Author 
Message 
Sue... science forum Guru
Joined: 08 May 2005
Posts: 2684

Posted: Sat Jul 08, 2006 11:33 pm Post subject:
Re: Magnetic Idyll



Edward Green wrote:
Quote:  The formal simularity of the Coriolis force and the Lorentz force law
2w x v vs. qB x v
suggests that the magnetic field may correspond to a local rotation of
space (inertial coordinate system) as seen by charge vs. that seen by
mass.
On the proside, one can easily list more hints that magentic effects
have to so with something or other rotating. On the con side, there
doesn't seem to be an obvious way in incorporate the centrifugal force
into this analogy  for purposes of "magnetic rotation", the test
particle is always on axis.
Comments?

What rotates is an ensemble of electric charges.
"The origin of permanent magnetism"
http://farside.ph.utexas.edu/teaching/302l/lectures/node62.html
"Visualizations"
http://web.mit.edu/8.02t/www/802TEAL3D/teal_tour.htm
If you take a Machian view of inertia, the the dielectric propeties
of free space don't make too bad an analogy to the gravitational/
inertial field established by nearby matter.
There are numerous way to incorporate the
magnetic force into gravity/inertia. You are building bricks
with little houses. Try it the other way round. )
http://www.esa.int/SPECIALS/GSP/SEM0L6OVGJE_0.html
http://www.mypage.bluewin.ch/Bizarre/GRAV.htm
Sue... 

Back to top 


Bill Hobba science forum Guru
Joined: 02 May 2005
Posts: 2138

Posted: Sun Jul 09, 2006 1:24 am Post subject:
Re: Magnetic Idyll



"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:1152400330.145973.161020@s13g2000cwa.googlegroups.com...
Quote:  The formal simularity of the Coriolis force and the Lorentz force law
2w x v vs. qB x v
suggests that the magnetic field may correspond to a local rotation of
space (inertial coordinate system) as seen by charge vs. that seen by
mass.

Cross products appear all over the place in physics. That does not imply
they are related any more than bacteria growth and monetary growth with
interest being exponential implies bacteria are related to money.
Quote: 
On the proside, one can easily list more hints that magentic effects
have to so with something or other rotating.

Sure  usually electron spin or electrons 'rotating' around atoms. Of
course these are quantum effects but in a very crude way it is rotation.
Bill
Quote:  On the con side, there
doesn't seem to be an obvious way in incorporate the centrifugal force
into this analogy  for purposes of "magnetic rotation", the test
particle is always on axis.
Comments?



Back to top 


Tom Roberts science forum Guru
Joined: 24 Mar 2005
Posts: 1399

Posted: Sun Jul 09, 2006 5:34 am Post subject:
Re: Magnetic Idyll



Edward Green wrote:
Quote:  The formal simularity of the Coriolis force and the Lorentz force law
2w x v vs. qB x v
suggests that the magnetic field may correspond to a local rotation of
space (inertial coordinate system) as seen by charge vs. that seen by
mass.

Not really.
The Lorentz force law, written in terms of physical quantities in 4d
spacetime using the language of tensors is:
f = q F.U
Where f is the covariant force 4vector, F is the electromagnetic field
2form (includes both B and E), and U is the 4velocity of the particle
with charge q.
Using the same language, the "Coriolis force" is:
f = 0
I see no similarity here at all ().
[Note, please, that "Coriolis force' is fictitious  merely
an artifact of one's coordinates (your formula applies only to
rotating coordinates). It is _not_ a tensor; Lorentz force is.]
Besides, if this were truly a good analogy there would be an
electromagnetic analog to "centrifugal force" (which is usually much
larger than the "Coriolis force"). With your identification above, the
EM analogy would be B x (B x r), which does not appear in any usual
formula of classical electrodynamics that I am aware of (one applies
"centrifugal force" to a particle sitting still on a carousel, but a
charge sitting still does not "feel" B at all).
Bill Hobba wrote:
Quote:  Cross products appear all over the place in physics. That does not imply
they are related any more than bacteria growth and monetary growth with
interest being exponential implies bacteria are related to money.

