Archive for December 2008
From the Moveable Type chuck-pearson.org blog, December 19, 2008.
I just had a brain-breaking moment.
I found a book on the shelf at the library today. The book was Quantum Generations, and it was written by Helge Kragh. I got terribly excited when I saw the book, because I had considered adopting it a couple of years back as one of the history texts for my Modern Physics class. I don’t teach a classic, calculus-based modern physics that’s a prep course for physics majors; the reason for this course to exist at Shorter is to give the students in secondary science education two extra credit hours to supplement the eight they get from the general physics sequence, so they have 10 credit hours in physics to get a secondary certification in a physics (to complement their primary certification in either biology or chemistry, and their inevitable secondary certification in the one they didn’t get the primary in. It’s a long story. See the Shorter catalog, page 82). And the class follows a trig-based physics, so I can’t fairly use calculus in there either; so I have to do some simple trig-based quantum and relativity and do a whole lot more conceptual stuff. Good history helps build that conceptual understanding, in my experience.
The introduction of Quantum Generations speaks very clearly of its intent:
The intended audience of the book is not primarily physicists or specialists in the history of science. It is my hope that it will appeal to a much broader readership and that it may serve as a textbook in courses of an interdisciplinary nature or in introductory courses in physics and history. With a few exceptions I have avoided equations, and although the book presupposes some knowledge of physics, it is written mainly on an elementary level.
It’s the phrase “the book presupposes some knowledge of physics” that was supposed to put me at ease selecting the book for PHY 2100, after all. We’ll get back to that later.
Start reading the text itself, and engaging in the history, and here’s what opens:
THE PHILOSOPHER and mathematician Alfred North Whitehead once referred to the last quarter of the nineteenth century as “an age of successful scientific orthodoxy, undisturbed by much thought beyond the conventions. . . .one of the dullest stages of thought since the time of the First Crusade” (Whitehead 1925, 148). It is still commonly believed that physics at the end of the century was a somewhat dull affair, building firmly and complacently on the deterministic and mechanical world view of Newton and his followers. Physicists, so we are told, were totally unprepared for the upheavals that took place in two stages: first, the unexpected discoveries of x-rays, the electron, and radioactivity; and then the real revolution, consisting of Planck’s discovery of the quantum of action in 1900 and Einstein’s relativity theory of 1905. According to this received view, not only did Newtonian mechanics reign supreme until it was shattered by the new theories, but the Victorian generation of physicists also naively believed that all things worth knowing were already known or soon would become known by following the route of existing physics. . .
Let me be clear up front: I’m not criticizing Kragh in the slightest, nor the history he’s constructing. His intent is to set the real stage for twentieth-century physics by expressing clearly that this is a measure of myth, and not every physicist believed as Albert Michelson did, that “most of the grand underlying principles have been firmly established and that further advances are to be sought chiefly in the rigorous application of these principles” – so that physics was a lot more ready for the early 1900’s revolutions than is commonly believed.
Okay, here’s question one: commonly believed by who?*
Go to your friendly neighborhood engineer, or your friendly neighborhood pharmacist, or your friendly neighborhood high school science teacher – I don’t care which of the above, but one of the people around you who is supposed to be reasonably science-literate. Ask them what they know about how the theories of quantum mechanics and relativity came to be.
Relativity they might be able to connect with Einstein; they might mention some of the thought experiments surrounding special relativity (the twin paradox is especially popular), maybe they know about time dilation and relativistic mass, maybe they know of the demonstration of general relativity’s accuracy that made Einstein the closest thing physics has ever had to a rock star. But why Einstein had to be demonstrated so comprehensively and strangely correct to turn him into that rock star, the central postulate surrounding the speed of light being the same in all inertial reference frames? Yeah, good luck with that.
And if they can tell you anything at all about quantum mechanics, it usually involves a roll of the eyes and a complaint about its difficulty.
Maybe I’m selling the people around you a little bit short, but I had to teach several of the same types, and I know how they generally approached the theory and the history behind the theory. It’s a curiosity. Nothing more, and nothing less.
