Tuesday, January 09, 2007

Physics Classes

I'm finally taking my last two classes this quarter. After that, I will probably never take another, at least not for credit. I can barely imagine never having to do homework again; I've been a student for so long, my whole life. I observed a while ago that I didn't feel ready to be done, didn't feel like I knew as much as I expected to, with only two classes left. A certain older, wiser graduate student with the initial "K" reminded me that I was supposed to be learning something from the research, too.

Surprisingly enough, I seem to have become a little less cynical since I wrote that last post. Just because you can't learn everything in grad school doesn't mean you learn nothing. And I have gotten a lot from independent study and bull-sessions with my co-workers (especially the one I married. I think we figured out what it meant to quantize the electromagnetic field while driving across France on our honeymoon. This was not as quite romantic as it sounds -- we nearly always get frustrated with each other when we talk about physics. But then, we nearly always understand things better afterward.)

Anyway, my last two classes are relativity, which I have been waiting to take, and the second quarter of quantum field theory. I think people might be kind of interested in what classes like that are like. The topics sound so... Deep. Don't they? Is it a profound experience, learning this stuff? Am I gaining access to the secrets of the universe?

Well... No. Physics classes aren't really like that. I mean, take Newton's laws, right? Everyone learned at least a little about Newton's laws at some point, and learned about gravity. Now, if you take a step back, Newton's ideas really are profound. They're universal. With them we can comprehend the motion of the planets, or how far a flea can jump. The same pattern underlies both. They allow us to build devices so powerful they might as well be magic, and, in the limited sense, even to predict the future.

But when you were sitting in your high school physics class, did it feel like a mystical experience?

Everybody who finds out what I do for a living tells me they hated physics in high school, and guess what? So did I. There's so much notation to learn, so many simplistic and unlikely problems to solve. I felt as mindless as a programable calculator, memorizing equations and plugging in numbers and getting out other numbers. It was dry and difficult and mechanical. Worst of all, the more basic questions that I was actually interested in, such as "Why are these equations true? Where do they come from?" were actively discouraged. Newton didn't know why his equations were true. He was just guessing. He figured he saw a pattern underlying a lot of the dynamics of the natural world, and he tried to describe it. It turned out to be a good description. That is all.

Nowadays we have even more sophisticated descriptions, and we can show that if those equations are true, then Newton's follow. So in that sense, we can explain his equations. But then, we can't explain the newer ones. Why do things obey Schroedinger's equation? We don't know. It's just how they seem to behave. Don't ask. Shut up and calculate.

This pragmatic approach continues to the very highest levels of physics education. You can think about "why?" on your own time. In class, we will address questions we can actually answer. Such as "what is the probability that an electron on a collision course with another electron will fly off at a 45 degree angle?"

Just so you know, when you hear physicists pontificating about different interpretations, "many worlds" theories and so on, those are just their own opinions. You don't learn interpretations in class. They aren't speaking for scientists in general.

I'm guilty of it myself. When I write or talk about science, I try to make it sound more interesting by injecting my own private sense of wonder, my own interpretations and opinions. Like I did up there with Newton's laws. But the day-to-day practice and study of science, in the lab and in class, is much more boring.

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