Lest anybody wonder why such different phenomena are described by
similar mathematics, let me point out that one makes similar
_approximations_ here: in the real world, the bacteria do not really
have exactly equal and constant reproduction rates, and the money does
not have exactly constant interest rate; by _approximating_ those as
constant one obtains similar differential equations with similar solutions.
Tom Roberts 

Back to top 


Sorcerer1 science forum Guru
Joined: 09 Jun 2006
Posts: 410

Posted: Sun Jul 09, 2006 8:36 am Post subject:
Re: Magnetic Idyll



"Edward Green" <spamspamspam3@netzero.com> wrote in message
news:1152400330.145973.161020@s13g2000cwa.googlegroups.com...
 The formal simularity of the Coriolis force and the Lorentz force law

 2w x v vs. qB x v

 suggests that the magnetic field may correspond to a local rotation of
 space (inertial coordinate system) as seen by charge vs. that seen by
 mass.

 On the proside, one can easily list more hints that magentic effects
 have to so with something or other rotating. On the con side, there
 doesn't seem to be an obvious way in incorporate the centrifugal force
 into this analogy  for purposes of "magnetic rotation", the test
 particle is always on axis.

 Comments?
1) Coriolis is a change of reference frame, not a force.
The laws of physics in this frame of reference say the ball curves
without being accelerated:
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/gifs/coriolis.mov
2) Single phase induction motors normally rotate in either direction, they
have
a starting winding to determine which. The Lorentz force is nothing more
than the equivalent of squeezing a dough ball so that it spreads out, or
stretching it so that it spreads in. A pastry chef understands physics
better than Lorentz, he knows what to do with a rolling pin.
3) This bottle is juggled from Mickey's left hand to his right and
back again. No forces are involved. If there were friction between
the bottle and the Mickey's frame then the bottle frame and Mickey
frame would try to combine. Then you have force.
http://www.androcles01.pwp.blueyonder.co.uk/Wilson/RotateMickeyLarge.gif
Androcles. 

Back to top 


Sue... science forum Guru
Joined: 08 May 2005
Posts: 2684

Posted: Sun Jul 09, 2006 8:53 am Post subject:
Re: Magnetic Idyll



Tom Roberts wrote:
Quote:  Edward Green wrote:
The formal simularity of the Coriolis force and the Lorentz force law
2w x v vs. qB x v
suggests that the magnetic field may correspond to a local rotation of
space (inertial coordinate system) as seen by charge vs. that seen by
mass.
Not really.
The Lorentz force law, written in terms of physical quantities in 4d
spacetime using the language of tensors is:
f = q F.U
Where f is the covariant force 4vector, F is the electromagnetic field
2form (includes both B and E), and U is the 4velocity of the particle
with charge q.
Using the same language, the "Coriolis force" is:
f = 0
I see no similarity here at all ().

Because you did your transformation wrong so why the
big grin ?
http://farside.ph.utexas.edu/teaching/jk1/lectures/node28.html
Quote: 
[Note, please, that "Coriolis force' is fictitious  merely
an artifact of one's coordinates (your formula applies only to
rotating coordinates). It is _not_ a tensor; Lorentz force is.]
Besides, if this were truly a good analogy there would be an
electromagnetic analog to "centrifugal force" (which is usually much
larger than the "Coriolis force"). With your identification above, the
EM analogy would be B x (B x r), which does not appear in any usual
formula of classical electrodynamics that I am aware of (one applies
"centrifugal force" to a particle sitting still on a carousel, but a
charge sitting still does not "feel" B at all).

