Re: [Phys-L] heat content

[John Denker <jsd@av8n.com>]

The devil can quote scripture to his purpose.
       (I know that because I got it from an authoritative source.)

I mention it because on 02/16/2014 02:07 PM, Trivilino, Herman wrote:

> Just read this in advertisement for a Fire Syringe appearing in TPT:
> "This is one of the most impressive demonstrations of the heat
> produced when a gas is rapidly compressed - the principle of the
> Diesel engine ignition."
>
> I wonder if the authors of that passage ever heard of the term
> "adiabatic compression" and looked up its definition!

Let's do the experiment and see what happens.  Let's start 
by looking up the word "heat", since the author actually used
that word (and didn't mention "adiabatic").

I quote from
  http://www.merriam-webster.com/dictionary/heat

> > Full Definition of HEAT
> > 1
> > a (1) : a condition of being hot : warmth (2) : a marked or notable
> >   degree of hotness
> > b :  pathological excessive bodily temperature
> > c :  a hot place or situation
> > d (1) : a period of heat (2) : a single complete operation of
> >   heating; also : the quantity of material so heated
> > e (1) : added energy that causes substances to rise in temperature,
> >   fuse, evaporate, expand, or undergo any of various other related
> >   changes, that flows to a body by contact with or radiation from
> >   bodies at higher temperatures, and that can be produced in a body
> >   (as by compression) (2) : the energy associated with the random
> >   motions of the molecules, atoms, or smaller structural units of
> >   which matter is composed
> > f :  appearance, condition, or color of a body as indicating its temperature 


The general rule is that if the author's usage conforms to /any/ 
of the definitions, then the usage is correct.

Maybe I'm missing something, but AFAICT the author's usage conforms
to /several/ of the dictionary definitions, including
   1a(1)
   1a(2)
   1c
   1e(2)
and especially
   1e(1), which explicitly mentions compression.

In any case, the fact is, anybody who wants to understand that 
advertisement can understand it.

   OTOH, as always, it remains true that anybody who wants to 
   misunderstand can find a way to misunderstand ... but there's 
   nothing any of us can do about that.


===================================

If somebody wants to claim that the dictionary definition is not
the /physics/ definition, then I will make a different argument.

Suppose you choose some narrow, specialized meaning.  I will
argue that this is lousy pedagogy, for several reasons.

 a) If you start by speaking the word in front of students with
  one meaning, in all likelihood they will hear it with a 
  different meaning, because they don't know any better.

 b) If you start by defining the word oh-so-carefully, the
  most likely outcome is that they won't believe you.  They
  have tons of independent evidence -- including the dictionary --
  that says that other definitions make sense.

 c) If you manage to train them to use your definition, in all
  likelihood they will learn it as a special case, valid within 
  the four walls of the classroom and nowhere else (which is
  IMHO what they should do).

  At this point you can check off the box that says you "taught"
  them the definition ... but what's the point?   Is that 
  really teaching?  The retention rate is zero.  The effect on 
  the real world is nothing but a waste of your time and their
  time.
   -- In most of the world, box-checking counts for nothing.
   -- I recognize that there are some parts of the world
    where box-checking is important, where people are allowed
    to use paperwork to "prove" things that cannot possibly
    be true ... but I assiduously stay away from such places.

=====================

If the dictionary definition of "adiabatic" when combined with
"heat" is inconsistent with the laws of physics, that's the
lexicographer's problem.  It's not my problem, because I don't
take any of that stuff seriously.

Ideas are primary.  Terminology is tertiary.  Terminology is
important only insofar as it helps us formulate and communicate
the ideas.

====

I don't recommend playing lawyer games, but if you insist on
playing anyway, it turns out that the dictionary definition
of "adiabatic" speaks of the /transfer/ of heat, whereas the
advertisement speaks of the /production/ of heat, so you
can't use the latter to contradict the former.

Whereas "heat" has at least four or five mutually-inconsistent
technical definitions, we are in luck because "adiabatic" has 
only two widely-used mutually-inconsistent technical definitions.

All of which is ridiculous.  None of which matters.

In reality, words acquire meaning from how they are used ...
not from some terse formal definition.  Students hate to be
told this, because they've been trained that if they memorize
by rote "the" definition they'll get the right answer on
The Almighty Test.  Nevertheless, it's the truth:  Words
acquire meaning from how they are used.