Bravo! to Mano Singham for his thoughtful Opinion piece. The course in
modern physics--the third part of the traditional first-year
calculus-based physics curriculum--is a very different creature from
either of the other two parts. Physics was once called natural philosophy,
but what seems "natural" in the first two physics courses is often torn
asunder in the third.

We have few intuitions or personal experiences that directly bear on the
problems of Albert Einstein, Erwin Schrodinger, Louis de Broglie, Arthur
Compton, Enrico Fermi, and others. How do we go up against what other
people believe, when we are asking them to believe modern physics
principles based on our historical claims that the theories work and that
the experiments suggest confirmation? The laboratory is an important part
of the modern physics course, especially as it differs so much from other
first-year lab exercises. But one still does not "find" the ratio of the
electron charge to its mass any more than a mechanics lab "proves"
Newton's second law.

Larry Oppliger at Western Michigan University has spent some time trying
to come up with a simple, tabletop experiment for, say, a third-grade
elementary classroom, to show both students and their non-physics-trained
teacher that atoms exist. Of my students who profess problems with
cosmology or evolution, none seems to have any problem with chemistry. The
stoichiometry of balanced chemical reactions, the limited number of
elements, and the presence of the periodic table all require or at least
suggest the atom. But where did our personal knowledge that atoms exist
come from?

I bring up these issues of how and why we know what is true on the first
day of the modern physics course. For example, certain students might want
to know how they can reconcile the Big Bang theory with a fundamentalist
religious upbringing. If this theory is "wrong," is all of modern physics
"wrong" too? But cosmology is simply the result of applying what we know
of physics to the description of a free-running, self-assembling system
without outside interference. In any first- semester mechanics problem, we
are always free to reset time to zero when we specify the initial
conditions--even while the equations continue to describe behavior for
times before the problem starts and for times beyond the end of the
problem, no matter where the actual object is or what it is doing. Without
arguing whether a literal reading of "creating the heavens and the earth
in seven days" means the same thing today as it did when it was written,
it is possible to have an individual belief of where the ultimate time
zero occurs, with its own set of initial conditions, and still achieve
some practical understanding from the results of modern physics. The 21st
century will still be a world of semiconductors, nuclear reactions, giant
particle accelerators, coherent phenomena, and wave­particle duality; our
students need to have some understanding and appreciation of these things,
even if most are not going to become physicists.

It is easy to say that we physics teachers do not teach "belief" because
we are teaching science. It is not so clear-cut to the students--and
sometimes to those of us teaching. And at the end of the day, like
Singham, I am grateful to those who have spent the time to think about
what they are being asked to think about, no matter their personal
conclusions.

Philip E. Kaldon
Western Michigan University
Kalamazoo

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