"EjP" wrote in message ...
Dave wrote:

The reciprocal effect of length contraction and time dilation, which
appears by logical necessity to emerge from the kinematic part of the
special theory of relativity, has been variously explained as

1. true but not really true
2. real
3. not real
4. apparent
5. the result of the relativity of simultaneity
6. determined by measurement
7. a perspective effect
8. mathematical.


When you realize that relativity is ultimately about observation,
the 4,5,7, and 8 are more or less equivalent (with some qualification).
Although 2 and 3 sound contradictory, it depends on your definition
of "real" (believe it or not, "real" is not a well-defined term,
scientifically). Some people would consider a "real" length
contraction to be something involving some sort of physical
compression, understandable in terms of the bulk modulus, and
by that definition, the length contraction is
not "real". On the other hand if "real" means that I could
devise an experiment to measure the length contraction of
something that is moving in my frame, the it is *real*, but
now "real" is entirely consistent
with 4,5,7, and 8. I believe this distinction is what Eddington
was alluding to in comment 1.

As for 6, I don't believe that there have been direct measurements
of length contraction (although I may be wrong), but is an implicit
part of such things as relativistic heavy ion interaction
calculations. It's also used more precisely when doing calculations
involving lasers interacting with relativistic beams, but in that
case it's so intimately wrapped up with Maxwell's equations that
it's impossible to disentangle it. For example, if you try to
calculate something like Compton scattering from a relativistic
beam using some sort of energy density model (rather than
tranforming the field), you'll find that unless you include
length contraction, you'll never reconcile it with reality.


It will be interesting to see how Dave responds to
this logical and obviously non-facetious reply.

Martin Hogbin

Bill Hobba wrote:
For those that doubt length contraction simply analyze a current
carrying
wire. If length contraction occurs then magnetic forces appear -
exactly
as found from experiment - if length contrition does not occur then
magnetic
forces do not appear - in disagreement with experiment.

Richard wrote:
This is not a good example. If you do the math you'll find that length
contraction cancels out of the equation, leaving the force as due to
only the relative velocity and proximity of the respective lines of
charge. Thus your example is actually a counter-argument to the
'reality' of length contraction, i.e. length contraction is unnecessary
and has nothing to do with the measured force.

I have carefully worked through the math many times. I have examined texts
that do the same eg page 488 of Griffiths - Introduction to Electrodynamics
where the derivation of this well known fact is given in full detail. The
analysis depends entirely on the existence of length contraction - the force
between two current carrying wires is zero if length contraction does not
occur and matches exactly what is observed if it does. AFAICS the only
attack that can reasonably be leveled is that electrons moving at constant
velocity though a wire is not really a good model for the complex QM
dependant process that is really occurring - but to my that is not really
germane to the point.

Richard wrote:
Thus I trust you'll see that the development of this force is no proof
or even the slightest indication that length contraction is real.

I trust you will post the flaw in my resoning or read the reference I gave
and point out the page and equation that is in error. To be precise my
claim is the Lorentz force between 2 current carrying wires is zero if
length contraction does not exist (which we know from experiment to be
false) and is exactly the value found by experiment if it does exist.

Thanks
Bill

Richard wrote:
This is not a good example. If you do the math you'll find that length
contraction cancels out of the equation, leaving the force as due to
only the relative velocity and proximity of the respective lines of
charge.

BTW if you do the math you will see that the force results from the fact the
charge density is no longer the same for the moving electrons as for the
stationary nuclei. In the rest frame (where for calculation convenience we
choose one where the electrons are moving at the same velocity in one
direction as the nuclei are moving in the opposite direction - but since the
velocity of electrons is quite small this is not a problem - the reason this
is done is that the wire would not really be neutral in the rest frame
otherwise) the wire is neutral but to a moving electron it is not - the
electrons in the other wire have a different density that the nuclei and
hence the wire is no longer neutral - thus the electron experiences a force.

