1 "rryker" 
Length contraction reality  zaterdag 5 oktober 2002 7:18 
2 ande452 
Re: Length contraction reality  zondag 6 oktober 2002 7:19 
3 "Bill Hobba" 
Re: Length contraction reality  donderdag 10 oktober 2002 2:37 
4 ande452 
Re: Length contraction reality  donderdag 10 oktober 2002 6:05 
5 "Pmb" 
Re: Length contraction reality  donderdag 10 oktober 2002 14:51 
6 "Nicolaas Vroom" 
Re: Length contraction reality  donderdag 10 oktober 2002 21:21 
7 "Terry Sampson" 
Re: Length contraction reality  vrijdag 18 oktober 2002 23:58 
8 "Stephen Speicher" 
Re: Length contraction reality  zaterdag 19 oktober 2002 5:46 
9 "Nicolaas Vroom" 
Re: Length contraction reality  zaterdag 19 oktober 2002 14:31 
10 "Stephen Speicher" 
Re: Length contraction reality  zaterdag 19 oktober 2002 19:14 
11 "Nicolaas Vroom" 
Re: Length contraction reality  zaterdag 19 oktober 2002 19:30 
12 "HenriWilson" 
Re: Length contraction reality  zaterdag 19 oktober 2002 22:27 
13 "Nicolaas Vroom" 
Re: Length contraction reality  zondag 20 oktober 2002 20:39 
14 "HenriWilson" 
Re: Length contraction reality  zondag 20 oktober 2002 21:15 
15 "Stephen Speicher" 
Re: Length contraction reality  zondag 20 oktober 2002 23:01 
16 "Bilge" 
Re: Length contraction reality  zondag 20 oktober 2002 23:32 
17 "Nicolaas Vroom" 
Re: Length contraction reality  maandag 21 oktober 2002 19:12 
18 "Randy Poe" 
Re: Length contraction reality  dinsdag 22 oktober 2002 19:54 
19 "HenriWilson" 
Re: Length contraction reality  dinsdag 22 oktober 2002 23:03 
20 ande452 
Re: Length contraction reality  woensdag 23 oktober 2002 4:36 
21 "Bilge" 
Re: Length contraction reality  woensdag 23 oktober 2002 7:55 
22 "Nicolaas Vroom" 
Re: Length contraction reality  woensdag 23 oktober 2002 14:57 
23 "Nicolaas Vroom" 
Re: Length contraction reality  woensdag 23 oktober 2002 17:45 
24 "Bill Hobba" 
Re: Length contraction reality  woensdag 23 oktober 2002 23:16 
25 "rryker" 
Re: Length contraction reality  donderdag 24 oktober 2002 6:20 
26 "HenriWilson" 
Re: Length contraction reality  donderdag 24 oktober 2002 20:52 
27 "Bill Hobba" 
Re: Length contraction reality  vrijdag 25 oktober 2002 13:21 
28 "rryker" 
Re: Length contraction reality  zaterdag 26 oktober 2002 4:03 
29 "Bill Hobba" 
Re: Length contraction reality  zondag 27 oktober 2002 1:45 
30 "Nicolaas Vroom" 
Re: Length contraction reality  zondag 27 oktober 2002 18:16 
31 "Bill Hobba" 
Re: Length contraction reality  zondag 27 oktober 2002 23:17 
32 "Dirk Van de moortel" 
Re: Length contraction reality  maandag 28 oktober 2002 8:42 
33 "Stephen Speicher" 
Re: Length contraction reality  maandag 28 oktober 2002 3:36 
34 "Nicolaas Vroom" 
Re: Length contraction reality  maandag 28 oktober 2002 21:04 
35 "Nicolaas Vroom" 
Re: Length contraction reality  maandag 28 oktober 2002 22:57 
36 "rryker" 
Re: Length contraction reality  dinsdag 29 oktober 2002 4:40 
37 "Nicolaas Vroom" 
Re: Length contraction reality  maandag 4 november 2002 11:53 
38 "Dirk Van de moortel" 
Re: Length contraction reality  maandag 4 november 2002 18:47 
39 "Nicolaas Vroom" 
Re: Length contraction reality  dinsdag 5 november 2002 16:53 
40 "Dirk Van de moortel" 
Re: Length contraction reality  dinsdag 5 november 2002 17:18 
Length contraction reality:
Do object's length's really contract? I say no, and offer a thought experiment below, where its results conclude no contraction will be observed. I must point out here that all events in different frames of reference will be observed by all other frames of reference. The differences being, times and coordinates of relative frames.
Thought experiment:
Two systems with observers in relative motion.
One system will be stationary.
Another system will move at a velocity with respect to the stationary system. Consisting of a light clock who's proper length's (as measured in their own frame), are as follows. A pulse laser, where a mirror is placed 1 light second directly vertically above the laser. And a detector placed directly horizontally a distance of .3 light seconds away from the laser in the direction of the motion as viewed by the stationary system. It is the intent of the mirror to reflect the light towards the detector.
As a reminder for the reader, if the light reaches the detector in one system's observance, then all system's in relative motion will observe the same, only at different times and coordinates.
If length contraction occurs, then clearly the light pulse will miss the detector, yet in reality this does not happen.
Therefore, this experiment concludes length contraction as folly.

Rod Ryker...
It is reasoning and faith that bind truth.
http://herr_ryker.tripod.com/
> 
Length contraction reality: Do object's length's really contract? I say no, 
Then you agree with SR that says that the intrinsic lengths of objects don't change, but the measured ones do. SR says that this is the result of a coordinate transformation, not an intrinsic change in the object.
John Anderson
>  rryker wrote: 
> > 
Length contraction reality: Do object's length's really contract? I say no, 
> 
>  Then you agree with SR that says that the intrinsic lengths of objects don't change, but the measured ones do. SR says that this is the result of a coordinate transformation, not an intrinsic change in the object. 
Hmmm. Certainly a legit interpretation. But I am not sure SR necessarily implies this. It is just as legit to suppose the lengths do change  not just out measurment of them. The problem is I am not sure how you tell the difference.
thanks bill
> 
> > 
rryker wrote: 
> > > 
Length contraction reality: Do object's length's really contract? I say no, 
> > 
> 
John Anderson Replied. 
> > 
Then you agree with SR that says that the intrinsic lengths of objects don't change, but the measured ones do. SR says that this is the result of a coordinate transformation, not an intrinsic change in the object. 
> 
Hmmm. Certainly a legit interpretation. But I am not sure SR necessarily implies this. It is just as legit to suppose the lengths do change  not just out measurment of them. The problem is I am not sure how you tell the difference. thanks bill 
SR interprets Lorentz transformations as coordinate transformations only.
Ether theory interprets them as due to intrinsic clock rate and length changes.
John Anderson
>  Do object's length's really contract? 
Depends. One has to be more specific. If you have a rod which is lying on the y axis and you measure it's length from a frame moving in the xdirection then no. The length will not contract. Length contraction only takes place in the direction of motion i.e. not when the rod is perpendicular to the motion of the 'moving' frame.
>  Consisting of a light clock who's proper length's (as measured in their own frame), are as follows. 
I'm not sure what you're calling the 'length of the clock' here. Luckily I've done this out before in the past. See
http://www.geocities.com/physics_world/time.jpg
The length is along the yaxis, perpendicular to the motion of the moving frame.
>  A pulse laser, where a mirror is placed 1 light second directly vertically above the laser. And a detector placed directly horizontally a distance of .3 light seconds away from the laser in the direction of the motion as viewed by the stationary system. It is the intent of the mirror to reflect the light towards the detector. 
Are these mirrors moving relative to the light clock? They don't need to be rotated as you've drawn them here
http://herr_ryker.tripod.com/herrryker/id1.html
> 
If length contraction occurs, then clearly the light pulse will miss the detector, yet in reality this does not happen. Therefore, this experiment concludes length contraction as folly. 
It seems to me that you'd missing something important here. You're not taking time dilation into account. Look at the correct way that this is done in the above link I gave. First off it appears to me that you've neglected the motion of the the emitter detector arrangement. I'm not quite sure what you're missing here. Let me get back to you. Note that it's not just enough to draw it. I can always draw a picture to come out the way I want. You have to take the phyusics into account.
Analyze this with the Lorentz transformation and note that similtaneity is a key issue when trying to understant length contraction.
Pmb
"Pmb"
> 
rryker 
> > 
Do object's length's really contract? 
