Timo Nieminen <timo@physics.uq.edu.au> wrote:
On Thu, 3 Jun 2004, greywolf42 wrote:

Gregory L. Hansen <glhansen@steel.ucs.indiana.edu> wrote:
John Schoenfeld <j.schoenfeld@programmer.net> wrote:
Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields? If so, what precisely is it that forces _all_
magnetic fields to be solenoidal (abductive reasoning is not good
enough)?

There's no theoretical reason to prohibit magnetic monopoles. It's an
experimental matter.

An utter falsehood. Maxwell's derivation of Maxwell's equations (On
Physical Lines of Force, 1861) explicitly prohibits magnetic monopoles.
Find a magnetic monopole, and disprove Maxwell's aether!

Maxwell's ether is already disproved,

Really? When did Maxwell's equations get disproved?

by the experimental observation of
symmetry under Lorentz transformations.

Symmetry is not an observable.

And 'symmetry under lorentz transformations'
is a mathematical statement.

Could you be more specific, here, about experimental observation?

Timo Nieminen <timo@physics.uq.edu.au> wrote:
On Thu, 3 Jun 2004, greywolf42 wrote:

Timo Nieminen <timo@physics.uq.edu.au> wrote:

It's simply the non-observation of magnetic charge. First noted,
AFAIK, by Gilbert back in around 1600.

It's also a conclusion from Maxwell's physical derivation. It's not
'just' an observation.

[cut]

These people do so because there is no fundamental reason why they
should not exist according to classical EM theory.

A false statement. You can't get more classical than Maxwell. And
Maxwell when explicitly derived his equations (On Physical Lines
of Force, 1861), the derivation found that magnetic monopoles
were theoretically impossible. Which is why they don't show up
in the equations.

Addressed in detail elsewhere in the thread.

Apparently you mean to do this later. Or my newsreader is acting up
again.....

To summarise:

Maxwell's ether model is not classical EM theory, as the term "classical
EM theory" is used today.

Ahhh, so!! The 'exclusion by definition' trick. This is as useful a
statement as:
A poodle is not a dog, as the term 'dog' is used today.

Maxwell's ether model is not classical EM theory, as the term "classical
EM theory" is used today.
is actually true. If you doubt this, try reading some classical EM theory

A poodle is not a dog, as the term 'dog' is used today.
which is (1) off-topic and (2) wrong is simply incorrect, since the former

Do note that people have looked for, and do look for, magnetic
monopoles.

They just have never found any. :)

And while absence of evidence is not evidence of absence, they *should*
have been found if they exist. (The probability of existence if
vanishingly small.)

Well, I don't think that magnetic monopoles exist. But then, the universe
is what the universe is, and can surprise us.

I like surprises. I just don't care for callous disregard for history, or
attempts to shade the truth within a supposedly scientific discourse.

Timo Nieminen <timo@physics.uq.edu.au> wrote:
On Fri, 3 Jun 2004, John Schoenfeld wrote:
Timo Nieminen <timo@physics.uq.edu.au> wrote:
On Thu, 2 Jun 2004, John Schoenfeld wrote:
Timo Nieminen <timo@physics.uq.edu.au> wrote:
On Thu, 2 Jun 2004, John Schoenfeld wrote:

Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields?

div B = 0 is an experimental observation.

Yes an observation from steady currents.

No. It's from observations of steady currents, slowly-varying currents,
rapidly varying currents, and zero currents.

I meant "charges in motion".

You wrote "steady currents". Exactly what do you mean? In any case,
div B = 0 is observed with moving charges, stationary charges,
accelerating charges, and in the absence of charge.

Yes, hence "charges in motion".

And Magnetic fields occur in the
absence of charge?

Or are you trying to say that the divergence of a
non-existent field is 0?

Note also that the necessary modifications to the Maxwell equations if
magnetic monopoles are found have been known for a long time. 1931 if not
earlier (possibly much earlier).

My question is _why_ would the Maxwell equations require
modifications? If a premise of a theory is that charges in motion
cause solenoidal magnetic fields, then even if magnetic charge can
exist in some other way, why would this the theory require alteration
since the original premise remains valid?

If magnetic charge is found, then you no longer have div B = 0.
Since div B = 0 is one of the Maxwell equations, then the Maxwell
equations require modification.

Read properly. Why does magnetic charge change div B = 0 for magnetic
fields of charges in motion?

