“I would never teach the Bohr model!” he exclaimed. “I don't believe in teaching things that are just wrong.” He was a respected teacher, and I knew I should listen to what he had to say, but in the end I wasn't convinced that his view was right for me and my classes.

In fact, I do believe in teaching things that are “just wrong”—selectively. For example, I like my introductory physicsstudents to learn the planetary model of Hydrogen, and not only so that we can discuss why it is deficient. It's a great opportunity to “spiral back”1 to Newton's second law, circular motion, conservation of energy, and the origin of electromagnetic radiation—and it does get the ionization energy right if you assume an empirically determined radius for the atom! In addition, knowing specifically when,why, and how a model is wrong is one of the hallmarks that distinguishes science from other endeavors. Furthermore, one might argue that there really are no perfect models (models that successfully incorporate gravitational and quantum effects in one philosophically cohesive whole, for example), so every model is “just wrong” in some sense. Finally, even if there was a “perfect” model of the atom to teach, it does not follow that good pedagogy involves teaching it. Let me explain.

Topics
Quantum effects, Energy conservation, Electromagnetic radiation, General physics, Newtonian mechanics, Atomic structure, Photon scattering, Ions and properties, Educational aids, Teaching
1.
Arnold
Arons
,
Teaching Introductory Physics
(
Wiley
,
1997
) is where I learned about the value of“spiraling back”—it's a must read for any physics teacher, in my view.
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2.
My friend and fellow physicist Jerry Bailey and I used to speculate on whether the phrase “full-scale map” might qualify as the shortest joke in the world,and it still strikes me as funny.
3.
This is a paraphrase of Richard Feynman's assertion in his Feynman Lectures on Physics, Chapter 1; Feynman also expresses this tension between the perfect and the useful (but imperfect) much more eloquently earlier in the same chapter.
4.
There is a puzzle lurking within the cover image. One pair of spheres apparently has greater average density than the others. Which pair?
© 2013 American Association of Physics Teachers.
2013
American Association of Physics Teachers
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