> 
Depends. One has to be more specific. If you have a rod which is lying on the y axis and you measure it's length from a frame moving in the xdirection then no. The length will not contract. Length contraction only takes place in the direction of motion i.e. not when the rod is perpendicular to the motion of the 'moving' frame. 
I do not fully agree with your reply
assuming my understanding of SR is correct.
a. When you have a rod which is lying on the x axis and which moves
in the x direction and you measure its length from the rest frame
then you will measure length contraction.
b. When you have a rod which is lying on the x axis and is at rest
and you measure its length from a frame which moves in the x direction
then you will measure length contraction.
c. If you have a rod at rest and you measure the length of the rod in the
rest frame then you will measure no length contraction.
d. If you have a rod which moves in the x direction and you measure
its length in a frame which also moves in the x direction with the same
speed then you will measure no length contraction.
In order to perform (a) you need a grid of clocks all equal spaced in the
rest
frame. The smallest distance between the clocks has to be much less than
the rest length of the rod.
In order to measure the length of the rod at 12.00 in the rest frame
1. you need two obervers at the rod: one at the front and one at the back.
2. each of those two observers has to identify the nearest clock
where the observer is at 12.00
The distance betwee those two selected clocks is the length of the moving
rod.
For a different method see http://users.pandora.be/nicvroom/length.htm and study the example: http://users.pandora.be/nicvroom/calc1.htm If you have spare time please fill in the questionary.
Nick
From:
Do object's length's really contract? I say no,
John Anderson wrote:
Then you agree with SR that says that the intrinsic lengths of objects don't change, but the measured ones do. SR says that this is the result of a coordinate transformation, not an intrinsic change in the object.
Terry Sampson:
Would you be kind enough to point out to me where in Einstein's original paper he states that lengths do not change.
http://www.genevalink.ch/Bernard.Gisin/physique/relativite/Paper_en1/Einstein.html
Thank you.
On Fri, 18 Oct 2002, Terry Sampson wrote:
> 
John Anderson wrote: 
> > 
Then you agree with SR that says that the intrinsic lengths of objects don't change, but the measured ones do. SR says that this is the result of a coordinate transformation, not an intrinsic change in the object. 
> 
Would you be kind enough to point out to me where in Einstein's original paper he states that lengths do not change. http://www.genevalink.ch/Bernard.Gisin/physique/relativite/Paper_en1/Einstein.html 
First, note that John mentions "intrinsic lengths," meaning the proper distance of an object as measured in its own frame. This is distinguished from measurements made of the object's length by observer's who are in relative motion to the object.
As to Einstein's seminal 1905 paper: the most relevant statement that must first be understood is where Einstein concludes:
"So we see that we cannot attach any absolute signification to the concept of simultaneity, but that two events which, viewed from a system of coordinates, are simultaneous, can no longer be looked upon as simultaneous events when envisaged from a system which is in motion relatively to that system.
The measurement of the length of an object is nothing more than the measurement of two events taken simultaneously, i.e., we simultaneously mark the two end points of the object and that distance represents its length. So, later on, Einstein states:
"Thus, whereas the Y and Z dimensions of the sphere (and therefore of every rigid body of no matter what form) do not appear modified by the motion, the X dimension appears shortened in the ratio 1 : sqrt(1  (v/V)^2)..."
Note Einstein says "appears shortened," meaning that such an _appearance_ is a consequence of the measurement process made by an observer in relative motion to the object, and in no way reflects any change to the intrinsic length of the object itself.

Stephen
sjs@speicher.com
Ignorance is just a placeholder for knowledge.
Printed using 100% recycled electrons.

"Stephen Speicher"
> 
First, note that John mentions "intrinsic lengths," meaning the proper distance of an object as measured in its own frame. This is distinguished from measurements made of the object's length by observer's who are in relative motion to the object. As to Einstein's seminal 1905 paper: the most relevant statement that must first be understood is where Einstein concludes: "So we see that we cannot attach any absolute signification to the concept of simultaneity, but that two events which, viewed from a system of coordinates, are simultaneous, can no longer be looked upon as simultaneous events when envisaged from a system which is in motion relatively to that system. The measurement of the length of an object is nothing more than the measurement of two events taken simultaneously, i.e., we simultaneously mark the two end points of the object and that distance represents its length. So, later on, Einstein states: "Thus, whereas the Y and Z dimensions of the sphere (and therefore of every rigid body of no matter what form) do not appear modified by the motion, the X dimension appears shortened in the ratio 1 : sqrt(1  (v/V)^2)..." Note Einstein says "appears shortened," meaning that such an _appearance_ is a consequence of the measurement process made by an observer in relative motion to the object, and in no way reflects any change to the intrinsic length of the object itself. 
When Einstein uses the verb APPEARS than IMO this implies that length contraction is not real and but something else for example a visible illusion.
However Abraham Pais in his book "Subtle is the Lord.."
at page 144 writes:
"From the Lorentz transformations to the FitzGeraldLorentz
contraction of rods and the dilation of time:
My interpretation of this is that:
For a moving rod Length contraction is real, compared
with its rest length or proper length or intrinsic length
(the rod its length is shortened)
and can be demonstrated
(Measured with a grid of clocks at rest)
by a resting observer
Nick
http://users.pandora.be/nicvroom/trainfb_form.htm
On Sat, 19 Oct 2002, Nicolaas Vroom wrote:
> 
"Stephen Speicher" 
> > 
First, note that John mentions "intrinsic lengths," meaning the proper distance of an object as measured in its own frame. This is distinguished from measurements made of the object's length by observer's who are in relative motion to the object. As to Einstein's seminal 1905 paper: the most relevant statement that must first be understood is where Einstein concludes: "So we see that we cannot attach any absolute signification to the concept of simultaneity, but that two events which, viewed from a system of coordinates, are simultaneous, can no longer be looked upon as simultaneous events when envisaged from a system which is in motion relatively to that system. The measurement of the length of an object is nothing more than the measurement of two events taken simultaneously, i.e., we simultaneously mark the two end points of the object and that distance represents its length. So, later on, Einstein states: "Thus, whereas the Y and Z dimensions of the sphere (and therefore of every rigid body of no matter what form) do not appear modified by the motion, the X dimension appears shortened in the ratio 1 : sqrt(1  (v/V)^2)..." Note Einstein says "appears shortened," meaning that such an _appearance_ is a consequence of the measurement process made by an observer in relative motion to the object, and in no way reflects any change to the intrinsic length of the object itself. 
> 
My interpretation of this is ... 
Your "interpretation" does not matter, since you continue to live in a world of selfimposed ignorance.

Stephen
sjs@speicher.com
Ignorance is just a placeholder for knowledge.
Printed using 100% recycled electrons.

"Stephen Speicher"
>  On Sat, 19 Oct 2002, Nicolaas Vroom wrote: 
> > 
"Stephen Speicher" 
> > > 
First, note that John mentions "intrinsic lengths," meaning the proper distance of an object as measured in its own frame. This is distinguished from measurements made of the object's length by observer's who are in relative motion to the object. As to Einstein's seminal 1905 paper: the most relevant statement that must first be understood is where Einstein concludes: "So we see that we cannot attach any absolute signification to the concept of simultaneity, but that two events which, viewed from a system of coordinates, are simultaneous, can no longer be looked upon as simultaneous events when envisaged from a system which is in motion relatively to that system. The measurement of the length of an object is nothing more than the measurement of two events taken simultaneously, i.e., we simultaneously mark the two end points of the object and that distance represents its length. So, later on, Einstein states: "Thus, whereas the Y and Z dimensions of the sphere (and therefore of every rigid body of no matter what form) do not appear modified by the motion, the X dimension appears shortened in the ratio 1 : sqrt(1  (v/V)^2)..." Note Einstein says "appears shortened," meaning that such an _appearance_ is a consequence of the measurement process made by an observer in relative motion to the object, and in no way reflects any change to the intrinsic length of the object itself. 
> > 
My interpretation of this is ... 
> 
Your "interpretation" does not matter, since you continue to live in a world of selfimposed ignorance. 
Thanks for this feedback.
