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On Models

Metaphors, Models & Theories

When I was in grade school we used to build model airplanes out of kits. The frame was made out precut pieces of balsa wood, each having been carefully pinned according to the plans along a preprinted arc to obtain the appropriate curvature, and then cemented, piece to piece, with airplane glue. The fuselage was made out of tissue paper, first glued to the balsa frame, trimmed, then dampened with water to shrink it taut, and finally, when dry, lacquered and painted to make it stiff and realistic. The engine was merely a long rubber band that ran the internal length of the fuselage, from propeller block at the nose to tail, wound up by rotating the propeller many times and then let loose to unwind for a flight of perhaps ten seconds at best. If you were a really ambitious model builder you followed the instructions very carefully: you were supposed to sand off any excess glue on the frame so as leave no imperfections at all.

What was model” about the model airplane? The Zippy in the kit I remember building was smaller than a real Zippy (I presume there was somewhere in the world of real airplanes an actual Zippy); it was lighter; it was made out of totally different materials. But it did capture two essential features of the putatively real Zippy: appearance and flight. The model looked a lot like a ‘plane, and it could (briefly) fly.

Nevertheless, the model wasn’t the Zippy. It wasn’t the thing in itself. It was a model Zippy. It lacked seats, ailerons, proper windows, and doors among many other real-life details, and focused on only a few important features. What features are important depends on the model user. In my case, aged about ten, appearance and flight sufficed. At age three or four, crudely shaped wings, a body and a throaty airplane engine noise might have been enough. A few years older and I would have wanted a combustion engine and radio control. But, however complex, none of these model Zippys would have been a Zippy.

What constrains the construction of a model Zippy?

First, the user and his needs. What aspects of the actual complex airplane and its surroundings is the user most interested in emulating, testing, playing or tinkering with? An engineer needs a different model than a child does. Second, engineering and construction: how to put together the model reliably and effectively, with as much accuracy in the key features as possible. Third, science: deep down below, even though the Wright Brothers probably didn’t know the partial differential equations of fluid flow, the possibility of heavier-than-air flight is built upon the science of mechanics and aerodynamics, on Newton’s laws and the Navier-Stokes equations.

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Published in Finance Models