On Sun, 31 Dec 2006 19:51:54 -0000, "George Dishman"
wrote:


"Jeff Root" wrote in message
roups.com...

George Dishman replied to Lester Zick:

measureable parameter

I don't grok the use of the term "parameter". I use the
term "quantity". Length, area, volume, time, speed, mass,
momentum, electric charge, electric current, thermodynamic
temperature, and light intensity are examples of measurable
quantities. On the other hand, "quantity" is also a
synonym for "amount", as in "the quantity of sand", "the
quantity of light", and so forth, which is a different
meaning, and likely to cause confusion.

To me, the term "parameter" indicates an engineering
specification rather than a measureable quantity-- even
though it *IS* a measureable quantity. Hmph!

What do you think?

The term to means has connotations of being an independent
variable, or an argument to a routine in software, but it
was what sprang to mind. "Quantity" to me is more to do with
a measure representing an assay, length of string, area,
volume and mass are good examples but the others I would
generally term just as "measurables" but really quantity
is just as good.

Can you explain to me why you think a contradiction
appears when this same rezoning is applied to lengths
instead of angles?

At another level, SR was published by Einstein over a
century ago and has been studied by thousands of people
over Avery conceivable situation.

Using a spelling checker, I see.

:-(

The serious point is a request for you to clarify what you
mean by "overlap". It can't mean two solid objects occupying
the same space at the same time while in relative motion.

I think that one use Lester makes of his term "interstitial
bodies" is the atoms and molecules within a body. Each
particle has its own instantaneous velocity, different from
the velocities of the other particles within the body, and
Lester cannot see how each one of those particles can have
a "contraction factor" different from the body as a whole.

I won't speculate here on what he means. Instead, look
at the various definitions thrown up by a Google search:

http://www.google.co.uk/search?q=define%3A+interstitial

Interstitial means lying in the interstices such as
carbon grains in the interstices between the steel
grains in cast iron, or fluid in the gaps between
cells in muscle. The particles comprising a body are
not interstitial but what I want is for Lester to
actually explain what he means rather than us guessing.

And I certainly don't mind but I can't really understand why you
insist the particles comprising a body are not interstitial. Every
body in the universe is interstitial to some other unless you're
trying to say bodies in the sense of experimental platforms are
somehow spatially preemptive. As I've already mentioned several times
MM could have been conducted between the earth and moon and another
body such as a satellite at right angles and a second MM could have
also been conducted on some satellite in between, and the second
experimental platform would be interstitial with respect to the first.
As far as velocity dependent frames of reference are concerned every
group of particles traveling at a common underlying velocity within
any body constitutes a different interstitial body. And that includes
both molecular and atomic subgroups of experimental platforms as well
as macroscopic groupings such as the earth-moon or satellites.

I am still looking for you to tell me where this supposed
contradiction appears.

The apparent contradiction is obvious, even if Lester
prefers to describe it in somewhat convoluted terms.

So you say but I don't think so. It is obvious that,
for a single body, you get different factors for
different observers moving at different speeds because,
as Lester said himself, the effects are velocity
dependent.

Sure. The problem is that the contraction factors are for the body not
the observers.

He seems to have some reasoning that says
this explanation doesn't work when more than one body
is involved _and_ we talk about spaces inside bodies
_and_ the bodies are overlapping. Why those extra
conditions are necessary is a mystery to me.

Well it really shouldn't be. Bodies traveling at different velocities
have different contraction factors associated with their respective
frames of reference wherever they're located. You seem to associate
contraction effects with observers rather than with the bodies. But
contraction is supposed to affect the bodies undergoing translation
through space at constant velocity independent of observation since
that's supposed to be how Lorentz's anisotropic transforms for the
speed of light relative to an experimental platform become isotropic.
When bodies traveling at different velocities are interstitial there
is an implicit contradiction between their respective contractions.

The extra conditions are only needed to show the contradiction
involved in necessary terms since overlapping regions of space cannot
be contracted by different amounts and still account for the null
results of different MM experiments carried out together in both
overlapping frames.

I think that instead of your current line of attack, you
should acknowledge that the apparent contradiction is
obvious, and then ask Lester to show that it is real and
not merely apparent.

No, I just want him to state why he thinks there is
a contradiction in such a way that it makes clear
why all these extra provisos are necessary. I'm not
going to make his case for him, there is no
contradiction in anything he has presented so far
so it is his task to try to justify his claim. I
don't think he can and he uses rhetorical questions
to cover it up in the hope that is readers will fill
it in for him.

Well, George, that's just absurd. I don't and rarely have needed my
readers to fill in anything. Certainly Jeff and Gurcharn get it even
if you don't.

I'm somewhat curious why he thinks his statement of the
apparent contradiction is more clear-cut than mine.

I am sure he is saying that your version doesn't
show the contradiction but his does.

I don't know what Jeff's version shows because it isn't my version. My
version says nothing about observers and measurement. It simply states
a case involving different interstitial bodies and coincident frames
of reference where spatial contraction is required to explain the
isotropic experimental results for MM produced despite Lorentz's
anisotropic transforms for the speed of light in various directions
relative to an experimental platform undergoing translation through
space at constant velocity. My case is definitive and Jeff's isn't
although I suspect Jeff's might be made more nearly definitive by
using only one observer instead of two. But that's an unrelated issue
where contraction of the space between and among interstitial bodies
in different frames of reference is considered.

