I recently started taking a physics class at Northwestern (yes, I definitely feel pretentious, and the funny thing is that I didn't expect to) because it's a prerequisite for me to attend IIT this Fall. Apparently it's important for an architect to know something about physics...
I was walking home from class today, which by the way has been consuming my life (the class) as it starts at 7AM and goes till noon and the work outside of class is generally a few hours, and something occurred to me as I pondered my ineptitude when it comes to understanding friction - physics is just like economics. Yup, everything I study is just like everything else I study.
In economics there are these theories which predict very precisely how one event will effect another, and they're always very elegant and in some sense idealistic. Then there is reality, and in reality the number of variables truly acting upon any given economic event is generally mind numbingly large. So some kind of a sluff factor is often included in equations to account for hard to account for variables. This is where Chicago school economists need to ease up a bit and become less rigid in their dogma (maybe it's just my reaction to the times). It may be more efficient to let the market dictate, but in reality a few people always screw it up for everyone in that system.
In physics it's the same deal. Elegant, simple, beautiful equations explain about 90-95% of any single event that happens at a very earthly level (read: masses, velocities, and forces that are familiar to you). The moment you start talking about speed as it relates to the speed of light or mass as it relates to a star... more or less everything starts to break down. Then you hit the speed of light time stands still, you become mass-less, and turn into pure energy. The factors that screw up your answer vary, but again, on an earthly level they generally include some sort of air resistance or friction which are kind of ridiculously hard to factor into the final answer.
Lesson: When few variables with reasonable quantities are involved the products of these equations is quite knowable. Things get complex (and to some extent unknowable in the predictive sense as of the present) when they hit reality and specifically, very messy situations involving "large" quantities or variables. What I'm trying to say is that models and theories are nice and extremely helpful but sometimes you just have to build a model and put it in a wind tunnel. Physicists have nature as their final arbiter as my professor is fond of saying. On the other hand progress in economics will most likely be brought about by making huge mistakes. And according to one of my favorite economists (one of the authors of Freakonomics, Steven Levitt) economists are often tasked with solving arcane math equations because there's more incentive to do so.
Reassuring I know.