What in the world do you think moves the currents toward
surface in this experiment ?
http://www.esa.int/SPECIALS/GSP/SEM0L6OVGJE_0.html
Oh! ... I forgot. That is probably something you'd really
rather not see isn't it.
Sue...
Quote: 
Bill Hobba wrote:
Cross products appear all over the place in physics. That does not imply
they are related any more than bacteria growth and monetary growth with
interest being exponential implies bacteria are related to money.
Lest anybody wonder why such different phenomena are described by
similar mathematics, let me point out that one makes similar
_approximations_ here: in the real world, the bacteria do not really
have exactly equal and constant reproduction rates, and the money does
not have exactly constant interest rate; by _approximating_ those as
constant one obtains similar differential equations with similar solutions.
Tom Roberts 


Back to top 


Edward Green science forum addict
Joined: 21 May 2005
Posts: 95

Posted: Sun Jul 09, 2006 6:01 pm Post subject:
Re: Magnetic Idyll



Bill Hobba wrote:
Quote:  "Edward Green" <spamspamspam3@netzero.com> wrote in message
news:1152400330.145973.161020@s13g2000cwa.googlegroups.com...
The formal simularity of the Coriolis force and the Lorentz force law
2w x v vs. qB x v

That should have been " 2mw x v ".
Quote:  suggests that the magnetic field may correspond to a local rotation of
space (inertial coordinate system) as seen by charge vs. that seen by
mass.
Cross products appear all over the place in physics. That does not imply
they are related any more than bacteria growth and monetary growth with
interest being exponential implies bacteria are related to money.

It at least implies that bacterial growth and monetary growth share a
common structural feature  namely the proportionality of increment to
the amont of stuff there already. And the points of simularity in the
present case go a little deeper than "both involve cross product".
Both forms describe a force as the cross product of velocity with a
given vector (w or B) and a scalar (m or q). So prima facie, the
Lorentz force law and the coriolis force share more common features
than bacteria and money. ;)
Tom Roberts wrote:
<Snip profound argument that if we express the Coriolis force in such a
way that there is no Coriolis force, then there is no Coriolis force>
Quote:  [Note, please, that "Coriolis force' is fictitious  merely
an artifact of one's coordinates (your formula applies only to
rotating coordinates). It is _not_ a tensor; Lorentz force is.]

I'm well aware that the Coriolis force is a socalled fictious force.
The suggestion was put on the table that the "the magnetic field may
correspond to a local rotation of space (inertial coordinate system) as
seen by charge vs. that seen by mass". In other words  I propose
simply in interesting speculation  inertial coordinates may undergo a
kind of split on charge and mass in the presence of magnetic fields, so
that it is not possible to null out fictitious forces applying to both
simultaneously.
Quote:  Besides, if this were truly a good analogy there would be an
electromagnetic analog to "centrifugal force" (which is usually much
larger than the "Coriolis force").

A stronger objection, though I anticipated it. If the idyll is not to
die an early death, than apparently effective "r" is always zero  the
charged particle seens a spinning world, but always sees itself at the
center of that world.
You and Mr. Hobba may find it ultimately more constructive, not to
treat every idle speculation as an occasion for yet more satisfying
error  as you imagine it  bashing. Assuming that is that your goal
is constructive. 

Back to top 


Igor science forum Guru
Joined: 15 May 2005
Posts: 315

Posted: Sun Jul 09, 2006 6:29 pm Post subject:
Re: Magnetic Idyll



Edward Green wrote:
Quote:  The formal simularity of the Coriolis force and the Lorentz force law
2w x v vs. qB x v
suggests that the magnetic field may correspond to a local rotation of
space (inertial coordinate system) as seen by charge vs. that seen by
mass.
On the proside, one can easily list more hints that magentic effects
have to so with something or other rotating. On the con side, there
doesn't seem to be an obvious way in incorporate the centrifugal force
into this analogy  for purposes of "magnetic rotation", the test
particle is always on axis.
Comments?

