Re: [Phys-l] teaching energy

[Jack Uretsky <jlu@hep.anl.gov>]

The objection to "fluid models" is of the nature of a "wrong religion" 
objection.  If a "fluid model" helps you calculate the results of 
experiments, as the diffusion equation helps us to calculate certain 
thermal phenomena (e.g., "heat conduction"), then the model is a success 
and should be taught, IMO.
				regards,
					Jack


On Fri, 29 Sep 2006, Rauber, Joel wrote:

> John C. wrote in part:
>
>
> | I certainly can not defend one point of view over the other 
> | as being more correct.  But I think that they are trying to 
> | get students to build a consistent model of energy, so one 
> | point of view may be more productive than the other.
> | 
>
> Granted, but the document referenced, is actually saying that the other
> viewpoint is *wrong*, implying incorrect physics?
>
> Later they claim:
>
> "If we claim that energy is stored in the gravitational field, and if a
> change in energy content is
> indicated by some change in the thing that stores it, then what changes
> in the field when it gains
> or loses energy? 
>
>
> R. McDermott wrote in part:
> | The central theme is that the energy must reside somewhere.  
> | Taken in that 
> | context, the only "place" for it to be is in the field itself.
> | 
>
> I don't understand the *must*; why not say it resides in the
> configuration of the system.  The change in the thing is . . .  The
> "thing" would be the two body system, the change in the thing would be
> its configuration.  For point-like objects that would be its separation
> distance.  Much like a mass-spring system.
>
>
> They appear to me to be coming dangerously close to re-enforcing a fluid
> & container model of energy; i.e. reifying the idea to a possibly
> dangerous degree.  Though I must admit to only a cursory glance at the
> document.  
>
> So while I found the document to be interesting and of value (I've
> actually bothered to print it off)  I worry about the reliance on the
> field concept at this level.  Both on grounds of practicality and
> principle.  In terms of principle, didn't Feynman and Wheeler write a
> paper in the 40's showing that you could dispense with the field concept
> in Electromagnetism.  In terms of practicality, the field concept is
> more abstract than the configuration of a system . . ., hence my worry.
>
> Just some rambling thoughts for discussion.
>
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