# Thread: Differing views of length contraction

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## Differing views of length contraction

While MacM's thread asking about length contraction was closed until he decides to resume discussion, it did seem to bring up other interesting questions. In particular it appears to me that not all "mainstream proponents" (for lack of a better word) have the same concept of length contraction. I would like to explore this in more depth.

I was taught in high school that a moving object is contracted in the direction of motion, and that this has been proven experimentally. However, a couple posts (1, 2) suggest mainstream physics does not believe this anymore. In fairness, both posts are from the same user, so this may just be a misunderstanding. But none of the other mainstream posters commented on this or corrected this, which makes me wonder what is going on.

So in summary, the topic of discussion here is:
Does mainstream physics still believe that a moving object is contracted in the direction of motion, and that this has been proven experimentally?

2. ## High school SR ?

... length contraction WITH time dilation ... Both.

Because the answer is so simple, everybody repeat it, it may not be tested (?!)

If you are looking for some ATM explanation, why not try the 4T instead of 3D1T ? start here http://www.draaisma.net/rudi/science...onal_time.html .

3. ## Reality Strikes Back

Originally Posted by Jonny
Does mainstream physics still believe that a moving object is contracted in the direction of motion, and that this has been proven experimentally?

The ambiguity is found in the words "moving object is contracted ... ". Contracted, according to whom? According to an observer on the object and moving with it, there will be no contraction of the object. According to an outside observer, moving with respect to the object, then it will appear to be contracted (in a purely 1-dimensional analysis, and therein lies the misleading part). However, the amount of contraction depends on the observer, and it is expected that a large number of different observers will report a large number of different contractions. So which contraction is "real", if any? You must specify the observer before the question can be answered.

As for the misleading part, in real, 3D space, there is never a contraction of any real 3D object, nor has the mainstream ever held that there was. The contraction you are thinking of is a teaching tool meant to simplify the problem and reveal fundamental physics, and is valid in one and only one dimension. All real, 3D objects, analyzed in all 3 dimensions, will appear to rotate in 3 dimensions and not contract. This is due to the mixing of multiple "contractions", simultaneously in all 3 dimensions. All of this is explained in excruciating detail in the best book on relativity ever written (in my own humble, but nevertheless correct, opinion): Spacetime Physics, by Taylor & Wheeler (W.H. Freeman, 2nd ed., 1992).

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Originally Posted by Jonny
While MacM's thread asking about length contraction was closed until he decides to resume discussion, it did seem to bring up other interesting questions. In particular it appears to me that not all "mainstream proponents" (for lack of a better word) have the same concept of length contraction. I would like to explore this in more depth.

I was taught in high school that a moving object is contracted in the direction of motion, and that this has been proven experimentally. However, a couple posts (1, 2) suggest mainstream physics does not believe this anymore. In fairness, both posts are from the same user, so this may just be a misunderstanding. But none of the other mainstream posters commented on this or corrected this, which makes me wonder what is going on.

So in summary, the topic of discussion here is:
Does mainstream physics still believe that a moving object is contracted in the direction of motion, and that this has been proven experimentally?

I'm going to tackle just the last part ("that this has been proven experimentally").

Let's leave aside "proven"* and concentrate on what "experimentally" might mean.

The first, and most powerful, experimental consistency goes something like this: what tests has SR been subject to? how well did it fare, in those tests?

The answer to the second is, as I'm sure everyone reading this post knows, along the lines of "SR has passed every test it has ever been subject to, within the limits of the experiments and observations designed to test it".

A more detailed answer can be found in lots of places (my favourite is Clifford Will's; it's about General Relativity, but since GR 'reduces to' SR in the limit, any test of GR is also a test of SR. Another good set of tests are those done on QED - they test both SR and QM at the same time, and some of those tests are the most exacting in science, ever).

Has anyone taken photographs of a macroscopic object, and analysed those to test whether the rotation expected (in SR, per Tim's post) matches what's observed? I (personally) don't know, but I rather doubt it (it'd be an extraordinarily difficult experiment to perform).

