Re: Mass/Energy

[Jim Green <JMGreen@SISNA.COM>]

I am being pressed privately to respond to Larry Smith's post of a few days
ago -- although I am not anxious to do so.  There doesn't seem to be much
interest -- Everyone is in one of the list's usual snarls. The list finds
much more interest in whether a photon can travel in a "region" for Pete's
sake.  Folks, if you would use language with precision, the snarls would
diminish.  Maybe, Jack, you might start over with the understanding that a
photon is an invention.  We just reify them to make ourselves happy.  Any
one of us can prove that photons don't exist.  It is also true the I can
drive my car somewhere in a citywide region.

Now back to Larry -- but I am old and senile so it may take a week or so:

> Jim,
>
> Let me see if I understand you correctly.

Pedagogy
> You are saying that not only should we stop _thinking_ of energy as stuff
> that can flow (a concept I'm sure many of us would already deny--unless
> light is "pure energy"), but you are further saying that we should stop
> _talking_ about energy as if it were stuff that can flow, and we should
> stop _teaching_ students with language (i.e. models) that might lead them
> to believe that energy is stuff that can flow.

Larry, this one is tough:

Here on the list, I think that we would understand ourselves much better if
we were to stop using the questionable language of Bill Nye et al.  But it
is difficult for us because this questionable language is lodged firmly in
the synapses of our brains.  However,  we owe it to ourselves and our
posterity to be precise and not use mythological imagery. So here you are
totally correct.

But elsewhere we have another problem: I haven't found a text that says it
correctly -- Even your favorite Knight text falters.  He has made some
strides, but he has the same synaptic flaws we all do.  (And his text is
far to heavy for the feeble.)   Leigh's response is to warn students
continually of such flaws and to use the text teachings cautiously.  I
don't see that  he has another choice.  Maybe you or others have a suggestion.

To be willy nilly about it is a failure of academic responsibility!  We end
up as meaningless as Count Rumford who recognized a major fault in the then
current teachings, but was unable to do anything about it. Let us try to
emulate Galileo.   As an example we have the issue of "heat":  several of
us have made comments re "heat."   Some texts even give a section which
decries the idea of caloric, but then go right ahead and reify the concept
for the remainder of the book.  I have given up thinking about rectifying
this.  It is someone else's turn.

Properties
> Further, you are saying that energy is just a property (like shape, color,
> or temperature) of a physical system, and its level can _only_ be changed
> by doing work (macroscopic work called W or microscopic work called Q) on
> the system.

Yes.  Young started us toward the powerful W/E "theorem."  Teach it!

Mass
> And further still, you are saying that energy isn't equivalent to mass, nor
> can it be transformed into mass, but that it _IS_ mass.  You would be
> comfortable saying that doing work on a system increases the level of the
> property of mass.  In fact, you would prefer that we stop talking about
> energy and mass separately, but that we always refer to them (it) as
> energy/mass in all contexts.

Well, Larry, I think that you are right here.  At least this position is
worthy of discussion.  Perhaps someone could give a counter example.

> Suppose you are correct about all of the above.  Some questions still linger:
>
> 1) How can the collective mind of physics teachers and authors be converted
> to this view?

Oh, Larry, I have no helpful idea.  WE could bribe or maybe give a tax
deduction.  Or for a several years we could strive to teach the next few
generations of teachers correctly -- and buy the Bil Nye the Science Guy TV
series and destroy it.

> 2) What language _should_ we use?  Could you rewrite the energy and thermo
> chapters of Serway or H&R to teach the students correctly?

Yes, I think that several of us could. But would a publisher print
it?  After all his synapses are polluted too.

> 3) Is there ever a place for "incorrect" models that students can
> understand en route to the "correct" understanding?  (The history of
> science says that today's correct understanding will be tomorrow's
> primitive, historical, and incorrect model.)  This question is in relation
> to John Clement's exposition on the Piagetian levels of cognitive
> development.

Leigh is the one to ask here.  He thinks that he can do it.  I haven't
seriously tried, but that was long ago.  I guess that I tried to do what
Leigh does, but I think that I was not as permissive.

> 4) What is "real"? (Thanks, Rick, for raising this one.)   Are EM fields real?

I haven't used the terms "real" or "imaginary" because I don't want to get
into the usual phys-l imbroglio.  But remember that words per se don't
always meant anything -- It is the speaker/writer who "means" things.  I
certainly won't get into a dictionary  war over a meaning of the word "real."

However, for _me_, fields are imaginary/inventions and are not "real."  I
don't remember who the inventor of "fields" was.  It was a very useful
invention -- as long as we don't reify the concept --as in emitting a
StarTrek "force field" to destroy an enemy.

I think of "gravity " as being "real" but I don't reify it.  I can picture
a magnetic field which surrounds the Earth. but I don't think I can get a
hand full of it.  I can use the invention of the idea of a field to solve
problems, but that is not required.

> 5) Can "inventions" be "real"?  Jim, you said photons are inventions; does
> that mean they aren't real?

I can use the invented concept of a photon to solve problems, but they
should not be reified.  You tell me what meaning I should attach to the
word "real" in a discussion with you -- It would likely be different in a
discussion with others.

> If photons aren't real, what about electrons?
> What's the difference?  Are neutrino's real?  Are waves real?  Ontology is
> important.

I don't have a firm opinion re electrons etc.  I am comfortable with
electrons moving along a copper wire.  But maybe I shouldn't be.  Let's
talk about it.

> 6) What is light?

No one has the foggiest idea of what light is.  Einstein received a Prize
for suggesting that light be modeled as a particle and that solved one of
the two big physics problems at the turn of that century.  If someone wants
a Prize now, s/he could tell us what Light really is.

As to the supposed "dual nature" of light I remember a parable by in a book
by someone famous ( Could a lister help out here?) something like the
following:

A Martian family wanted to vacation on the Earth.  They realized that they
must learn the language, but there are so many.  They chose French and
German and decided to vacation in Europe.  But as luck would have it they
landed in Omaha.  They heard the language there -- some of the words seemed
to have aspects of French but other words seemed to have aspects of
German.  Oh my!  Sometimes German and sometimes French.

Light isn't like a particle nor like a wave.  It is like light.

Jim


Jim Green
mailto:JMGreen@sisna.com
http://users.sisna.com/jmgreen