Basically the centrifugal force is equivalent to the electric field in
this analogy. Taken together, the combined coriolis and centrifugal
forces represent the inertial analog of the Lorentz force. One can
even derive vector and scalar potentials corresponding to these
inertial forces. 

Back to top 


Timo Nieminen science forum Guru Wannabe
Joined: 12 May 2005
Posts: 244

Posted: Sun Jul 09, 2006 7:34 pm Post subject:
Re: Magnetic Idyll



On Sun, 8 Jul 2006, Edward Green wrote:
Quote:  The formal simularity of the Coriolis force and the Lorentz force law
2w x v vs. qB x v
suggests that the magnetic field may correspond to a local rotation of
space (inertial coordinate system) as seen by charge vs. that seen by
mass.

Very Maxwellian. Have you read Maxwell's papers on this kind of thing?
(Although he would have said "local rotation of the (a)ether", not space.)
For some insight: one can obtain Maxwell's equations from Coulomb's law
and special relativity. What happens if you start from Newton's law of
universal gravitation and SR? Surely you must get a gravitomagnetic term.
Heaviside did this, and it's a nice exercise. It isn't necessarily easier
to follow Heaviside than to do it from scratch.
Consider that E and B are defined in terms of the Lorentz force,
F=q(E+vxB), while D and H are defined in terms of source densities (charge
and current densities) and are thus in different units. So, even in free
space, you need constitutive relations for unit conversion (unless you
choose a perverted set of units). What are the gravitational constitutive
relations?
When I set this as a P/F openbook exam, one student was cunning enough to
find it on www, so you can search for it rather than doing it, but I
recommend trying it for an hour or so first.

Timo Nieminen  Home page: http://www.physics.uq.edu.au/people/nieminen/
Eprints: http://eprint.uq.edu.au/view/person/Nieminen,_Timo_A..html
Shrine to Spirits: http://www.users.bigpond.com/timo_nieminen/spirits.html 

Back to top 


Tom Roberts science forum Guru
Joined: 24 Mar 2005
Posts: 1399

Posted: Sun Jul 09, 2006 7:53 pm Post subject:
Re: Magnetic Idyll



Sue... wrote:
Quote:  Tom Roberts wrote:
The Lorentz force law, written in terms of physical quantities in 4d
spacetime using the language of tensors is:
f = q F.U
Using the same language, the "Coriolis force" is:
f = 0
I see no similarity here at all ().
Because you did your transformation wrong so why the
big grin ?

Those are all tensor equations, there is _NO_ transformation involved.
That is, those equations are completely independent of coordinates or
choice of frame.
Tom Roberts 

Back to top 


Igor science forum Guru
Joined: 15 May 2005
Posts: 315

Posted: Sun Jul 09, 2006 7:56 pm Post subject:
Re: Magnetic Idyll



Edward Green wrote:
Quote:  The formal simularity of the Coriolis force and the Lorentz force law
2w x v vs. qB x v
suggests that the magnetic field may correspond to a local rotation of
space (inertial coordinate system) as seen by charge vs. that seen by
mass.
On the proside, one can easily list more hints that magentic effects
have to so with something or other rotating. On the con side, there
doesn't seem to be an obvious way in incorporate the centrifugal force
into this analogy  for purposes of "magnetic rotation", the test
particle is always on axis.
Comments?

Here's a good link:
http://abacus.bates.edu/~msemon/Noteon.pdf 

Back to top 


Tom Roberts science forum Guru
Joined: 24 Mar 2005
Posts: 1399

Posted: Sun Jul 09, 2006 8:01 pm Post subject:
Re: Magnetic Idyll



Edward Green wrote:
Quote:  Tom Roberts wrote:
Not really.
Snip profound argument that if we express the Coriolis force in such a
way that there is no Coriolis force, then there is no Coriolis force

Not at all! You ignored the fact that my equations used
_physical_quantities_.
Quote:  I'm well aware that the Coriolis force is a socalled fictious force.

