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On Aug 11, 2007, at 1:49 PM, Brian Whatcott wrote:_______________________________________________________
At 09:20 AM 8/11/2007, you wrote:
Antti Savinainen is certainly correct when he says, "it is 'new
science' to
many (if not most) high school and college level textbooks." . . . . .
In this regard I would like to congratulate Antti and his student
Mikko for
their contribution in helping spread the word about the correct
interpretation of this demonstration.
I seem to recall mention of the wire through ice demonstration
several times on PHYS-L in the last few years.
THIS thread is the very first I recall that mentions the
crucial observation of no motion in sub freezing environments.
This points helpfully to the wire conductivity model as a
preferred explanation. Strange that I don't recall mention of
that other crucial experiment before - the one that uses
nylon filament.
I read the paper of Mikko Valjus (see English part of the attached
file) with pleasure and admiration. I have one comments and one
suggestion.
Comment:
The sentence “The line was not fitted through Ag (extreme right)
because it seems to be a flawed result,” in the caption of Figure 4, is
not convincing, considering the error bars. There is nothing wrong with
not including the silver points but justification should have been
different. A disagreement with a model is not a good reason for
rejecting an experimental data point.
Suggestion:
Mikko and Antti should write a shorter paper, for example, for The
Physics Teacher, emphasizing the scientific method aspects of this old,
and well known, experiment. The scenario, to be created before writing,
could be as follows:
a) Read a description of the experiment, and its traditional
explanation, from a textbook.
b) Tell students that this explanation has be questioned, but do not
explain why.
c) Expecting enthusiastic “Yes,” I would ask students if they want to
see the experiment.
d) Perform the experiment in class. It is not necessary to wait till
the wire cuts through the block of ice; one or two cm would be
sufficient.
e) The fact is undeniable but is the explanation acceptable? What kind
of test can be performed to invalidate the explanation? You might guide
students toward the desirable answer, using a fishing road nylon
instead of copper, as suggested by Mikko.
f) Perform the experiment with the nylon filament (same diameter as
copper).
d) Discuss scientific methodology in the context of this experience.
If I were still teaching, I would try to create such scenario, and to
describe it in a short note for other teachers. Please share other
situations in which rejections of textbook explanations can easily be
demonstrated in a classroom.
_______________________________________________________
Ludwik Kowalski, a retired physicist
5 Horizon Road, apt. 2702, Fort Lee, NJ, 07024, USA
Also an amateur journalist at http://csam.montclair.edu/~kowalski/cf/
_______________________________________________
Forum for Physics Educators
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