sci.physics.electromag

On Nov 28, 8:28 am, p.kins...@ic.ac.uk wrote:

> Crikey. In contrast, the textbooks I recall looking at seemed perfectly
> happy to give formulae for the energy density of the EM field. Neither
> do I recall any odd claims that that energy (or its flux) is somehow unreal.

I guess you just don't get around enough, doctor. The following from
The Classic EM fields text by Plonsey and Collin:

"However it must be kept in mind that it is not possible to state
where energy is located. Only total energy associated with a given
field has a physical meaning."

And again in the same textbook:

"While the interpretation of of E x H as representing power density at
a point is ordinarily a useful one, it should be noted that [equation]
9.16 states only that the total surface integral of P gives a net
power flow across a closed surface."

> Perhaps there's a factor of \imath [1] that gets silently omitted? [2]
>
> [1] \imath = \sqrt{-1}
> [2] ha ha ha

Yeah, ha, ha! Sure. Perhaps it is the sqrt{-1} that gets "silently"
omitted given it is the integral of 1/2 the real part of the complex
Poynting vector over the surface of a volume (sinusoids only, please)
that represents the time-average power-flow into that volume.
However, the above cautions about interpretations as a power density
still apply. :-0

Of course this was from a 'murcan textbook rather than one of yours
from the Yoo Kay. But since you guys over there seem to believe that
disarming victims and arming criminals will reduce violent crime, I
shudder to think what "eccentric" concepts can be found in your EM
texts!

What I want to know is when in hell did it happen in physics that
somehow mathematics came to be regarded as more "real" than the
universe in which we reside? Just what exactly is an "imaginary
number" anyway? And what kind of objects in our universe do they
represent? Come on. ALL math is simply human constructs. Sure, some
of it is useful as analogs (analogues to you) to reality, but it sure
as hell isn't more real than reality! There are few reasons to suppose
that such systems should even be good fits to reality! When did
natural philosophers turn into mathematicians?

Think first. THEN calculate!