The original premise is div B = 0, and this would no longer be valid.

No, it would still be valid.

Richard Herring <junk@[127.0.0.1]> wrote in message
news:<5sxmXUCc5DwAFwuq@baesystems.com>...
In message <a98beaaa.0406031501.6f8f9de9@posting.google.com>, John
Schoenfeld <j.schoenfeld@programmer.net> writes
Richard Herring <junk@[127.0.0.1]> wrote in message
news:<po3i2pa7mxvAFwUB@baesystems.com>...
In message <a98beaaa.0406021802.20b74de4@posting.google.com>, John
Schoenfeld <j.schoenfeld@programmer.net> writes
"Robert J. Kolker" <robert_kolker@hotmail.com> wrote in message
news:<aSrvc.37813$eY2.10359@attbi_s02>...
John Schoenfeld wrote:

Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields? If so, what precisely is it that forces _all_
magnetic fields to be solenoidal (abductive reasoning is not good
enough)?

It will have to do. The only magenetic fields that have been seen are
solenoidal and at right angles to the current. If someone does come up
with a magnetic monople Maxwells's Equations will have to be altered.

I don't see why they would require alteration since the equations are
considering only the special case of steady currents

Really? Which part of Maxwell's equations implies steady current?

I meant charges in motion, forgetting the reserved words steady current.

Sense no makes that.

Having trouble reading again?

On Sat, 4 Jun 2004, John Schoenfeld wrote:

Timo Nieminen <timo@physics.uq.edu.au> wrote:
On Fri, 3 Jun 2004, John Schoenfeld wrote:
Timo Nieminen <timo@physics.uq.edu.au> wrote:
On Thu, 2 Jun 2004, John Schoenfeld wrote:
Timo Nieminen <timo@physics.uq.edu.au> wrote:
On Thu, 2 Jun 2004, John Schoenfeld wrote:

Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields?

div B = 0 is an experimental observation.

Yes an observation from steady currents.

No. It's from observations of steady currents, slowly-varying currents,
rapidly varying currents, and zero currents.

I meant "charges in motion".

You wrote "steady currents". Exactly what do you mean? In any case,
div B = 0 is observed with moving charges, stationary charges,
accelerating charges, and in the absence of charge.

Yes, hence "charges in motion".

Note "absence of charge" in the list above.

And Magnetic fields occur in the
absence of charge?

What is the magnetic moment of a neutron? What is the charge of a neutron?
That's about the closest to magnetic field in the absence of a charge
that's been observed.

Or are you trying to say that the divergence of a
non-existent field is 0?

No, I'm saying that div B = 0 for all magnetic fields that have been
observed.

Note also that the necessary modifications to the Maxwell equations if
magnetic monopoles are found have been known for a long time. 1931 if not
earlier (possibly much earlier).

My question is _why_ would the Maxwell equations require
modifications? If a premise of a theory is that charges in motion
cause solenoidal magnetic fields, then even if magnetic charge can
exist in some other way, why would this the theory require alteration
since the original premise remains valid?

If magnetic charge is found, then you no longer have div B = 0.
Since div B = 0 is one of the Maxwell equations, then the Maxwell
equations require modification.

Read properly. Why does magnetic charge change div B = 0 for magnetic
fields of charges in motion?

Why don't you read properly? The Maxwell equations are not restricted to
fields of charges in motion; they describe the behaviour of electric and
magnetic fields, irrespective of their sources. Since this behaviour does
depend on sources, all known sources of electric and magnetic fields must
appear in the Maxwell equations. At the moment, only electric charge and
electric current are included, since these are the only known sources. If
magnetic charge is found, then magnetic charge and current will need to be
included. Until then, they're not needed. (But you might note that
magnetic currents are sometimes used as equivalent sources.)

The original premise is div B = 0, and this would no longer be valid.

No, it would still be valid.

No, it would not. Think about what div B = 0 actually means.

Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields?

Timo Nieminen <timo@physics.uq.edu.au> wrote:
On Sat, 4 Jun 2004, John Schoenfeld wrote:

Timo Nieminen <timo@physics.uq.edu.au> wrote:
On Fri, 3 Jun 2004, John Schoenfeld wrote:

I meant "charges in motion".

You wrote "steady currents". Exactly what do you mean? In any case,
div B = 0 is observed with moving charges, stationary charges,
accelerating charges, and in the absence of charge.