*If it's science we're dealing with, then nothing can be 'proven'. IMHO, the best you can do is the 'three (theory) consistencies': internally consistent; consistent with (other) good theories whose domains of applicability overlap; and (above all) consistent with all good, relevant experimental and observational results.

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Originally Posted by Nereid
.........since GR 'reduces to' SR in the limit, any test of GR is also a test of SR.
I am not in disagreement generally but I always have a problem with this position for the simple reason that SR has reciprocity in its affects, GR does not.

It is the reciprocity in SR that seems completely unobserved, unsupported by emperical data or logic.

How does reciprocity fit within your statement of equality?

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Originally Posted by MacM
I am not in disagreement generally but I always have a problem with this position for the simple reason that SR has reciprocity in its affects, GR does not.
In what way? If you use the flat Minkowski metric, in GR, the GR equations can be reduced to SR, in the limit. Do you have something that shows otherwise?

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Originally Posted by Tensor
In what way? If you use the flat Minkowski metric, in GR, the GR equations can be reduced to SR, in the limit. Do you have something that shows otherwise?
No. That is why I said I am not in general disagreement. The confusion comes because SR has reciprocity in its affects and GR does not.

Can you give an example of where a GR test has demonstrated or supported the assertions of reciprocity in SR?

8. I think that MacM has a problem with the concept of sub-groups. IMHO if I take an empty minkowskian space and two near massless particles, you will find reciprocity.
But let us take a simple example, of 1 to 1 projections in 2D. There is one group of projections that can be described as the sum of a rotation and a translation. However, a subgroup of this is just rotation, which has a very interesting property that there is a 2pi multiplicity, which you will not find in the overall group. Therefore, one cannot simply assume that all properties of a sub-group are also a property of the overall group.

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Originally Posted by tusenfem
I think that MacM has a problem with the concept of sub-groups. IMHO if I take an empty minkowskian space and two near massless particles, you will find reciprocity.
But let us take a simple example, of 1 to 1 projections in 2D. There is one group of projections that can be described as the sum of a rotation and a translation. However, a subgroup of this is just rotation, which has a very interesting property that there is a 2pi multiplicity, which you will not find in the overall group. Therefore, one cannot simply assume that all properties of a sub-group are also a property of the overall group.
Actually, no. I think you over complicate the issue. Reciprocity of time dilation, relavistic mass (even though that is old hat) and length contraction are at issue.

Not only does accepting them mean accepting things in physics which simply seem unacceptable (not just a matter of logic but physical possibilities).

Getting back to the issue of this thread however:

1 - It was said in my thread that to propose a relativity of superluminal velocities and no length contraction was a major step in physics.

2 - Yet objectors argued in the same thread that the Terellel-Penrose rotation replaced lorentz contraction long ago and that contraction is no longer considered to exist.

3 - 2 above actually supports my contention and means superluminal travel is the only way relativity can survive.

All this is butressed by the experiment and findings that the life of cosmic muons actually correspond with its absolute velocity to the CMB rather than its relative velocity to the earth.

http://redshift.vif.com/JournalFiles...F/V03N2MON.PDF

There is also the matter of the lack of reciprocity found in GPS calibration and synchronizing of clocks (as well as all relavistic data for 100 years). I know there are arguements about GPS not being an inertial frame but an accelerating frame but I have also seen it argued that it is inertial in that it is free falling. But I don't want to hinge my position on an issue which has counter arguement so easily.

10. ## Reciprocity

Originally Posted by MacM
I am not in disagreement generally but I always have a problem with this position for the simple reason that SR has reciprocity in its affects, GR does not.
What, specifically, do you mean by "reciprocity"?

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Originally Posted by Tim Thompson
What, specifically, do you mean by "reciprocity"?
As described here in the equivelence of inertial frames.

http://www.mathpages.com/home/kmath307/kmath307.htm

It is my contention that this view places equivlence of observation with equivelance of physical reality. I do not believe emperical data or logic support such conclusion.

