Measurement length of an object will not be changed by motion

[Jeremy0922]

"Time dilation" and "space contraction" are the important deductions from Einstein's special relativity(SR), based on "the principle of constant speed of light in vacuum" and the observation of moving objects in his thought experiment.

Actually, Einstein's thought experiment is one kind of observation of length for a moving object with an invariable velocity, and there are many methods for us to be selected to measure the length of a moving object. for an experimental measurement, the errors caused by the method and equipment must be considered and be applied to correct the results.

 

Lorentz's transformation from SR, which is only satisfied to the special example in Einstein's thought experiments, should not be understood as space-time transformation for any moving object, because a different result will be given by a different measurement.

 

Selecting two points (D1, D2) on the trajectory of the moving object, testing the times that the moving object reach at and leave these two points D1 and D2, separately, t1, t1' and t2, t2', the length (Lb) and the velocity (V) of the moving object will be gotten by the measurement results of these times and the distant (L) between D1 and D1, as shown in following figure.

 

 

 

the velocity V is:

V= L/(t2-t1) or

V=L/(t2'-t1')

the length Lb is:

Lb=V(t1'-t1)=L(t1'-t1)/(t2-t1) or

Lb=V(t2'-t2)=L(t2'-t2)/(t2'-t1')

Clearly, the measured result Lb does not relate to the velocity of the moving object V and light speed c by above measurement.

Therefor, Space would not be changed by motion.

Is that right ?

Edited December 4, 2010 by Jeremy0922

[ajb]

The length of a rod will depend on the frame used to measure it. This is quite inescapable assuming Lorentz invariants and the standard definitions of length of an object. This is the well-know length contraction phenomena.

 

I don't know of any direct experimental test of this phenomena, however there is plenty of evidence for special relativity. I believe the the length contraction of objects at speeds achievable in the lab is so small it would get swamped by experimental errors.

[Jeremy0922]

The length of a rod will depend on the frame used to measure it. This is quite inescapable assuming Lorentz invariants and the standard definitions of length of an object. This is the well-know length contraction phenomena.

 

I don't know of any direct experimental test of this phenomena, however there is plenty of evidence for special relativity. I believe the the length contraction of objects at speeds achievable in the lab is so small it would get swamped by experimental errors.

 

 

If “length contraction phenomena” is true, then any measurement will get the same result, but the above method get a different one. So, I think the space-time transformation is the experimental system error caused by the observation method in Einstein's thought experiment for a moving rod.

[TonyMcC]

Is not the problem the fact that a clock attached to the moving bar and a clock attached to the fixed table will not be running at the same at the same rate?

[Sisyphus]

You're just describing the classical situation. i.e., "if relativity doesn't exist, then it isn't true." Let the speed of light be constant in any reference frame, and times and distances no longer are.

[Jeremy0922]

Is not the problem the fact that a clock attached to the moving bar and a clock attached to the fixed table will not be running at the same at the same rate?

 

 

Space and time are the basic conception used to describe the physical events taking place in, lighting is one of them. Lighting and its speed could be applied to measure the time interval, but should not effect on the definitions of time and space.

 

You're just describing the classical situation. i.e., "if relativity doesn't exist, then it isn't true." Let the speed of light be constant in any reference frame, and times and distances no longer are.

 

 

If the velocity is very high and closed to light speed c, according SR, the space contraction will be obvious. But for the above measurement, the length of moving rod is also the same with rest frame, because Lb is not related to c and V.

Edited November 29, 2010 by Jeremy0922

[Sisyphus]

If the velocity is very high and closed to light speed c, according SR, the space contraction will be obvious. But for the above measurement, the length of moving rod is also the same with rest frame, because Lb is not related to c and V.

 

If C is constant in all reference frames, then the length of an object in a given reference frame changes with its velocity. What your example describes is a situation where C cannot be constant between reference frames (like it wouldn't be in classical physics), and is therefore non-physical, as the constancy of C has been thoroughly demonstrated.

[Jeremy0922]

If C is constant in all reference frames, then the length of an object in a given reference frame changes with its velocity. What your example describes is a situation where C cannot be constant between reference frames (like it wouldn't be in classical physics), and is therefore non-physical, as the constancy of C has been thoroughly demonstrated.

 

 

Space and time are not related to C and motion of object essentially.

Einstein introduced his thought experiment to observe moving object, is only optical test method with errors. these errors relate to speed of light, the observe position, and the velocity of moving object, and blong to experimental errors caused by test method.

Edited November 29, 2010 by Jeremy0922

[swansont]

Space and time are not related to C and motion of object essentially.

Einstein introduced his thought experiment to observe moving object, is only optical test method with errors. these errors relate to speed of light, the observe position, and the velocity of moving object, and blong to experimental errors caused by test method.

 

Time dilation has been measured, though, in many experiments. Space and time are related if c is a constant, and the experiments we can do confirm that this is indeed the case.

 

The length of a rod will depend on the frame used to measure it. This is quite inescapable assuming Lorentz invariants and the standard definitions of length of an object. This is the well-know length contraction phenomena.

 

I don't know of any direct experimental test of this phenomena, however there is plenty of evidence for special relativity. I believe the the length contraction of objects at speeds achievable in the lab is so small it would get swamped by experimental errors.

 

I agree. I was under the impression that it is necessary to include length contraction effects for particle colliders, in order for the cross sections and interaction strengths to be correct. While that's not a direct measurement, it is evidence nonetheless.

