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Re: [Phys-l] "Flow"



Where is the boundary between imaginary and real? It it between something
you can see and something you can't see. If so, blind people are actually
dealing with imaginary concepts all the time because they can see nothing.

Real is in the mind of the beholder. If you look at most of the concepts in
physics they are quantities that you can not directly see or what Lawson has
called theoretical concepts. He has also shown that only theoretical
thinkers can easily deal with such concepts. Only a small fraction of
college students get to this level of thinking, and practically no HS
students get there.

Reification or using concrete examples is an important way of dealing with
concepts when you are not at this level. Indeed it may actually be the way
that all people deal with such concepts either at the conscious or
unconscious level.

The proof of this idea is that making students do drawings such as free body
diagrams helps them to form a mental picture of forces that can aid them in
doing problems. The bar charts (invented by VanHeuvelin?) can be used along
with the idea that energy is transferred to help students understand what is
happening in energy conservation.

The real problem comes in when students do not understand conservation
reasoning. Then they will produce random bar heights and will not
understand how to translate the bar chart into math.

There are theories of learning that propose that all of the ideas you use as
you progress in an advanced subject are actually present when you start.
You just refine and modify how you use them. In other words the concept of
transfer could be a primitive that you build the later model for
conservation of quantities. The theory also proposes that many mistakes are
misapplications of existing ideas. An example here is that energy in sound
is conserved and adds up, but decibels do not.

I think that reification is an absolutely necessary step on the way to
understanding, but it can be discarded later as the person becomes more
experienced. Also once you get to a certain level you usually forget what
it was like to be at the previous level. This is quite evident when a
formal operational thinker says that 9 year olds are illogical. I have
heard this statement and had to challenge it. The teenager who said it had
already forgotten how she thought when she was 9.

John M. Clement
Houston, TX


/// what's wrong with
talking about the components of a model as if the components were real?
Energy is a concept... so what? If the model (in which the concept of
energy is used) describes energy as flowing, and if the model has proven
and is proving useful, then so what?
///
Michael D. Edmiston, Ph.D.

For some people, worthy, people, there are concepts they know to be real,
and what is real need not be reified - it is already real:
but other concepts are imaginary, so reifying them is making some
imaginary thing out to be real.
( ??)

:-)