That is the old arguement that when the train accelerates away from the station the station is also accelerating away from the train is actually an illusion and is not equivelent.

Therefore the fact of relative velocity created is not also equivelent. That is it seems emperical data actually supports the idea that only objects which undergo the F = ma acceleration experience undergo physically measureable relavistic changes.

This fact seems to better support an absolute concept than a relative velocity concept.

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Originally Posted by Nereid
I'm going to tackle just the last part ("that this has been proven experimentally").
Oh come on guys.
I appologize for not being more precise in my wording, but I assumed everyone could understand what I meant by that phrase. (Yes, I agree with everything Nereid said in case there is still confusion.)

Originally Posted by Tim Thompson

The ambiguity is found in the words "moving object is contracted ... ". Contracted, according to whom? According to an observer on the object and moving with it, there will be no contraction of the object.
I don't see how the word "moving" is ambiguous (unless you try to claim there is some kind of "universal frame"). By definition an object is not moving in its rest frame. So of course an observer in its rest frame does not see it contracted.

Originally Posted by Tim Thompson
According to an outside observer, moving with respect to the object, then it will appear to be contracted (in a purely 1-dimensional analysis, and therein lies the misleading part).
I don't understand where this is coming from. The only thing that changes between the "1-dimensional" analysis and the 3D when doing the Lorentz transformations is that the other two coordinates remain unaffected in the transformation. In other words, in the "3D" analysis the object is contracted in the direction of motion, but not in the perpendicular directions.

Originally Posted by Tim Thompson
However, the amount of contraction depends on the observer, and it is expected that a large number of different observers will report a large number of different contractions.
Yes, of course. Remember, I have had special relativity. I can do the calculations. I know four vectors, invarience of the dot product, etc, etc.

The issue at hand is that I saw some mainstream proponents saying that a moving object did not contract in the direction of motion. I felt this was wrong, and wanted to see if opinion on this had changed.

Originally Posted by Tim Thompson
So which contraction is "real", if any? You must specify the observer before the question can be answered.
But for all observers who indicate that the object is moving, the object is contracted (and more precisely, contracted in the direction of motion). Why insist on me being more exact when it appears to not be necessary here.

So the question is: under special relativity, is the object contracted in the direction of motion?
(I'll drop the "experimental tested" part of the question for now.)

Since everyone is so picky on words, let me try to be extra precise, but please meet me half-way and not complain if you know what I am trying to ask.

Let's take two small rockets (I'll just treat them as points, if you really want to be picky the points I am referring to are their center of masses) and an observer. All three are initially at rest with respect to each other.

Initially have the rockets laying horizontally some distance d apart. To be even more unambiguous, have the observer set up a coordinate system according to Einsteins conventions. Now, program the rockets to launch simultaneously according to the observer and use constant thrust for a set amount of time. Will the distance between the rockets decrease according to the observer? Do the calculations, blah blah, and the answer is no.

Okay, now let's take this farther. Put an elastic string between the two rockets (initially straight / no slack but also no tension). Give them extra strong thrusters so that they can maintain their correct path no matter what (basically, make sure the string's effect on the rockets' trajectory is negligible). Same thing, launch simultaneously. Now again the distance between the rockets does not change according to the observer. But, will there be tension in the string? Do the calculations, blah blah, and the answer is yes.

At what length would there be no tension in the string? It's at the normal length contracted distance.

In short, if an object WASN'T length contracted in the direction of motion, there would be tension trying to bring it into the now shorter equilibrium length.

The mainstream followers at this site seem to be claiming otherwise. (refer to my first post for details, as well as some claims in this thread as well)

Maybe we are actually in agreement but using different meanings in our phrases (which is fine, I would just like to make sure this is the case and then we can be aware of it).