So again I ask: commonly believed by who?
By people who care about physics. By people who have already heard the simple version of the history. By people who think knowing and understanding physics is important.
And it was that realization that led me to the brain-breaking.
When I first went through this textbook, I knew it wasn’t right for the modern physics course I taught, but I couldn’t put my finger on why – all I knew was, another book started with the story of Ernest Rutherford and Hans Geiger assigning Ernest Marsden the problem that immediately led to the discovery of the nucleus, and that was far, far more interesting. Now, on second pass, I get it – the book wasn’t right for the audience who would be enrolling in PHY 2100. I had to assume those students had never studied the development of modern physics ideas before, and that it would be sufficient to engage them in the history for the first time.
And again – back to the introduction. Quantum Generations was written for a general knowledge, not a class of physicists. It presupposed some knowledge of physics, but should be generally accessible. I should be able to assign that book to a group of students who has had an introductory physics sequence, then, right? Why did I have to resort to a lower level text?
Among most of the academic ranks, there has always been an assumption of a certain level of canon, a certain knowledge set we expect students to have when they walk through our doors for the first time. I honestly am not going to pretend like I know what that set is in other academic disciplines; I would certainly leave myself exposed as the poseur I am when I made my assessment of what a graduating high school senior “should” know in terms of American, British and world literature. I wouldn’t know that Steppenwolf was anything but a bad 70’s rock band were it not for quiz bowl.
But in the physical sciences, what goes into that canon? For example, you should know how to construct a molecular formula of a compound. You should know the basic thermodynamics – the difference between heat and work, the difference between enthalpy, entropy, and free energy. You should know the difference between velocity and acceleration. You should know the basic principles that lead to those quantum numbers that electrons carry in the atom. And you should know enough about relativity and cosmology to know that spacetime is curved, and the universe is expanding.
Anybody want to take a wild guess as to how many freshmen we see who actually do know all that?
I’ve been pretty good most of my career at packaging physics in an accessible way, mainly (I think) because I remember how much some of the topics in physics killed me as an undergrad and how bitterly I had to fight to get the explanations of those ideas right as a grad student and a novice professor. But the longer I’ve taught physical chemistry, and the more I’ve seriously considered the textbooks in the field from the perspectives of the students who actually have to take the class, the more I’m becoming convinced that too many of us – and from time to time, I fall into this trap – teach what we teach to the students we think we should have, not to the students we actually have. I can talk to as many teachers about as much curriculum as I want, and I can emphasize time and time again what I think should be down cold when the student walks out the door, but the student still learns in a world that thinks that physics is one of life’s least important things. I have a sales job to do to convince the student that it’s one of life’s most important things – or that it even takes a place in the top 100. Trying to find a way to package the ideas in a way that I can get core topics across, in a way that the whole room can understand, and do that sales job at the same time is a task (a whole set of tasks?) that I’ve had so much difficulty throughout my whole career finding help on, and a lot of the problem has been that I’ve had difficulty seeing that whatever I might have known walking through the door, I can’t fairly assume my students have seen any of it – or, even if they have seen it, I can’t assume that they remember it.
And again, we can blame the students for not taking the prerequisites seriously enough or not taking the necessary energy to get the additional information on their own, but that goes right back to teaching the students we think we should have. Knowing that new learning should build on old knowledge is not something that comes naturally to the modern undergraduate. They have to be convinced. Again, it’s the sales job.
We can’t expect that the whole student population is going to come to us and ask us what they have to do to be academically successful. We have to go to them. We have to go to them deliberately, and with understanding, and with the conviction that we’re about to show them the coolest stuff ever.
And once upon a time, to us, it was. And I don’t know about you, but in my case, it was because Dr. Moloney and Dr. Ditteon and Dr. McInerney and Dr. Bunch and Dr. Western opened it up to me. I received so much from them as their student; the least I could do for them is provide that same excitement to my own students.
*I’m half intentionally not saying whom there. I know this might rub some kind grammarians the wrong way, but this is what I normally say, and if you think closely enough, you might get my point.