Nick
On Sat, 19 Oct 2002 18:30:22 GMT, "Nicolaas Vroom"
> 
"Stephen Speicher" 
>>  On Sat, 19 Oct 2002, Nicolaas Vroom wrote: 
>> > 
"Stephen Speicher" 
>> > > 
First, note that John mentions "intrinsic lengths," meaning the proper distance of an object as measured in its own frame. This is distinguished from measurements made of the object's length by observer's who are in relative motion to the object. As to Einstein's seminal 1905 paper: the most relevant statement that must first be understood is where Einstein concludes: "So we see that we cannot attach any absolute signification to the concept of simultaneity, but that two events which, viewed from a system of coordinates, are simultaneous, can no longer be looked upon as simultaneous events when envisaged from a system which is in motion relatively to that system. The measurement of the length of an object is nothing more than the measurement of two events taken simultaneously, i.e., we simultaneously mark the two end points of the object and that distance represents its length. So, later on, Einstein states: "Thus, whereas the Y and Z dimensions of the sphere (and therefore of every rigid body of no matter what form) do not appear modified by the motion, the X dimension appears shortened in the ratio 1 : sqrt(1  (v/V)^2)..." Note Einstein says "appears shortened," meaning that such an _appearance_ is a consequence of the measurement process made by an observer in relative motion to the object, and in no way reflects any change to the intrinsic length of the object itself. 
>> > 
My interpretation of this is ... 
>> 
Your "interpretation" does not matter, since you continue to live in a world of selfimposed ignorance. 
> 
Thanks for this feedback. Nick 
Clearly impossible.
See my demo 'contractions.exe' for an animation of this if you don't believe me.
Of course this also proves that clock rates don't physically change with velocity too  and so makes a mockery of the whole SR time dilation business.
Henri Wilson. Technologist.
See my animations at:
http://www.users.bigpond.com/rmrabb/HW.htm
"HenriWilson"
>  there is no physical length change due to velocity. The proof of that is trivial. 
> 
A rod changing speed can be either accelerating or decelerating depending
on which arbitrary observer you wish to use. It would therefore have to
both decrease and increase physical length simultaneously.
Clearly impossible. See my demo 'contractions.exe' for an animation of this if you don't believe me. 
The screen can show the situation in the rest frame.
In the rest frame at each pixel of this screen should show a clock.
All those clocks are synchronised in the rest frame and as such
all should show the same time.
When at rest the rod occupies the pixels in the x direction
from 100 to 200.
The moving rod moves to the left and at 12.00 occupies the
pixels in the x direction from 350 to 400.
You can demonstrate this by two observers, one at the front
and one at the back of the rod who monitor the clocks in the
rest frame and who write down the nearest pixel location
at 12.00 ie the numbers 400 and 350.
This means that the length of the moving rod is shortened.
The issue ar hand is how do you describe this phenomena:
1) The rod appears to be shortened (Einstein 1905)
2) It "really" exists (Einstein 1911)
3) It really exists (it is) ie something that is physical identical as
when you heat or cool an iron rod, which also expands or contracts.
>  See my animations at: http://www.users.bigpond.com/rmrabb/HW.htm 
You can also use the screen to show the situation from a moving frame which has the same speed as the moving rod. In that (moving) frame the (moving) rod is at rest and has the same length as in the previous situation ie 100 pixels. You can use the same clocks as previous with one exception: they have to be synchronised in this moving frame. The previous rod at rest now moves to the left and its length is now shortened.
All this is accordingly to SR.
There is one main problem: "it is a rather difficult effect to see experimentally, because it is hard to accelerate macroscopic rods to high enough velocities to make the effect noticeable."
See Clifford M. Will "Was Einstein Right" page 273
Nick http://users.pandora.be/nicvroom/trainfb_form.htm
On Sun, 20 Oct 2002 19:39:41 GMT, "Nicolaas Vroom"
> 
"HenriWilson" 
>> 
there is no physical length change due to velocity. The proof of that is trivial. 
>  I think that your definition and my definition of how you prove something is different. 
>> 
A rod changing speed can be either accelerating or decelerating depending on which arbitrary observer you wish to use. It would therefore have to both decrease and increase physical length simultaneously. Clearly impossible. See my demo 'contractions.exe' for an animation of this if you don't believe me. 
>  Your animation is niece but it proves nothing. This does not mean that your animation is wrong but your animation is not in agreement with SR. 
The logic behind the animation is sound. SR says that length contraction increases with velocity. That means a rod length get shorter as it speeds up. It get longer if it slows down. that is straight SR. It obviously cannot PHYSICALLY increase and decrease length simultaneously.
So that means SR is obviously wrong.
> 
The screen can show the situation in the rest frame. In the rest frame at each pixel of this screen should show a clock. All those clocks are synchronised in the rest frame and as such all should show the same time. When at rest the rod occupies the pixels in the x direction from 100 to 200. The moving rod moves to the left and at 12.00 occupies the pixels in the x direction from 350 to 400. You can demonstrate this by two observers, one at the front and one at the back of the rod who monitor the clocks in the rest frame and who write down the nearest pixel location at 12.00 ie the numbers 400 and 350. 
That is an observational effect only. The rod length doesn't PHYSICALLY alter in any way.
> 
This means that the length of the moving rod is shortened. 
Only if you accept an absolute spatial reference..
> 
The issue ar hand is how do you describe this phenomena: 
>> 
See my animations at: http://www.users.bigpond.com/rmrabb/HW.htm 
> 
You can also use the screen to show the situation from
a moving frame which has the same speed as the moving
rod. 
The length of the same rod is lengthened wrt an observer initially moving faster than the moving rod. this is not hard to understand, surely.
> 
All this is accordingly to SR. 
Even John Anderson insists that there is no physical length change and that no SRian would ever claim that there was. next time he popints that out to me I will give him your name.  Or are you really an Aetherist?
> 
There is one main problem: "it is a rather difficult effect to see experimentally, because it is hard to accelerate macroscopic rods to high enough velocities to make the effect noticeable." See Clifford M. Will "Was Einstein Right" page 273 
If they did, which velocity reference would be used?
Henri Wilson. Technologist.
See my animations at: http://www.users.bigpond.com/rmrabb/HW.htm
On Sat, 19 Oct 2002, Nicolaas Vroom wrote:
> 
"Stephen Speicher" 
> >  On Sat, 19 Oct 2002, Nicolaas Vroom wrote: 
> > > 
"Stephen Speicher" 
> > > > 
Note Einstein says "appears shortened," meaning that such an _appearance_ is a consequence of the measurement process made by an observer in relative motion to the object, and in no way reflects any change to the intrinsic length of the object itself. 
> > > 
My interpretation of this is ... 
> > 
Your "interpretation" does not matter, since you continue to live in a world of selfimposed ignorance. 
> 
Thanks for this feedback. 
You are welcome. I aim to please.
If you are desirous of feedback containing a bit more detail, you will have to do a bit more of what you have steadfastly refused to do for these many years that you continue to post to this group; that is, you will actually have to educate yourself in at least the fundamentals of relativity so that you can establish a basis for discussion of even the most simple ideas.
You _choose_ to remain ignorant and instead invest your mental effort in your absurd madeup "interpretations" of relativity. Better you should empty your mind of all of the absurdities which you have accumulated, and start fresh from the beginning and learn the way that things really are. But, alas, as I have said a dozen times, you prefer a state of selfimposed ignorance, so do not expect anything more than you are given.

Stephen
sjs@speicher.com
Ignorance is just a placeholder for knowledge.
Printed using 100% recycled electrons.

Nicolaas Vroom said some stuff about Re: Length contraction reality to usenet:
>  My interpretation of this is that: For a moving rod Length contraction is real, compared with its rest length or proper length or intrinsic length (the rod its length is shortened) and can be demonstrated 
What it means is that measurements made by an observer are exactly that  measurements made by an observer. The lorentz transforms tell you how to reconcile measurements of the same phenomena made by different observers. Whatever "reality" you wish to attach to that is up to you. The reality physicists attach to it is that which offers the most intuition to answer questions that haven't been answered with a century of metaphysics to intervene and confuse the physics.
>  (Measured with a grid of clocks at rest) by a resting observer 
You really need to think about this and figure out what's wrong with this idea. Here's a hint: if the clocks are causally related, then having more than one in an inertial frame is really pointless and if the clocks aren't causally related, there is still no point, since you can't time order them.
"Bilge"
>  Nicolaas Vroom said some stuff about Re: Length contraction reality to usenet: 
> > 
My interpretation of this is that: For a moving rod Length contraction is real, compared with its rest length or proper length or intrinsic length (the rod its length is shortened) and can be demonstrated 
> 
What it means is that measurements made by an observer are exactly that  measurements made by an observer. 