Originally Posted by Tim Thompson
As for the misleading part, in real, 3D space, there is never a contraction of any real 3D object, nor has the mainstream ever held that there was. The contraction you are thinking of is a teaching tool meant to simplify the problem and reveal fundamental physics, and is valid in one and only one dimension.
As explained above, I believe this is wrong. Please redo your calculations and if you still disagree, please post your calculations and we can compare.

Originally Posted by Tim Thompson
All real, 3D objects, analyzed in all 3 dimensions, will appear to rotate in 3 dimensions and not contract. This is due to the mixing of multiple "contractions", simultaneously in all 3 dimensions.
I am not sure if you are aware of it (if you are, then now it is me being picky) but you have suddenly changed your meaning of appear.

The "terrell rotation" is what "appears" to an observer in the direct sense of what he sees. In other words, before correcting for the fact that light from different parts of the object take different amounts of time to reach the observer. So this is just an optical effect, and we need to account for the finite speed of light to obtain the object's actual orientation and size in this frame.

You are then trying to use this change in the meaning of "appear" to go back and claim that the contraction only happens in the 1-D case and not in the 3-D case.

We're all in agreement that special relativity matches experiment and yet we're still disagreeing on whether a moving object contracts in the direction of motion. This scares me quite a bit. Hopefully we can sort this out.

Also, to aid in this discussion, I would appreciate it if other topics not related to this thread were continued elsewhere (if that is okay to request).
Last edited by Jonny; 2006-Mar-20 at 04:16 PM.

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Originally Posted by Jonny
The issue at hand is that I saw some mainstream proponents saying that a moving object did not contract in the direction of motion. I felt this was wrong, and wanted to see if opinion on this had changed.

The mainstream followers at this site seem to be claiming otherwise. (refer to my first post for details, as well as some claims in this thread as well)

The "terrell rotation" is what "appears" to an observer in the direct sense of what he sees. In other words, before correcting for the fact that light from different parts of the object take different amounts of time to reach the observer. So this is just an optical effect, and we need to account for the finite speed of light to obtain the object's actual orientation and size in this frame.
Interesting. It is my contention that spatial length contraction does not occur and it is because of Terrell-Penrose that one could claim it would appear to occur.

That is I have seen discussion of the Terrell-Penrose rotation where an example of a sphere is given and the sphere displays absolutely no geometric change. It is only given non-spherical geometry that rotation can cause "Apparent" contraction.

Envision a 12 inch ruler orthogonally oriented to your line of sight, now rotate it around its length. As the viewing angle changes the length appears to change.

We're all in agreement that special relativity matches experiment and yet we're still disagreeing on whether a moving object contracts in the direction of motion. This scares me quite a bit. Hopefully we can sort this out.
Your "We're" and "matches" are to broad. No** emperical data has ever demonstrated or supported directly the concept of length contraction. As I have tried to point out it isn't necessary and still have a mathematically consistant concept of relativity.

**Note: I have seen ONE recent claim by experimenters that they may have observed length contraction but it was in a magnetic field, not of an object.

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Originally Posted by MacM
I am not in disagreement generally but I always have a problem with this position for the simple reason that SR has reciprocity in its affects, GR does not.

It is the reciprocity in SR that seems completely unobserved, unsupported by emperical data or logic.

How does reciprocity fit within your statement of equality?
It doesn't, directly.

Remember, I am commenting on the 'experimental' side.

You can look at it like this, if you like: there's a black box (GR, SR, QED, whatever), you put parameters in, you turn the handle, and predictions come out. You go and do the appropriate experiment, and find that the results match the predictions (to within the experimental limits).

You repeat this, for a million (a billion, whatever) experiments, trying to test as many different kinds of predictions as is possible, within the limits of your experimental capabilities.

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Originally Posted by Jonny
[snip]

The issue at hand is that I saw some mainstream proponents saying that a moving object did not contract in the direction of motion. I felt this was wrong, and wanted to see if opinion on this had changed.

[snip]
Well, the theory is what it is, n'est pas?

