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Jonny
2006-Mar-19, 12:09 PM
While MacM's thread (http://www.bautforum.com/showthread.php?t=39342) 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 (http://www.bautforum.com/showpost.php?p=705041&postcount=12), 2 (http://www.bautforum.com/showpost.php?p=704523&postcount=6)) 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?

Your comments are much appreciated.

johntsang
2006-Mar-19, 01:30 PM
The question was asked and answered ...
... 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 .

Tim Thompson
2006-Mar-19, 11:52 PM
Does mainstream physics still believe that a moving object is contracted in the direction of motion, and that this has been proven experimentally?
The question is ambiguous & misleading, and therefore impossible to answer.

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 (http://www.amazon.com/gp/product/0716723271/qid=1142812011/sr=2-1/ref=pd_bbs_b_2_1/103-2879456-7642219?s=books&v=glance&n=283155), by Taylor & Wheeler (W.H. Freeman, 2nd ed., 1992).

Nereid
2006-Mar-20, 12:24 AM
While MacM's thread (http://www.bautforum.com/showthread.php?t=39342) 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 (http://www.bautforum.com/showpost.php?p=705041&postcount=12), 2 (http://www.bautforum.com/showpost.php?p=704523&postcount=6)) 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?

Your comments are much appreciated.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 (http://relativity.livingreviews.org/Articles/lrr-2001-4/index.html); 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.

MacM
2006-Mar-20, 02:31 AM
.........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?

Tensor
2006-Mar-20, 03:21 AM
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?

MacM
2006-Mar-20, 03:27 AM
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?

tusenfem
2006-Mar-20, 11:39 AM
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.

MacM
2006-Mar-20, 01:56 PM
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/Pre2001/V03NO2PDF/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.

Tim Thompson
2006-Mar-20, 03:07 PM
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"?

MacM
2006-Mar-20, 03:21 PM
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.

Jonny
2006-Mar-20, 03:51 PM
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.)


The question is ambiguous & misleading, and therefore impossible to answer.

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.


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.


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.


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).


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.


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).

MacM
2006-Mar-20, 07:52 PM
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.

Nereid
2006-Mar-21, 02:37 AM
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.

Nereid
2006-Mar-21, 02:52 AM
[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 (http://www.bautforum.com/showthread.php?t=39521), 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?

MacM
2006-Mar-21, 04:02 AM
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?

Jonny
2006-Mar-21, 08:38 AM
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.

tusenfem
2006-Mar-21, 10:11 AM
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.

wisp
2006-Mar-21, 11:14 AM
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.

Tensor
2006-Mar-21, 12:30 PM
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.

MacM
2006-Mar-21, 01:43 PM
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.

MacM
2006-Mar-21, 01:46 PM
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.

Nereid
2006-Mar-21, 02:49 PM
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.
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?

Nereid
2006-Mar-21, 02:51 PM
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.

Nereid
2006-Mar-21, 02:53 PM
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!

MacM
2006-Mar-21, 03:22 PM
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.

MacM
2006-Mar-21, 03:28 PM
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.:lol:

MacM
2006-Mar-21, 03:36 PM
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.

Nereid
2006-Mar-21, 03:59 PM
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 (http://en.wikipedia.org/wiki/Quantum_electrodynamics). 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 (http://www.bnl.gov/bnlweb/pubaf/pr/2001/g-2_backgrounder.htm) have even been performed (let alone produce a clear result)?

Nereid
2006-Mar-21, 04:10 PM
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 (http://en.wikipedia.org/wiki/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).

MacM
2006-Mar-21, 07:05 PM
So, what experiment or observation could be done - in principle - to 'clear the head'?Aye, but there you have it, don't you?

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).

No that would not be the conclusion. Keep in mind that for most all testing that has been done the absolute motion to the CMB is 1/1,000 c and the one way gamma effect predicted by SR would be 23 times larger than any anisotropy due to the absolute affect.

This would not be noticed unless you are specifically looking for it. You would take your data as proof of SR disregarding the variation as test or measurement efficiency. A cyclotron would not be effective it would have to be a linear accelerator operated at different times such that the cosmic orientation varied repeatably to the CMB motion and compare repeatable tests looking for the 4% synchronized deviation.

clj4
2006-Mar-21, 07:18 PM
No that would not be the conclusion. Keep in mind that for most all testing that has been done the absolute motion to the CMB is 1/1,000 c and the one way gamma effect predicted by SR would be 23 times larger than any anisotropy due to the absolute affect.

This would not be noticed unless you are specifically looking for it. You would take your data as proof of SR disregarding the variation as test or measurement efficiency. A cyclotron would not be effective it would have to be a linear accelerator operated at different times such that the cosmic orientation varied repeatably to the CMB motion and compare repeatable tests looking for the 4% synchronized deviation.