His version is that SR says multiple bodies in the same
place, moving relative to one another, simultaneously
have different "contraction factors".

No, his version has the space between bodies being
contracted and remember he first said each observer
only observed his _own_ MMX.

And remember I first said nothing of the kind having anything to do
with observers. My case first stated spatial contraction as determined
according to different frames of reference for interstitial bodies.
The contraction was of both space and bodies. Your reference to my
comment regarding observers was only made in response to your own
insistence on having some kind of observer measuring something to show
that observers and measurements were irrelevant to the problem posed.

My version is that SR says a body simultaneously has
different "contraction factors" for different observers
in different states of motion relative to the body.

The two statements are equivalent, but I think mine is
more shockingly obvious in its apparent contradiction.

Yours is the classic statement but Lester seems to
think he has a new problem that goes beyond the
standard resolution of your statement.

Only because Lester does.

The apparent contradiction that Lester is complaining
about is probably the single most common hangup when
just starting to learn about relativity. I would not
be surprised to learn that the majority of people are
confounded by it for at least a short time.

Perhaps, but let's not invent our own problems, Lester
needs to make a clear statement of the problem. Maybe
it is just what you have said but maybe he has some
other problem in mind.

You know I find it rather curious, George, that you insist on talking
as if I've said nothing at all in any of these posts and severly mis
construing everything I have said in absurdly bizarre ways which
completely misrepresent what I've said repeatedly. The fact is that
Jeff understands the problem even if he insists on casting it in terms
of observation and measurement. At least he gets it. Gurcharn gets it.
You don't get it. To me that says much more about your own reading
comprehension than anything else.

~v~~

George Dishman replied to Jeff Root:

George Dishman replied to Lester Zick:

The serious point is a request for you to clarify what you
mean by "overlap". It can't mean two solid objects occupying
the same space at the same time while in relative motion.

I think that one use Lester makes of his term "interstitial
bodies" is the atoms and molecules within a body. Each
particle has its own instantaneous velocity, different from
the velocities of the other particles within the body, and
Lester cannot see how each one of those particles can have
a "contraction factor" different from the body as a whole.

I won't speculate here on what he means. Instead, look
at the various definitions...

Lester has made clear enough what he means by the term
"interstitial bodies". His application of it to atoms
and molecules is just one particular but representative
way that things can overlap.

Lester believes that SR implies that multiple "contraction
factors" can apply to a single volume of space, and that
such a situation is patently impossible. Which shows that
he believes "contraction factors" are location-dependant.
Although he claims that he doesn't!

The particles comprising a body are not interstitial

Every thing is in gaps between other things. All bodies
are "interstitial bodies".

I am still looking for you to tell me where this
supposed contradiction appears.

The apparent contradiction is obvious, even if Lester
prefers to describe it in somewhat convoluted terms.

So you say but I don't think so. It is obvious that,
for a single body, you get different factors for
different observers moving at different speeds because,
as Lester said himself, the effects are velocity
dependent. He seems to have some reasoning that says
this explanation doesn't work when more than one body
is involved _and_ we talk about spaces inside bodies
_and_ the bodies are overlapping. Why those extra
conditions are necessary is a mystery to me.

His belief that there is a contradiction is independant
of his reasoning.

His belief is based purely on what is immediately
obvious. It is obvious to him that one thing cannot be
contracted by two different amounts simultaneously, so
he believes that to be a contradiction. He constructed
the description involving overlapping MMXs or overlapping
reference frames or "interstitial bodies" to explain to
others what is immediately obvious to him. He has no
need for the description to make any sense because he
knows that there is a contradiction whether or not the
description makes sense.

It is obvious to us that we get different factors for
different observers. It is equally obvious to me what
it is that Lester considers to be a contradiction. He
sees different factors applying simultaneously to bodies
in a single volume of space, and to him that is obvious
nonsense. An obvious contradiction. He has no need to
explain why. It is simply obvious to him.

I think that instead of your current line of attack, you
should acknowledge that the apparent contradiction is
obvious, and then ask Lester to show that it is real and
not merely apparent.

No, I just want him to state why he thinks there is
a contradiction in such a way that it makes clear
why all these extra provisos are necessary.

I think you can ask him to do that even after acknowledging
that the apparent contradiction is obvious.

I'm not going to make his case for him, there is no
contradiction in anything he has presented so far
so it is his task to try to justify his claim. I
don't think he can and he uses rhetorical questions
to cover it up in the hope that is readers will fill
it in for him.

Yes, I agree completely.

After you first commented that Lester uses rhetorical
questions to make his points, and before Lester responded
to that comment, I wrote (but never posted) a reply which
agreed that that is indeed what he does, and complimented
you on your perceptive and accurate characterization of
his technique. From his response, it appears that he did
not understand what you meant by "rhetorical questions".

Or he may have understood but only pretended not to.

My main point is just that the apparent contradiction
is not at all mysterious, and in fact is very obvious.
So obvious that he can't explain it in simpler terms.

I'm somewhat curious why he thinks his statement of the
apparent contradiction is more clear-cut than mine.

I am sure he is saying that your version doesn't
show the contradiction but his does.

It could be interesting to see how he explains that.

His version is that SR says multiple bodies in the same
place, moving relative to one another, simultaneously
have different "contraction factors".