SNIP
> >  (Measured with a grid of clocks at rest) by a resting observer 
> 
You really need to think about this and figure out what's wrong with this idea. 
I do not think there is anything wrong with this idea.
I also use it frequently at my homepages in order to explain
certain concepts and so do E.F Taylor and J.A Wheeler in their book:
"Spacetime physics: introduction to special relativity"
(except they use the word latticework and I use grid)
At page 64 they write: "Measurement employs the latticework of
rods and clocks that constitutes a freefloat frame."
IMO their is nothing wrong to use that concept in order
to measure the length of a rod in order to establish
length contraction.
For more detail see my reply to HenriWilson in this thread.
(Of course their is the issue if it can not be done in practice)
The question is how do you describe this:
1. By the verb "appears" (Einstein 1905)
2. It "really" exists (Einstein 1911)
3. It is real.
May be the following quote by Ray d'Inverno is helpful: "This is rather different from the length contraction of SR, which is not to be regarded as illusory but is a very real effect" However later on d'Inverno again uses the word appears: "i.e. a rod fixed in S appears contracted in S'. "
What I learn from all of this that SR is very difficult, specific you have to be very carefull with which wordings to use.
You can also ask the same 3 questions above for Time Dilation. I expect, based on how it influences GPS, that many people will select answer 3 i.e. it is real.
Nick
http://users.pandora.be/nicvroom/length.htm
>  The logic behind the animation is sound. SR says that length contraction increases with velocity. That means a rod length get shorter as it speeds up. It get longer if it slows down. that is straight SR. It obviously cannot PHYSICALLY increase and decrease length simultaneously. 
It can't do both in its own rest frame, certainly. But then nobody is claiming that it does either.
>  So that means SR is obviously wrong. 
No, it means the interpretation that the effect leads to something observable in the rest frame of the rod is wrong.
But that's not SR.
 Randy
On Tue, 22 Oct 2002 14:54:21 0400, Randy Poe
>  HenriWilson wrote: 
>>  The logic behind the animation is sound. SR says that length contraction increases with velocity. That means a rod length get shorter as it speeds up. It get longer if it slows down. that is straight SR. It obviously cannot PHYSICALLY increase and decrease length simultaneously. 
> 
It can't do both in its own rest frame, certainly. But then nobody is claiming that it does either. 
the same applies to clocks.
> 
>> 
So that means SR is obviously wrong. 
> 
No, it means the interpretation that the effect leads to something observable in the rest frame of the rod is wrong. But that's not SR. 
many still seem to think an actual physical change occurs.
> 
 Randy 
Henri Wilson. Technologist.
See my animations at:
http://www.users.bigpond.com/rmrabb/HW.htm
> 
>  many still seem to think an actual physical change occurs. 
But people who understand SR (and not ether theory) don't think that. So why challenge the SRists? Go after the ether theorists.
John Anderson
Nicolaas Vroom said some stuff about Re: Length contraction reality to usenet:
> 
"Bilge" 
>>  Nicolaas Vroom said some stuff about Re: Length contraction reality to usenet: 
>> > 
My interpretation of this is that: For a moving rod Length contraction is real, compared with its rest length or proper length or intrinsic length (the rod its length is shortened) and can be demonstrated 
>> 
What it means is that measurements made by an observer are exactly that  measurements made by an observer. 
> 
SNIP 
>> > 
(Measured with a grid of clocks at rest) by a resting observer 
>> 
You really need to think about this and figure out what's wrong with this idea. 
> 
I do not think there is anything wrong with this idea. 
What exactly do you find wrong with the idea of using physically realizable measurements and apparatus to illustrate physical things?
> 
I also use it frequently at my homepages in order to explain
certain concepts and so do E.F Taylor and J.A Wheeler in their book: "Spacetime physics: introduction to special relativity" (except they use the word latticework and I use grid) At page 64 they write: "Measurement employs the latticework of rods and clocks that constitutes a freefloat frame." IMO their is nothing wrong to use that concept in order to measure the length of a rod in order to establish length contraction. 
IMO, anything used to establish the existence of length contraction needs to establish it using apparatus that doesn't rely on constructs which violate the physics you are trying to establish. What is the problem with simply establishing the result using the resources this universe provides?
>  For more detail see my reply to HenriWilson in this thread. 
Henry is a prime example of someone that is incapable of comprehending the limitations of a pedagogical construct and sets out to find paradoxes that arise from using unphysical objects, impossible measuring devices and omniscient observers as literal fact, independent of any context required for those things to make physical sense.
>  (Of course their is the issue if it can not be done in practice) 
It cannot be done in practice and that was what I said you needed to think about. So, again, explain how your "apparatus" might be set up as described using apparatus which may be constructed from what this universe has to offer. I don't care if the devices exist, only that they _can_ exist. One must argue that either the devices employed are physically realizable in principle, or that any unphysical aspects of the devices are not pertinent to the question the devices are supposed to address. The constant barrage of socalled "disproofs" and paradoxes posted here daily, frequently by those who have been told this often to know better, is a glaring example how anyone can prove anything by employing apparatus which violates the premises of the physics its used to describe.
> 
The question is how do you describe this: 1. By the verb "appears" (Einstein 1905) 2. It "really" exists (Einstein 1911) 3. It is real. 
By saying that I don't really care about the semantics used for pedagogic reasons in a couple of 100 year old documents. A construct used to motivate the physics, is not the same thing as being able to perform a real experiment that reproduces the details of the construct.
> 
May be the following quote by Ray d'Inverno is helpful:
"This is rather different from the length contraction of SR,
which is not to be regarded as illusory but is a very real effect"
However later on d'Inverno again uses the word appears:
"i.e. a rod fixed in S appears contracted in S'. "
What I learn from all of this that SR is very difficult, specific you have to be very carefull with which wordings to use. 
That only reinforces my point. I don't believe the predictions and results expected from a physical theory should hinge on the semantics of unphysical constructs. I don't believe special relativity would be any more "difficult" and probably less so, if the "gedanken" experiments dispensed with the idea of omniscience from the start. For example, what observer can observe the clocks on your grid ticking as you imagine them to be ticking to keep time? What observer exists who can observe the experiment as you describe it?
>  You can also ask the same 3 questions above for Time Dilation. I expect, based on how it influences GPS, that many people will select answer 3 i.e. it is real. 
And? On this newsgroup, asking that question is likely to get a lot of "yes, it's real" answers from a number of people that disagree on what the reality of it happens to be, and a number of people that start with the correct relativitic argument only to draw the wrong conclusion, and claim, "no, it's not real". What's the point and why is there a problem with using gps as your example to prove what you want to prove, rather than a fictitious set of clocks and rigid rods?
>  HenriWilson wrote: 
> > 
> 
[snip] 
> > 
many still seem to think an actual physical change occurs. 
> 
But people who understand SR (and not ether theory) don't think that. 
That means if you have two rods A and B and which
each rod an Observer A and B
and rod A (Observer A) is at rest
and rod B (Observer B) moves
that:
1.There "really" does not exist LC when Observer A
measures the length of rod A (its rest length)
2.There "really" does not exist LC when Observer B
measures the length of rod B (its rest length)
3.There "really" exists LC when Observer A
measures the length of rod B
4.There "really" exists LC when Observer B
measures the length of rod A
If you keep the two rods A and B together in the
same (rest) frame and if their lengths are then identical
then the results of step 1 and 2 will be identical.
You can also interpret step 3 and 4 as follows:
Observer A will measure that rod B has shortened physically.
Observer B will measure that rod A has shortened physically.
This is done by A using a latticework of rods and clocks (at rest) B also uses a latticework but his clocks are synchronised in his reference frame and run differently (they run slower)
>  So why challenge the SRists? 
I want to understand SR, and that is not always that easy specific if you compare different books.
Nick
http://users.pandora.be/nicvroom/trainfb_form.htm
"HenriWilson"
> 
The logic behind the animation is sound.
SR says that length contraction increases with velocity. That means a rod
length get shorter as it speeds up. It get longer if it slows down. that is
straight SR. It obviously cannot PHYSICALLY increase and decrease length
simultaneously.
So that means SR is obviously wrong. 
See also my reply to John Anderson
Starting point are three rods A, B and C
1) rod A is at rest, rod B and C move with speed v to right
2) rod A is at rest, rod B has speed v to right
rod C has speed 0.5v to the right. (C moves to left rel from B)
Each observer A,B and C will ALWAYS measure that their own rod in their own frame have the same rest length. (This is also called proper length or intrinsic length)
In case 1) A will measure that the length of both
rod B and C have shortened.
