RE: Gedankening

["Dewey Dykstra, Jr." <dykstrad@bsumail.idbsu.edu>]

> Dewey-
> 	Thanks for your comments.  I think that your discussion confuses
> the first and second laws.  The problem is to make a statement of the
> first law that is independent of the second.
> 					Jack

Jack, you're welcome.

It may be as you say, _after_ the laws have been worked out and thought
about, but in the particular avenue to the first law that I have watched
students work out, they generate the notion we call the first law _after_
they have noticed that what we call the second law is apparently the case
in their lab explorations.  The point is that my discussion describes how
_the students_ under these circumstances seem to first come to _actually_
decide for themselves that what _we_ call the first law could make sense.
In their terms, in the context of this particular approach, they are coming
up with an explanation for the maintenance of constant velocity that is
consistent with what they've just decided about what maintains constant
acceleration.

If you look at the chapter I refered to in the previous note you will see
how they do this (see Chapter 12 in (_Constructivism:  Theory, Perspectives
and Practice_, C. Fosnot (ed), Teacher's College Pr, 1996).  Another place
to look for a description of the sequencing in the course materials is the
Appendix to an article in Science Education 76(6): 615 - 652 (1992)*, but
it does not give much of the flavor of _how_ students work it out, found in
the book chapter.

I think that what both Joel and I are trying to say is that how one first
comes on to or develops or constructs an idea for oneself is not
necessarily how one ends up viewing that idea and its relationship to other
ideas, later, when all of the shifts and readjustments made possible by
that new idea are accomplished.

Gedanken experiments are, _among other things_, heuristics which can enable
one to come to new realizations, it seems.

Dewey
* This particular approach I first learned from Jim Minstrell.


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Dewey I. Dykstra, Jr.                   Phone: (208)385-3105
Professor of Physics                    Dept:  (208)385-3775
Department of Physics/MCF421/418        Fax: (208)385-4330
Boise State University                  dykstrad@bsumail.idbsu.edu
1910 University Drive                   Boise Highlanders
Boise, ID 83725-1570                       novice piper

"Physical concepts are the free creations of the human mind and
are not, however it may seem, uniquely determined by the external
world."--A. Einstein in The Evolution of Physics with L. Infeld,
1938
"Don't mistake your watermelon for the universe."  --K. Amdahl in
There Are No Electrons, 1991.
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