No, his version has the space between bodies being
contracted and remember he first said each observer
only observed his _own_ MMX.

Everything is contracted. The bodies, the spaces between
the bodies, the frames defined by the bodies.

Each observer only observes his own MMX, but Lester is
imagining what each of them observes, so he is unwittingly
the one observing across reference frames when he compares
different "contraction factors".

I don't think there is any conflict between your and my
descriptions of Lester's version.

My version is that SR says a body simultaneously has
different "contraction factors" for different observers
in different states of motion relative to the body.

The two statements are equivalent, but I think mine is
more shockingly obvious in its apparent contradiction.

Yours is the classic statement but Lester seems to
think he has a new problem that goes beyond the
standard resolution of your statement.

What Lester thinks is new is actually so trivial that
there isn't anything to analyze. He thinks that multiple
overlapping reference frames is a new idea that nobody
ever considered before, when it is really the fundamental
basis of all relativity, even Galilean relativity.

The apparent contradiction that Lester is complaining
about is probably the single most common hangup when
just starting to learn about relativity. I would not
be surprised to learn that the majority of people are
confounded by it for at least a short time.

Perhaps, but let's not invent our own problems, Lester
needs to make a clear statement of the problem. Maybe
it is just what you have said but maybe he has some
other problem in mind.

He has stated it clearly enough for me to identify with
certainty what problem he has in mind, but I agree that
he needs to state it more clearly than he has. For me to
merely identify what he is talking about is not adequate.
He needs to state it explicitly.

-- Jeff, in Minneapolis

Lester Zick replied to Jeff Root:

Jeff Root replied to George Dishman:

George Dishman replied to Lester Zick:

My point here is that you are trying to force your own
view into the conversation as a given

That is exactly what I wanted to say in my last post, but
couldn't articulate, so I gave up and deleted my attempts.
You said more than I was attempting to say, with 1/3 the
number of words.

But the problem is who is trying to force what view on whom.
I haven't gotten to George's reply as yet but I'm simply
posing a problem as far as contraction is concerned. I don't
see anyone imposing anything on anyone. If SR answers the
objection I'd simply like to know how.

An example of you forcing your view as a given is when
you say below:

Uniform contraction can't apply to both because the
frames of reference overlap...

You assert that as if it were obvious, not requiring
explanation. I understand why you think so, but my
understanding is not enough. You need to say explicitly
why uniform contraction can't apply to overlapping MMXs
in overlapping reference frames. Neither George nor I
can say it for you.

The serious point is a request for you to clarify what you
mean by "overlap". It can't mean two solid objects occupying
the same space at the same time while in relative motion.

I think that one use Lester makes of his term "interstitial
bodies" is the atoms and molecules within a body. Each
particle has its own instantaneous velocity, different from
the velocities of the other particles within the body, and
Lester cannot see how each one of those particles can have
a "contraction factor" different from the body as a whole.

I agree. However exactly the same objection applies even if
macroscopic interstitial bodies are considered.

Certainly.

Previously I've mentioned MM conducted between the earth
and moon and some other body at right angles. Same principle
applies if we consider another MM conducted on a satellite
between the earth and moon. Uniform contraction can't apply
to both because the frames of reference overlap whether
microscopic or macroscopic bodies are considered.

I understand why you see a problem. I see no problem.
To resolve this contradiction between your view and mine,
explain precisely what the problem is that you see.

I am still looking for you to tell me where this supposed
contradiction appears.

The apparent contradiction is obvious,

Well thank goodness someone besides Gurcharn gets it.

But you still need to explain why you see a contradiction
in the situation you describe above. Although I understand
what you mean, it is up to you to state it explicitly.
You haven't done that yet.

even if Lester
prefers to describe it in somewhat convoluted terms.

I think the more accurate description would be "general"
than "convoluted". I'm trying to point out certain
implications of velocity dependent frames of reference
when it comes to contraction hypotheses.

Neither George nor I understand why you think your
scenario is different from, more definitive, or more
general than mine. But I have no objection to your
scenario other than that it involves unnecessary
conditions, and you haven't explained why you think
those conditions are essential.

I think that instead of your current line of attack, you
should acknowledge that the apparent contradiction is
obvious, and then ask Lester to show that it is real and
not merely apparent.

Well, Jeff, the definition of bodies and frames of reference
in corporeal and geometric terms is purely velocity dependent.
Appearances have nothing to do with how they're defined or
whether or how they can contract if they do.

I can't make any useful reply to this at present.

I'm somewhat curious why he thinks his statement of the
apparent contradiction is more clear-cut than mine.

His version is that SR says multiple bodies in the same
place, moving relative to one another, simultaneously
have different "contraction factors".

My version is that SR says a body simultaneously has
different "contraction factors" for different observers
in different states of motion relative to the body.

Why bring "observers" into the problem at all?

Because without observers there are no observations,
and without observations there are no facts to discuss.

Either frames of reference are defined according to a
common velocity or they aren't.

I agree that frames of reference are defined according
to a common velocity.

If they are[,] either different contraction factors
apply to each[,] or they don't.

I agree that different "contraction factors" apply to
each: The "contraction factor" depends on the relative
velocity between the observer and the observed.

And if different contraction factors apply to
overlapping bodies

I agree that different "contraction factors" apply to
"overlapping bodies" whenever and wherever they are
observed from reference frames moving relative to the
bodies.

either they contradict one another or they don't.

