Re: A wave or not a wave ?

[John Denker <jsd@MONMOUTH.COM>]

I wrote:
>The general question as to what can be simplified and what cannot is a
>monumental question.  It's one of the reasons why teaching is hard.

Whereupon at 07:25 PM 7/2/00 -0600, Jim Green wrote:

> Aren't you one of those who say that the language of having energy flow or
> move or generally reify the concept is tolerable if not accurate

That's a pretty pale shadow of what I actually say.

I say energy is real.  Energy is as real as hydrogen.  Indeed energy obeys
a local conservation law more strictly than the number of hydrogen atoms
does.  Energy flows.  This concept is a prerequisite to the formulation of
the local conservation law.  Anybody who thinks energy doesn't flow, who
thinks that the local energy-conservation law is not important, is missing
an important piece of 19th and 20th century physics and doing students a
great disservice.

> -- and the all time favorite: "heat flow".

There are two inconsistent technical definitions of the word "heat", each
of which is used within the physics community.  Nothing anyone says on this
list will change that fact any time soon.

I do not consider either definition to be a simplification of the
other.  They are both complete, careful definitions.  They just describe
different concepts.

I have an opinion as to which concept is more pedagogically useful.

Wrangling over the definitions is a poor substitute for exploring the concepts.

>  Are you not one of those who bridle at Leigh or me
> or others on the list when we object to these malformed expressions?

I am astonished any time I see someone try to deny the local conservation
of energy.

> All the while we sit in our little corners and claim that it is just as
> easy to say it correctly. ... I guess [a certain student]
> would say that it is in fact _easier_ to say it correctly!

I do not consider my statements about energy to be an approximation or a
simplification of Jim's statements.

I agree that saying things correctly is very often _easier_ than presenting
a bogus concept and trying to repair it later.