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Re: Energy, etc (fwd)



On Fri, 13 Aug 1999, Jim Green wrote:

I repeat: It is just as easy and far more pedagogically profitable to say
it correctly.

My argument is that the traditional "correct" explanation hobbles our
understanding and is therefor detrimental. I'm convinced that we should
take a detailed look at these issues, and see if maybe we can make some
improvments. Maybe the usual way to explain things has a down side. If
we repair this, the "correct" way to say it will be even more "correct"
as a result.



Arguments to the contrary just show an unwillingness to
learn physics or how to teach it,

Because my arguments spring from my personal flaws, they need not be
refuted? Arguments should always stand on their own, regardless of the
negative forces which spawned them.

Also, if I am wrong, then there is a danger: I might accidentally sway the
other subscribers to my flawed way of thinking. If you can reveal the
embarassing defects which destroy my arguements, then nobody else will be
mislead.

-----------------------


If we only care about "right" and "wrong", and if we ignore anything that
happens to students after they leave the classroom, then in my opinion our
priorities are screwy. "Right" and "wrong" concepts are extremely
important, but so are "revealing" versus "obscuring". I see this Energy
problem as an apparant collision between the above two necessities. It's
a situation where our learning of rigorously "correct" information will
derail our pursuit of insights and therefor will stand in the way of our
understanding.

The solution is not to declare that "correct" must always win the battle.
The solution is to look for a solution. Examine the problem, and find a
way to remain "correct", but at the same time find a way to avoid erecting
any barriers to understanding.


The Great Feynman notwithstanding.

Ah, you didn't read his article. The Great Feynman supports *you.*

He attacks those K-6 textbooks which treat energy as a substance. I was
offering everyone a club with which to beat me.



Since I have no experience in classroom teaching, my opinion must only
apply to the EFFECTS of classroom teaching, and specifically, to the
effects it had on me personally.

I've always found the concept of "energy is a substance" to be incredibly
useful. Up until this particular phys-L thread, I hadn't thought deeply
about whether energy is "real" or not. I see that its reality is
questionable. However, its great usefulness as an explanatory concept
is not. I therefor offer a compromise.

We should always make clear that energy is NOT always substance-like, that
it changes with changing reference frames, and therefor we should explain
that "energy as substance" is a limited concept. It's an extremely useful
tool, but it is not a Universal Truth. It has limits. If we declare that
its limits are actually "flaws", then we'd better be prepared to declare
the same thing about all other limited conceptual tools.

In my opinion, if we refuse to teach people the utility of viewing energy
as a substance, then we hurt them. We hurt them in the same way as if we
refused to introduce the "energy" concept at all. "Energy" is not real,
therefor we should never mention it? Yet "energy" is a useful tool,
therefor we should be required to mention it. The same is true of energy
flow. It is not real, in the same way that energy itself is not real.
But it is useful in the same way that the idea of "energy" is useful.


Is Energy "only" the state of a system? No, and here's a situation which
illustrates this. Suppose I move a parcel of air suddenly forwards. I've
given it KE. That parcel pushes on its neighbor, and as a result, the
neighbor speeds up and the first parcel stops. The same thing repeats
again and again. An acoustic wave spreads from the original disturbance.
What spreads? "State of the system" spreads, but air does not. Each
parcel of air gains energy and then loses energy, and only the energy
propagates along. Energy is moving forwards independantly of the systems
involved. (And sound can be measured in terms of joules per second.)

Because one "system" can lose its energy at the same time that the
neighboring coupled "systems" gain the same energy, energy is not JUST an
abstract "state of the system". If energy is locally conserved, Energy
can travel along, even though the "systems" involved remain in one spot.
Is this not a central idea in wave mechanics? The medium sits in place,
and only the "waves" move along. Waves do not "flow," only the medium can
"flow." This gives us a convenient term: propagate.

Waves "propagate". Therefor energy cannot "flow", yet it certainly does
"propagate".


Here are some of my ravings/insights regarding energy flow:

"ACOUSTOMAGNETOELECTRICISM"
http://www.amasci.com/miscon/a-rant.txt


Warning: if "energy flow" seems like blasphemy, then the above article
comes directly from the hand of Satan himself! :)


((((((((((((((((((((( ( ( ( ( (O) ) ) ) ) )))))))))))))))))))))
William J. Beaty SCIENCE HOBBYIST website
billb@eskimo.com http://www.amasci.com
EE/programmer/sci-exhibits science projects, tesla, weird science
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