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| Richard Herring |
 Posted: Thu Jun 03, 2004 9:59 am |
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Guest
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In message <20040603105845.02623.00000418@mb-m28.aol.com>, BllFs6
<bllfs6@aol.com> writes
[quote:352a0f4d98]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)?
I seem to vaguely recall that one/some/all/current? theory(s) required at least
ONE magnetic monopole in the whole"universe"....but of course if there was only
ONE your chances of detecting it would be pretty slim :)
Does anyone else know/recall such a thing and have a better recollection of the
how and why of such a thing....assuming I am remotely remembering right in the
first place?
I guess what you're thinking of is that the existence of a monopole is a[/quote:352a0f4d98]
sufficient (but not necessary) condition for the quantisation of
electric charge. IOW it's not required, but finding it would explain a
lot.
Jackson explains it, but don't ask me to.
--
Richard Herring |
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| John Schoenfeld |
| Posted: Thu Jun 03, 2004 10:32 am |
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Timo Nieminen <timo@physics.uq.edu.au> wrote in message news:<Pine.LNX.4.50.0406031217100.12049-100000@localhost>...
[quote:2f3730080e]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?
No. See, for example, Jackson, Classical electrodynamics, 3rd ed, section
6.11.
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.
[/quote:2f3730080e]
I meant "charges in motion".
[quote:2f3730080e]It's simply the non-observation of magnetic charge. First noted, AFAIK, by
Gilbert back in around 1600.
The observation does not
conclude in any way that all magnetic fields are caused by charges in
motion, does it?
To stray somewhat from classical EM, is there any particle with an
intrinsic magnetic moment? Is the field from such a particle caused by
charges in motion?
Do note that people have looked for, and do look for, magnetic monopoles.
These people do so because there is no fundamental reason why they should
not exist according to classical EM theory.
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).
[/quote:2f3730080e]
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? |
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| John Schoenfeld |
| Posted: Thu Jun 03, 2004 10:40 am |
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moroney@world.std.spaamtrap.com (Michael Moroney) wrote in message news:<c9m5ci$d28$1@pcls4.std.com>...
[quote:991481a13c]"Robert J. Kolker" <robert_kolker@hotmail.com> writes:
John Schoenfeld wrote:
Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields? If so, what precisely is it that forces _all_
magnetic fields to be solenoidal (abductive reasoning is not good
enough)?
It will have to do. The only magenetic fields that have been seen are
solenoidal and at right angles to the current. If someone does come up
with a magnetic monople Maxwells's Equations will have to be altered.
As written, Maxwell's Equations describe a world with no such thing as
magnetic monopoles. If magnetic monopoles exist, you'd have to change
the div B term,
[/quote:991481a13c]
Why does the existence of magnetic charge suddenly change the fact
that electric charges in motion cause solenoidal magnetic fields?
[quote:991481a13c]and most likely the curl E term (a "current" of monopoles
would generate an electric field around it).
[/quote:991481a13c]
Why do you believe that would that occur?
[quote:991481a13c]The modified Maxwell's
Equations would be symmetric, you could swap every electric and magnetic
field reference and every electric and magnetic "charge" and it would be
unchanged.
[/quote:991481a13c]
I would like to see such modified equations. Can pleas you provide
such references? |
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| greywolf42 |
| Posted: Thu Jun 03, 2004 10:53 am |
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Robert J. Kolker <robert_kolker@hotmail.com> wrote in message
news:aSrvc.37813$eY2.10359@attbi_s02...
[quote:8132e960ba]
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.
Maxwell's Equations were not graven on tablets of stone and brought down
from a mountain peak. The were formulated to describe and predict
certain phehomena some of which were known empirically.
[/quote:8132e960ba]
A false statement. Maxwell's equations were derived. Not just empirical
relationships.
Empirical relationships existed for 3 of 4 of the ME, prior to Maxwell.
(The fourth was incorrect, prior to Maxwell).
[quote:8132e960ba]M.E. cannot be
deduced a prior from a necessary synthetic a prior principle.
[/quote:8132e960ba]
A pathetically unsupportable lie. Since Maxwell did exactly that (derive
Maxwell's Equations from a specfic, physical model of a corpuscular,
superfluid aether).
--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail} |
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| Gregory L. Hansen |
| Posted: Thu Jun 03, 2004 11:11 am |
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Guest
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In article <10buv5u3gruce1d@corp.supernews.com>,
greywolf42 <mingstb@marssim-ss.com> wrote:
[quote:d1e5eda3e3]Gregory L. Hansen <glhansen@steel.ucs.indiana.edu> wrote in message
news:c9ncjm$k7l$4@hood.uits.indiana.edu...
