sci.physics.electromag

"Timo A. Nieminen" wrote in message
news:Pine.WNT.4.64.0803090613190.296@serene.st...
> On Sat, 8 Mar 2008, Benj wrote:
>
>> On Mar 7, 7:17 pm, "Timo A. Nieminen" wrote:
>>
> No. If you use the Maxwell equations, you are taking retardation into
> account. Notice that you can extract the wave equation from the Maxwell
> equations.

Sorry, Timo, but Maxwell's equations are a wonderful example of action at a
distance. Retardation plays no part whatsoever in their constitution.

Likewise, extracting the wave equation has nothing to do with retardation.
It is interesting that "Displacement Current" provides the missing
ingredient without which the wave equation does not exist. And THAT has led
several generations of scientists and engineers to believe in the physical
existence of Displacement Current as a *cause* of a magnetic field, even
though over a century of measurements have not detected any such magnetism.

Bill

>>> While fields introduce some problems into physics, I believe they
>>> resolve
>>> more than they introduce. The mathematical convenience is immense.
>>> Whether
>>> they are "real" or not, they are certainly useful. The only stance that
>>> is
>>> certain to be properly aligned with reality is agnosticism wrt the
>>> reality
>>> of fields or otherwise. However, I'd say that, on balance, it's
>>> reasonable
>>> to assume that fields exist. This opinion may well be coloured by the
>>> practical engineering usefulness of assuming that they exist.
>>
>> Wow. Major exposition!
>>
>> Do you see what you've just said here? You've said in essence that
>> it's OK to assume fields exist because that mathematics gives me lots
>> of practical answers to questions I have and the answers seem
>> reasonably close to what I'm measuring!
>
> Ah, I see! You want to completely ignore the discussion of the problems
> with AAAD electromagnetic theories, the problems with field theories,
> radiation, and conservation laws, and focus instead on the last sentence.
> You could try addressing what was actually said instead of trying your
> usual cheap debating tricks. (Btw, didn't you claim to have kill-filed me,
> or was that another cheap debating trick?)
>
>> You are saying that physics
>> (science) is a religion where the important thing is how you feel
>> rather than what is true. If believing in fields gives you comfort
>> then, who is to say that you shouldn't do it? Well, I say that
>> philosophers say you shouldn't do it. They say that one has to be
>> careful in your definitions of what is reality and what is merely a
>> model mimicking reality. And to them that difference is fundamental.
>> In religion the difference doesn't matter. But science is supposed to
>> be tested constantly against observation and if you don't do that then
>> it ain't science anymore.
>
> No, _you_ are saying that physics is a religion. I don't see how a
> reasonable person could interpret a statement that the only definitely
> correct stance is agnosticism as "religion".
>
> Physics isn't about "truth", because we don't know, and perhaps can't
> know, what is "true". Physics is about what works, and fields work very
> well. While your last sentence is OTT (there's no need for "constantly" in
> practice), field theories of electromagnetism are pretty much tested
> constantly against observation. And they work, and work well. Where they
> fail (entering the quantum domain) is well-known.
>
> --
> Timo Nieminen - Home page: http://www.physics.uq.edu.au/people/nieminen/
> E-prints: http://eprint.uq.edu.au/view/person/Nieminen,_Timo_A..html
> Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html
>