Yes, hence "charges in motion".

Note "absence of charge" in the list above.

That is an extraordinary claim, which I hope you can back up with
references. The only known cause of magnetic fields are electric
charges in motion.

And Magnetic fields occur in the
absence of charge?

What is the magnetic moment of a neutron? What is the charge of a neutron?
That's about the closest to magnetic field in the absence of a charge
that's been observed.

Quantum Theory and scattering experiments both show neutron's are
internally charged.

No, I'm saying that div B = 0 for all magnetic fields that have been
observed.

I do not disagree with that.

My question is _why_ would the Maxwell equations require
modifications? If a premise of a theory is that charges in motion
cause solenoidal magnetic fields, then even if magnetic charge can
exist in some other way, why would this the theory require alteration
since the original premise remains valid?

If magnetic charge is found, then you no longer have div B = 0.
Since div B = 0 is one of the Maxwell equations, then the Maxwell
equations require modification.

Read properly. Why does magnetic charge change div B = 0 for magnetic
fields of charges in motion?

Why don't you read properly? The Maxwell equations are not restricted to
fields of charges in motion; they describe the behaviour of electric and
magnetic fields, irrespective of their sources. Since this behaviour does
depend on sources, all known sources of electric and magnetic fields must
appear in the Maxwell equations. At the moment, only electric charge and
electric current are included, since these are the only known sources. If
magnetic charge is found, then magnetic charge and current will need to be
included. Until then, they're not needed. (But you might note that
magnetic currents are sometimes used as equivalent sources.)

This is where I disagree. By design, Maxwell's theory is constrained
to the special case of electric charges in motion.

The original premise is div B = 0, and this would no longer be valid.

No, it would still be valid.

No, it would not. Think about what div B = 0 actually means.

div B = 0 is an experimentally verified premise which the remainder of
the equations are based off. Maxwell's equations are true for div B =
0.

On Fri, 4 Jun 2004, greywolf42 wrote:

Timo Nieminen <timo@physics.uq.edu.au> wrote:

Sure, Maxwell is definitely classical, and it may well be that
Maxwell's ether model prohibits divergence in magnetic fields.
However, Maxwell's ether model is not classical EM theory.

ROTFLMAO!!!!

Have you not stated in the past that in Maxwell's theory, the Maxwell
equations are only approximations valid in the case of low speed
relative to the ether of both observer and source?

I have indeed so stated.

Then Maxwell's ether model is not classical EM theory.

Do note that
"classical electromagnetic theory" is a technical term with a meaning more
precise than "classical" "electromagnetic theory". Ritz's and Weber's
electromagnetic theories are classical as well, but they're not "classical
electromagnetic theory", either.

What bearing, then, does
Maxwell's model have on classical EM theory?

Well, Maxwell's equations were derived from Maxwell's classical model.
That makes them classical.

No, that isn't what makes them classical.

Note well that Lorenz obtained the Maxwell equations almost
simultaneously without recourse to an ether or a mechanical
model,

Well, this is news to me. Do you have a reference for this work of
Lorenz?

Given that the paper by Jackson & Okun (RMP 2001) you have been previously
referred to, and the content of which you did discuss over the course of
many posts in a previous thread, discusses the work of Lorenz, and gives
references to Lorenz's original publication, I am somewhat surprised that
this is news to you.
Jackson & Okun also note that Maxwell refers to Lorenz's work in his
Treatise.

and Hertz did the same later.
And then there are the modern derivations.

But none of these are physical derivations. They are merely mathematical
manipulations.

Why? Both Lorenz and Hertz made use of the physical behaviour of
electromagnetic systems in their derivations. How they merely mathematical
manipulations?

The modern derivations are very firmly based on a small set of
well-observed physical phenomena.

All more physical than Maxwell's model, in that they don't invoke the
mechanical properties of a non-existent ether.

Irrelevant to the fact that the only physical derivation of Maxwell's
equations prohibits magnetic monopoles.

But, as you have repeatedly said, the Maxwell equations are only an
approximation of the behaviour of Maxwell's mechanical model.

Is div B = 0 an approximation, or is it actually exact?

If it is exact, in
what way are the Maxwell equations an approximation?

div B = 0 is simply an experimental observation.

That would imply that there are *no* theoretical explanations. And
Maxwell's derivation is clearly theoretical. That Lorenz, Hertz, and
modern 'derivations' do not have this same theoretical limitation
does not mean that there are *no* theoretical derivations.