What do you mean by "contradict one another"?

I don't see there is any "appearance" or apparent
contraction involved.

You have said something about such a contraction
being required to explain the results of the MMX.
I agree. There is an apparent contraction involved.

The contradiction doesn't apply to any hypothetical
observers but to a body in relative motion.

What contradiction?

It is possible that in the above two quoted sentences
you meant "contradiction" when you said "contraction",
and "contraction" when you said "contradiction". To
cover that possibility, I'll give alternative replies:

I don't see there is any "appearance" or apparent
[contradiction] involved.

If it appears to you that there is a contradiction,
then there is an apparent contradiction.

If it does not appear to you that there is a
contradiction, then there is no apparent contradiction.

The [contraction] doesn't apply to any hypothetical
observers but to a body in relative motion.

A "contraction factor" applies to anything moving
relative to an observer. If you and I are moving
relative to each other, then a "contraction factor"
quantifies the difference between my own measures
of myself and your measures of me, and the difference
between your measures of yourself and my measures of
you. The "contraction factor" only ever applies
between an observer and an observed. I will see you
as being contracted, and you will see me as being
contracted. George, moving relative to both of us,
will see each of us contracted by different amounts.
I will see George contracted by an amount different
from the amount you see him contracted. George will
see me contracted by an amount different from the
amount you see me contracted.

Whether observers observe anything is irrelevant
to whether there is a contradiction between contractions.

What do you mean by "a contradiction between contractions"?

The two statements are equivalent, but I think mine is
more shockingly obvious in its apparent contradiction.

Actually the two statements are not quite equivalent,
Jeff. If you insist on observation consider the identical
case where only one observer is involved for MM in both
interstitial bodies.

Okay, what about that case?

Your peculiar terminology ("both interstitial bodies")
makes it hard to be sure what you mean, so you will have
to spell it out.

The apparent contradiction that Lester is complaining
about is probably the single most common hangup when
just starting to learn about relativity. I would not
be surprised to learn that the majority of people are
confounded by it for at least a short time.

But the real problem here is that they can't put the
problem into words.

I don't believe that.

A lot of people recognize the problem but can't quite
put their fingers on the contradiction involved. As far
as I know I'm the first to put the issue in definitive
terms: that both coporeal and geometric contraction
operates across spatial definitions which are velocity
dependent.

That reads like word salad.

What is "corporeal contraction"?

What is "geometric contraction"?

What are "spatial definitions"?

What does "across spatial definitions" mean?

What does it mean for a "spatial definition" to be
velocity dependant?

At least despite considerable research I've never read of
anyone else who managed to describe the problem in definitive
terms.

You have not actually described the "problem" yet,
yourself.

Everyone talks about observers and measurements but the
really curious thing is that despite all the talk no one
observes or measures anything.

I think you will agree that you used hyperbole there.
Many people do observe and measure many things on many
different occasions, but an observation or measurement
can be recorded for future use by others, and does not
need to be constantly repeated. Also, what you are doing
is conducting thought experiments, where you imagine what
happens in various scenarios. If there are no imagined
observations or measurements in the thought experiment,
then there are no results and nothing to analyze.

They all talk about

Who, specifically, are "they"? Name names.

this and that resolution of the paradox

What paradox?

but no one actually shows how contradictory contractions
are supposed to occur.

You're the one who will have to do that. You're the one
claiming that contradictory contractions are supposed to
occur.

You have to remember that these contradictory contraction
factors are not just nominal. They're supposed to reflect
the speed of light as it transits the space contracted this
way or that.

What do you mean by "reflect the speed of light"?

The Lorentz transforms which describe the speed of light
in various directions relative to an underlying platform
at constant velocity are anisotropic and apply across space
independent of the platform. Einstein's speed of light
results across space are isotropic.

The Lorentz transforms don't describe the speed of light,
though of course they include the speed of light as a
constant. Your expression "underlying platform" appears
to be a synonym for "observer". I'm guessing that you
don't mean it as a synonym for "aether".

And what we're looking for in that context is some
explanation as to how that is possible. It isn't that
observers can measure this or that according to these
or those rods or cones. It's that light has to transit
space independent of any platform and do so at different
velocity to make Lorentz transforms isotropic.

SR explains it to the limit of measurement error in
situations where gravity is not a significant factor.

Having said which however I have to mention you at least
seem to get it. I think Gurcharn also gets it. However
I'm not sure George does. In any event I appreciate the
contribution and look forward to further discussion.

Read the story "Forgetfulness", by John W. Campbell, Jr.,
originally published in the June 1937 issue of 'Astounding'
under the pen name 'Don A. Stuart', for my view of George's
level of understanding of the apparent contradiction. :-)
I found the story in the 1989 anthology 'The World Treasury
of Science Fiction', edited by David G. Hartwell. You may
be able to find it elsewhere. It is a "must read".

-- Jeff, in Minneapolis

George Dishman replied to Lester Zick:

As far as I'm concerned contraction has to be a
real physical-spatial effect ...

And that is where I disagree. I previously asked Jeff
this following question and I'd like both you and him
to give me your views so we can compare attitudes.
Is the ship "really" shorter? Does the silhouette
"really" subtend a smaller angle? The aim is to find
out what we all mean by the concept of "real".

