Eugene
Mishchenko
Teaching
Philosophy (Physics)
First, I want to stress that what is
written here is meant to apply specifically to teaching physics majors, rather
than those majoring in chemistry, biology or engineering, much less so to teaching
physics as part of a liberal arts curriculum. This is not to say that I believe
the stated philosophy is not relevant or would be totally wrong in those other
instances, but simply that I have a rather narrow objective here.
It is my view that the importance of the
classic lecture format for education of professional physicists should not be
underestimated. Short of individual or small-group instruction the lecture is
the most viable means of communicating the most important element of learning –
how to think like a physicist. This
includes knowledge of how to approach the problem in an efficient way, how to
assess the correctness of the answer by analyzing it in various limits, and the
ability to grasp its implications including doing so in the context of other related
phenomena, and many other things. Such know-how is not easily transferrable via
a concise textbook. I have used peer-instruction and group discussions more or
less effectively over the course of my 9-year career as a university physics
teacher, but I would not be willing to promote them beyond a supplementary role
in the classroom. No one could probably argue that reading a medical textbook
and then discussing with your fellow students how to treat a patient under an
occasional supervising eye of the instructor is the proper way of becoming a
physician. Physics might be different in some respects but not dramatically so.
Watching an experienced practitioner performing the process of thinking and
applying his knowledge in a particular situation is as important in studying
physics as it is in learning medicine or mastering wood-carving. Furthermore,
expertise in physics comes no earlier than the student develops intuitive
understanding of complicated concepts, or, as Dirac formulated it, the ability to
predict the properties of solutions of equations
without actually solving them. Developing such intuition is a long process
impossible without systematic exposure of students to qualitative ways of
analyzing physical situations, such as evaluating characteristic scales,
applying dimension analysis, developing an ability to sort different factors by
their relative importance, and finally, making a bold simplifying assumption
only later to be confirmed (or not!) by the solution of the simplified problem
itself. Such “secrets of the trade” are notoriously difficult to communicate in
a textbook, and rare (even otherwise excellent) textbooks seriously attempt
doing so.
Hold on, but are not
students retaining very little from passive listening, while learning much more
by actively doing something? This argument is usually made to promote various
forms of group discussions in place of a traditional lecture. Well, in my
argument for lecturing I do not presume that the classroom time is the only (or
even major) time students work on the material. Quite
the opposite, a lecture was never supposed to be but a small part of the total
studying time. If that practice is not followed the outcome will be a disaster
no matter what exactly the classroom time is spent upon -- passive lecturing
with no meaningful hands-on practice, or active “doing” after a superficial
reading of the textbook prior to the class. I suspect that the perceived
“failure” of the lecture might simply be related to the contemporary
unwillingness on the part of us instructors to insist on the same commitment
from students as used to be the standard in the past. Let us not forget that
the lecture-based education somehow coexisted with the remarkable scientific
and technological progress for centuries, and who knows, could have been not
completely unrelated to it.
Occasional peer
instruction is a great way of enlivening a difficult lecture but I would not
fathom using this medicine too much. One should be cautious of some side
effects. While it is true that below average students are uniformly helped by
peer instruction, its benefits for top students are questionable. Such students
certainly acquire deeper and clearer understanding of the concepts when they
explain those concepts to their lagging peers, but when they are forced to do
so very often the law of diminishing returns quickly sets in. Beyond some
threshold the time spent instructing peers is the time taken away from learning
more advanced things. In my view the reliance on peer instruction is not the
right way to train future professional scientists. Also some of the best
students often (and correctly) feel that group discussions saddle them
with the job the instructor himself is supposed to be doing instead.
Finally, even if it might look like a minor
technical issue, I hold strongly that the instructor should refrain completely
from using notes during a lecture whenever technically possible. One thing, as
aptly pointed by David Griffiths in his Millikan prize
acceptance talk, is that reliance of the instructor on the notes breaks
that very delicate intellectual trust between the audience and the teacher. The
other point might appear counterintuitive. A good lecture does not necessarily
equate to a great delivery. Sleek artistic performance often creates an
illusion of simplicity which does not serve students well. This is not to say
that the lecture must be boring or lousy, but simply that you should not fear
embarrassment. There is hardly anything more instructive to a motivated student
than seeing her teacher facing a difficult situation, and observing his thought
process while (hopefully) successfully resolving the problem. Not having the
notes to distract you also makes it easier to pay more attention to the
audience and to remain more susceptible to its reactions. It keeps your mind
sharper and conditions you better for unexpected questions. If you have never
ventured into your classroom without notes, the idea of leaving them on your
desk could be as unsettling as riding a two-wheeled bicycle for the first time,
but the impact of your teaching can
only improve as a result.
04/14/2013