Thanks
Bill

[EL]
Thank you Dave, for documenting this tragedy.
It is a fascinating phenomenon that the foundation of misconception is
too obvious that it had been repeatedly overlooked.

Misconceptions are related here in this context to vectors of
velocity.

The inverse of velocity had never been named as "dilatency", which
should have been done but never.

Relativity (not any specific theory) is in the fact that you could run
on the surface of a huge spinning sphere in any direction and we do
that all the time on the surface of earth.

By reducing the surface to a plane we can construct *Velocity
Projections*.
The idea was that any vector event could be expressed as three
components parallel to the axis of a constructed coordinate space such
that the interaction's outcome of any two such vectors could be
estimated.

Velocity vectors happen to be expressed as direction-relevant
magnitudes of Length but not just any length.
The length being concerned is a variant measured per unit of time.

Those direction-relevant magnitudes of length CAN be analysed
trigonometrically.

The inverse of velocity is the time dilatency of the moving body in
the same direction but the magnitude is that of a scalar while the
reference unit of length IS the vector's direction bearing dimension.

*** The crux of misconception was in analysing time as a vector
quantity. ***

{{{All vector components of any motion take exactly the same time of
the vector.}}}

Velocity vector components' dilatency magnitudes are not the same
quantity because they are per unit length in each direction but
proportionality must end up equating the components' time-intervals to
that of the vector.

There is a huge gap in the mental concept between the time it takes to
traverse the same distance at different velocities (hence different
time) and the time it takes to traverse different distances at the
same velocity [c].

In the later it takes exactly the same time to traverse the same unit
of length, and that is why vectors may not be divided by scalars or
else a dimensionless ratio would show up expressing a
direction-specific ratio of "time" that makes no sense concurrently;
and that is because a velocity vector per speed scalar makes no sense
either.

The magnitude of a velocity is Length variant and time invariant,
while the inverse of a speed scalar [1/c] is light time dilatency per
meter in vacuum and that time quantity is a constant.

There is no way to make sense out of equating a constant time interval
by another variant time interval based on direction and dimensionless
ratios. What we can make sense of is the relative time it takes to
complete a finite motion interval as compared to the time it takes
light to traverse one unit of length in vacuum; and that means that
time as a dimension did not shrink or expand but a competition was set
between slower velocities and light in vacuum as a reference standard
to evaluate the dilatency of the variant speed motion or the variant
length over invariant time units.

It is a physically false operation to estimate the time of velocity
vector components to differ from the time of a velocity vector.

And all the paradoxes and humiliation of the theories of relativity
arises from this criterion of misconception.

Kindest regards.

EL




Dave wrote in message ...
The reciprocal effect of length contraction and time dilation, which
appears by logical necessity to emerge from the kinematic part of the
special theory of relativity, has been variously explained as

1. true but not really true
2. real
3. not real
4. apparent
5. the result of the relativity of simultaneity
6. determined by measurement
7. a perspective effect
8. mathematical.

Unless placed in quotation marks, authors' assessments are summarized.

1. Effects are true but not really true:

Eddington [1928, pp33-34]:

"The shortening of the moving rod is true , but it is not really true."

2. Effects are real:

Arzelies [1966, pp120-121]:

The Lorentz Contraction is a Real Phenomenon. ...
Several authors have stated that the Lorentz contraction only seems to
occur, and is not real. This idea is false. So far as relativistic
theory is concerned, this contraction is just as real as any other
phenomenon. Admittedly ... it is not absolute, but depends upon the
system employed for the measurement; it seems that we might call it an
apparent contraction which varies with the system. This is merely
playing with the words, however. We must not confuse the reality of a
phenomenon with the independence of this phenomenon of a change of
system. ... The difficulty arises because we have become accustomed to
the geometrical concept of a rigid body with a definite shape, whatever
the measuring system. This idea must be abandoned. ... We must use the
term "real" for every phenomenon which can be measured ... The Lorentz
Contraction is an Objective Phenomenon. ...
We often encounter the following remark: The length of a ruler depends
upon its motion with respect to the observer. ... From this, it is
concluded once again that the contraction is only apparent, a subjective
phenomenon. ... such remarks ought to be forbidden.