I want to say first that I don't think very highly of
most philosophical questioning about "reality". I wasn't
particularly impressed by the movie "The Matrix", I don't
wonder if I was just created a minute ago with a mass of
false memories planted in my mind, I don't wonder whether
a photon is "really" a particle or a wave, and I most
certainly don't think that all opinions are equally valid.
Nevertheless, distinguishing reality from non-reality is
clearly one of the major labors of mankind, and something
I can't avoid having to do.

Plus, we have the question of what "physical" means,
which is probably just as difficult.

I don't know yet whether I can answer the question, but I
think it will be easier for me than for Lester, because I
can use analogies, which he shuns.

The shortening is not something that happens to the ship
or to the observer. The shortening is a change in the
relationship between the ship and the observer. The
relationship is certainly real, in my view, and the change
in the relationship is equally real.

It is like me walking around to the south side of my desk.
Is the desk then "really" north of me? Yes, it is. As the
ship speeds up relative to me, it really contracts relative
to me. And I know that I contract relative to the ship.
But the ship doesn't change, and I don't change. It is
only the relationship which changes.

I'm not sure I can or need to go any farther than that.

Lester wrote:

Jeff seems to think it's only apparent or nominal and
is to be explained by observers and measurement.

That is not at all what I think.

I have used the expression "apparent contradiction" many
times in the past few weeks. I do not recall ever saying
or implying that the contraction effects of relative motion
are only apparent or only nominal. Possibly I have said
such a thing at some time, but not recently, and I don't
recall ever saying it.

When I say that there is an apparent contradiction, I mean
that Lester sees a contradiction. The contradiction is
apparent to him. I understand the apparent contradiction
he sees, and I know that there is no real contradiction.

I have never said or implied that the contraction effects
are "to be explained by observers and measurement." The
effects are observed and measured by observers. Observing
and measuring are not acts of explication. They do not
explain anything. The observations and measurements are
what need to be explained.

-- Jeff, in Minneapolis

"Jeff Root" wrote in message
oups.com...

George Dishman replied to Lester Zick:

...
.. I previously asked Jeff
this following question and I'd like both you and him
to give me your views so we can compare attitudes.
Is the ship "really" shorter? Does the silhouette
"really" subtend a smaller angle? The aim is to find
out what we all mean by the concept of "real".

I want to say first that I don't think very highly of
most philosophical questioning about "reality". I wasn't
particularly impressed by the movie "The Matrix", I don't
wonder if I was just created a minute ago with a mass of
false memories planted in my mind, I don't wonder whether
a photon is "really" a particle or a wave, and I most
certainly don't think that all opinions are equally valid.

Understood, but my question isn't about the philosophical
nature of reality, rather I am trying to set some baseline
mutual understanding of terms. My answer would be simply

a) The ship is not really shorter, it is the same length
but has changed its orientation to point from which
it is being observed.

b) The reduction of subtended angle is real. The angle
between two threads stretched from bow and stern to
the observing point can be measured with a protractor
and will be less than when the ship lies at 90 degrees
to the line of sight.

Nevertheless, distinguishing reality from non-reality is
clearly one of the major labors of mankind, and something
I can't avoid having to do.

Plus, we have the question of what "physical" means,
which is probably just as difficult.

I don't know yet whether I can answer the question, but I
think it will be easier for me than for Lester, because I
can use analogies, which he shuns.

The shortening is not something that happens to the ship
or to the observer. The shortening is a change in the
relationship between the ship and the observer. The
relationship is certainly real, in my view, and the change
in the relationship is equally real.

It is like me walking around to the south side of my desk.
Is the desk then "really" north of me? Yes, it is. As the
ship speeds up relative to me, it really contracts relative
to me. And I know that I contract relative to the ship.
But the ship doesn't change, and I don't change. It is
only the relationship which changes.

I'm not sure I can or need to go any farther than that.

That sounds as though you are saying the same as I, at
least I will take it that way unless you object.

Now for Lester's answer:

"Lester Zick" wrote in message
...
On 31 Dec 2006 17:52:33 -0800, "George Dishman"
wrote:
...
.. I previously asked Jeff this
following question and I'd like both you and him to give
me your views so we can compare attitudes. Is the
ship "really" shorter? Does the silhouette "really"
subtend a smaller angle? The aim is to find out
what we all mean by the concept of "real".

Well that's not really all that difficult in the context of MM because
we only have two variables: physical dimensions of the interferometer
and the relative speed of light in various directions along those arms
independent of the interferometer itself.

Now I know that SR theorists see this as only a problem in apparent
reality. But the experimental results themselves are not only apparent
but real and they're what is to be explained in mechanical terms of
the actual experiment. Neither Michelson nor Morley used rods and
cones to measure anything. Measurements were implicit in the fringe
shift and there were no fringe shifts of an experimentally significant
magnitude. But it was the interferometer itself which was doing the
measuring and not Michelson or Morley.

In other words what there is to explain is not an apparent effect but
a real effect or at least an effect independent of how observers would
measure things in terms of visual effects and subtended angles etc.


Sorry Lester, you don't seem to have said anything about the
ship at anchor. Can you have another attempt please, these
are the questions:

...
The fun starts when you consider a ship swinging
at anchor on the horizon where all you can see is
a silhouette. When it lies at right angles to your
vision, it "appears" longer than when it lies at
30 degrees, and multiplying the subtended angle
by the distance to the horizon really does "measure"
a shorter length, but is the ship "really" shorter ;-)

a) Is the ship "really" shorter?

b) Does the silhouette "really" subtend a smaller angle?