In article <a98beaaa.0406021336.196c4a30@posting.google.com>,
John Schoenfeld <j.schoenfeld@programmer.net> wrote:
Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields? If so, what precisely is it that forces _all_
magnetic fields to be solenoidal (abductive reasoning is not good
enough)?
There's no theoretical reason to prohibit magnetic monopoles. It's an
experimental matter.
An utter falsehood. Maxwell's derivation of Maxwell's equations (On
Physical Lines of Force, 1861) explicitly prohibits magnetic monopoles.
Find a magnetic monopole, and disprove Maxwell's aether!
[/quote:d1e5eda3e3]
Maxwell's equations can easily be symmetrized to include electrical and
magnetic charge, and nobody cares what quaint pictures of swirling fluids
Maxwell might have had in mind at the time.
--
"The main, if not the only, function of the word aether has been to
furnish a nominative case to the verb 'to undulate'."
-- the Earl of Salisbury, 1894 |
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| Franz Heymann |
| Posted: Thu Jun 03, 2004 12:35 pm |
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"John Schoenfeld" <j.schoenfeld@programmer.net> wrote in message
news:a98beaaa.0406021802.20b74de4@posting.google.com...
[quote:4cd94dfa3a]"Robert J. Kolker" <robert_kolker@hotmail.com> wrote in message
news:<aSrvc.37813$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
[/quote:4cd94dfa3a]
The equations would have to be changed so as to become symmetrical in
E<->H and D<->B
[quote:4cd94dfa3a]since the equations are
considering only the special case of steady currents
[/quote:4cd94dfa3a]
That is wrong
[snip]
Franz |
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| greywolf42 |
| Posted: Thu Jun 03, 2004 1:24 pm |
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Gregory L. Hansen <glhansen@steel.ucs.indiana.edu> wrote in message
news:c9ncjm$k7l$4@hood.uits.indiana.edu...
[quote:56044636bb]In article <a98beaaa.0406021336.196c4a30@posting.google.com>,
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.
[/quote:56044636bb]
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!
{snip}
--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail} |
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| greywolf42 |
| Posted: Thu Jun 03, 2004 1:28 pm |
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Timo Nieminen <timo@physics.uq.edu.au> wrote in message
news:Pine.LNX.4.50.0406031217100.12049-100000@localhost...
[quote:ecc1877184]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?
No. See, for example, Jackson, Classical electrodynamics, 3rd ed,
section
6.11.
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.
It's simply the non-observation of magnetic charge. First noted, AFAIK, by
Gilbert back in around 1600.
[/quote:ecc1877184]
It's also a conclusion from Maxwell's physical derivation. It's not 'just'
an observation.
[quote:ecc1877184]The observation does not
conclude in any way that all magnetic fields are caused by charges in
motion, does it?
To stray somewhat from classical EM, is there any particle with an
intrinsic magnetic moment? Is the field from such a particle caused by
charges in motion?
Do note that people have looked for, and do look for, magnetic monopoles.
[/quote:ecc1877184]
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.)
[quote:ecc1877184]These people do so because there is no fundamental reason why they should
not exist according to classical EM theory.
[/quote:ecc1877184]
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.
[quote:ecc1877184]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).
[/quote:ecc1877184]
Yep. There just would no longer be any theoretical support for Maxwell's
equations.
--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail} |
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| greywolf42 |
| Posted: Thu Jun 03, 2004 1:29 pm |
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Timo Nieminen <timo@physics.uq.edu.au> wrote in message
news:Pine.LNX.4.50.0406030856080.11833-100000@localhost...
[quote:8599d84144]On Thu, 2 Jun 2004, John Schoenfeld wrote:
Is there anything in classical e&m that _prohibits_ a divergence in
magnetic fields?
No. See, for example, Jackson, Classical electrodynamics, 3rd ed, section
6.11.
[/quote:8599d84144]
Sorry, Maxwell is definitely classical. And his original definition of
"Maxwell's equations" prohibited divergence in magnetic fields. (On
Physical Lines of Force, 1861)
[quote:8599d84144]div B = 0 is an experimental observation.
[/quote:8599d84144]
Yes, despite decades of looking, there are no magnetic monopoles.
--
greywolf42
ubi dubium ibi libertas
{remove planet for return e-mail} |
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| Timo Nieminen |
| Posted: Thu Jun 03, 2004 4:14 pm |
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On Thu, 3 Jun 2004, Sam Wormley wrote:
[quote:6c30c072db]I read Jackson section 6.11 last night... excellent reading.
[/quote:6c30c072db]
That's the nice thing about Jackson. There's always something interesting
and educational to found therein.
Of course, part of this is due to the difficulty in digestion the first
time through, but that again is partly due to the depth of content.