Krane [1983, pp23-25]:

It must be pointed out that time dilation is a real effect that applies
not only to clocks based on light beams but to time itself. All clocks
will run more slowly as observed from the moving frame of reference. ...
The length measured by the moving observer is shorter. It must be
emphasized that this is a real effect.

Matveyev [1966, p305]:

The dimensions of bodies suffer contraction in the direction of motion
... A body is, therefore, "flattened" in the direction of motion. This
effect is a real effect ...

Møller [1972, p44]:

Contraction is a real effect observable in principle by experiment. It
expresses, however, not so much a quality of the moving stick itself as
rather a reciprocal relation between measuring-sticks in motion relative
to each other. ... According to relativistic conception, the notion of
the length of a stick has an unambiguous meaning only in relation to a
given inertial frame. ... This means that the concept of length has lost
its absolute meaning.

Pauli [1981, pp12-13]:

We have seen that this contraction is connected with the relativity of
simultaneity, and for this reason the argument has been put forward that
it is only an "apparent" contraction, in other words, that it is only
simulated by our space-time measurements. If a state is called real only
if it can be determined in the same way in all Galilean reference
systems, then the Lorentz contraction is indeed only apparent, since an
observer at rest in K' will see the rod without contraction. But we do
not consider such a point of view as appropriate, and in any case the
Lorentz contraction is in principle observable. ... It therefore follows
that the Lorentz contraction is not a property of a single rod taken by
itself, but a reciprocal relation between two such rods moving
relatively to each other, and this relation is in principle observable.

Schwinger [1986, p52]:

Each will observe the other clock to be running more slowly. This is an
objective fact. It is not a property of clocks but of time itself.

Tolman [1987, pp23-24]:

Entirely real but symmetrical.

3. Relativistic effects are not physically real:

Taylor & Wheeler [1992, p76]:

Does something about a clock really change when it moves, resulting in
the observed change in the tick rate? Absolutely not! Here is why:
Whether a clock is at rest or in motion ... is controlled by the
observer. You want the clock to be at rest? Move along with it. ... How
can your change of motion affect the inner mechanism of a distant clock?
It cannot and it does not.

4. Relativistic effects are apparent:

Aharoni [1985, p21]:

The moving rod appears shorter. The moving clock appears to go slow.

Cullwick [1959, pp65, 68]:

[A] rod which is at rest in S' ... appears to the observer O to be
contracted ... Similarly, a rod at rest in S will appear in S' to be
contracted....

Eddington [1920, p23-24]

"It is the reciprocity of these appearances-that each party should think
the other has contracted-that is so difficult to realise. Here is a
paradox beyond even the imagination of Dean Swift. Gulliver regarded the
Lilliputians as a race of dwarfs; and the Lilliputians regarded Gulliver
as a giant. That is natural. If the Lilliputians had appeared dwarfs to
Gulliver, and Gulliver had appeared a dwarf to the Lilliputians-but no!
that is too absurd for fiction, and is an idea only to be found in the
sober pages of science.....It is not only in space but in time that
these strange variations occur. If we observed the aviator carefully we
should infer that he was unusually slow in his movements; and events in
the conveyance moving with him would be similarly retarded-as though
time had forgotten to go on. His cigar lasts twice as long as one of ours."

In the preface to modern editions of this book written in 1986 by
Hermann Bondi, Bondi identifies an "erratum" by Eddington
"There is only one point in the whole book to which (i) can be applied:
the Fitzgerald contraction cannot be seen. Eddington was in no way alone
in the error that it could be seen, indeed it now seems astonishing that
it was well over fifty years after Einstein's paper that Terrel,
stimulated by Weisskopf, showed that the Fitzgerald effect could not be
seen."