As I said, the aim is to find out what we all mean by
the concept of "real" _before_ we try to apply that
word to the MMX.

George

(original lost in the ISP, reposted with some minor
corrections).

"Lester Zick" wrote in message
...
On Sun, 31 Dec 2006 19:51:54 -0000, "George Dishman"
wrote:
...
http://www.google.co.uk/search?q=define%3A+interstitial

Interstitial means lying in the interstices such as
carbon grains in the interstices between the steel
grains in cast iron, or fluid in the gaps between
cells in muscle. The particles comprising a body are
not interstitial but what I want is for Lester to
actually explain what he means rather than us guessing.

And I certainly don't mind but I can't really understand why you
insist the particles comprising a body are not interstitial.

Let me try to explain then. Look at the use of the word
relating to muscles. There are water molecules inside
every cell and the are others between the cells. The
interstices are the gaps between the cells and the
interstitial water molecules are those lying within those
interstices. The word is used to differentiate between
the water molecules lying in the gaps and those within
the cells.

Every
body in the universe is interstitial to some other unless you're
trying to say bodies in the sense of experimental platforms are
somehow spatially preemptive.

"preemptive" is also an odd choice of word but basically,
yes, the purpose of the word interstitial is to allow us
to distinguish whether we are talking about the particles
that make up some class of bodies (cells, experiments or
whatever) and similar particles lying between those bodies.
The rods forming an MMX are not interstitial while identical
rods lying in the gaps between MMXs and not forming part of
those MMXs would be interstitial though it is easier to
follow when the objects in question enclose a volume.

As I've already mentioned several times
MM could have been conducted between the earth and moon and another
body such as a satellite at right angles ..

OK, so you have fixed one rod between Earth and Moon and
another from Earth to the satellite. The rods are fixed
length so you have changed the Moon's orbit to be circular
and you are holding them rigidly at 90 degrees. Tricky in
practice but we can go with that for a thought experiment.

and a second MM could have
also been conducted on some satellite in between,

Yep, no problem.

and the second
experimental platform would be interstitial with respect to the first.

No, you have defined a class of bodies called "experimental
platforms" and interstitial means in the space lying between
the two "experimental platforms".

As far as velocity dependent frames of reference are concerned every
group of particles traveling at a common underlying velocity within
any body constitutes a different interstitial body.

No, you could say they constitute a subset of the body,
or if they are distinguishable in some way as an object
in their own right you might say they were an embedded
body but interstitial would mean a group of particles
_outside_ the body.

And that includes
both molecular and atomic subgroups of experimental platforms as well
as macroscopic groupings such as the earth-moon or satellites.

Sure, the dispute here is that interstitial means
outside, not inside.

I am still looking for you to tell me where this supposed
contradiction appears.

The apparent contradiction is obvious, even if Lester
prefers to describe it in somewhat convoluted terms.

So you say but I don't think so. It is obvious that,
for a single body, you get different factors for
different observers moving at different speeds because,
as Lester said himself, the effects are velocity
dependent.

Sure. The problem is that the contraction factors are for the body not
the observers.

No, that is probably where the confusion lies. The length
contraction factor is a ratio of two measurements which
can be of the same body at the same time.

He seems to have some reasoning that says
this explanation doesn't work when more than one body
is involved _and_ we talk about spaces inside bodies
_and_ the bodies are overlapping. Why those extra
conditions are necessary is a mystery to me.

Well it really shouldn't be. Bodies traveling at different velocities
have different contraction factors associated with their respective
frames of reference wherever they're located. You seem to associate
contraction effects with observers rather than with the bodies. But
contraction is supposed to affect the bodies undergoing translation
through space at constant velocity independent of observation since
that's supposed to be how Lorentz's anisotropic transforms for the
speed of light relative to an experimental platform become isotropic.

That is Lorentz's approach though, and I am not discussing
that.

When bodies traveling at different velocities are interstitial there
is an implicit contradiction between their respective contractions.

The extra conditions are only needed to show the contradiction
involved in necessary terms since overlapping regions of space cannot
be contracted by different amounts and still account for the null
results of different MM experiments carried out together in both
overlapping frames.


To get away from the dispute over the meaning of interstitial,
let's simplify it by talking of just a single body. The length
is measured by some instrument which we personify as "observer"
A. Let's assume that instrument is at rest relative to the body
and "he" measures length L repeatedly over some period of time
(thus the length is not changing). A second identical instrument
which I will call "observer" B moves past the same body and
measures length L'. This occurs during the period when the
length is being continuously monitored by A.

The length contraction factor is the ratio L'/L. That is the
ratio of two measurements of the same body at the same time by
identical instruments.

Now add a third identical observing instrument C also moving
past the same body but at a different speed from B. The length
measured by C is L" and the observed contraction ratio is L"/L.
You now have two different contraction ratios, L'/L and L"/L
applying to the same measured body.

Do you consider there is any contradiction in that statement
of the problem (which is the one I have used in the past) or
do you think that is OK but the contradiction only appears
when we start talking about two bodies instead of one? If so
you will still need to explain why having the extra body is
significant.

I think that instead of your current line of attack, you
should acknowledge that the apparent contradiction is
obvious, and then ask Lester to show that it is real and
not merely apparent.

