Reality of E&M (was: wave momentum)

[James McLean <jmclean@CHEM.UCSD.EDU>]

David Bowman wrote:
> Regarding:
> > Thus an e/m wave doesn't "carry" mass thus no momentum -- there is a charge
> > at the "originating" site which does impose a force on the distant site
> > thus it may cause some momentum at that site.   We just  imagine a  wave
> > momentum which we hope will make calculations easier -- just as we talk
> > about  E/M "fields" which are not "real" either but  are sometimes helpful
> > to imagine.
>
> This is simply incorrect. [...] Any attempt
> (even at the purely classical, nonquantum level) to "integrate out" the
> field degrees of freedom from the (charged matter + EM field + their
> mutual interactions) Lagrangian results in a very nonlocal particle-only
> theory which can only be solved perturbatively in inverse powers of c^2.
> [...]

Although I'm inclined to agree, let me play devil's advocate.  What your
message mostly says is that it is possible, but extremely inconvenient,
to avoid the field degrees of freedom.  I don't suppose that nature is
required to be convenient.

So are you basically saying that your notion of reality is based on
obtaining simpler equations, at the expense of having more ethereal
things (pun intended) be considered 'real'.  Or do you have a deeper
reason to lump electric fields into the same category as, say, my desk.

--
--James McLean
jmclean@chem.ucsd.edu
post doc
UC San Diego, Chemistry