400km/sec is good enough. There are experiments (some of them 20 years old) that employ equipment that is sensitive enough to have detected effects not only in v/c but in (v/c)^2.

MacM
2006-Mar-21, 07:29 PM
400km/sec is good enough. There are experiments (some of them 20 years old) that employ equipment that is sensitive enough to have detected effects not only in v/c but in (v/c)^2.

I agree it is possible to detect this affect as has been done in the muon experiment but if you are biased (even unconciously) to be predisposed to expect SR predictions then your test data confirms your expectation.

I don't know if sufficient records are available to correlate testing historically done at different times and with sufficient repeated conditions to actually review existing data to look for the affect or if one needs to do specific testing.

But at this juncture it certainly is not adequate to merely take data produced
and declare it supports the SR relative velocity view without specific consideration of the possible absolute background affect.

Jonny
2006-Mar-21, 07:34 PM
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?
I am not against the mainstream. I felt some of the "mainstream proponents" here weren't understanding SR and I felt this needed to be corrected. To be fair, I had to consider the possibility that I was wrong as well. I'm sorry if wording my questions as such made you think that I was against the mainstream. I am merely trying to get all the mainstream proponents to come to consensus here. The fact that two (clj4, Tim) have already blatantly denied length contraction seems horrifying to me.

Since this is the point of the thread, MacM would you mind starting a new thread with your ideas. It is difficult to keep a discussion going with two discussions overlapped.


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.
Length contraction is not a "teensy weansy" part of SR. SR states that the physical laws have the same form in all inertial frames ... this is not possible without length contraction and time dilation. They are required by the theory.

Experimental proof: if length contraction was not there, then applying maxwell's equations in a frame in which the Michelson-Morley experiment was moving would predict a non-null shift. Similarly with the Kennedy-Thorndike experiment. Length contraction is predicted by SR, and is supported by experiment.

Why can't all the mainstream proponents agree on this?
Now that clj4 is posting again. Can you please read my post
http://www.bautforum.com/showpost.php?p=707177&postcount=12
and comment on why you disagree with the conclusion that SR predicts a moving object contracts in the direction of motion?

MacM
2006-Mar-21, 07:45 PM
I am not against the mainstream. I felt some of the "mainstream proponents" here weren't understanding SR and I felt this needed to be corrected. To be fair, I had to consider the possibility that I was wrong as well. I'm sorry if wording my questions as such made you think that I was against the mainstream. I am merely trying to get all the mainstream proponents to come to consensus here. The fact that two (clj4, Tim) have already blatantly denied length contraction seems horrifying to me.

Since this is the point of the thread, MacM would you mind starting a new thread with your ideas. It is difficult to keep a discussion going with two discussions overlapped.

1 - I am not interested in hijacking your thread. It parallels my thread. The issue of reciprocity is relevant to length contraction but I think it misses your issue.

2 - I see your issue as being more about what does SR predict. I don't believe anybody here thinks SR does not predict length contraction. It does. The comments made which you seem to disagree with is "Is the SR prediction true as physical reality". Therein lies the disagreement, not in the prediction but in the reality.


Length contraction is not a "teensy weansy" part of SR. SR states that the physical laws have the same form in all inertial frames ... this is not possible without length contraction and time dilation. They are required by the theory.

Here is where I think your thinking is flawed. My presentation covers this issue. Emperical data can be generated without length contraction by understanding that in absence of such contraction the moving frame will calculate a higher velocity due to the same physical distance being covered in less time by his dilated clock.

Nereid
2006-Mar-21, 07:49 PM
400km/sec is good enough. There are experiments (some of them 20 years old) that employ equipment that is sensitive enough to have detected effects not only in v/c but in (v/c)^2.I agree it is possible to detect this affect as has been done in the muon experiment but if you are biased (even unconciously) to be predisposed to expect SR predictions then your test data confirms your expectation.Waaaait a minute; if an experiment had the sensitivity to detect a (v/c)^2 effect, then any v/c variation of the size you're considering MacM (~1000 ppm) would utterly swamp any ~1 ppm signal! I mean, not only would the output show this nice ~12 hour period, but it would take only ~1 minute for a ~v/c effect to show up in an experiment that was sensitive to ~1 ppm (I'm using OOM, so none of these numbers is 'right', but they should be close enough for the purposes of the illustration).

But perhaps I've misunderstood? Perhaps this 'absolute frame, v/c effect' wouldn't show up as a ~0.1% signal after all?

Could you clarify please?
I don't know if sufficient records are available to correlate testing historically done at different times and with sufficient repeated conditions to actually review existing data to look for the affect or if one needs to do specific testing.

But at this juncture it certainly is not adequate to merely take data produced
and declare it supports the SR relative velocity view without specific consideration of the possible absolute background affect.Well, since we have ATM rules, you need to find the relevant experiments (I'm sure clj4 will give you some pointers where you might dig up the papers), and show - to whatever level of detail BAUT members may wish to ask for - that these experiments could not have detected this ~12 hour periodic ~0.1% signal.