Then you should abide by the consequences.
Quote:  The suggestion was put on the table that the "the magnetic field may
correspond to a local rotation of space (inertial coordinate system) as
seen by charge vs. that seen by mass".

This does not make sense  the rotation of a coordinate system can have
no physical effects; something _physical_ must be rotating for there to
be physical effects. Magnetism certainly has physical effects.
Quote:  In other words  I propose
simply in interesting speculation  inertial coordinates may undergo a
kind of split on charge and mass in the presence of magnetic fields,

This, too, makes no sense. Changes ("kind of split") in the
_coordinates_ can have no physical consequences.
Quote:  Besides, if this were truly a good analogy there would be an
electromagnetic analog to "centrifugal force" (which is usually much
larger than the "Coriolis force").
A stronger objection, though I anticipated it. If the idyll is not to
die an early death, than apparently effective "r" is always zero  the
charged particle seens a spinning world, but always sees itself at the
center of that world.

Hmmm. Stranger than even quantum mechanics.... Solipsists of the world
unite!
Quote:  You and Mr. Hobba may find it ultimately more constructive, not to
treat every idle speculation as an occasion for yet more satisfying
error  as you imagine it  bashing.

To bring this up to the level of "speculation", you need to find
something _physical_ that is rotating. Imagining effects on coordinates
is irrelevant.
If you consider my pointing out errors in your thoughts as "error
bashing", then why did you post in the first place???
Tom Roberts 

Back to top 


Tom Roberts science forum Guru
Joined: 24 Mar 2005
Posts: 1399

Posted: Mon Jul 10, 2006 12:19 am Post subject:
Re: Magnetic Idyll



Igor wrote:
The authors forgot to mention that the putative E field:
E = (m/q) w x (w x r) (eq. 5)
does not satisfy Maxwell's equations, because div E != 0 yet there are
no charges present.
Tom Roberts 

Back to top 


Edward Green science forum addict
Joined: 21 May 2005
Posts: 95

Posted: Mon Jul 10, 2006 1:27 am Post subject:
Re: Magnetic Idyll



Timo A. Nieminen wrote:
Quote:  On Sun, 8 Jul 2006, Edward Green wrote:
The formal simularity of the Coriolis force and the Lorentz force law
2w x v vs. qB x v
suggests that the magnetic field may correspond to a local rotation of
space (inertial coordinate system) as seen by charge vs. that seen by
mass.
Very Maxwellian. Have you read Maxwell's papers on this kind of thing?
(Although he would have said "local rotation of the (a)ether", not space.)

No I haven't. As regards rotation of the "aether" vs. "space", that is
of course merely (rather emotionally loaded, for some) semantics;
though we could say that if one of the watermarks of the aether is
"preferred rest frame", then the rotational aether, so to speak, has
never gone away.
Quote:  For some insight: one can obtain Maxwell's equations from Coulomb's law
and special relativity.

The whole package? I knew that we could get a magnetic effect from SR
+ electric field (well, so I've heard), but I didn't know we could get
the whole deal. Actually, I've heard mixed comments about this: the
derivations I've seen centered on length contraction, and charge
consequently appearing bunched up, and I've seen those dismissed as at
best heuristic (which I guess means plausibility results we don't
happen to like) and at worst nonsensical  i.e., as an example of a
failed oolie, like the infamous "flow above and below the wing must
meet up".
I suppose a proper relativistic derivation doesn't care how the distant
sources look to us, but focuses on the local properties of the field
and the requirements of Lorentz invariance. Something like?
Quote:  What happens if you start from Newton's law of
universal gravitation and SR? Surely you must get a gravitomagnetic term.
Heaviside did this, and it's a nice exercise. It isn't necessarily easier
to follow Heaviside than to do it from scratch.
Consider that E and B are defined in terms of the Lorentz force,
F=q(E+vxB), while D and H are defined in terms of source densities (charge
and current densities) and are thus in different units. So, even in free
space, you need constitutive relations for unit conversion (unless you
choose a perverted set of units). What are the gravitational constitutive
relations?
When I set this as a P/F openbook exam, one student was cunning enough to
find it on www, so you can search for it rather than doing it, but I
recommend trying it for an hour or so first.