It would be nice to test this, by taking some piccies of Van Rijn's deer, as they fly by us at 0.1c, 0.3c, 0.5c, 0.9c, and see just what sort of contraction is recorded in the piccies.

Until we can do such an experiment, surely the best we can do is to test SR in as many ways as we can, in our labs?

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Originally Posted by Nereid
Until we can do such an experiment, surely the best we can do is to test SR in as many ways as we can, in our labs?
But if you advocate (or accept) Terrell-Penrose rotation does not that preclude the simultaneous advocation that physical length contraction of SR is real?

Recall that a sphere in TP rotation does not change geometry.

Also isn't it a requirement that something be testable (falsifiable) to be considered scientific theory? If length contraction is not falsifiable isn't SR disqualified as valid theory?
Last edited by MacM; 2006-Mar-21 at 02:04 PM.

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Originally Posted by Nereid
Well, the theory is what it is, n'est pas?
Are you saying that you agree with my statements about the predictions of SR: that a moving object is contracted in the direction of motion?

If the mainstream proponents agree on this then we can move onto the experiment discussion. (I'm still not sure what Nereid's stance is. Tim Thompson flat our denied the length contraction in 3d. And clj4 (the one who's comments started this) denies the contaction as well. So we have quite a ways to go before consensus on the theory's predictions.)

To help reach this consensus, I would appreciate comments on my previous post where I show: SR predicts that a moving object is contracted in the direction of motion.

18. Originally Posted by MacM
As described here in the equivelence of inertial frames.

http://www.mathpages.com/home/kmath307/kmath307.htm

It is my contention that this view places equivlence of observation with equivelance of physical reality. I do not believe emperical data or logic support such conclusion.

That is the old arguement that when the train accelerates away from the station the station is also accelerating away from the train is actually an illusion and is not equivelent.

Therefore the fact of relative velocity created is not also equivelent. That is it seems emperical data actually supports the idea that only objects which undergo the F = ma acceleration experience undergo physically measureable relavistic changes.

This fact seems to better support an absolute concept than a relative velocity concept.
you have to be kidding here, there is only reciprocity between inertial frames. There cannot be reciprocity in the train case you state, as one object (te train) clearly experiences a force, whereas the other (the station) does not. Your examples misses your point of argument completely.

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Originally Posted by Jonny
I was taught in high school that a moving object is contracted in the direction of motion, and that this has been proven experimentally...
There is no experimental proof that an object contracts in its direction of motion relative to another observer.

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Originally Posted by Jonny

To help reach this consensus, I would appreciate comments on my previous post where I show: SR predicts that a moving object is contracted in the direction of motion.
I'm on Tim's side. It's a rotation, not a contraction for actual 3-D items. And, as he points out, it's described quite well in "Spacetime Physics". If someone doesn't post it by then, I'll find the page number for the explanation when I get home from work.

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Originally Posted by tusenfem
you have to be kidding here, there is only reciprocity between inertial frames. There cannot be reciprocity in the train case you state, as one object (te train) clearly experiences a force, whereas the other (the station) does not. Your examples misses your point of argument completely.
No I am not kidding. Of course the frames are different and that is MY point. The fact that at some future time the train becomes inertial and you have mere relative velocity IS the point.

Emperical data only supports relavistic affects being recorded in the F = ma accelerated frame and the relative velocity view is not supported.

But we are diverging the discussion from Johnny's thread. If you like open a thread on "Reciprocity" and I will participate there.
Last edited by MacM; 2006-Mar-21 at 02:16 PM.

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Originally Posted by Tensor
I'm on Tim's side. It's a rotation, not a contraction for actual 3-D items. And, as he points out, it's described quite well in "Spacetime Physics". If someone doesn't post it by then, I'll find the page number for the explanation when I get home from work.
If there is no contraction then that supports my conclusion that the correct physics is an enhanced velocity calculation in the moving frame due to time dilated clocks.

Contraction becomes an illusion of object rotation and there is no affect on space.

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Originally Posted by Jonny
Are you saying that you agree with my statements about the predictions of SR: that a moving object is contracted in the direction of motion?

