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Re: PHYS-L Digest - 19 Oct 2004 to 20 Oct 2004 (#2004-296)



On 19-Oct-04, in response to my posting:

I have great respect for Michael's grasp of physics, but it is my
judgment that in holding this opinion he commits a heresy, and by
teaching it to his students he commits a venial sin.

The orthodox view, which I hold to be correct: The energy is not
substantial; it is not a real entity. The energy is an abstraction.
The
energy did not exist before it was invented. The energy is a state
function, a quantity which may be calculated for any isolated physical
system from the values of all the parameters that characterize its
state.

Jim Green wrote:

Oh, Leigh, font of much knowledge, the above is clearly valid -- You
could
have given credit to Thomas Young, wasn't it, for the invention of the
idea
of energy.

No. The idea has been invented by several contributors, each of whom has
added essential ingredients to the concept.

But then you embrace the Feynman block parable. Leigh, true enough
energy
is not a substance -- it does not flow nor can it be tossed out a
window
nor is it a block nor should it be represented by blocks. The Feynman
parable is not helpful in my world.

You must read the entire verse, my son. Feynman's point is exactly that
energy is *not* like blocks. He says clearly:

"What is the analogy of this to the conservation of energy? The most
remarkable aspect that must be abstracted from this picture is that
*there are no blocks*."

and, in the next paragraph:

"It is important to realize that in physics today, we have no
knowledge
of energy *is*."

You may feel that the substantial energy description has absolutely no
place in teaching, though I have never seen you state that extreme
position. As others have pointed out, the analogy is necessary to the
partial enlightenment and admittedly imperfect edification (q.v.) of the
less able students.

It is appropriate that I cite scripture at this point: Feynman I: 4-1.
If you have not read this short (less than two pages) parable and
given
it the contemplation it deserves, I recommend you do so.

Feynman's point is exactly what I am preaching here, Jim. I would make
only one change to scripture; I would prepend the definite article to
"energy" and refer to "the energy" instead, as a reminder to the student
that the object referred to is merely a state function like the entropy.
Note that above I use asterisks (rather than the TeXish prefix) to
indicate where Feynman uses italics.

Leigh