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[Phys-L] Re: Private Universe and the Seasons

Two comments

First, I think changing students belief systems takes more than getting
them interested. Sometimes it seems the new experience has to really
get their attention, almost wack them over the head, before they begin
to rethink. I support this by having students overtly discuss their
predictions and experiences with each other, working to come to
consensus before we have a whole class discussion.

Second, I have found ray diagrams less then obvious to students unless
you spend some time working with them in a simple context. I use
McDermott's...no relation??...material on projecting light through
holes to do this. We take ray diagrams as simple and straight (pardon
the pun) forward. My experience is that they are not to the
uninitiated.

cheers,

joe


On Aug 7, 2005, at 8:57 AM, R. McDermott wrote:

----- Original Message -----
From: "Bernard Cleyet" <anngeorg@PACBELL.NET>
To: <PHYS-L@LISTS.NAU.EDU>
Sent: Friday, August 05, 2005 4:44 PM
Subject: Re: Private Universe and the Seasons


I just received the DVD. On viewing I discovered I had a private
theory. The one on viewing one's image in a mirror. I'm 67 taught a
little at the HS and JC level (not optics tho.), demonstrated (TA'd)
much, and earned a Ph.D.. I wonder if they'll take it away from me.
But bernard is a rationalizer. How many of you shave a meter from the
mirror?


Here's another contradictory common effect. After failing the Private
Universe mirror test, I doubted my common sense theory on how to use a
mirror to check what's behind me. Oh, thank god (note the lower
case).
Yes the closer one is to the mirror the greater field of view.
Finally,
on this matter, how tall must a mirror be to just see one's whole
body?
This is a question I remember from ca. 1956 intro. Phys. I had to
check the answer I remembered.


My impression is the major point in "Minds of Our Own" is students
come
not "tabula rasa" *. Like paradigm shifts the incorrect must be
destroyed before the correct may be believed. I didn't catch if the
program suggested this, but it's obvious basic physics must begin very
early, and in an experiential way (This they did stress.) Here in
Salinas I don't think kids get Phys. 'till third grade; is not this
too
late?

* Do we blame Locke?

no shame cleyet, who also wonders what other private theories are
undiscovered.


p.s. I'm amazed by how I still hold on to my private theory. Perhaps,
if I draw ray diagrams, I'll lose it. The answer to the mirror height
question proves I did if once and I didn't integrate it.

I certainly agree that we all come into new situations carrying along
baggage from previous attempts to make sense of the observations we
have
made. What often happens, of course, is that people are simply very
poor
observers (without specific training) and form very poor or simplistic
explanations for what they observe. A compounding problem is
unconscious
reinforcement from poor instruction (diagrams that greatly distort the
eccentricity of the Earth's orbit around the Sun in many textbooks, for
example). The tenacity with which our students retain their
misconceptions
is mostly a function of lack of engagement (interest?), and our task
becomes
one of motivating them to really observe and think DEEPLY about what
the
data "says", as well as presenting situations/tools that allow
unambiguous
observation of the the concept(s) involved.

I appear to have missed the earlier messages (your private theory),
but a
set of ray diagrams would seem to be the most efficient way to
establish
"the closer observer, the greater the field of view at a specified
point/distance" concept as well as the minimum size mirror (and
positioning)
concept. Anything involving mirrors pretty much requires ray diagrams
for
understanding, but an entertaining lead in for students is the short
sequence in one of the Marx brothers' movies where they use a doorway
to
simulate a mirror. I have the clip, but can't remember the movie.


Joseph J. Bellina, Jr. Ph.D.
Professor of Physics
Saint Mary's College
Notre Dame, IN 46556