On Fri, 22 Dec 2000, Don wrote:
> Have you done much "work" on energy misconceptions taught in grammar
> school science? How should we teach kids about what energy is (ie., a
> property of objects, or a magical "substance") and how it is transfered?
Hi Don! Grammar school nothing, this is a hot topic in education at the
graduate level! Fierce debates have broken out on the PHYS-L forum about
just this issue. Should university physics professors see energy as "just
a property?" Or is energy "substance-like?"
I have lots of strong opinions, so brace yourself.
:)
The controversy goes directly to the heart of science. More than that, it
goes directly to the heart of existence itself. The problem is that the
"substance-like" character of a thing is only our limited mental model, a
model which was created by humans. I'm not talking about energy. I'm
talking about everything.
Is water a substance? Or is it actually "just a property" of a collection
of H2O molecules? We can take it apart into hydrogen and oxygen. We can
take apart the molecules, atoms, continuing
all the way down to the subatomic particles, and we'll find no "water"
anywhere, because water is indeed just a property of something else.
Or more to the point, what we call "water" is a mental model: it is a
convenient
and very useful illusion that humans have created in order to be able to
deal with the world. "Water" is unreal. What is "real" is a set of
exitations in the realm below the level of quarks which makes up spacetime
vacuum. In other words, if you can take something apart, then only its
pieces are "real", and the original object was just a property of its
pieces. So take the world apart all the way down to the deepest level,
and all you are left with is weird quantum physics fluffy stuff, where
particles and empty space are basically the same thing.
Another way to look at this: line up three bottlecaps on the desk. Is
the line "real?" Now move one, and the line has vanished. Form them into
a triangle. It the triangle "real?" This is important, since the world
is made up of things like the line and the triangle, yet at the bottom of
everything, all that is really real is a cloud of bottlecaps. To human
beings, the patterns are more real than the primoridal stuff that forms
the patterns!
"Energy" is like "water," in that if you deeply believe that energy is
really a stuff, you'll get messed up, but if you deeply believe that it is
just a property, then you'll also get messed up. The word "just" is the
sticking point. Everything you experience in your entire life is
just a
property. If we want to say that energy is not a substance, then that's
the same as saying that the everyday world we experience is not real and
we shouldn't be teaching kids about it.
Energy, water, and the rest of reality is really out there, but we can
only know it by recognizing patterns and building internal mental
models. Our models are real to us, and they are incredibly useful. They
are the world we know.
The upshot: the concept of "Energy is a Substance" is a very
very useful
tool for all students to have in their repertoires. Anyone who argues that
energy is just a property is correct... but they are directly interfering
with education, and are spreading their willfull ignorance to students in
their misguided quest for "that consistancy which is the hobgoblin of
little minds."
(whew!)
On the other hand, once you get to the college level in physics, you learn
that this "energy-substance" has some strange characteristics which are
unlike those of a conventional substance such as water. This is not a
problem for students. They just learn that energy, if it is a substance,
is an unusual
substance. Belief that energy is a substance does not
create horrible misconceptions. The small misconceptions it does create
are effectively treated in college physics classes. People who don't take
college physics can safely go on believing that energy is purely
substance-like. At the gradeschool level, we can teach that energy is a
strange substance, but "substance" it is. This is analogous to teaching
that electrons orbit around atoms like a tiny solar system. It is a
useful concept, and it paves the way for more advanced concepts taught in
higher grades.
ON THE OTHER HAND... heh heh.
In physics, any property which is a "conserved" property is also a
substance-like entity. Mass is "conserved", which means that you can't
make mass disappear: you can only remove it from a box by transporting it
through the walls of the box. If you push mass down in one place, it
instantly pops up again in the neighboring place. You can't get rid of
it. It's very stuff-like. It's even more stuff-like than water! You can
dissasemble water into subatomic particles. The water is gone. But you
can't get rid of the water's mass. I conclude that mass is more real, and
more substance-like, than water.
But... energy is like mass! It is a "conserved" quantity too. You can't
get rid of energy except by moving it from place to place. If mass is
like the "ultimate stuff;" if it's like "god's tinkertoys", then the same
is true of energy. Know what I'm going to say next? E equals M times
c^2. Mass-energy equivalence. It says that mass and energy are basically
the same "stuff." Mass-energy is the ultimate "stuff." All other
concepts of substance pale in comparison.
But because we think that water is "normal", we get the wrong idea that
energy is something strange and abstract. The truth is the total
opposite. Water is exceedingly strange and bizarre. What's simple, and
what's most "normal" of all "substances", is Mass-energy.
Which pieces of the above are appropriate for school kids? I dunno.
I would have to become a K-6 teacher to be able to judge. But maybe I've
pointed out some new "mental tools" that might help you to do the job?
Also see:
Reality vs. Reductionism (energy)
.