In case 1) B (and C) will measure that the length of rod A
has shortened.
In case 2) A will measure that the length rod B has shortened
the most. C is also shortened, but less
In case 2) B will measure that rod A has shortened the most
and C is shortened less.
You can consider two more cases.
3) rod C stops.
4) rod C has a speed 0.5v to the left (C moves towards A)
In case 4) A will measure that the length rod B has shortened
the most. C is also shortened, but less
This is identical as case 2.
In case 4) B will measure that rod A has shortened the least
and C is shortened the most.
All accordingly to my understanding of SR
I do not see anything obvious wrong.
Nick http://users.pandora.be/nicvroom/length.htm
Bilge wrote regarding length contration reality:
>  What it means is that measurements made by an observer are exactly that  measurements made by an observer. The lorentz transforms tell you how to reconcile measurements of the same phenomena made by different observers. Whatever "reality" you wish to attach to that is up to you. The reality physicists attach to it is that which offers the most intuition to answer questions that haven't been answered with a century of metaphysics to intervene and confuse the physics. 
Thanks for writing that. I was beginning to think I was going batty. Of course 'Whatever "reality" you wish to attach to that is up to you' The reality you use is whatever offers the most utility in the problem you are considering. This just seems absolutely obvious to me. I still do not understand how anyone could interpret any other way.
Thanks Bill
>  Bilge wrote regarding length contration reality 
> >  What it means is that measurements made by an observer are exactly that  measurements made by an observer. The lorentz transforms tell you how to reconcile measurements of the same phenomena made by different observers. Whatever "reality" you wish to attach to that is up to you. The reality physicists attach to it is that which offers the most intuition to answer questions that haven't been answered with a century of metaphysics to intervene and confuse the physics. 
> 
Thanks for writing that. I was beginning to think I was going batty. Of course 'Whatever "reality" you wish to attach to that is up to you' The reality you use is whatever offers the most utility in the problem you are considering. This just seems absolutely obvious to me. I still do not understand how anyone could interpret any other way. Thanks Bill 
Rod: You're batty and Bilge is hatty, but i'm the one in Cincinnati. The Transforms are measurments. Mathematical and not actual. How many transforms equal a light second?
You see Batty, the transforms: ASSUME LENGTH CONTRACTION BEFOREHAND!!! IT'S IN THE MATHEMATICS< CAN YOU SEE IT???!!!
If one were to use a measuring stick, one would record
no such folly.

Rod Ryker...
It is reasoning and faith that bind truth.
http://herr_ryker.tripod.com/
http://herr_ryker.tripod.com/herrryker
Quotes from Dirk Van de Moortel: "I can lie and cheat and use all the dirty tricks of the trolling business." "And I guess negative attention is less frightening than no attention at all. "All the lonely people, where do they all come from?""
On Wed, 23 Oct 2002 16:45:54 GMT, "Nicolaas Vroom"
> 
"HenriWilson" 
>> 
The logic behind the animation is sound. SR says that length contraction increases with velocity. That means a rod length get shorter as it speeds up. It get longer if it slows down. that is straight SR. It obviously cannot PHYSICALLY increase and decrease length simultaneously. So that means SR is obviously wrong. 
> 
See also my reply to John Anderson
Starting point are three rods A, B and C Each observer A,B and C will ALWAYS measure that their own rod in their own frame have the same rest length. (This is also called proper length or intrinsic length)
In case 1) A will measure that the length of both
rod B and C have shortened. You can consider two more cases. 3) rod C stops. 4) rod C has a speed 0.5v to the left (C moves towards A) In case 4) A will measure that the length rod B has shortened the most. C is also shortened, but less This is identical as case 2. In case 4) B will measure that rod A has shortened the least and C is shortened the most. All accordingly to my understanding of SR I do not see anything obvious wrong. 
I think you are basiclly saying the same thing as I am.
My demo 'contractions.exe' puts the issue beyond doubt.
NOTHING ACTUALLY HAPPENS TO THE PHYSICAL STATE OF RODS OR CLOCKS BECAUSE OF VELOCITY VARIATION.
> 
Henri Wilson. Technologist.
See my animations at: http://www.users.bigpond.com/rmrabb/HW.htm
"rryker"
> 
Bill Hobba wrote: 
> > 
Bilge wrote regarding length contration reality 
> > >  What it means is that measurements made by an observer are exactly that  measurements made by an observer. The lorentz transforms tell you how to reconcile measurements of the same phenomena made by different observers. Whatever "reality" you wish to attach to that is up to you. The reality physicists attach to it is that which offers the most intuition to answer questions that haven't been answered with a century of metaphysics to intervene and confuse the physics. 
Bill Hobba wrote:
> >  Thanks for writing that. I was beginning to think I was going batty. Of course 'Whatever "reality" you wish to attach to that is up to you' The reality you use is whatever offers the most utility in the problem you are considering. This just seems absolutely obvious to me. I still do not understand how anyone could interpret any other way. 
Ryker replied:
> 
Rod: You're batty and Bilge is hatty,
but i'm the one in Cincinnati. You see Batty, the transforms: ASSUME LENGTH CONTRACTION BEFOREHAND!!! IT'S IN THE MATHEMATICS< CAN YOU SEE IT???!!! If one were to use a measuring stick, one would record no such folly. 
Calling me batty is useless  I hold no pretention to be anything other than what I say. But Bilge is another matter. For the benefit of those with an ounce of intelligence who read this newsgroup with the intention of actually learning something of relativity it must be said Bilge is a genuinely knowledgeable. What he writes can be trusted.
SR is a theory about spacetime. In particular it is a theory about how
spacetime events transform between inertial reference frames and is
specified by the Lorentz transformation. That is the mathematics of it.
Any interpretation you want above that is up to you. The lorentz
transformation does not assume length contraction beforehand  it is a
logical consequence of it or rather it should be said the measured
shortening of a length relative to its rest frame is a consequence of it.
It is up to you if you consider the shortening real or only that the
measurements differ. Within the entirely conventional definitions of
intrinsic length given by Stephen Spiecher in a previous part of this thread
it would be more natural to assume that the length does not change, only our
measurment of it. But that is a consequence of the definitions made and
what then becomes the natural way of looking at it.
Thanks Bill
> 
"rryker" 
> > 
Bill Hobba wrote: 
> > > 
Bilge wrote regarding length contration reality 
> > > >  What it means is that measurements made by an observer are exactly that  measurements made by an observer. The lorentz transforms tell you how to reconcile measurements of the same phenomena made by different observers. Whatever "reality" you wish to attach to that is up to you. The reality physicists attach to it is that which offers the most intuition to answer questions that haven't been answered with a century of metaphysics to intervene and confuse the physics. 
> > > 
> 
Bill Hobba wrote: 
> > > 
Thanks for writing that. I was beginning to think I was going batty. Of course 'Whatever "reality" you wish to attach to that is up to you' The reality you use is whatever offers the most utility in the problem you are considering. This just seems absolutely obvious to me. I still do not understand how anyone could interpret any other way. 
> 
Ryker replied: 
> > 
Rod: You're batty and Bilge is hatty, but i'm the one in Cincinnati. The Transforms are measurments. Mathematical and not actual. How many transforms equal a light second? You see Batty, the transforms: ASSUME LENGTH CONTRACTION BEFOREHAND!!! IT'S IN THE MATHEMATICS< CAN YOU SEE IT???!!! If one were to use a measuring stick, one would record no such folly. 
> 
Calling me batty is useless  I hold no pretention to be anything other than what I say. But Bilge is another matter. For the benefit of those with an ounce of intelligence who read this newsgroup with the intention of actually learning something of relativity it must be said Bilge is a genuinely knowledgeable. What he writes can be trusted. 
Rod: No that mad hatter parrots, and that's all.
>  SR is a theory about spacetime. In particular it is a theory about how spacetime events transform between inertial reference frames and is specified by the Lorentz transformation. That is the mathematics of it. 
Rod: WRT length contraction and time dilation for sure it is nothing but mathematics Bill.
>  Any interpretation you want above that is up to you. The lorentz transformation does not assume length contraction beforehand  it is a logical consequence of it or rather it should be said the measured shortening of a length relative to its rest frame is a consequence of it. 
Rod: Yes length contraction is THE consequence of this mathematical mayhem.
