SI and nothing else.

[LUDWIK KOWALSKI <kowalskil@alpha.montclair.edu>]

On Fri, 19 Sep 1997 19:30:27 Herb Gottlieb wrote:

> I'm not sure that a degree celsius is the same size as a degree kelvin.  
> However, I like your idea of standardizing one or the other for the SI 
> system of units. Let's work on it. Send a note on your idea to the
> AAPT Metric Committee.

You send it and I will have fun watching. But I would not mind to start 
a serious discussion on the wisdom of sticking to SI from the beginning. 
Jim's message came at the moment I stopped typing this. It is shown at 
the end. Think about this.

Kilogram is now officially defined in terms of the mass of C-14. Is
it possible to make this new definition meaningful to somebody who
just starts learning physics? (By making it meaningful I mean without
saying something which has to be taken for granted. For example, that
carbon has isotopes and that masses of ionized atoms and molcules can 
be compared, very accurately, in magnetic spectrometers.) 

Why bother to talk about speed of light, ions, isotopes and atomic 
clocks too early? This can only reinforce the feeling that "physics is 
not comprehensible". What is gained? My goal, at this stage, is to show
that we can be objective by measuring things in some agreed upon units.

The same goes for using 4186 J/(kg*K) instead of 1 cal/(g*C), for water, 
when we start teaching calorimetry. How can you explain Joule's paddle
experiment without calorimetry? How can you explain 4186 without a 
reference to an experiment which students are not ready to understand?

                                                       Ludwik Kowalski 

> It seems to me that unless there is a *clear* and *compelling* advantage 
> to the use of a non-SI unit and only in a class intended for non-physical
> science people, that the SI be used exclusively -- no matter what the
> instructor is more *comfortable* with -- let the instructor get off his/her
> mental rear end and be professional about it.
>
> This philosophy pervades many of the threads on this list. We often hear
> things like "Well you are correct (strictly), but why can't I do it my 
> old fashioned (read 'incorrect') way none-the-less."  This is often the 
> same as saying "I am too lazy to improve my teaching."
>                                                            Jim Green
     I am trying to be professional. And my question is:
        Does sticking to SI always improve teaching?

My personal preference is to begin with calories and switch to joules
later. This approach protects me from explaining today's topics in terms
of what they will learn tomorrow. "Borrowing from the future" should be
kept to a minimum. I know how to do this while dealing with units of 
internal energy.