Of course, the theory
would need to be modified if a counter-observation is made,

I believe that would crisp Maxwell's theory completely. I'm not sure
how one could salvage it.

Maybe it would crisp Maxwell's model completely. But so what? Maxwell's
mechanical model is already defunct.

Classical EM theory, as the term is
currently used in physics, would have no difficulty accomodating it.

[cut remainder]

On Fri, 4 Jun 2004, greywolf42 wrote:

Timo Nieminen <timo@physics.uq.edu.au> wrote:
On Thu, 3 Jun 2004, greywolf42 wrote:

Timo Nieminen <timo@physics.uq.edu.au> wrote:

It's simply the non-observation of magnetic charge. First noted,
AFAIK, by Gilbert back in around 1600.

It's also a conclusion from Maxwell's physical derivation. It's not
'just' an observation.

[cut]

These people do so because there is no fundamental reason why they
should not exist according to classical EM theory.

A false statement. You can't get more classical than Maxwell. And
Maxwell when explicitly derived his equations (On Physical Lines
of Force, 1861), the derivation found that magnetic monopoles
were theoretically impossible. Which is why they don't show up
in the equations.

Addressed in detail elsewhere in the thread.

Apparently you mean to do this later. Or my newsreader is acting up
again.....

Odd. Your reply to the post where this was addressed in more detail shows
up as posted earlier than this one on both my local newsserver and google.

To summarise:

Maxwell's ether model is not classical EM theory, as the term
"classical EM theory" is used today.

Ahhh, so!! The 'exclusion by definition' trick. This is as useful a
statement as:
A poodle is not a dog, as the term 'dog' is used today.

Are you wanting to discuss physics, or are you just trolling? First, you
introduce a misleading and irrelevant point into an already existing
discussion, and then you start with cheap debating tricks like the one
above.

Do note that the statement:
Maxwell's ether model is not classical EM theory, as the term
"classical EM theory" is used today.
is actually true. If you doubt this, try reading some classical EM theory
textbooks.

Your statement that the above statement is as useful as:
A poodle is not a dog, as the term 'dog' is used today.
which is (1) off-topic and (2) wrong is simply incorrect, since the former
is (1) relevant to your intended diversion into an irrelevant discussion
of Maxwell's ether model, and (2) correct.

So away with your cheap debating tricks!

Do note that I did not invent any new definitions above, just reminded you
of the industry standard definition that is in common use. Your claim to
be a victim of "exclusion by definition" is rather flimsy.

Well, I don't think that magnetic monopoles exist. But then, the
universe is what the universe is, and can surprise us.

I like surprises. I just don't care for callous disregard for history,
or attempts to shade the truth within a supposedly scientific
discourse.

Neither do I. That's why I think cheap debating tricks should be avoided.

Stick to the physics.

Timo Nieminen <timo@physics.uq.edu.au> wrote in message
news:Pine.LNX.4.50.0406070853280.13486-100000@localhost...
On Fri, 4 Jun 2004, greywolf42 wrote:

Timo Nieminen <timo@physics.uq.edu.au> wrote:

{snip higher levels}

Maxwell's derivation of Maxwell's equations (On
Physical Lines of Force, 1861) explicitly prohibits magnetic
monopoles. Find a magnetic monopole, and disprove
Maxwell's aether!

Maxwell's ether is already disproved,

Really? When did Maxwell's equations get disproved?

As you have repeatedly written, the Maxwell equations are only an
approximate description of Maxwell's ether.

Not quite. What I've pointed out is that Maxwell's equations are
approximations that hold only under certain conditions.

One can therefore disprove
Maxwell's ether without disproving the Maxwell equations. In fact, one
can disprove Maxwell's ether by failing to disprove the Maxwell
equations.

Your logic is inverted. And incorrect.

One cannot claim that because Maxwell's equations have not yet been
disproven, that they are proved true.

One must set up experiments that can distinguish where Maxwell's equations
should break down -- according to Maxwell's theory.

Note "absence of charge" in the list above.

That is an extraordinary claim, which I hope you can back up with
references. The only known cause of magnetic fields are electric
charges in motion.

... with a possible exception of free radiation fields. But this is a
matter of definition.

I don't see why you believe the claim above to be extraordinary. Do you
know of an observation of div B != 0 in the absence of charge?