> 
It is up to you if you consider the shortening real or only that the
measurements differ. Within the entirely conventional definitions of
intrinsic length given by Stephen Spiecher in a previous part of this thread
it would be more natural to assume that the length does not change, only our
measurment of it. But that is a consequence of the definitions made and
what then becomes the natural way of looking at it.
Thanks Bill 
Rod: Bill, The Lorentz Transforms are being used _AS_
the measuring stick etc.
Is this clear?

Rod Ryker...
It is reasoning and faith that bind truth.
http://herr_ryker.tripod.com/
http://herr_ryker.tripod.com/herrryker
Quotes from Dirk Van de Moortel:
"I can lie and cheat and use all the dirty tricks of the trolling business."
"And I guess negative attention is less frightening than no attention at
all. "All the lonely people, where do they all come from?""
"rryker"
> 
Bill Hobba wrote: 
> > 
"rryker" 
> > > 
Bill Hobba wrote: 
> > > > 
Bilge wrote regarding length contration reality 
> > > > >  What it means is that measurements made by an observer are exactly that  measurements made by an observer. The lorentz transforms tell you how to reconcile measurements of the same phenomena made by different observers. Whatever "reality" you wish to attach to that is up to you. The reality physicists attach to it is that which offers the most intuition to answer questions that haven't been answered with a century of metaphysics to intervene and confuse the physics. 
> > > > 
> > 
Bill Hobba wrote: 
> > > > 
Thanks for writing that. I was beginning to think I was going batty. Of course 'Whatever "reality" you wish to attach to that is up to you' The reality you use is whatever offers the most utility in the problem you are considering. This just seems absolutely obvious to me. I still do not understand how anyone could interpret any other way. 
> > 
Ryker replied: 
> > > 
Rod: You're batty and Bilge is hatty,
but i'm the one in Cincinnati. You see Batty, the transforms: ASSUME LENGTH CONTRACTION BEFOREHAND!!! IT'S IN THE MATHEMATICS< CAN YOU SEE IT???!!! If one were to use a measuring stick, one would record no such folly. 
> > 
Bill Hobba wrote:
> >  Calling me batty is useless  I hold no pretention to be anything other than what I say. But Bilge is another matter. For the benefit of those with an ounce of intelligence who read this newsgroup with the intention of actually learning something of relativity it must be said Bilge is a genuinely knowledgeable. What he writes can be trusted. 
> 
Rod Ryker wrote:
>  Rod: No that mad hatter parrots, and that's all. 
If I had a parrot that demonstrated Bilges ability I could make a fortune. His posts clearly demonstrate not only an excellent knowledge of physics but an ability to reason with that knowledge, a quality a parrot does not possess. Even an amateur like me can spot an expert when he sees one, Bilge is the real thing. You could no better than put you prejudices aside, read what Bilge writes and follow the leads he gives. BTW I have no idea who Bilge is in real life or what his background it. But, without question, he knows physics
Bill Hobba wrote:
> >  SR is a theory about spacetime. In particular it is a theory about how spacetime events transform between inertial reference frames and is specified by the Lorentz transformation. That is the mathematics of it. 
Rod Ryker replied:
>  Rod: WRT length contraction and time dilation for sure it is nothing but mathematics Bill. 
Do you have any idea of mathematics relation to physics? Physics is written in the language of mathematics. But to understand physics you must interpret what the equations are saying. The Lorentz transformations clearly imply length contration and time dilation. Mathematics relationship is discussed in more detail in the Feynman Lectures on Physics. Here Feynman points out that the great physicist, Dirac (one of Feynamans heroes), would turn equations around and around until he understood exactly what they are trying to say. I suggest you read Feynmans lectures on physics. Not only will you get a good grounding in physics you will understand much better what mathematics is all about in physics.
Bill Hobba wrote:
> >  Any interpretation you want above that is up to you. The lorentz transformation does not assume length contraction beforehand  it is a logical consequence of it or rather it should be said the measured shortening of a length relative to its rest frame is a consequence of it. 
> 
Rod Ryker replies:
>  Rod: Yes length contraction is THE consequence of this mathematical mayhem. 
Mayhem? PHYSICS IS WRITTEN IN THE LANGUAGE OF MATHEMATICS. Engrave it in your skull. Ignore it at your peril. Only then will you be a fit position to discuss physics.
Bill Hobba wrote:
> >  It is up to you if you consider the shortening real or only that the measurements differ. Within the entirely conventional definitions of intrinsic length given by Stephen Spiecher in a previous part of this thread it would be more natural to assume that the length does not change, only our measurment of it. But that is a consequence of the definitions made and what then becomes the natural way of looking at it. 
> 
Rod Ryker wrote:
>  Rod: Bill, The Lorentz Transforms are being used _AS_ the measuring stick etc. Is this clear? 
Not at all. The Lorentz transformation describes space time event transformations. Consider a rod at rest in an inertial frame. Measure the length of the rod in a moving frame by considering the following. Measure its length at time 0 in the rest frame. Measure the start position of the rod, measure the end position of the rod. The difference in length gives the length of the rod. Transfer these space time coordinates to the moving frame. This still results in time zero for both space time events ie for the start position of the rod and the end position. Thus the difference forms the rod length as measured in the moving frame. It is found to be shorter. This is all part of what Dirac did and part of what any physicist would do. The clear and unambiguous implication of the Lorentz transformations is length contration occurs. The equations have spoken. What you are failing to do is LISTEN.
Thanks Bill
"Bill Hobba"
>  Rod Ryker wrote: 
> >  Rod: Bill, The Lorentz Transforms are being used _AS_ the measuring stick etc. Is this clear? 
The problem with Bill's reply that in General it is not clear. He does not give a clear recipe what to do.
>  Not at all. The Lorentz transformation describes space time event transformations. 
>  Consider a rod at rest in an inertial frame. Measure the length of the rod in a moving frame by considering the following. Measure its length at time 0 in the rest frame. 
>  Measure the start position of the rod, measure the end position of the rod. 
>  The difference in length gives the length of the rod. 
>  Transfer these space time coordinates to the moving frame. 
>  This still results in time zero for both space time events ie for the start position of the rod and the end position. 
>  Thus the difference forms the rod length as measured in the moving frame. 
>  It is found to be shorter. 
>  This is all part of what Dirac did and part of what any physicist would do. 
>  The clear and unambiguous implication of the Lorentz transformations is length contration occurs. 
>  The equations have spoken. 
>  What you are failing to do is LISTEN. 
My advice is if you want to explain something please do it in small steps and every time only change one parameter. Please study: http://users.pandora.be/nicvroom/calc1.htm
Nick.
> >  Rod Ryker wrote: 
> > >  Rod: Bill, The Lorentz Transforms are being used _AS_ the measuring stick etc. Is this clear? 
>  The problem with Bill's reply that in General it is not clear. He does not give a clear recipe what to do. 
It is not clear what you consider is not clear. Maybe reading you reply further will help.
Bill Hobba wrote:
> >  Not at all. The Lorentz transformation describes space time event transformations. 
Nicolaas Vroom replied:
>  okay 
Bill Hobba wrote:
> >  Consider a rod at rest in an inertial frame. Measure the length of the rod in a moving frame by considering the following. Measure its length at time 0 in the rest frame. 
Nicolaas Vroom> How ?
By any method you like. The axioms of Euclidian geometry, assumed valid for an inertial reference frame, guarantee this. Also be careful of this line of reasoning. While valid it will take you down the path of operationalism. This philosophy will only cloud the essential issues. It is best you understand them before dealing with subtleties.
Bill Hobba wrote:
> >  Measure the start position of the rod, measure the end position of the 
>  rod. 
Nicolaas Vroom wrote:
>  How ? 
By any reasonable method you like. Again guaranteed possible by the axioms of Euclidian geometry. Remember an inertial reference frame has a coordinate system that you can use to specify positions.
Nicolaas Vroom wrote:
>  Of a moving rod ? In which frame ? 
As stated, in the frame the rod is at rest in.
Bill Hobba wrote:
> >  The difference in length gives the length of the rod. 
Nicolaas Vroom wrote:
>  Okay. 
Bill Hobba wrote:
> >  Transfer these space time coordinates to the moving frame. 
Nicolaas Vroom replied::
>  How ? Why ? 
Using the Lorentz transformation. To determine the length in the moving frame.
Bill Hobba wrote:
> >  This still results in time zero for both space time events ie for the start position of the rod and the end position. 
Nicolaas Vroom wrote:
>  Please explain. 