If the mainstream proponents agree on this then we can move onto the experiment discussion. (I'm still not sure what Nereid's stance is. Tim Thompson flat our denied the length contraction in 3d. And clj4 (the one who's comments started this) denies the contaction as well. So we have quite a ways to go before consensus on the theory's predictions.)

To help reach this consensus, I would appreciate comments on my previous post where I show: SR predicts that a moving object is contracted in the direction of motion.
Originally Posted by MacM
But if you advocate (or accept) Terrell-Penrose rotation does not that preclude the simultaneous advocation that physical length contraction of SR is real?
I'm going to address these two at the same time.

First, I have no disagreement with "Spacetime Physics" (and when Tensor gets us the page number, we can go through the derivation, line by line. Though, for the life of me, I can't understand why a simple exercise like this needs to be in the ATM section of BAUT).
Recall that a sphere in TP rotation does not change geometry.
Second, it is unlikely that we'll be able to take piccies of VanRijn's high speed deer within any of our lifetimes (though I wouldn't rule out a particularly clever experiment that does essentially the same thing), so talk of experimental validation is unrealistic for us.

So, since the most powerful thing we can do with a theory is test it, let's examine the tests that SR has been subject to, and see if it's failed any of them. If it hasn't, then we can move on; if it has, then we can discuss such failures.
Also isn't it a requirement that something be testable (falsifiable) to be considered scientific theory? If length contraction is not falsifiable isn't SR disqualified as valid theory?
Third, 'length contraction' is entirely 'falsifiable' ... it's simply that we can't (yet) take piccies of VanRijn's deer zipping past us at relativistic speeds.

But worst of all, 'length contraction' is merely a teensy, weansy part of SR. Sure, it might be nice to test it, but there are a zillion other tests that we can do (and have done) ... and it's passed those tests. A theory doesn't cease to be a scientific theory simply because some minor aspect of it can't be tested ... yet.

So, can I hear it from Jonny and MacM please - to what extent (in your view) has SR been tested, experimentally? To what extent has it passed those tests?

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Originally Posted by MacM
No I am not kidding. Of course the frames are different and that is MY point. The fact that at some future time the train becomes inertial and you have mere relative velocity IS the point.

Emperical data only supports relavistic affects being recorded in the F = ma accelerated frame and the relative velocity view is not supported.

But we are diverging the discussion from Johnny's thread. If you like open a thread on "Reciprocity" and I will participate there.
It's your (ATM) idea MacM; so it's up to you to start that thread.

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Originally Posted by MacM
If there is no contraction then that supports my conclusion that the correct physics is an enhanced velocity calculation in the moving frame due to time dilated clocks.

Contraction becomes an illusion of object rotation and there is no affect on space.
And what other effects would follow from this 'conclusion' of yours? What sorts of experiments could we do - in principle - to test this (other than taking piccies of high speed deer)?

Surely there will be many other implications, including (for example) in QED!

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Originally Posted by Nereid
But worst of all, 'length contraction' is merely a teensy, weansy part of SR. Sure, it might be nice to test it, but there are a zillion other tests that we can do (and have done) ... and it's passed those tests. A theory doesn't cease to be a scientific theory simply because some minor aspect of it can't be tested ... yet.

So, can I hear it from Jonny and MacM please - to what extent (in your view) has SR been tested, experimentally? To what extent has it passed those tests?
For me that is simple. There have been an abundance of emperical data which confirms a ONE WAY Gamma function but NONE confirming reciprocity. SR requires recioprocity.

That is the emperical data actually suggests an absolute view not a relative velocity view. Length contraction is part of that issue. The muon experiment I linked is part of that in that the findings that muon decay was a function of absolute motion to the CMB and not relative velocity to the earth impacts the concept of length contraction in SR as part of the arguement that muon data supports SR. It doesn't.

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Originally Posted by Nereid
It's your (ATM) idea MacM; so it's up to you to start that thread.
I'll give it some thought but I don't have a problem with my view.

