Yesterday’s post about differences between intro physics and chemistry sparked an interesting discussion in comments that I didn’t have time to participate in. Sigh. Anyway, a question that came up in there was why we have physicists teach intro physics courses that are primarily designed to serve other departments.
It’s a good question, and in my more cynical moments, I sort of suspect it’s because engineering faculty are canny enough to outsource the weeding-out of the students who can’t hack it in engineering. But I think there are good reasons, particularly at a liberal arts school like Union, to have intro physics taught by physicists, because there’s a fundamental difference between the way physicists approach things and the way other scientists and engineers approach them. As I said not that long ago, physics is about rules, not facts. The goal of physics is to come up with the simplest possible universal rules to describe the behavior of the universe, through breaking everything down to the most basic case imaginable. Once you’ve got those rules, then you build back up to more complex cases.
Completely coincidentally, I had a meeting yesterday with one of my advisees, who has recently been taking a couple of chemistry courses to fulfill our graduation requirement that students take two science courses outside the physics major. I asked him how that was going, and he said he’s found it intensely frustrating, because their treatment of the systems they’re studying stops at a higher level of abstraction than he would like. “I keep asking ‘Yes, but why does that happen?’ I think I’m annoying the other students and the professors.”
This neatly mirrors a story a colleague told some years back about how he wound up in physics after going to college planning to major in chemistry. He said he kept asking the same sort of questions– “Yes, but why do p shells contain six electrons?” Eventually, he got to the class that was supposed to explain everything, which started by just writing the Schrödinger equation on the blackboard, and declaring that its solutions provided the explanation for everything. At which point he asked “Yes, but where the hell does that equation come from?” and ended up taking physics in an effort to find out. Ironically, most physics classes don’t do much to explain where the Schrödinger equation comes from, either– I remember my undergrad quantum prof spending some time making analogies to wave and diffusion equations, but nothing approaching a derivation. He found the general approach much more congenial, though, and switched career paths as a result.
I’m not relating these simply to take Rutherfordian shots at the stamp-collecting sciences, but because I think there really is a difference in the approach, and that approach can be valuable to see. Physics is more fundamentally reductionist than most other sciences, and much more likely to abstract away inconvenient details in search of universal rules. This can make physics as frustrating for students from other fields as chemistry is for some physics students– I got a student evaluation comment a few years back complaining that we “approximated away all the interesting stuff, like friction and air resistance.” Which struck me as funny, because in my world, friction and air resistance aren’t interesting– they’re mathematically messy and inelegant, and obscure the universal rules that are the real point of physics. But for somebody who wants to be the right sort of engineer, those are the interesting points.
Some time ago, I read something about science communication where a researcher mentioned the “five-year-old game.” The claim was that most people, even Ph.D. scientists can easily be reduced to sputtering incoherence if you ask them to explain something and then keep asking “Why?” like a five-year-old. In some sense, then, physics students like my frustrated advisee or my ex-chemist colleague are eternally five years old, always asking “Why does that happen?” to the increasing annoyance of people who are more inclined to stop with a slightly higher level of approximation in order to accomplish some particular useful task.
I think it’s useful, in a cultural sense if nothing else, for students to see both sides of that process. The engineers and chemists ought to understand the physics approach of getting to the basic, universal rules that underlie everything, and the physicists ought to get a little experience working with non-ideal cases. And the ones who find even physics too messy and approximate can go on to become math majors…