For inertial reference frames in the standard configuration (see Rindler  Introduction to Special Relativity) a time of zero always transforms to time of zero in inertial reference frames. This is from the Lorentz transformation.
Bill Hobba wrote:
> >  Thus the difference forms the rod length as measured in the moving 
Nicolaas Vroom replied::
>  I do not understand 
This follows from the axioms of Euclidian geometry, again assumed valid in a moving reference frame. It is even clearer if you consider the rod positioned at the origin.
Bill Hobba wrote:
> >  It is found to be shorter 
Nicolaas Vroom replied.
>  I' am lost 
Then do the math. If you can't do the math then increase your math knowledge. If you do not wish to do that forget about physics, it is not for you. Do something else. PHYSICS IS WRITTEN IN THE LANGUAGE OF MATHEMATICS. You would not attempt to read a French novel in the original French without an understanding of French. Do not attempt physics without math. You will not succeed.
> >  This is all part of what Dirac did and part of what any physicist would do. 
Nicolaas Vroom replied::
>  I have great doubts. 
Why? You accuse me of not making things clear. Here you make a statement whose basis is not argued in the least. Exactly what do you know of Dirac? Dirac was a great physicist and an excellent mathematician. Whether you like it or not this is exactly the type of thing Dirac would have done. And much more besides. He would have manipulated the Lorentz transformation every which way possible until he was sure he understood just what it was saying. Have you read Feynamans Lectures on Physics? My statement was founded on this. This was stated clearly in my post. What was your statement founded on?
Bill Hobba wrote:
> >  The clear and unambiguous implication of the Lorentz transformations is length contration occurs. 
Nicolaas Vroom replied::
>  Maybe that that is true, but you did not demonstrate it. 
Nicholas my dear fellow. When you talk to someone do you explain evey detail or do wait for some feedback on what the person does nor does not understand or agree with?
If you have read what I have said in the past you will know I expect the people who I converse with to do a bit of work themselves, just a I expect to do a bit of work in understanding the replies of some of the more knowledgeable people who reply to me. I do not expect them to hold my hand and spoon feed me. I hope I am dealing with mature people. Read Rindler  Introduction to Special Relativity or Wheeler and Taylor Spacetime physics. Then we can have a reasoned discussion.
Nicolaas Vroom replied:
>  NO. 
How have they not spoken? What assumptions, other than the Lorentz transformations and the definition of an inertial reference frame have I used?. I have in fact used some quite subtle ones. However for me to deal with them for you I would prefer you think a bit and see if you can figure out what they are. Note they are very subtle and no one would seriously doubt them. You may even come up with one I have not thought of. But for heavens sake THINK. Then post a reasonable query.
Bill hobba wrote:
> >  What you are failing to do is LISTEN. 
By listen I mean make a reasonable stab at applying the equations. All I see here are people who want the answer to magically fall in their laps. When it does not they claim what I am saying is not true. Instead of complaining think, post a REASONED response pointing out where you think the error in logic is and I, or others, will give a reasoned reply.
Nicolaas Vroom replied:
> 
You put all the blame on one side i.e. with Rod
Maybe....
My advice is if you want to explain something please do it in small steps and every time only change one parameter. 
My advice to you is to make a stab at understanding things yourself. Do the math. Post any problems you have and do not speak in broad generlisations on issues that you have not worked through.
Thanks Bill
"Nicolaas Vroom"
> 
[snip]
> 
My advice is if you want to explain something please do it in small steps and every time only change one parameter. Please study: http://users.pandora.be/nicvroom/calc1.htm 
Nicolaas, you might enjoy having a close look at my first reply of a recent thread started on 27Oct 04:37 by "AllYou!". The title of the thread is "Help with Lorentz". My first reply uses very small steps and explains something about time dilation and length contraction.
Dirk Vdm
On Sun, 27 Oct 2002, Nicolaas Vroom wrote:
> 
"Bill Hobba" 
> > 
Rod Ryker wrote: 
> > >  Rod: Bill, The Lorentz Transforms are being used _AS_ the measuring stick etc. Is this clear? 
> 
The problem with Bill's reply that in General it is not clear. 
No. the "problem" with Bill's reply is that it was read by a dunce who, through all his years has not taken the time to actually learn the basics of the standard theory of relativity  namely, you. By contrast Bill has studied hard on his own, starting from the beginning of the books and working his way towards the end, and the result is that he writes more clearly than you can ever hope to do.
Like some other cuckoo birds on this group, you are a oneissue man, in your case a fanatic about length contraction. You seem to devote all of your effort into this one area, yet have never taken the time to properly learn even the essentials. As I told you before, purge your mind of all of your distortions, pick up _Spacetime Physics_ and read it from front to end, in that order. However, as you have demonstrated for years, you have no real interest in learning, and would rather spout out a bunch of nonsensical commentary about length contraction when you get the chance.
Before you can judge the clarity of others, you first need to shake the cobwebs out of your own mind. But, little chance of that, and you will probably just keep babbling for as long as you remain here.

Stephen
sjs@speicher.com
Ignorance is just a placeholder for knowledge.
Printed using 100% recycled electrons.

"Stephen Speicher"
>  On Sun, 27 Oct 2002, Nicolaas Vroom wrote: 
> > 
The problem with Bill's reply that in General it is not clear. 
>  By contrast Bill has studied hard on his own, starting from the beginning of the books and working his way towards the end, and the result is that he writes more clearly than you can ever hope to do. 
The subject of this newsgroup is physics.
The subject of this thread is about length contraction.
In general it is about scientific subjects.
It is not about the behaviour of people, what they personnal do
or what they don't do.
I had a quick look about the reply of Bill and I enjoyed reading it.
He answers all my comments and objections in detail
and that is what everybody in this newsgroup should do.
>  Before you can judge the clarity of others, you first need to shake the cobwebs out of your own mind. 
I'am the last to claim that all what I write is clear and unambiguous and if I make mistakes I will acknowledge them, however if I write something that is not clear, PLEASE point that out to me in DETAIL and do not answer in general.
You can always write to ME an email.
http://users.pandora.be/nicvroom/calc1.htm Please study the above and tell me if it is (not ?) clear.
Nick
"Bill Hobba"
>  Bill Hobba wrote: 
> > > 
1. Consider a rod at rest in an inertial frame. 2. Measure the length of the rod in a moving frame by considering the following. 3. Measure its length at time 0 in the rest frame. 
> 
Nicolaas Vroom> How ? By any method you like. 
>  Bill Hobba wrote: 
> > >  4. Measure the start position of the rod, measure the end position of therod. 
> 
Nicolaas Vroom wrote: 
> >  Of a moving rod ? In which frame ? 
> 
As stated, in the frame the rod is at rest in. 
>  Bill Hobba wrote: 
> > >  The difference in length gives the length of the rod. 
>  Nicolaas Vroom wrote: 
> >  Okay. 
> 
Bill Hobba wrote: 
> > >  Transfer these space time coordinates to the moving frame. 
> 
Nicolaas Vroom replied:: 
> >  How ? Why ? 
> 
Using the Lorentz transformation. To determine the length in the moving frame. 
The problem is you still did not explain what you wanted to do in sentence 2: To measure in the moving frame.
>  Bill Hobba wrote: 
> > >  This still results in time zero for both space time events ie for the start position of the rod and the end position. 
> 
Nicolaas Vroom wrote: 
> >  Please explain. 
> 
For inertial reference frames in the standard configuration (see Rindler  Introduction to Special Relativity) a time of zero always transforms to time of zero in inertial reference frames. This is from the Lorentz transformation. 
>  Bill Hobba wrote: 
> > >  Thus the difference forms the rod length as measured in the moving frame. 
>  Nicolaas Vroom replied:: 
> >  I do not understand 
> 
This follows from the axioms of Euclidian geometry, again assumed valid in a moving reference frame. It is even clearer if you consider the rod positioned at the origin. Bill Hobba wrote: 
> > >  It is found to be shorter 
> 
Nicolaas Vroom replied. 
> > 
I' am lost 
>  Then do the math. 
>  PHYSICS IS WRITTEN IN THE LANGUAGE OF MATHEMATICS. Do not attempt physics without math. You will not succeed. 
I do not agree with you. The first step in Physics comes from observations and experiments The second step comes from mathematics. (The third step is to predict new discoveries)
> > >  This is all part of what Dirac did and part of what any physicist would do. 
