Re: Demos, simulations, and activities for Modern Physics

[Maurice Barnhill <mvb@UDel.Edu>]

Leigh Palmer wrote:
> Dennis Krause asked:
>
> >        I would like to enlist the help of all those on this list for
> > suggestions on how to make the topics of modern physics more real to my
> > students.  What demonstrations, computer simulations, and/or other
> > activities have you found useful in illustrating (in a fun and stimulating
> > way!) the far-out concepts of relativity (special and general) and quantum
> > mechanics to non-science students?
>
> and he was rewarded with computer simulations. Will these really help any
> students (especially humanities students) appreciate the reality of the
> phenomena under discussion? I don't think they will; they certainly would
> not have convinced me.
First, I really like the list of real demos that I have editted out of
Leigh's post; I will attempt to use some of them when I teach my
nonscience majors course next spring.

Nonetheless, I think that there is a complementary role for computer
demonstrations.  Students have to understand our interpretations before
they can be convinced that they do or do not describe nature.  As an
example from classical physics, last night I held a help session for an
exam tomorrow in a calculus-level introductory course.  One of the
students was puzzled about circular motion, the usual "why am I pushed
outward?"  Now I had 1) Spun a cork on a string and shown that it went
straight when I let go "I know that the object goes straight when you
quit pushing on it, but ..."; 2) Talked about what causes the nerves in
our muscles to fire and give an impression of an outward force, and why;
3) worked several problems from stationary frames; 3) shown how a block
on top of a second block appears to fall backward when the lower block
is accelerated but really goes forward; 4) even got the entire class to
chant the direction of the force (they memorized the answer I wanted but
didn't believe it, of course); etc. ad nauseum. We are all used to this
phenomenon.

So last night I hauled the entire class to my office and showed them a
computer program which shows two things: First, the path of an
unaccelerated moving object on a merry-go-round as view from above in
the stationary and in the rotating frame; and second, the path followed
in the stationary frame by a object which is acted on only by a series
of hammer blows.  Bingo.  The picture of an object going around in an
essentially circular path made up of many short-line segments between
points where the object was kicked inward did the trick, for all of
them.  

Now granted, all the things I had done before had gotten them to the
point that they had two sets of discordant explanations, each of which
they thought ought to be true.  This condition is what is really needed
in order to make conceptual progress.  Also, there is no guarantee that
they won't have more problems with the concept when they get away from
my insistent and perhaps persuasive presence.  Moreover, I teach a small
class and have no way of testing whether using the computer program does
any good.  Still, visualization of what we are talking about, especially
of time-dependent processes, is a problem, and computer programs can
help.  We should make use of them.

Aside:  Does the program mentioned in this thread that shows a
diffraction pattern being built up in time by the appearance of
individual dots actually exist or should I write one?  I would love to
have that to follow up a (real) laser diffraction pattern when teaching
nonmajors.
-- 
Maurice Barnhill, mvb@udel.edu                
http://www.physics.udel.edu/~barnhill/          
Physics Dept., University of Delaware, Newark, DE 19716