No, I just want him to state why he thinks there is
a contradiction in such a way that it makes clear
why all these extra provisos are necessary. I'm not
going to make his case for him, there is no
contradiction in anything he has presented so far
so it is his task to try to justify his claim. I
don't think he can and he uses rhetorical questions
to cover it up in the hope that is readers will fill
it in for him.

Well, George, that's just absurd. I don't and rarely have needed my
readers to fill in anything. Certainly Jeff and Gurcharn get it even
if you don't.

I freely admit I don't see why you need the two bodies
rather than one to illustrate the supposed contradiction.

I'm somewhat curious why he thinks his statement of the
apparent contradiction is more clear-cut than mine.

I am sure he is saying that your version doesn't
show the contradiction but his does.

I don't know what Jeff's version shows because it isn't my version. My
version says nothing about observers and measurement. It simply states
a case involving different interstitial bodies and coincident frames
of reference where spatial contraction is required to explain the
isotropic experimental results for MM produced despite Lorentz's
anisotropic transforms for the speed of light in various directions
relative to an experimental platform undergoing translation through
space at constant velocity.

However, your bodies aren't interstitial, frames cannot be
coincident (or they are the same frame) and IMO, Lorentz
was wrong anyway, the speed of light is isotropic.

My case is definitive and Jeff's isn't
although I suspect Jeff's might be made more nearly definitive by
using only one observer instead of two. But that's an unrelated issue
where contraction of the space between and among interstitial bodies
in different frames of reference is considered.

Not really, with only one observer there is no such thing
as length contraction since the term denotes the ratio
of lengths measured by two different observers.

His version is that SR says multiple bodies in the same
place, moving relative to one another, simultaneously
have different "contraction factors".

No, his version has the space between bodies being
contracted and remember he first said each observer
only observed his _own_ MMX.

And remember I first said nothing of the kind having anything to do
with observers. My case first stated spatial contraction as determined
according to different frames of reference for interstitial bodies.
The contraction was of both space and bodies. Your reference to my
comment regarding observers was only made in response to your own
insistence on having some kind of observer measuring something to show
that observers and measurements were irrelevant to the problem posed.

The term "observer" is a personification of an instrument
whose motion defines a frame of reference for a measurement.


My version is that SR says a body simultaneously has
different "contraction factors" for different observers
in different states of motion relative to the body.

The two statements are equivalent, but I think mine is
more shockingly obvious in its apparent contradiction.

Yours is the classic statement but Lester seems to
think he has a new problem that goes beyond the
standard resolution of your statement.

Only because Lester does.

Well again I can only say you need to explain why you
think the same contradiction isn't apparent with the
classic version of a single body and two observing
instruments.

The apparent contradiction that Lester is complaining
about is probably the single most common hangup when
just starting to learn about relativity. I would not
be surprised to learn that the majority of people are
confounded by it for at least a short time.

Perhaps, but let's not invent our own problems, Lester
needs to make a clear statement of the problem. Maybe
it is just what you have said but maybe he has some
other problem in mind.

You know I find it rather curious, George, that you insist on talking
as if I've said nothing at all in any of these posts and severly mis
construing everything I have said in absurdly bizarre ways which
completely misrepresent what I've said repeatedly. The fact is that
Jeff understands the problem even if he insists on casting it in terms
of observation and measurement. At least he gets it. Gurcharn gets it.
You don't get it. To me that says much more about your own reading
comprehension than anything else.

Actually I think I have always 'got it' but some of
your early replies suggested that there wasn't a
contradiction in the simpler version so I was looking
for something more complex. Maybe your response to my
own statement of the apparent problem above will shed
some light on it.

George

George,

When I replied to your post this morning my answer
to your questions was skewed because I didn't see the
paragraph explaining the questions, and didn't know
which ship you were referring to. (I had seen the
paragraph last year, though-- one day earlier. :-)

The fun starts when you consider a ship swinging
at anchor on the horizon where all you can see is
a silhouette. When it lies at right angles to your
vision, it "appears" longer than when it lies at
30 degrees, and multiplying the subtended angle
by the distance to the horizon really does "measure"
a shorter length, but is the ship "really" shorter ;-)

Oh, *that* ship.

It may be a good thing that I misunderstood what ship
you were asking about. It could help me answer the real
questions.

I think I disagree about this being a philosophical
question. It *is* a philosophical question.

a) Is the ship "really" shorter?

My knee-jerk reaction is to ask "What do you mean by
'really'?" :-)

b) Does the silhouette "really" subtend a smaller angle?

The answer here appears to be easy and unambiguous.
The silhouette of the ship really does subtend a smaller
angle from my vantage point. I think everyone can agree
on this one.

Back to:

a) Is the ship "really" shorter?

It doesn't depend on what the meaning of 'is' is.

My other knee-jerk reaction is to say "No, of course
the ship isn't really shorter, you idiot! It's just
turned at an angle to my line of sight!"

However, I could as well say that for some purposes it
really is shorter. If I'm trying to hit it with a dumb
torpedo that is propelled in a straight line on the
surface of the water, then as far as I'm concerned the
ship really is changing length as it turns. But in
saying that, I'm not distinguishing between angle and
length. I know that angle and length are two entirely
different... um... quantities... but in this case I seem
to be able to use them interchangeably. My torpedo has
limited accuracy. The ship has an angular width which
varies as it turns. The wider the angle, the better the
chance my torpedo will hit. At the distance of the ship,
the ship needs to be 100 feet wide **perpendicular to my
line of sight** for my torpedo to have a 50% chance of
hitting it. I can convert between angle and width if I
know the distance.