Jackson [1975, p520]:

The time as seen in the rest system is dilated.

Joos [1958, pp243-244]:

The interval appears to the moving observer to be lengthened. A body
which appears to be spherical to an observer at rest will appear to a
moving observer to be an oblate spheroid.

McCrea [1954, pp15-16]:

The apparent length is reduced. Time intervals appear to be lengthened;
clocks appear to go slow.

Nunn [1923, pp43-44]:

A moving rod would appear to be shortened. An interval is always less
than measured by the other observer.

Whitrow [1980, p255]:

Instead of assuming that there are real, i.e. structural, changes in
length and duration owing to motion, Einstein's theory involves only
apparent changes, and these are independent of the microscopic
constitution and hidden mechanisms controlling the structure of matter.
[Unlike]... real changes, these apparent phenomena are reciprocal.

5. Relativistic effects are the result of the relativity of simultaneity:

Bohm [1965, p59]:

When measuring lengths and intervals, observers are not referring to the
same events.

French [1968, p97],
Rosser [1967, p37],
Stephenson & Kilmister [1987, pp38-39]:

Measurements of lengths involve simultaneity and yield different
numerical values.

6. Relativistic effects are determined by measurements:

Schwartz [1972, p113]:

Each observer determines distances to be foreshortened.

7. Relativistic effects are comparable to perspective effects: Rindler
[1991, pp25-29]:

Moving lengths are reduced, a kind of perspective effect. But of course
nothing has happened to the rod itself. Nevertheless, contraction is no
illusion, it is real. Moving clocks go slow, a 'velocity-perspective'
effect. Nothing at all happens to the clock itself. Like contraction,
this effect is real.

8. Relativistic effects are mathematical:

Eddington [1924, pp16-18]:

The connection between lengths and intervals are problems of pure
mathematics. A travelling clock gives a low reading.

Minkowski [1908, p81]:

[The] contraction is not to be looked upon as a consequence of
resistances in the ether, or anything of that kind, but simply as a gift
from above, - as an accompanying circumstance of the circumstance of motion.

Rogers [1960, p496]:

Thus we have devised a new geometry, with our clocks and scales
conspiring, by their changes, to present us with a universally constant
speed of light.

References:

Aharoni, J., The Special Theory of Relativity, (1965), Dover, 1985.

Arzelies, H., Relativistic Kinematics, Pergamon, Oxford, 1966.

Bohm, D., The Special Theory of Relativity, W.A. Benjamin, New York, 1965.

Cullwick, E.G., Electromagnetism and Relativity, 2nd ed., Longmans,
London, 1959.

Eddington, A.S. Space, Time & Gravitation (1920) CUP, Cambridge Science
Classics, 1999

Eddington, A.S. The Mathematical Theory of Relativity, 2nd ed., CUP 1924.

Eddington, A. S., The Nature of the Physical World , 1928, CUP /
MacMillan (NY).

French, A.P., Special Relativity, Chapman & Hall, London, 1968.

Jackson J.D., Classical Electrodynamics, 2nd ed., John Wiley, New York,
1975.

Joos, G., Theoretical Physics, (1934), 3rd ed., Blackie, London, 1958.

Krane, K.S., Modern Physics, J. Wiley, New York, 1983.

McCrea, W.H., Relativity Physics, 4th ed., Methuen, London, 1954.

Matveyev, A., Principles of Electrodynamics, Reinhold, New York, 1966.

Minkowski, H., "Space and Time" (1908), in H.A. Lorentz et al., The
Principle of Relativity, Dover, 1952,75-91.

Møller, C., The Theory of Relativity, 2nd ed., OUP 1972.

Nunn, T.P., Relativity and Gravitation, University of London Press, 1923.

Pauli, W., Theory of Relativity (1921), Dover 1981.

Rindler, W., Introduction to Special Relativity, 2nd ed., Clarendon,
Oxford, 1991.

