Chronology Current Month Current Thread Current Date
[Year List] [Month List (current year)] [Date Index] [Thread Index] [Thread Prev] [Thread Next] [Date Prev] [Date Next]

Re: energy in the tank



This is, I think, a wonderfully Wittgensteinian answer. Wittgenstein
said that the problem with the logical inconsistencies in
mathematics...Russell's paradox: In a town the barber shaves only those
people who do not shave themselves...so who shaves the barber...the
logical inconsistency arrises from identifying relations as the same
sorts of things as specific objects.
I think Wittgenstein would insist that we not think of energy as the
same sort of thing as a chair if we are to avoid logical problems in our
models.

cheers,

joe

On Wed, 6 Feb 2002, Hugh Haskell
wrote:

Everything we do in physics is done with one goal in mind--to
describe in as consistent a manner as we can what we see.

Is what we see real? Who knows? Are we seeing the real thing or only
some platonic shadow or is it all a dream? As far as I know, there is
no way to answer this question definitively. But we build models,
relentlessly. Models which, for the past few centuries, more or less,
have included concepts we label as energy, momentum, force, field,
mass, charge, and what have you.

The models describe what we see in mathematical terms. Is mathematics
real? Just what does that mean?
Whether we describe what we see by means of mathematics or pretty
pictures or ornate language, doesn't affect what, if anything, is out
there in the least, only the context in which we see it.

But we remain habitual model-builders, and the models are manifestly
*not* real, merely descriptions of what we (for convenience, mostly)
take to be "real." Thus we should not treat any of the things we use
to describe the world "out there" as real, and that includes all of
the items listed above and more.

Having said that, I respond to myself with a rousing "so what?" Since
we can never "know" the "real world," if it even exists, we take the
next best thing, our time-varying models, and treat them as if they
are "real," in whatever sense one can make of that. So, deep in our
heart of hearts, we know that, to return to the subject, *energy* is
not real, but a mathematical construct we use to describe the world,
but if we have to continually remind ourselves that we use a
shorthand that sounds suspiciously like we are treating energy as
some substance with properties like ordinary matter, then we are
going to make useful communications awfully difficult. So we continue
using our various modes of shorthand because we get tired of the
circumlocutions that become necessary if we are to keep the concepts
"pure."

I see an even worse linguistic trap that we have fallen into--that of
anthropomorphism--much worse than reism. Not only is it harder to
spell and much harder to pronounce than reism, but it has a much
higher potential for confusing students. We ask "How does the
electron no which way to go when it enters the magnetic field?" as
though where the electron goes is some sort of optional decision
process. More subtly, we ask "Why does an electron travel in a circle
(or helix) when it enters a magnetic field?" as though the electron
has a will of its own and can decide what to do. We all know that we
use these words as a shorthand for more precise language that overtly
describes what transpires, without imputing any impetus to it. But do
our students?

The ones who continue on in science, mostly eventually realize what's
going on and understand the shorthand, but I'd guess that a majority
or more of those for whom our class is their last exposure to science
never make that connection.

So in the scheme of things, I see reifying energy to be a sin of
relatively minor proportion compared to anthropomorphism, and yet I
see little outcry against anthropomorphism.

But if anyone wants to say that, in the final analysis we have no
idea what energy is, but that so far, in every physics problem we
have ever attacked, there has been some property of our closed system
(read: model of a closed system) that, no matter how it is
calculated, has the units of newton-meters (joules), and remains
constant throughout., then I will agree. We can say no more without
getting into water that is way over all our heads. We call this
property energy, and, for convenience, we treat it kind of like a
quasi-fluid that we can move around within the model of our system,
more or less at will. As long as we remember, and frequently remind
our students that naming the thing is not understanding the thing, I
see little wrong with this practice, and I will continue to do it.

So there.

Hugh
--

Hugh Haskell
<mailto://haskell@ncssm.edu>
<mailto://hhaskell@mindspring.com>

(919) 467-7610

Let's face it. People use a Mac because they want to, Windows because they
have to..
******************************************************


Joseph J. Bellina, Jr. 219-284-4662
Associate Professor of Physics
Saint Mary's College
Notre Dame, IN 46556