I have no idea whether:

a) I answered your question,
b) The answer is useful,
c) The answer is what you expected.

-- Jeff, in Minneapolis

George,

I disagree with your objections to Lester's use of the
term "interstitial". I would say that his use of the
term is inappropriate, unnecessary, and unhelpful, but
it is not wrong.

The term means "in the gap(s) between". What the gap
or gaps is/are between is completely arbitrary. Lester's
arbitrary use of the term here is no more arbitrary than
any other use. I think you should accept what he uses it
for and go on from there.

What he uses "interstitial" for is clearly to point out
the co-location of multiple differently-moving reference
frames, and whatever defines those frames.

the dispute here is that interstitial means outside,
not inside.

This I disagree with. "Interstitial" means "in the gap(s)
between", which would be outside some things and inside
other things.

I can imagine little MMXs inside a big MMX, so that they
are simultaneously in the same location in space. That's
all Lester means. It shouldn't be a problem.

The problem is that the contraction factors are for the
body not the observers.

No, that is probably where the confusion lies.

Ya think?

The length contraction factor is a ratio of two measurements
which can be of the same body at the same time.

And they can be imaginary thought experiment measurements
of multiple imaginary bodies by multiple imaginary
observers, all being observed in imagination by a real
thought experimenter sitting at his computer. This
scenario is unnecessarily complicated, but it works.

I was looking for something more complex.

No way. He is stuck on the kindergarten cunundrum of one
thing having two different values simultaneously.

-- Jeff, in Minneapolis

On 2 Jan 2007 07:31:13 -0800, "Jeff Root" wrote:


George,

I disagree with your objections to Lester's use of the
term "interstitial". I would say that his use of the
term is inappropriate, unnecessary, and unhelpful, but
it is not wrong.

Well, Jeff, my original objective was to find a definitive adjective
to describe exactly what I had in mind. I think it fair to say that my
use of "interstitial" is unusual and not customary. But I think it is
accurate given the general context I'm trying to establish. Most
people probably don't recognize that the definition of "bodies" is
pretty much arbitrary for experimental purposes where the subject of
the experiment, the relative velocity of light, traverses space mostly
independent of the experimental platform. I don't think Michelson or
Lorentz considered this nor do I think Einstein recognized it or that
"bodies" in this sense were not spatially preemptive so as to preclude
overlapping experimental platforms in different frames of reference.

The term means "in the gap(s) between". What the gap
or gaps is/are between is completely arbitrary. Lester's
arbitrary use of the term here is no more arbitrary than
any other use. I think you should accept what he uses it
for and go on from there.

What he uses "interstitial" for is clearly to point out
the co-location of multiple differently-moving reference
frames, and whatever defines those frames.

Correct.

the dispute here is that interstitial means outside,
not inside.

This I disagree with. "Interstitial" means "in the gap(s)
between", which would be outside some things and inside
other things.

I can imagine little MMXs inside a big MMX, so that they
are simultaneously in the same location in space. That's
all Lester means. It shouldn't be a problem.

True. And if I had to rely on a single adjective to describe the
situation in definitive terms I would choose "interstitial" again.

The problem is that the contraction factors are for the
body not the observers.

No, that is probably where the confusion lies.

Ya think?

Well the contraction factor applies to the frame of reference which
includes spatial geometry and objects described by the geometry. I
suspect that those who argue observers, measurements, rods, and cones,
etc. imagine it only refers to observers etc. I don't say there is no
observational effect but what I'm discussing is not any kind of
experimental measurement of an observational effect but the actual
contraction which is assumed present to account for the transition
between anisotropic Lorentz transforms describing the velocity of
light relative to an experimental platform undergoing translation
through space at constant velocity and isotropic null results of MM.

The length contraction factor is a ratio of two measurements
which can be of the same body at the same time.

And they can be imaginary thought experiment measurements
of multiple imaginary bodies by multiple imaginary
observers, all being observed in imagination by a real
thought experimenter sitting at his computer. This
scenario is unnecessarily complicated, but it works.

Why is it unnecessarily complicated? I'm not sure I understand why
anyone considers observers relevant and I think all the complication
stems from the observers, measurements, techniques, etc. and not from
the actual problem I posed which has to do with contraction and not
measurement of contraction which is an entirely different problem. I'm
not trying to measure contraction.

I was looking for something more complex.

No way. He is stuck on the kindergarten cunundrum of one
thing having two different values simultaneously.

Which may indeed be a kindergarten conundrum if the differences are
supposed to apply to a common region of space together. And perhaps
it's time we get beyond kindergarten physics to analyze the issue.

~v~~

"Lester Zick" wrote in message ...
| But the problem is who is trying to force what view on whom. I haven't
| gotten to George's reply as yet but I'm simply posing a problem as far
| as contraction is concerned. I don't see anyone imposing anything on
| anyone. If SR answers the objection I'd simply like to know how.

Like this:
http://www.androcles01.pwp.blueyonde...ket/Rocket.htm
http://www.androcles01.pwp.blueyonde...mart/Smart.htm