Rogers, E.M., Physics for the Inquiring Mind, Princeton U. P. 1960.

Rosser, W.G.V., Introductory Relativity, Butterworths, London, 1967.

Schwartz, M., Principles of Electrodynamics, McGraw Hill, New York, 1972.

Schwinger, J., Einstein's Legacy, Scientific American Library, New York,
1986.

Stephenson, G., & Kilmister, C.W., Special Relativity for Physicists
(1958), Dover, 1987.

Taylor, E.F., & Wheeler, J.A., Spacetime Physics: Introduction to
Special Relativity, 2nd ed., W.H. Freeman, New York, 1992.

Tolman, R.C., Relativity Thermodynamics and Cosmology (1934), Dover, 1987.

Whitrow, G.J., The Natural Philosophy of Time, 2nd Ed. OUP 1980.



No wonder the relativists in this newsgroup just give facetious replies
and never bother to answer questions. Even the "expert" relativists who
have written textbooks don't have a clue what's going on.

"Ken S. Tucker" wrote:

Richard wrote in message ...
Bill Hobba wrote:

EjP wrote:
When you realize that relativity is ultimately about observation,
the 4,5,7, and 8 are more or less equivalent (with some qualification).
Although 2 and 3 sound contradictory, it depends on your definition
of "real" (believe it or not, "real" is not a well-defined term,
scientifically). Some people would consider a "real" length
contraction to be something involving some sort of physical
compression, understandable in terms of the bulk modulus, and
by that definition, the length contraction is
not "real". On the other hand if "real" means that I could
devise an experiment to measure the length contraction of
something that is moving in my frame, the it is *real*, but
now "real" is entirely consistent
with 4,5,7, and 8. I believe this distinction is what Eddington
was alluding to in comment 1.

For those that doubt length contraction simply analyze a current carrying
wire. If length contraction occurs then magnetic forces appear - exactly
as found from experiment - if length contrition does not occur then magnetic
forces do not appear - in disagreement with experiment.

Thanks
Bill

This is not a good example.

Sure it is, (I've read your post)
See Purcells, "Electricity and Mangnetism" pg. 153
and read on.

If you do the math you'll find that length
contraction cancels out of the equation, leaving the force as due to
only the relative velocity and proximity of the respective lines of
charge.

IMO, this is a narrow intrepretation. Purcell has
done a very good job of relating Magnetism to
the Lorentz Transformation.

Thus your example is actually a counter-argument to the
'reality' of length contraction, i.e. length contraction is unnecessary
and has nothing to do with the measured force. As an analogy let's
suppose that instead of length contraction we substitute line density
increase via spontaneous creation of extra electrons.

Oh boy, in another thread Rich converted my
mirror into a light bulb, and now a wire is being
converted into a generator!

Now it should be
obvious that this will provide exactly the same outcome,

I think you screwed charge conservation in the process!

since the
relativistic length contraction hypothesis provides just this same line
density increase. Now let's suppose that instead of either of these we
postulate that the lines of charge simply 'appear' closer to each other
from their respective points of view when they are in relative motion.
Again we get the same result. In short, any ad hoc presumption that will
increase the force as a function of relative velocity will work equally
as well as any other that does the same, each will provide correctly for
the observed force.

Thus I trust you'll see that the development of this force is no proof
or even the slightest indication that length contraction is real.
Now look at
http://www.cswnet.com/~rper
and you'll find a mathematical treatment of this force that makes no
assumptions at all about the 'cause' of the force, it simply quantifies
it directly as a function of relative velocity (in a sense this reduces
to the actual cause), and thus by virtue of Ockham's Razor, it is a much
superior approach, eliminating as it does all of the excess baggage that
you brought along above.
Richard Perry

Is Rich pulling my leg, or is he serious?
A lot of people respect Purcell, and I agree
with Hobba, who is usually careful. Rich, I
think you are having a *bad hair day* or
your theories are very complex. Is there
some need to correct the theory of magnetism?

