Re: [Phys-l] Wire through ice experiment

[Ludwik Kowalski <kowalskil@mail.montclair.edu>]

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/