Uncertain Principles

Today's note: Opposable thumbs are really remarkably useful. This is the sort of thing you don't really appreciate until you get whacked during a lunchtime basketball game, and sprain your right thumb.

This, on a day when I need to send a whole slew of emails out to students. Thank God I don't touch-type...

Posted at 3:48 PM | link | follow-ups | 3 comments

It's been a thooroughly hellish week here, and while I meant to follow up the surprisingly popular post on introductory physics pedagogy with another post on "Physics for Poets" type classes, events have conspired to keep me from blogging this week. And I'm a little too tired for Deep Thoughts right at the moment, so here's some fluff.

This is a mix tape I made back in 1993, when I first moved to the DC area, and started working at NIST. Since the "guess the lyrics" thing was fairly entertaining last time out, we'll do that again. A couple of these are absolute meatballs, despite my best efforts to pick a fairly obscure line. All of them can be found by Googling, but that would be cheating...

• 1) "You never understood that it ain't no good, you shouldn't let other people get your kicks for you."
• 2) "If I don't meet you no more in this world, I'll see you in the next one, don't be late."
• 3) "I have come to save the day, and I won't leave until I'm done."
• 4) "I ain't tellin' you a secret, I ain't tellin' you goodbye."
• 5) "And the time flies by, like a vulture in the sky."
• 6) "Run around until mornin' and we'll stay awake all night."
• 7) "My grandfather went down, with the Monte Video."
• 8) "Baby's got some new rules, baby said she's had it with me."
• 9) "Jesus rides beside me, he never buys any smokes."
• 10) "Well I'm on your trail, sussed your M.O."
• 11) "You knifed me in my dirty, filthy basement."

• 12) "She had a west coast strut that was sweet as molasses."
• 13) "Your whole life is a fantasy, and I'm playing the clown."
• 14) "There is so much to astound me, as the whirlpool spins around me."
• 15) "I wish I could swim, like the dolphins, like dolphins can swim."
• 16) "Hong Kong is up for grabs, London is full of Arabs."
• 17) "She just wanted him to love her, but he didn't."
• 18) "Nothing attracts a crowd, like a crowd."
• 19) "I get all my secrets back, it's quite a shock."
• 20) "Going where nobody says hello, they don't talk to anybody they don't know."
• 21) "If he was from Mars, wouldn't that be cool?"
• 22) "I would gladly give up musical genius."
• 23) "I've slept in your treehouse, my middle name is Earl."

Posted at 9:17 PM | link | follow-ups | 13 comments

I'm teaching the second term of our introductory sequence for science and engineering majors for the first time this term. It's mostly a class on electricity and magnetism, but we added a few weeks' worth of "modern physics" topics at the beginning of the term, in order to get some more interesting material in there.

As with every other class I've taught (see, for example, this old post), I'm gradually coming to loathe the textbook. It's not a book that was chosen for any really compelling reason-- basically, it just had all the material we were trying to cover in the intro classes, at roughly the right level-- and I'm beginning to think it was a bad choice. Not that I'm any happier with most of the other introductory calculus-based physics books out there.

The problem I have with the book isn't just a matter of not liking its coverage of certain topics (though I think it's really bad in some areas), but rather a disagreement with the entire approach to teaching physics that it's using. It's a book about physics, all right, but at its core, it's not really a physics book.

To unpack that a little bit, my problem with it is really that it doesn't approach the material in the way that a physicist would. It's very much a classic intro text, however much it's been tarted up with nifty little pedagogical features: it's set up so that someone at a semester school can mechanically grind through a chapter a week, and it proceeds by the time-honored process of introducing new topics by just presenting the relevant formulae to be memorized, and working a few example problems. While this may be an effective method of teaching students to work problems like those done in the examples (and it's the preferred approach of the engineers in the class), it's not especially effective at teaching the actual concepts of physics, as dozens of studies have shown over the years. Beyond that, though, it's pretty much the antithesis of what the actual practice of physics is like.

The great glory of physics, as I see it, lies in the way it reaches down to the simplest and most fundamental principles governing the behavior of the universe, and builds up from there to explain complex systems. For example, you start with the idea that electric charges experience a force when placed in an electric field, look at how that translates to the motion of electrons in a conductor, and from that you very naturally arrive at both Ohm's Law (relating voltage, current, and electrical resistance) and some important facts about the origin and behavior of electrical resistance. That's a physics approach to the problem of current flow, and it's what you'll find in the best new introductory texts (the version I used in class was adapted from Thomas Moore's Six Ideas That Shaped Physics. Insert your own Utopia joke).

The book we're using turns this all around. The relevant chapter opens with the definition of electric current, then Ohm's Law, and only after all the formulae and example problems does it present the full microscopic picture, which is split off into its own subsection, to make it easier for students to skip it entirely when reading the book. What ought to be one of the main points of the chapter-- that Ohm's Law is a natural result of simple interactions between charged particles-- gets turned into little more than a footnote.

What's wrong with this? First and foremost, it creates a wrong impression of what physics is about. It gives students the idea that physics is intrinsically boring, and based entirely on the memorization and manipulation of equations that are only tenuously connected. This helps contribute to the popular fear of physics that makes people flinch when I tell them what I do for a living. "I hated that in college," they say. Well, yeah. I'd hate that sort of class, too.

When it comes to considering changing our approach, one big problem is that introductory physics is basically a service course-- very few of the students will go on to take more physics. They're mostly engineers, and they're happier with a class in which they have clearly defined formulae to memorize, so why not just give them what they want?

Philosophically, I object to this on the grounds that this runs counter to the mission of a liberal arts college. The whole reason we're here is because we want students to be exposed to lots of different ways of looking at the world. We make all of our students take some science classes, some literature classes, and some history classes because we feel that it's important for them to have some breadth of intellectual experience. In that light, part of the purpose of introductory physics is to expose students to the ways that physicists look at the world. That's why it's taught in the physics department, after all-- if the only purpose is to convey relevant formulae to freshman engineers, then the engineering division should teach their own physics classes, and I'll go work somewhere else. We should be teaching students how to think like a physicist, and that's not what we're doing when we focus exclusively on the rote manipulation of equations. If we pitch the class directly at the average engineer, we're presenting physics as nothing but engineering with dimmer employment prospects, rather than a vital discipline in its own right, with its own way of looking at the world.

Of course, I'm not emperor of the world (yet)-- I'm not even tenured-- so I don't get to arrange things to suit myself. I'm fairly tightly constrained in what I can do with my sections of the intro class, because I need to keep pace with the other sections. But I find more and more that when I go into the classroom, I'm giving what are basically Six Ideas lectures, with the notation changed to agree with the textbook we're actually using.

Posted at 7:41 PM | link | follow-ups | 33 comments