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Re: Models...

> But i am REAL reluctant to accept models that have known violations 
> of reality in them.

You must not accept many models then.  Nearly everything interesting 
that I remember from Physics and electronics made assumptions that 
weren't necessarily true in all cases, but were made so you didn't have 
to deal with complicated, intractible non-linear equations.  We can't 
even solve the equations that describe the motions of more than two 
gravitationally-bound bodies, much less anything really complicated!

> I believe (i know) that we know a great deal about a great deal.  That
> is a lot less than knowing All about Everything...We know a great deal 
> more than that.

I said that at a basic level, we KNOW nothing about anything.  To be 
pedantic, we have a lot of good models that we use to make verifiable 
predictions, but that's really all you can say.  At a basic level, we don't 
KNOW anything, i.e. - what is mass, what is charge, why does a proton 
have the same charge as an electron (only positive), etc...  Everything 
we "know" is built up from AXIOMS and derivative theorems and proofs. 
 At the basic, axiomatic level, all you can do is throw up your hands 
and say "Just because, that's why!".  It's even been proven that no 
formal mathematical (or logical) system can be complete or even 
self-consistent, but that doesn't stop us from using these systems.

> "we" (working professionals)  know that the earth is not a perfect 
> conductor, in bulk or on the surface.  Any model starting with that is at 
> risk.

To pick some more nits, I have had a full-time job for 15 years (i.e. - I 
am "working"), and although I don't have my PhD yet, I am in a 
technical engineering field and would consider myself a "professional", 
so presumably your "working professional" actually refers to 
"professionals working in the field of radio engineering"?

As to the model being at risk, any and every model is at risk if the 
limits of the model are not properly specified or respected.  Granted, I 
haven't read a lot of technical journals for the "working engineer", but 
what I have read concerning the conducting earth "model" and the 
context in which it was presented makes me think that there is at least 
some justifiable basis for it's use when dealing with terrestrial 
electromagnetics.


Steven Roys (sroys-at-radiology.ab.umd.edu)