sci.physics.electromag

On Sat, 8 Sep 2007, maxwell wrote:

> On Sep 7, 1:16 pm, "Timo A. Nieminen" wrote:
>> On Fri, 7 Sep 2007, maxwell wrote:
>> ...
> 1.
>> Present-time field theory is just an alternative formulation of a
>> retarded-time AAAD theory ( ., Wheeler-Feynman). Is it just a
>> mathematical convenience?
>>
> Present time theories result from assuming the existence of
> instantaneous interactions across space (the consequence of the
> incorrect Coulomb gauge used by Maxwell - only the Lorenz gauge is
> real as this represents the real time difference between emission and
> absorption!) This is just another example of mathematicians ignoring
> physics so they can continue to use (single-time) calculus.

Not necessarily. That is, you don't need to assume instantaneous
interaction across space - that's the whole point of having a field. The
field is a present-time device that includes the effect of all present and
past charges/currents.

This was my point. We can either track the present-time field (and it's
first derivative wrt time), or we can track all present and past charges
and currents. Sometimes the field is more convenient, sometimes the
charges/currents.

If it was not for radiation, then everything would be very clear - the
field would simply be a useful calculational tool. With radiation, one is
tempted to think that the field is physically real.

[And a general, but not linearly connected response to the rest of your
post:]

A very large part of physics is done by beginners. Students and postdocs
are the fuel thrown in the fire of research in physics. They produce the
results, but they are inexperienced. This surely affects the way they
write papers. Equations have a place in scientific communication, but it
seems at times that they are overused. Jargon, too.

One of my students challenged me to do a conference presentation not only
with no equations on the overheads, but also no words. Pictures only. I'm
still working on it. Not so easy.

--
Timo Nieminen - Home page: http://www. /people/nieminen/
E-prints: /view/person/Nieminen,_Timo_A..html
Shrine to Spirits: /timo_nieminen/