Granted, if one excludes free radiation fields and fields of particles
such as neutrons, div B = 0 in the absence of charge reduces to the rather
tautologous div 0 = 0, but this certainly doesn't harm the correctness of
the claim.

And Magnetic fields occur in the
absence of charge?

What is the magnetic moment of a neutron? What is the charge of a neutron?
That's about the closest to magnetic field in the absence of a charge
that's been observed.

Quantum Theory and scattering experiments both show neutron's are
internally charged.

As I said, that's about the closest observed. What else would you expect
in the absence of magnetic charge?

But note that your original question restricted the matter to classical EM
theory, and bringing in the question of particulate matter is somewhat
beside the point, especially elements of quantum theory.

My question is _why_ would the Maxwell equations require
modifications? If a premise of a theory is that charges in motion
cause solenoidal magnetic fields, then even if magnetic charge can
exist in some other way, why would this the theory require alteration
since the original premise remains valid?

If magnetic charge is found, then you no longer have div B = 0.
Since div B = 0 is one of the Maxwell equations, then the Maxwell
equations require modification.

Read properly. Why does magnetic charge change div B = 0 for magnetic
fields of charges in motion?

Why don't you read properly? The Maxwell equations are not restricted to
fields of charges in motion; they describe the behaviour of electric and
magnetic fields, irrespective of their sources. Since this behaviour does
depend on sources, all known sources of electric and magnetic fields must
appear in the Maxwell equations. At the moment, only electric charge and
electric current are included, since these are the only known sources. If
magnetic charge is found, then magnetic charge and current will need to be
included. Until then, they're not needed. (But you might note that
magnetic currents are sometimes used as equivalent sources.)

This is where I disagree. By design, Maxwell's theory is constrained
to the special case of electric charges in motion.

Then you're quibbling about a philosophical matter of opinion, and not
physics.

If you really, truly, believe that the Maxwell equations are intended to
be restricted only to classical electromagnetic phenomena produced by
electric charges in motion (presumably including the special case of
stationary charges), then what was the point of your original question,
since in that case, classical EM theory can have nothing at all to say
about magnetic charge?

Perhaps you would be more content if I rephrase the statement on
modification of the Maxwell equations to:

The modifications that would be required for a classical EM theory
desribing all classical EM phenomena, were magnetic charge to be
discovered, are simple and well-known.

The original premise is div B = 0, and this would no longer be valid.

No, it would still be valid.

No, it would not. Think about what div B = 0 actually means.

div B = 0 is an experimentally verified premise which the remainder of
the equations are based off. Maxwell's equations are true for div B =
0.

If magnetic charge is observed, div B = 0 will no longer be an
experimentally verified premise. And therefore will require modification.

How can div B = 0 be valid if contradicted by observation?

If magnetic charge is observed, div B = 0 will no longer be an
experimentally verified premise. And therefore will require modification.

snip

Timo Nieminen <timo@physics.uq.edu.au> wrote:
On Fri, 4 Jun 2004, greywolf42 wrote:

Timo Nieminen <timo@physics.uq.edu.au> wrote:

{snip higher levels}

Sure, Maxwell is definitely classical, and it may well be that
Maxwell's ether model prohibits divergence in magnetic fields.
However, Maxwell's ether model is not classical EM theory.

ROTFLMAO!!!!

Have you not stated in the past that in Maxwell's theory, the Maxwell
equations are only approximations valid in the case of low speed
relative to the ether of both observer and source?

I have indeed so stated.

Then Maxwell's ether model is not classical EM theory.

Non sequiteur.

Do note that
"classical electromagnetic theory" is a technical term with a meaning more
precise than "classical" "electromagnetic theory". Ritz's and Weber's
electromagnetic theories are classical as well, but they're not "classical
electromagnetic theory", either.

Then why don't you avoid silly quibbling about what is contained in the
definition of the three words 'classical electromagnetic theory' and address
the substantive issue?

The point is, that a boldfaced lie was made, when it was claimed that there
was no theoretical argument against the existence of magnetic monopoles.

That you wish to ignore Maxwell's derivation of his equations is merely
propaganda.

What bearing, then, does
Maxwell's model have on classical EM theory?

Well, Maxwell's equations were derived from Maxwell's classical model.
That makes them classical.

No, that isn't what makes them classical.