Jonny
2006-Mar-21, 08:01 PM
I don't believe anybody here thinks SR does not predict length contraction. It does.
Tim stated the exact opposite. clj4 seems to as well. So I'd like to resolve this.


The comments made which you seem to disagree with is "Is the SR prediction true as physical reality". Therein lies the disagreement, not in the prediction but in the reality.
If they wish to make some metaphysical distinction, that is their business. But they should be aware that they are making such distinctions ... we need to agree on the predictions, and then they can decide what is "real" for themselves. I prefer Nereid's approach: what is the prediction, and does experiment support it. SR predicts a moving object will length contract in the direction of motion and experiment does support this.

If you want to step away and call length contraction "not real", fine ... but to be consistent you must also call time dilation "not real". Again, I don't care about people's personal metaphysics. I just want all the mainstream proponents on this page to be in agreement on the predictions of SR and the experimental evidence for SR.

Nereid
2006-Mar-21, 08:04 PM
No that would not be the conclusion. Keep in mind that for most all testing that has been done the absolute motion to the CMB is 1/1,000 c and the one way gamma effect predicted by SR would be 23 times larger than any anisotropy due to the absolute affect.

This would not be noticed unless you are specifically looking for it. You would take your data as proof of SR disregarding the variation as test or measurement efficiency. A cyclotron would not be effective it would have to be a linear accelerator operated at different times such that the cosmic orientation varied repeatably to the CMB motion and compare repeatable tests looking for the 4% synchronized deviation.There are plenty of lineacs around, and a 4% signal - especially one that had a nice ~12 hour period - would stand out like a sore thumb.

Don't forget that many hospitals now have lineacs in their oncology departments; suppose this 4% somehow got realised as a signal in power used, or physiological effects on the irradiated body - there are lots of astute financial controllers who would notice (fluctuating power usage - "hey it seems the lineac uses less power {insert time statement here}, let's operate it only then!"), not to mention doctors.

I don't 'get' the '23 times larger' part - can you please explain?

And you need to consider not just lineacs, but ALL devices whose proper working involves relativistic electrons ... anywhere - find one used for precise measurements, in a specialist engineering firm, for example, and even a periodic 0.1% signal would certainly be noticed (especially true if the device were 'fixed', say to an optical bench).

clj4
2006-Mar-21, 09:38 PM
Tim stated the exact opposite. clj4 seems to as well. So I'd like to resolve this.


If they wish to make some metaphysical distinction, that is their business. But they should be aware that they are making such distinctions ... we need to agree on the predictions, and then they can decide what is "real" for themselves. I prefer Nereid's approach: what is the prediction, and does experiment support it. SR predicts a moving object will length contract in the direction of motion and experiment does support this.

If you want to step away and call length contraction "not real", fine ... but to be consistent you must also call time dilation "not real". Again, I don't care about people's personal metaphysics. I just want all the mainstream proponents on this page to be in agreement on the predictions of SR and the experimental evidence for SR.


Looks like you like setting up strawmen to fight and defeat them. Either way, you seem not to understand the previous postings , neither Tim or myself deny the Einstein-Poicaire length contraction. Try reading one more time John Baez (carefully)

http://math.ucr.edu/home/baez/physics/Relativity/SR/penrose.html

It was also pointed out to you that your questions are not correctly set , so there is no correct answer to them. Therefore: no answer.
Now, after you've been admonished about the incorrectly stated questions you advanced this theory:


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 rules of this forum say that if you advance a theory you need to defend it. Could you please show the members of this thread your calculations (i.e, the math)?

Nereid
2006-Mar-21, 10:04 PM
I've reviewed this thread, and I am of the opinion that it's a bit of a mess.

We have at least two different ideas in play (Jonny's OP, since modified considerably; and MacM's, which seemed to start out in a similar direction but has since diverged quite markedly).

On top of which, both Jonny and MacM are (relatively) new to BAUT, and seem to be not particularly familiar with how this ATM section works - while the Rules (http://www.bautforum.com/showthread.php?t=32864) are (IMHO) pretty straight-forward (for ATM see #13), getting used to them when you're writing posts isn't so easy.

I'd thought of trying to do some thread surgery - separate MacM's ideas and discussion thereof into a new thread - but it would be a mess.

So, for now, I'm locking this thread.

My preference would be for each of Jonny and MacM to start new, separate threads, with the OP in each being a clear, concise statement of exactly what the ATM idea they are proposing is. If either (or both) of you do so, I would ask that you: write only any ATM idea that you are prepared to defend be clear, in the OP, on the extent to which the idea is testable (in principle) via experiment or observation reserve any comments about the extent to which the idea differs from the mainstream until either the end of the post or one or more subsequent posts.