Yours Truly
Ken S. Tucker

Could be you're a bit sore at me for arguing against tired light? Mind
you, it was not a slam, just a logical argument

Now as for my argument above, yes there is a need to correct the theory
of magnetism, more precisely the 'model'.

Richard Perry

Bill Hobba wrote:

Bill Hobba wrote:
For those that doubt length contraction simply analyze a current
carrying
wire. If length contraction occurs then magnetic forces appear -
exactly
as found from experiment - if length contrition does not occur then
magnetic
forces do not appear - in disagreement with experiment.

Richard wrote:
This is not a good example. If you do the math you'll find that length
contraction cancels out of the equation, leaving the force as due to
only the relative velocity and proximity of the respective lines of
charge. Thus your example is actually a counter-argument to the
'reality' of length contraction, i.e. length contraction is unnecessary
and has nothing to do with the measured force.

I have carefully worked through the math many times. I have examined texts
that do the same eg page 488 of Griffiths - Introduction to Electrodynamics
where the derivation of this well known fact is given in full detail. The
analysis depends entirely on the existence of length contraction - the force
between two current carrying wires is zero if length contraction does not
occur and matches exactly what is observed if it does. AFAICS the only
attack that can reasonably be leveled is that electrons moving at constant
velocity though a wire is not really a good model for the complex QM
dependant process that is really occurring - but to my that is not really
germane to the point.

Why isn't it? It is exactly these complexities that make your
interpretation contradictory. Consider once again: If the
'electrostatic' field density increases, and this causes the observed
force between the conductors, then the motions (the complexities that
you referred to) of the charge quanta must also cause the same
generation of force between the components of charge in the conductor
even when no currents are flowing in them, that is, the electrostatic
field is itself due to the relative motion of the charges.

Now this is not really that tricky, and so it amazes me how few have
followed the argument though it's been repeated infinite times in
infinite ways, and is so extremely uncomplicated. Pay close attention.
If the electrostatic force between the, say, electrons in the conductors
is itself generated by the relative motion of the quanta of charge
within the conductor, then what field is it that you are supposed to be
compressing with your length contraction? What follows is that you are
compressing a field and then stating that the field is generated by this
compression!!! This leads to the general conclusion that "The magnetic
force between between moving lines of charge is created by the
compression of itself." 'Absurd' is putting it mildly. Thus, and in
contrast to your carefully constructed arguments, the compressed field
is not an electrostatic field, which is to say if two quanta of charge
are at rest wrt each other then no force whatsoever is exerted between
them.

There is a field, a radial vector field, but it is not the electrostatic
field.
You may, if you wish, still claim that compression of this field is the
cause of its increasing effect on other charges, though your equations
would have to be altered a bit, since at zero velocity the density of
the field is also zero. OTOH, you could simply quantify the interaction
and state "I frame no hypothesis."

As I've already illustrated there is no end to the ad hoc models that we
can conjure up, but the reality is that the force can only be
objectively defined as associated directly with the relative motion and
the displacement of the charges, these are the only measurable
parameters, and they are all we need to frame a physical law that
accurately describes the effect. Since I have already done just that,
then that's all the proof I need to state unequivocally that you are
thinking on a plane just a few steps lower than mine. For that reason
you won't get what I've said until you're ready, and it simply doesn't
matter how many pages of text you've mastered, that's just the way it
is.

Richard Perry
http://www.cswnet.com/~rper
Electromagnetism: First Principles


Richard wrote:
Thus I trust you'll see that the development of this force is no proof
or even the slightest indication that length contraction is real.

I trust you will post the flaw in my resoning or read the reference I gave
and point out the page and equation that is in error. To be precise my
claim is the Lorentz force between 2 current carrying wires is zero if
length contraction does not exist (which we know from experiment to be
false) and is exactly the value found by experiment if it does exist.