--
Timo Nieminen - Home page: http://www.physics.uq.edu.au/people/nieminen/
Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html |
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| Gregory L. Hansen |
| Posted: Thu Jun 03, 2004 4:18 pm |
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Guest
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In article <Pine.LNX.4.50.0406040812270.17435-100000@localhost>,
Timo Nieminen <timo@physics.uq.edu.au> wrote:
[quote:b29131945d]On Thu, 3 Jun 2004, Sam Wormley wrote:
I read Jackson section 6.11 last night... excellent reading.
That's the nice thing about Jackson. There's always something interesting
and educational to found therein.
Of course, part of this is due to the difficulty in digestion the first
time through, but that again is partly due to the depth of content.
[/quote:b29131945d]
And also because he covers so danged much material. It's a big book, but
it's also a concise book! It's tersely written, and the students are
expected to provide sometimes significant and profound material themselves
at the end of each chapter.
There's a reason Jackson is a classic. And there's a reason he's loathed
by students everywhere.
--
"Things should be made as simple as possible -- but no simpler."
-- Albert Einstein |
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| Timo Nieminen |
| Posted: Thu Jun 03, 2004 4:36 pm |
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On Fri, 3 Jun 2004, John Schoenfeld wrote:
[quote:47a363f36a]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?
No. See, for example, Jackson, Classical electrodynamics, 3rd ed, section
6.11.
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".
[/quote:47a363f36a]
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.
[quote:47a363f36a]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?
[/quote:47a363f36a]
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.
The original premise is div B = 0, and this would no longer be valid.
--
Timo Nieminen - Home page: http://www.physics.uq.edu.au/people/nieminen/
Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html |
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| Old Man |
| Posted: Thu Jun 03, 2004 4:44 pm |
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"John Schoenfeld" <j.schoenfeld@programmer.net> wrote in message
news:a98beaaa.0406030840.2363d28@posting.google.com...
[quote:decc2efcc9]moroney@world.std.spaamtrap.com (Michael Moroney) wrote in message
news:<c9m5ci$d28$1@pcls4.std.com>...
"Robert J. Kolker" <robert_kolker@hotmail.com> writes:
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.
As written, Maxwell's Equations describe a world with no such thing as
magnetic monopoles. If magnetic monopoles exist, you'd have to change
the div B term,
Why does the existence of magnetic charge suddenly change the fact
that electric charges in motion cause solenoidal magnetic fields?
[/quote:decc2efcc9]
It doesn't. Adding terms to Maxwell's equations that
permit magnetic monopoles, doesn't change the field /
current relationship for a current loop or solenoid.
[quote:decc2efcc9]and most likely the curl E term (a "current" of monopoles
would generate an electric field around it).
Why do you believe that would that occur?
The modified Maxwell's
Equations would be symmetric, you could swap every electric and magnetic
field reference and every electric and magnetic "charge" and it would be
unchanged.
I would like to see such modified equations. Can pleas you provide
such references?
[/quote:decc2efcc9]
http://www.iw.net/~jakoepke
[Old Man] |
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| Timo Nieminen |
| Posted: Thu Jun 03, 2004 4:54 pm |
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On Thu, 3 Jun 2004, greywolf42 wrote:
[quote:ec6981e2a7]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?
No. See, for example, Jackson, Classical electrodynamics, 3rd ed, section
6.11.
Sorry, Maxwell is definitely classical. And his original definition of
"Maxwell's equations" prohibited divergence in magnetic fields. (On
Physical Lines of Force, 1861)
[/quote:ec6981e2a7]
So what? 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.
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? What bearing, then, does
Maxwell's model have on classical EM theory?
Note well that Lorenz obtained the Maxwell equations almost simultaneously
without recourse to an ether or a mechanical model, and Hertz did the same
later.
And then there are the modern derivations.
div B = 0 is simply an experimental observation. Of course, the theory
would need to be modified if a counter-observation is made, but that's not
the same as a theory prohibiting something.
[quote:ec6981e2a7]div B = 0 is an experimental observation.
Yes, despite decades of looking, there are no magnetic monopoles.
[/quote:ec6981e2a7]
Better to say that, despite decades of looking, no magnetic monopoles have
been found.
--
Timo Nieminen - Home page: http://www.physics.uq.edu.au/people/nieminen/
Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html |
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| Timo Nieminen |
| Posted: Thu Jun 03, 2004 5:00 pm |
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On Thu, 3 Jun 2004, greywolf42 wrote:
[quote:faf37650f8]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.
[/quote:faf37650f8]
Addressed in detail elsewhere in the thread.
To summarise:
Maxwell's ether model is not classical EM theory, as the term "classical
EM theory" is used today.
[MOVED]
[quote:faf37650f8]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.)
[/quote:faf37650f8]
Well, I don't think that magnetic monopoles exist. But then, the universe
is what the universe is, and can surprise us.
--
Timo Nieminen - Home page: http://www.physics.uq.edu.au/people/nieminen/
Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html |
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