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Originally Posted by Nereid
And what other effects would follow from this 'conclusion' of yours? What sorts of experiments could we do - in principle - to test this (other than taking piccies of high speed deer)?
I'm not sure physical testing of length contraction is required to come to a conclusion. One needs only to clear their head of the confusion created by the shifty sands of merging time-space and realize that the trip time "physically" recorded by the moving frame is fully accounted for by the dilated tick rate of the clock used to compute distance.

It is only by equating t = t' (or making altered measurement standards equivelent) that spatial contraction even occurs mathematically.

i.e. rest frame v = d/t and d = vt while in the moving frame based on known data from the rest frame v' = d/t' and d = v't'.

Surely there will be many other implications, including (for example) in QED!
Well QED is certainly out of my league but I would think it is incombant to demonstrate a falsification of the view since it is generally accepted that nothing can be proven but only disproved.

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Originally Posted by MacM
For me that is simple. There have been an abundance of emperical data which confirms a ONE WAY Gamma function but NONE confirming reciprocity. SR requires recioprocity.
I'm curious about relativistic quantum phenomena.

As you know, a huge advance in quantum theory came with the incorporation of SR, resulting in (among other things) QED. Now, QED is the most accurately tested of all theories in physics (perhaps in all of science).

In what sense is the 'reciprocity' of your idea incorporated in all (or any) relativistic quantum theories? How dependent are these theories solely on "a ONE WAY Gamma function"?
That is the emperical data actually suggests an absolute view not a relative velocity view. Length contraction is part of that issue. The muon experiment I linked is part of that in that the findings that muon decay was a function of absolute motion to the CMB and not relative velocity to the earth impacts the concept of length contraction in SR as part of the arguement that muon data supports SR. It doesn't.
And that's it? There are no other experiments or observations whose results seem to be inconsistent with SR?

On this observation, if I've understood it correctly, the result was that there seemed to be some (time) variability in the observed half-life of (atmospheric) muons, which the PI felt correlated with a sky position (RA, dec) that is similar to one pole of the CMB dipole; did I get that right?

Anyway, in terms of this idea (absolute motion), what would be observed in experiments done in collider labs? Would the power needed to run the colliders vary - by some small %-age - depending on the time of day/month/year (the plane of the collider wrt the CMB dipole)? Would the observed half-lives of all unstable particles vary in a similar fashion (or perhaps their widths would be greater than otherwise, because the data was integrated over multiple directions wrt the CMB dipole)?

If there is, indeed, an effect of the kind this experiment claims to have detected, how could the muon g-2 experiment have even been performed (let alone produce a clear result)?

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Originally Posted by MacM
I'm not sure physical testing of length contraction is required to come to a conclusion. One needs only to clear their head of the confusion created by the shifty sands of merging time-space and realize that the trip time "physically" recorded by the moving frame is fully accounted for by the dilated tick rate of the clock used to compute distance.

It is only by equating t = t' (or making altered measurement standards equivelent) that spatial contraction even occurs mathematically.

i.e. rest frame v = d/t and d = vt while in the moving frame based on known data from the rest frame v' = d/t' and d = v't'.
So, what experiment or observation could be done - in principle - to 'clear the head'?
Well QED is certainly out of my league but I would think it is incombant to demonstrate a falsification of the view since it is generally accepted that nothing can be proven but only disproved.
Aye, but there you have it, don't you?

Particle colliders and detectors work just as advertised (i.e. according to theories which incorporate (special) relativity into quantum theory); all kinds of effects in condensed matter physics are predicted from similar applications (and observed, the latest craze seems to be graphene); and so on.

So, it would seem that the thing you're concerned about has either been shown - every day, perhaps even in your computer - to be wrong (if the behaviour of relativistic electrons is different, in your idea, than in SR, in certain electronics devices), or irrelevant (the difference between your idea and SR - in anything that really happens to relativistic electrons in certain electronics devices - is zero).

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