Thanks
Bill

Richard wrote in message ...
"Ken S. Tucker" wrote:

Richard wrote in message ...
....
Thus I trust you'll see that the development of this force is no proof
or even the slightest indication that length contraction is real.
Now look at
http://www.cswnet.com/~rper
and you'll find a mathematical treatment of this force that makes no
assumptions at all about the 'cause' of the force, it simply quantifies
it directly as a function of relative velocity (in a sense this reduces
to the actual cause), and thus by virtue of Ockham's Razor, it is a much
superior approach, eliminating as it does all of the excess baggage that
you brought along above.
Richard Perry

Is Rich pulling my leg, or is he serious?
A lot of people respect Purcell, and I agree
with Hobba, who is usually careful. Rich, I
think you are having a *bad hair day* or
your theories are very complex. Is there
some need to correct the theory of magnetism?
Ken S. Tucker

Could be you're a bit sore at me for arguing against tired light? Mind
you, it was not a slam, just a logical argument

I generally find your arguments well reasoned
and clearly presented, so it seems uncharacter-
istic to dismiss classical magnetic theory. OTOH
if you don't understand something, I'd be happy
to help if I can. Magnetism is NOT simple, alot
of electronic engineers dread the theory. I've
worked as a technician and we had many
very bright engineering students who had some
serious problems with the subject. When I
used Purcell's method of presentation it really
helped them.

Now as for my argument above, yes there is a need to correct the theory
of magnetism, more precisely the 'model'.
Richard Perry

Ok, I'll have a look at the recommended site.
Ken S. Tucker

Regrading the Lorentz force between two currenbt carrying wires Bill Hobba
wrote:
I have carefully worked through the math many times. I have examined
texts
that do the same eg page 488 of Griffiths - Introduction to
Electrodynamics
where the derivation of this well known fact is given in full detail.
The
analysis depends entirely on the existence of length contraction - the
force
between two current carrying wires is zero if length contraction does
not
occur and matches exactly what is observed if it does. AFAICS the only
attack that can reasonably be leveled is that electrons moving at
constant
velocity though a wire is not really a good model for the complex QM
dependant process that is really occurring - but to my that is not
really
germane to the point.


Richard relied:
Why isn't it? It is exactly these complexities that make your
interpretation contradictory. Consider once again: If the
'electrostatic' field density increases, and this causes the observed
force between the conductors, then the motions (the complexities that
you referred to) of the charge quanta must also cause the same
generation of force between the components of charge in the conductor
even when no currents are flowing in them, that is, the electrostatic
field is itself due to the relative motion of the charges.

I think your logic is askew. First the exact experiment that is considered
is the force experienced by a single moving charge caused by a current
carrying wire and the Lorentz force is deduced. It is later in the analysis
that the existence of the Lorentz force is used to predict the force between
two current carrying wires. Hence for the first part of the analysis your
objection that we are ignoring the density imbalance between the moving
electrons and the nuclei in the current carrying wire is a not an issue.
For the second part (ie where we deduce the force between the current
carrying wires) we consider the nuclei at rest and the electrons as moving
it is not an issue either. Of course from the POR we could have done all
our calculations from the viewpoint of the moving electron - but all the
calculations I have done and have seen done do not do that - for obvious
calculational convenience. But the POR guarantees the results will be the
same - if not you have found a violation of the POR and your place in
history is assured. As an exercise it might be illuminating to do this
calculation but I must admit I have not done so because the POR tells me it
is not really an interesting thing to do.

Hence I consider the existence of a force between 2 current carrying wires
as strong evidence of the existence of length contraction.

Thanks
Bill

"Martin Hogbin" wrote in message ...

It will be interesting to see how Dave responds to
this logical and obviously non-facetious reply.

Nothing so far.

Martin Hogbin

"Martin Hogbin" wrote in message ...

"Martin Hogbin" wrote in message ...

It will be interesting to see how Dave responds to
this logical and obviously non-facetious reply.

Nothing so far.

I guess it is back to facetious replies then
folks.

Martin Hogbin