards (in relative motion) at the air speed of the aircraft (in which case they are said to be part of the free air stream). While not trivial to describe, and governed by atrocious equations, the boundary layer is, in essence, a fairly straightforward concept best described by the diagram below (the length of the arrows indicates the speed of the air above the wing; the close the air is to the wing, the slower).
Why bring up the marginally arcane concept of boundary layer on this blog? I had a frustrating discussion recently with someone who was unable to grasp simple logic, and who kept bringing up circular and irrelevant arguments. That person happened to be a flight instructor… And I connected dots. Hence my theory:
In the absence of outside constraints, people tend to organize into social layers of comparable intellectual capabilities.
In other words, the friction resulting from interactions between people of significantly uneven intellect (dumb people confused by smarter people, and smart people feeling impatient dealing with dumber people) provides a social disincentive that leads to a natural-forming IQ strata (or whatever other yardstick measures one’s ability to deal with abstraction, logic, etc.). My evidence is only personal and empirical, and I might be stating the obvious here, so I look forward to see what my dear readers think about this.