Thanks for the constructive comments. One knows one should not be
sucked into profitless "no, what I said wasn't totally stupid"
arguments, but in the absence of positive feedback, one sometimes
falters. (Was it Pauli who said "You know, what professor Einstein says
is not so stupid...")?
I was just about prepared to stubbornly stand my ground: if we adopt as
the operational _meaning_ of "in the presence of a magnetic field
charged particles seem to see themselves at the center of a different
rotational rest frame than neutral massive particles" as "they obey an
appropriate Coriolis law analogue", then my musuing is a tautology.
And if one thinks about the geometric meaning of the cross product 
rotating the force relative to the velocity around a fixed axis in a
fixed sense, and proprotional in magnitude to the projection of the
velocity in a plane perpendicular to that axis  the sense of having
something to do with rotation is inescapable. I also venture that
every static magnetic source (even an infinitely long straight wires)
involves effective circulation of charge.
Frame dragging? 

Back to top 


Bilge science forum Guru
Joined: 30 Apr 2005
Posts: 2816

Posted: Mon Jul 10, 2006 2:04 am Post subject:
Re: Magnetic Idyll



Edward Green:
Quote:  The formal simularity of the Coriolis force and the Lorentz force law
2w x v vs. qB x v

Actually, you mean 2m w x v.
Quote:  suggests that the magnetic field may correspond to a local rotation of
space (inertial coordinate system) as seen by charge vs. that seen by
mass.

I'm not sure what you mean by the ``formal similarity...''
However, note that for a neutral particle, changing coordinates
to a rotating frame does not give it a charge and two different
particles with the same charge but different masses have different
radii of curvature in the same magnetic field.
What we call spacetime coordinates are numbers we can use to describe
all of the objects we observe in experiments in the same way. The
only reason that gravity can be described as spacetime curvature
(and hence transformed away locally by a suitable change of coordinates)
is that the equivalence principle, in which gravitational and inertial
masses are postulated to e equivalent, holds to the precision experiments
can so far test.
Quote:  On the proside, one can easily list more hints that magentic effects
have to so with something or other rotating. On the con side, there
doesn't seem to be an obvious way in incorporate the centrifugal force
into this analogy  for purposes of "magnetic rotation", the test
particle is always on axis. 


Back to top 


Bilge science forum Guru
Joined: 30 Apr 2005
Posts: 2816

Posted: Mon Jul 10, 2006 4:34 am Post subject:
Re: Magnetic Idyll



Timo A. Nieminen:
Quote:  On Sun, 8 Jul 2006, Edward Green wrote:
The formal simularity of the Coriolis force and the Lorentz force law
2w x v vs. qB x v
suggests that the magnetic field may correspond to a local rotation of
space (inertial coordinate system) as seen by charge vs. that seen by
mass.
Very Maxwellian. Have you read Maxwell's papers on this kind of thing?
(Although he would have said "local rotation of the (a)ether", not space.)
For some insight: one can obtain Maxwell's equations from Coulomb's law
and special relativity. What happens if you start from Newton's law of
universal gravitation and SR? Surely you must get a gravitomagnetic term.
Heaviside did this, and it's a nice exercise. It isn't necessarily easier
to follow Heaviside than to do it from scratch.

Actually, jackson devotes several pages to explaining precisely why
one _cannot_ derive maxwell's equations from special relativity and
coulomb's law, giving gravitation as a counterexample as well a second
counterexample for a particle interacting with a scalar force.
(``Classical Electrodynamics,'' Jackson, J.D., 2nd ed. section 12.2). 

Back to top 


Google


Back to top 



The time now is Mon Mar 17, 2014 4:20 am  All times are GMT