What does? It doesn't use quantum mechanics. It doesn't use SR. It is
entirely based on Newtonian mechanics. That qualifies for 'classical' in my
book.

Note well that Lorenz obtained the Maxwell equations almost
simultaneously without recourse to an ether or a mechanical
model,

Well, this is news to me. Do you have a reference for this work of
Lorenz?

Given that the paper by Jackson & Okun (RMP 2001) you have been previously
referred to, and the content of which you did discuss over the course of
many posts in a previous thread, discusses the work of Lorenz, and gives
references to Lorenz's original publication, I am somewhat surprised that
this is news to you.
Jackson & Okun also note that Maxwell refers to Lorenz's work in his
Treatise.

That Maxwell's Treatise (and Jackson & Okun) refer to Lorenz does not equate
with Lorenz having derived all of Maxwell's equations.

The thread to which
you refer was with regard to the origin of the concept of gauge invariance.

http://www.google.com/groups?selm=102id1b3b17soe5%40corp.supernews.com

You'll note that I caught Jackson being freely creative with history.

"(Jackson's) 'imprecision' with Maxwell does not make me confident of his
abilities
with Lorenz, Hertz or Heaviside."

and Hertz did the same later.
And then there are the modern derivations.

But none of these are physical derivations. They are merely mathematical
manipulations.

Why? Both Lorenz and Hertz made use of the physical behaviour of
electromagnetic systems in their derivations. How they merely mathematical
manipulations?

Because there was never any attempt to handle the symbols as anything
physical. (Hint: "Electromagnetic systems" begs the question.)

The modern derivations are very firmly based on a small set of
well-observed physical phenomena.

But there are no phenomena at all used in these 'modern' derivations. It's
all pure symbolism. Arbitrary constants. Nothing physical.

All more physical than Maxwell's model, in that they don't invoke the
mechanical properties of a non-existent ether.

Without physical properties, they aren't physical.

Irrelevant to the fact that the only physical derivation of Maxwell's
equations prohibits magnetic monopoles.

But, as you have repeatedly said, the Maxwell equations are only an
approximation of the behaviour of Maxwell's mechanical model.

But a very good approximation for most laboratory work.

Is div B = 0 an approximation, or is it actually exact?

That part is exact.

If it is exact, in
what way are the Maxwell equations an approximation?

The same way they have been described literally dozens of times for you,
Timo.

http://www.google.com/groups?selm=101vu9m7c668ua4%40corp.supernews.com

1) Green's identities hold (the continuum approximation for fluid
mechanics).
2) The motion of the source and/or the motion of the receiver through the
aether is small relative to the speed of light.
3) The energy density of the effects are small relative to the energy
density of the medium.
4) Maxwell's assumption of incompressibility is not violated by attempting
to get too "close" to a charge.
5) The distances involved do not exceed the limits of the dynamic viscosity
of the fluid.

div B = 0 is simply an experimental observation.

That would imply that there are *no* theoretical explanations. And
Maxwell's derivation is clearly theoretical. That Lorenz, Hertz, and
modern 'derivations' do not have this same theoretical limitation
does not mean that there are *no* theoretical derivations.

Of course, the theory
would need to be modified if a counter-observation is made,

I believe that would crisp Maxwell's theory completely. I'm not sure
how one could salvage it.

Maybe it would crisp Maxwell's model completely. But so what? Maxwell's
mechanical model is already defunct.

That you want to ignore historical fact because it is inconvenient to your
personal religion is your problem.

Classical EM theory, as the term is
currently used in physics, would have no difficulty accomodating it.

But the term is a meaningless social farce. If you simply scrawl marks on
paper, anything is possible. However, teh real universe requires physical
action.

Timo Nieminen <timo@physics.uq.edu.au> wrote:
On Fri, 4 Jun 2004, greywolf42 wrote:

Timo Nieminen <timo@physics.uq.edu.au> wrote:
On Thu, 3 Jun 2004, greywolf42 wrote:

Timo Nieminen <timo@physics.uq.edu.au> wrote:

It's simply the non-observation of magnetic charge. First noted,
AFAIK, by Gilbert back in around 1600.

It's also a conclusion from Maxwell's physical derivation. It's not
'just' an observation.

[cut]

These people do so because there is no fundamental reason why they
should not exist according to classical EM theory.

