re:Flow of energy

[Leigh Palmer <palmer@sfu.ca>]

> > You can paint a rocket green and send it to the Moon. Can you now say
> > that green flows? The paint may be said to flow; its color does not
> > flow, even though somehow green has been transported over distance -
> > there is now more green on the Moon than there was before the rocket
> > arrived. (I discount reports that the Moon is made of green cheese.)
>
> I'd have to disagree.  It may sound funny, but my understanding of the
> world MIGHT force me to say that yes, green flowed to the moon.  However,
> first we must answer the question: is green a CONSERVED property?
> Conserved properties are substance-like.  Push them down in one place,
> they pop up somewhere else, and we say that a "flow" took place in
> between.

So far as I know green is not a conserved quantity. The important thing
is that green is not a substance (or a substantial entity). In that way
it is like energy. Energy is insubstantial; it is abstract. It's not real.

> Another example: *charge* is simply a property of matter.  If I place a
> charge on the rocket and send it to the moon, was there a flow of charge?
> I could say no, since charge is merely a property of matter, and there is
> no way to send pure charge to the moon.  But I prefer to say yes, that
> there was a flow of charge, this because charge is conserved and we
> should be allowed to say that conserved quantities can "flow."

Charge is substantial. It is locally conserved. It can't appear in two
places at the same time. *Energy can*! The total energy of a system
depends upon the frame of reference from which the system is observed.
The total charge on a system is independent of the frame of reference
from which it is observed. Charge is real; it can certainly flow in the
common meaning of that term, and it can do so independently of the
system with which it is associated.

> ...

> > Energy may be an attribute of something that propagates, but there is no
> > such thing as pure energy.
>
> But also there is no such thing as pure mass, pure charge, or any other
> property that is concerved.  Should we ban "charge flow" as being a
> misleading concept, since charge cannot flow, only electrons, protons,
> ions, etc. can flow?

Well, charge can flow from one sort of particle to another. Radioactive
decay of the neutron is an example. Charge flows from the neutron to the
electron and the proton.

> > It seems to be a hard sell, but that's what
> > Richard Feynman means when he says there are no blocks. Until that simple
> > concept is mastered it is difficult to approach other abstract concepts,
> > notably entropy, which is on exactly the same conceptual footing. Entropy
> > is easily conceived once energy has been conceived properly.
>
> Maybe so, since I've yet to attain a deeply intuitive understanding of
> Entropy.  (However, entropy is not conserved, it can increase without
> having to decrease elsewhere, so entropy and energy are entirely different
> classes of property.)

You have indeed missed the concept of entropy. Rudolf Clausius named it
entropy because it was so *similar* to energy. It is not conserved, but
thermodynamic textbooks formulate processes in terms of the flow of
entropy just as they formulate "heat transfer" in other processes. We
keep in mind always, however, that these constructs are unphysical. If
we lose sight of that fact then entropy becomes a difficult concept.

Leigh