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

[rmcder at PEOPLEPC.COM (R. McDermott)]

----- 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.