>  Nicolaas Vroom replied:: 
> >  I have great doubts. 
> 
Why? You accuse me of not making things clear. 
>  Bill Hobba wrote: 
> > >  The clear and unambiguous implication of the Lorentz transformations is length contration occurs. 
I'am not saying that that is not true. If you study the formula L = L0 * SQRT(1v*v/c*c) = L0/gamma then of course L < L0 for v>0
>  Nicolaas Vroom replied:: 
> >  Maybe that that is true, but you did not demonstrate it. 
>  When you talk to someone do you explain every detail ? 
Yes I do (as much as possible) Please study http://users.pandora.be/nicvroom/calc1.htm All comments are appreciated.
In three steps I explain:
1. How and what you should measure for a rod at rest
in the rest frame.
2. How and what you should measure for a moving rod
in the rest frame.
This includes Length Contraction.
3. How and what you should measure for a moving rod
in the moving frame.
This includes both Length Contraction and Time Dilation.
The result (rod length) of 1 and 3 is the same.
Nick.
>  On Mon, 28 Oct 2002, Nicolaas Vroom wrote: 
> > 
"Stephen Speicher" 
> > >  On Sun, 27 Oct 2002, Nicolaas Vroom wrote: 
> > > > 
The problem with Bill's reply that in General it is not clear. 
> > 
> > > 
By contrast Bill has studied hard on his own, starting from the beginning of the books and working his way towards the end, and the result is that he writes more clearly than you can ever hope to do. 
> > 
The subject of this newsgroup is physics. 
> 
Specifically, relativity physics. 
Rod: We are all happy to know this, since from your posts we may have concluded an uprising of king Speicher.
> >  The subject of this thread is about length contraction. 
> 
Which is the same subject that you have been utterly confused about for all the many years you have been posting to this group. Instead of telling people such as Bill that their writing is unclear, spend the time learning the basics of the subject. If you were to do that (little chance, since for years Nicolaas prefers to remain in a state of selfimposed ignorance) instantly other's 'unclear' writings will be transformed into clarity. This is known as the Knowledge transformation  try it some time.

Stephen Ignorance is just a placeholder for knowledge.
Printed using 100% recycled electrons. 
Rod: The electrons are not recycled,
their energy is.

Rod Ryker...
It is reasoning and faith that bind truth.
http://herr_ryker.tripod.com/
http://herr_ryker.tripod.com/herrryker
Quotes from Dirk Van de Moortel:
"I can lie and cheat and use all the dirty tricks of the trolling business."
"And I guess negative attention is less frightening than no attention at all. "All the lonely people, where do they all come from?""
"Dirk Van de moortel"
> 
"Nicolaas Vroom" [snip] 
> > 
My advice is if you want to explain something please do it in small steps and every time only change one parameter. Please study: http://users.pandora.be/nicvroom/calc1.htm 
> 
Nicolaas, you might enjoy having a close look at my first reply of a recent thread started on 27Oct 04:37 by "AllYou!". The title of the thread is "Help with Lorentz". My first reply uses very small steps and explains something about time dilation and length contraction. 
The most important part are the interpretations. IMO what you try to say is that you can have: length contraction without time dilation and time dilation without length contraction.
When you compare two rods each at rest in two different frames are then both effects not applicable ? and is than Born's claim not valid ?
You wrote:
> 
And so you see why Born's comment:

As part of my struggle to understand the train experiment I wrote a special section about the mathematics involved in the train experiment as described by d'Inverno http://users.pandora.be/nicvroom/trainfb_form.htm#math IMO in the way he describes it length contraction is involved. Your opinion is highly regarded. and of anybody else.
I also wrote a new section describing how IMO the train experiment really should be performed. http://users.pandora.be/nicvroom/trainfb_form.htm#hoax Please give your opinion.
Nick
"Nicolaas Vroom"
> 
"Dirk Van de moortel" 
> > 
"Nicolaas Vroom" [snip] 
> > > 
My advice is if you want to explain something please do it in small steps and every time only change one parameter. Please study: http://users.pandora.be/nicvroom/calc1.htm 
> > 
Nicolaas, you might enjoy having a close look at my first reply of a recent thread started on 27Oct 04:37 by "AllYou!". The title of the thread is "Help with Lorentz". My first reply uses very small steps and explains something about time dilation and length contraction. 
> 
I studied your reply and I agree with you explain in small steps in detail something about time dilation and length contraction. IMO there are no errors within the mathematics you use. The most important part are the interpretations. 
Yes, and more difficult than the mathematics. And talking about the interpretations is even more difficult :)
>  IMO what you try to say is that you can have: length contraction without time dilation and time dilation without length contraction. 
Almost.
I was trying to explain that one cannot have the "standard
textbook" type of length contraction L=L'/g and the
"standard textbook" type of time dilation T=T'*g together
on one single pair of events.
Step 5 shows a case T=T'*g where a clock marks two events
that happen at the same place in the frame of the clock (L' = 0)
Step 6 shows a case L=L'/g where a rod marks two events
that happen at the same time in the other frame (T=0)
Step 4 o.t.o.h. shows the general situation where two arbitrary
events show a combination of length contraction/expansion and
time dilation/shrinking. There are many possible combinations.
> 
When you compare two rods each at rest in two different frames are then both effects not applicable ? and is than Born's claim not valid ? 
When you measure (from within your frame) two rods in their frames, you get for rod_1
Born's claim of reciprocity creates the i.m.o. false illusion that the cases 5 and 6 can be considered together. If this was true then L*T = L'*T' would be an invariant. The post I made shows that it is invariant only if everything is zero ;)
> 
You wrote: 
> > 
And so you see why Born's comment: 
> 
Where did Born write this ? 
Yes, the 1962 edition, page 250, immediately after he has derived L=L'/g and T=T'*g.
> 
As part of my struggle to understand the train experiment I wrote a special section about the mathematics involved in the train experiment as described by d'Inverno http://users.pandora.be/nicvroom/trainfb_form.htm#math IMO in the way he describes it length contraction is involved. Your opinion is highly regarded. and of anybody else. 
(I'm not so fond of your notations l and l0, since they are easily confused with 1 and 10, so I have used 2L (your l) for the (proper) distance between the marks on the track and 2M' (your l0) as the proper length of the train)
If the proper length of the train is 2M' and the distance
between the marks in the frame of the track is 2L, then
A (track observer in the middle between the marks)
will *see* the flashes simultaneously if M' = gamma * L.
I have not tried to follow your calculation, but I used
the equations of motion of the front and back pieces
of the train and of the light flashes, combined with the
Lorentz transformation.
Unless I made a mistake, we get for the times of seeing
the flashes by observer A:
Likewise, the observer C in the middle of the train will
see the flashes at times:
> 
I also wrote a new section describing how IMO the train experiment really should be performed. http://users.pandora.be/nicvroom/trainfb_form.htm#hoax Please give your opinion. 
Haven't looked at this one. Maybe some other time.
Dirk Vdm
"Dirk Van de moortel"
> 
If the proper length of the train is 2M' and the distance between the marks in the frame of the track is 2L, then A (track observer in the middle between the marks) will *see* the flashes simultaneously if M' = gamma * L. 
I agree with you. However I prefer the notation L = M'/gamma which implies that whenever you change the speed v of the rod (and you repeat the whole experiment) and if Observer A wants to see the two flashes simultaneous than you have to change the position of both marks (contacts), assuming the position of A does not change.
>  So your answer http://users.pandora.be/nicvroom/trainfb_form.htm#answer2 is right. 
> > 
I also wrote a new section describing how IMO the train experiment really should be performed. http://users.pandora.be/nicvroom/trainfb_form.htm#hoax Please give your opinion. 
> 
Haven't looked at this one. Maybe some other time. 
Any feedback is appreciated.
Nick.
"Nicolaas Vroom"
> 
"Dirk Van de moortel" 
[snip]
> > > 
I also wrote a new section describing how IMO the train experiment really should be performed. http://users.pandora.be/nicvroom/trainfb_form.htm#hoax Please give your opinion. 
> > 
Haven't looked at this one. Maybe some other time. 
> 
Any feedback is appreciated. 
I had a quick look at hoax questions 1 and 3 and at
answers 2 and 4. Both are right.
Haven't looked at the rest though.
I prefer drawing spacetime diagrams, marking the relevant
events, calculating the coordinates, finding the equations of
worldlines and lightlines, and transforming. I have some
difficulty following your drawing system :)
Dirk Vdm
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