I’m back, after two weeks of teaching non-experts in a short course covering particle physics, the Higgs field, and the discovery of the Higgs particle. (The last third of the course, on the politics and funding of particle physics and science more broadly, is wisely being taught by a more disinterested party, an economist with some undergraduate physics background.) And I’ve been reminded: One of the great joys (and great secrets) of teaching is that the teacher always learns more than the students do.
At least, this is generally true for a new class that the teacher hasn’t taught before. In many university physics departments, and elsewhere, there is an informal requirement that professors teach a class no more than three years in a row. [Let us ignore for the moment that all of this will be overturned in the coming years by the on-line revolution; we can discuss the possible consequences later.] After the third year, they are expected to switch and teach something else. Now you might think that the benefits of the division of labor would suggest a different approach; after all, shouldn’t each professor perfect a course, become the expert, and teach it year in, year out? This usually doesn’t work (though there are exceptions) because each professor’s interaction with a new course has a natural life cycle.
The first time a professor teaches a course, he or she has to review material learned long ago, and sometimes learn it anew. You might think this is only difficult for advanced classes, but that’s not the case. Advanced classes can indeed be difficult to teach because the material is intrinsically complex. But beginning classes are also difficult to teach because the material, while less complex, is just as complex for the students, and meanwhile the teacher has to remember how to think like a beginner, which is an experience long forgotten. If you can’t put yourself into your students’ heads, you can’t teach them very effectively… and this is extremely challenging.
Typically, this initial year of a course is quite exhausting, with the professor spending many more hours in preparation than in class. (I personally found it typical to spend 3 to 5 hours of preparation for each hour in front of students.) But the benefits are also considerable. I have often found myself learning several different ways of explaining a concept — my students only get to learn one, because that’s all the time we have, but I learn them all. And along the way I’ve often discovered links between disparate concepts that I hadn’t previously realized were related, or filled in a surprising gap in my understanding, or learned an application of a concept to a real-world phenomenon that I hadn’t previously known about. Often my students don’t get the immediate benefit because what I’ve learned is beyond the scope of the course. So they struggle to learn some fraction of what I teach them, which is typically much less than what I’ve learned myself.
Year two in the life cycle is the opportunity to fix everything that went wrong in year one, and it is usually the best year. I have usually found myself completely rewriting the first year’s notes, streamlining them, re-ordering them, and improving everything from the overall course structure to the details of how I explain certain subtle points. And I find I still learn quite a bit in the process, particularly about little loose ends that I didn’t have time to tie up during the frantic class preparations of the previous go-round.
But by year three, the whole thing is becoming routine. There isn’t much left for the professor to learn about the class material, and the struggle to master the content and perfect the presentation is no longer so severe. Sure, there’s always more that can be done to help the students deal with the technical material more effectively, but diminishing returns are setting in; any particularly creative ideas for how to convey the most problematic concepts have probably already appeared. So year three is not quite at the point of boredom… but beware year four. And you do not want to be taught anything by a bored professor.
And so the professor is sent on to begin the cycle anew, to re-learn another subject, and to struggle to find the words and means to explain it clearly.
Two years ago, when I first wrote the Higgs FAQ (here’s the old 1.0 version and the new 2.0 version) I didn’t do a very complete or satisfying job of explaining the most important conceptual issues in particle physics: what are particles and what are fields? One really can’t understand modern physics, and the current notion of what ordinary matter actually is, what forces are, what mass is, etc., without these basic concepts. I promised a full article on the matter, but didn’t really deliver. I had done something brief in the my Secret Science Club presentation, but I didn’t feel it was as good as I wanted.
Then a bit under a year ago, having learned a great deal from writing articles for this site, from encountering and attempting to answer readers’ questions, and from preparing and delivering a number of public lectures on the search for the Higgs particle, I wrote a set of articles entitled “Fields and Their Particles (with math)” and “How the Higgs Field Works (with math)“, which boiled the issues down to the point that they could be understood by a first-year undergraduate college physics student. At the time, I promised a set of articles without the math, yet found myself unable to find the right strategy to do it. In particular, I did not want to make compromises that would require me to lie. Sure, some amount of compromise is necessary when explaining a difficult concept to someone who’s never seen anything like it. But that shouldn’t go as far as telling someone something they will later have to un-learn, or that will confuse them because it is actually false. (For instance: saying “the Higgs field is like molasses; it gives mass to things by slowing them down” is a lie. [As one of my students pointed out last week, you'll find this lie right at the top of http://simple.wikipedia.org/wiki/Higgs_field.] Molasses exerts drag, like air resistance; the Higgs field’s effect is obviously not a form of drag, because it affects stationary objects as well as moving ones.)
I believe I finally found a workable strategy while preparing a one-hour public lecture this March, and in preparing my recent course, which I described to the students as “non-technical” (i.e. no use of math except very simple and conceptual equations, such as E = m c² and E = h f) “but sophisticated” (i.e., you can’t tell the truth and yet make everything as simple and effortless as breathing). In four 9o-minute lectures, I managed to describe the known particles and forces, explain how both arise from fields (which are the fundamental ingredients of nature), clarify what particles really are and what a particle’s mass really means, and finally, explain how the Higgs field gives mass to particles; then it wasn’t that hard to explain how the Higgs particle was discovered and how that discovery convinces us the Higgs field really exists. And I don’t believe I lied once, though I should check that…
As usual, my students’ questions taught me a lot about all of the issues I’d forgotten to explain, and about little loose ends in my presentation that I hadn’t tied off. Though they may not realize it, I owe them a big thank you! Because now, given what I learned from preparing and teaching the course, I think I can finally begin planning the promised set of articles: “Fields and Their Particles (without math)”, to be followed by “How the Higgs Field Works (without math)”.
And meanwhile I hope I’ll get to teach that course again soon — since the second time around is when you fix what you messed up the first time…