A false statement. You can't get more classical than Maxwell. And
Maxwell when explicitly derived his equations (On Physical Lines
of Force, 1861), the derivation found that magnetic monopoles
were theoretically impossible. Which is why they don't show up
in the equations.

Addressed in detail elsewhere in the thread.

Apparently you mean to do this later. Or my newsreader is acting up
again.....

Odd. Your reply to the post where this was addressed in more detail shows
up as posted earlier than this one on both my local newsserver and google.

Oh, you meant your statements about what you would include in the term
'classical EM theory.' Your words implied that you were going to address
Maxwell's derivation. Which you didn't.

To summarise:

Maxwell's ether model is not classical EM theory, as the term
"classical EM theory" is used today.

Ahhh, so!! The 'exclusion by definition' trick. This is as useful a
statement as:
A poodle is not a dog, as the term 'dog' is used today.

Are you wanting to discuss physics, or are you just trolling? First, you
introduce a misleading and irrelevant point into an already existing
discussion, and then you start with cheap debating tricks like the one
above.

LOL! Your 'cutting' of the text in no way means that it didn't exist!

The historical fact that Maxwell has a very explicit theoretical prohibition
on magnetic monopoles, is by no means 'misleading' or 'irrelevant' to the
false claim that there exists no theoretical reason why MMs should not
exist.

Timo Nieminen <timo@physics.uq.edu.au> wrote in message
news:Pine.LNX.4.50.0406070853280.13486-100000@localhost...
On Fri, 4 Jun 2004, greywolf42 wrote:

Timo Nieminen <timo@physics.uq.edu.au> wrote:

{snip higher levels}

Maxwell's derivation of Maxwell's equations (On
Physical Lines of Force, 1861) explicitly prohibits magnetic
monopoles. Find a magnetic monopole, and disprove
Maxwell's aether!

Maxwell's ether is already disproved,

Really? When did Maxwell's equations get disproved?

As you have repeatedly written, the Maxwell equations are only an
approximate description of Maxwell's ether.

Not quite. What I've pointed out is that Maxwell's equations are
approximations that hold only under certain conditions.

One can therefore disprove
Maxwell's ether without disproving the Maxwell equations. In fact, one can
disprove Maxwell's ether by failing to disprove the Maxwell equations.

Your logic is inverted. And incorrect.

One cannot claim that because Maxwell's equations have not yet been
disproven, that they are proved true.

One must set up experiments that can distinguish where Maxwell's equations
should break down -- according to Maxwell's theory.

by the experimental observation of
symmetry under Lorentz transformations.

Symmetry is not an observable.

You can look at something with mirror symmetry and see that it is
symmetric about its plane of symmetry?

Your statement is circular. You cannot 'observe' symmetry.

And 'symmetry under lorentz transformations'
is a mathematical statement.

... with a physical meaning.

Mathematics is not physical. Mathematics are mere words.... i.e. symbols
describing reality.

They are not themselves reality.

Mathematical fact: the Maxwell equations are Lorentz symmetric.

A true, but irrelevant statement.

Physical fact: the Maxwell equations describe classical EM for all
observed velocities of sources, for inertial reference frames.

That is not a 'fact,' it is an assumption in SR. It is also untrue.

Could you be more specific, here, about experimental observation?

Wolf et al, PRL 90, 060402 (2003) for starters.

"Tests of Lorentz Invariance using a Microwave Resonator", by Peter Wolf, et
al.

Abstract:
"The frequencies of a cryogenic sapphire oscillator and a hydrogen maser are
compared to set new constraints on a possible violation of Lorentz
invariance. We determine the variation of the oscillator frequency as a
function of its orientation (Michelson-Morley test) and of its velocity
(Kennedy-Thorndike test) with respect to a preferred frame candidate. We
constrain the corresponding parameters of the Mansouri and Sexl test theory
to -+ 1/2 = (1.5±4.2)×10-9 and --1 = (-3.1±6.9)×10-7 which is of the same
order as the best previous result for the former and represents a 30-fold
improvement for the latter."

This paper says nothing whatsoever about "experimental observation of
symmetry under Lorentz transformations."

For Wolf did not attempt to move
the oscillator at relativistic speeds w.r.t. the lab.

I should also point
out that Lorentz (1904) pointed out the futility of attempting to measure
speed variations through the use of interference effects.

But there are plenty more.

That is always the assertion of the Relativists. But the references never
seem to actually address the issue at all when you actually get a Relativist
to give you a citation.