Re: misconception re ice melting under skates

[Leigh Palmer <palmer@sfu.ca>]

> ...Finally, I apologize for possible distortion of Hewitt's conceptual
> presentation of regelation phenomenon which I think was correct (including
> the across heat transfer).  His remark that [plastic] string would not do
> it could be understood within reasonable approach.   Of course, nylon
> thread will do it [if a copper wire did!], but slowly.  How slowly? -  In
> correspondence to its heat conductivity, which is not zero.  In a
> conceptually oriented course, it is legal to idealize  illustrations and, I
> think, it is OK.

I believe you have just stated clearly the correct situation, without
resorting to misconception, in words only, and with little obfuscating
mathematics. Saying that plastic string won't do it is a misconception
of the simplest kind. It is not a simplification; it is (simply) wrong.
Would it have exceded the bounds of reading level to say that the
plastic string would pass through the cube much more slowly because it
has a much lower capability for transferring heat than the metal wire?
(Sorry, Ludwik; that's the way I would do it in a course for
unsophisticated students.)Leave out the "In correspondence to its heat
conductivity", but why lie? Hewitt obviously knows the truth and he
*oversimplifies*. I think that is clearly unjustifiable in this case,
and I can't imagine any reasonable defense of Hewitt's (reported)
statement. It can only be defended as a matter of taste, and it tastes
awful to me!

> 	For me this discussion illustrates the everlasting contradiction
> between the demands of phenomenological and rigorous presentations of
> physics.  Both extremes are simply not feasible.  Each physics teacher
> prepares  a unique ratio of mixture of both approaches in each particular
> circumstances.  A beautiful play.
> Igal.

I remain inflexible.

Leigh