From: glhurst@onr.com (Gerald L. Hurst)
Newsgroups: sci.physics
Subject: Re: THE NEUTRON
Date: 9 Jan 1996 01:56:49 GMT

In article <4cs33l$chk@spider.rmplc.co.uk>, John Lawrenson <johnl@atlas.co.uk> says:

>bds@ipp-garching.mpg.de (Bruce Scott TOK ) writes:
>> Erik Max Francis (max@alcyone.com) wrote:
>> : johnloz@msn.com (John Lawrenson) wrote:
>> : >How can the international community take seriously a book which uses 
>> : >the unit "erg" ?
>> : >
>> : >Is this in common use in the USA?
>> 
>> : Huh?  The erg as a unit of energy is part of c.g.s., which is an accepted
>> : international system of units.
>> 
>> : It is, however, pretty ugly.  It has since been superceded by SI (which is
>> : derived from m.k.s.), in which the unit of energy is the joule.
>> 
>> 
>> This is nonsense.  SI and mks are the product of petty bureaucrats
>> totally ignorant of physics who want to force on all of us a standard
>> which ignores the fact that E and B are two parts of the same thing and
>> should be in the same units.
>>
>The erg [sic] is known over here but I haven't seen it in print since 
>1969 or so!
> 
>I take the point but I am afraid cgs are not accepted anymore and we 
>have by International Agreement the SI system. Does anyone have any 
>suggestions about how can we teach E and B fields at High School 
>level in the same units? Remember that today we  would have virtually 
>no physics students if calculus was a prerequirement of physics for 
>16-18 year olds! I guess the Max Planck Institute uses "eV's" as well 
>..... why not the foot pound ...or poundal wasn't it?
>I think my point is that there is enough to put young students 
>wishing to take up physics without the additional confusion of 
>idiosyncratic units.

Poor John, are you confused by ancient terms like "foot-pound"?
Oh well, better stay out of conversations regarding internal
ballistics; the tables are still full of data in ounces and 
feet/sec. How about thermodynamic tables - most of the
existing data are listed in calories. Done any surface tension
calculations lately; the data are mostly in dynes/cm. How about
thermal conductivity data - calories again. Interested in 
diffusion rates for gases in plastics? --- Look up your 
information in terms of cc-mil/100sq.in.-24hr.-atm. You don't
want to know some of the standard units used for other physical 
properties of synthetic materials.

In the real world outside of the ivory towers of government
funded research and education, you use data as you find them,
and you create handy standards for your own work or products
in terms that are most comfortable for the people who pay
your wages by buying your product or services.

Unit conversions are trivial exercises for working scientists
and engineers. The people who form international committees
and decide what units are acceptable are the accountants of
science. Yes, it is very nice that they organize everything
so neatly. Eventually their work will infiltrate the greater
body of assembled data and we will reach the purity of a
uniform and well balanced metric ledger - but not in my 
lifetime.

If you haven't seen any printed cgs or "English" units, such
as ergs or psi, since 1969, you have led a very sheltered 
life far removed from the such dirty-hands material as tables 
of the  physical properties of thermoplastics.

You can expect chemists to continue using cgs units and
calories for a long time to come. The relatively convenient
magnitude of the former and the relationship of the latter
to the specific heat of water make them too tempting to 
resist.

I'm not sure the world needs a new crop of physicists who
would be bothered by poundals or cubits. We already have 
enough cab drivers. 

As the inventor of the so-called "Mylar" balloon once said
"Here's to the minimization of grams of lift per thousand 
square inches per year."

Jerry (Ico)