[Jeremy0922]

Time dilation has been measured, though, in many experiments. Space and time are related if c is a constant, and the experiments we can do confirm that this is indeed the case.

 

 

 

I agree. I was under the impression that it is necessary to include length contraction effects for particle colliders, in order for the cross sections and interaction strengths to be correct. While that's not a direct measurement, it is evidence nonetheless.

 

 

The observation result need corrections for different methods, but space and time do not need.

Edited November 29, 2010 by Jeremy0922

[mississippichem]

To prove that the rod in motion is not relativistically contracting, one would have to report the observed length the rod at rest and in motion to many many decimal places with a confidence interval approaching 100% in order to draw any conclusions outside of the relatively large measurement error that is inevitable when dealing with margins this small. I hope you've got some serious lab technique.

 

Am I right in saying that the rod's Lorentz factor should be vanishingly small anyway at velocities attainable in a lab for a macro object?

Edited November 29, 2010 by mississippichem

[ajb]

Am I right in saying that the rod's Lorentz factor should be vanishingly small anyway at velocities attainable in a lab for a macro object?

 

It would be very close to unity so that the proper length is nearly the same as the length of the moving object. Experimental errors would then swamp the length contraction.

 

I was under the impression that it is necessary to include length contraction effects for particle colliders, in order for the cross sections and interaction strengths to be correct. While that's not a direct measurement, it is evidence nonetheless.

 

I think you are right. Heavy ions do "suffer" Length contraction. They get flattered in the direction of motion.

 

Other indirect evidence is the fact that relativistic theories have been tested to some huge degree of accuracy. There seems no reason to think length contraction is not "real". It is like all the apparent troubles of SR, the want to keep hold of 3+1 rather than 4.

[Jeremy0922]

To prove that the rod in motion is not relativistically contracting, one would have to report the observed length the rod at rest and in motion to many many decimal places with a confidence interval approaching 100% in order to draw any conclusions outside of the relatively large measurement error that is inevitable when dealing with margins this small. I hope you've got some serious lab technique.

 

Am I right in saying that the rod's Lorentz factor should be vanishingly small anyway at velocities attainable in a lab for a macro object?

 

 

I think that is an important and serious problem for us to understand the conceptions of space and time correctly. I do not hope we get a new theory which comes from a misunderstanding about the observation error.

Edited November 29, 2010 by Jeremy0922

[swansont]

I think you are right. Heavy ions do "suffer" Length contraction. They get flattered in the direction of motion.

 

Other indirect evidence is the fact that relativistic theories have been tested to some huge degree of accuracy. There seems no reason to think length contraction is not "real". It is like all the apparent troubles of SR, the want to keep hold of 3+1 rather than 4.

 

That rings a bell. You get a quadrupole moment from the length contraction, which is not present under classical conditions.

[Jeremy0922]

Heavy ions do "suffer" Length contraction. They get flattered in the direction of motion.

 

 

That is an observation, or the deduction from SR?

 

That rings a bell. You get a quadrupole moment from the length contraction, which is not present under classical conditions.

 

 

That is an observation, or the deduction from SR?

[ajb]

That is an observation, or the deduction from SR?

 

My understanding is that the "heavy ion pancake" geometry is needed to explain the detail of the collisions. In particular the increase in density.

 

It is true that these "pancakes" (at least as far as I know) have never been observed directly.

 

 

The experimental observation is suggested in [1] by detecting the de-excitation quadrupole radiation of a rapidly moving spherical excited nucleus. (I think this is what swansont is referring to). I have no idea about the experimental status today.

 

 

References

[1] Ai Hsiao-Bai, The direct detection of Lorentz contraction is possible Il Nuovo Cimento B, vol.110, issue 7, pp. 823-828 (1995)

[Jeremy0922]

My understanding is that the "heavy ion pancake" geometry is needed to explain the detail of the collisions. In particular the increase in density.

 

It is true that these "pancakes" (at least as far as I know) have never been observed directly.

 

 

The experimental observation is suggested in [1] by detecting the de-excitation quadrupole radiation of a rapidly moving spherical excited nucleus. (I think this is what swansont is referring to). I have no idea about the experimental status today.

 

 

References

[1] Ai Hsiao-Bai, The direct detection of Lorentz contraction is possible Il Nuovo Cimento B, vol.110, issue 7, pp. 823-828 (1995)

 

 

It is nice to discuss the problems about foundation of physics with you and the scientists on SFN.

By my opinion, Lorentz's transformation from SR is only satisfied to the special example in Einstein's thought experiment, because the different length and time will be gotten for different observation position in rest frame for the same moving rod at same time.

So, Lorentz transformation should be related to observation position. The space-time transformation from SR is not reliable, and the discussions about the deductions from SR (such as "pancake") will become to be unimportant.

Edited November 30, 2010 by Jeremy0922

[ajb]

I take the Lorentz transformations as the fundamental thing in special relativity. That is, the group of isometries of the Minkowski metric is special relativity.

[Jeremy0922]

I take the Lorentz transformations as the fundamental thing in special relativity. That is, the group of isometries of the Minkowski metric is special relativity.

 

 

The image given by relativity theory is only a phantasm, but not an actual description for real phenomena, because the observation method selected by Einstein has obvious error for moving object.

So, SR and its consequences need us to rethink.

[ajb]

But special relativity has been proven to be consistent with nature over and over again. Both direct and indirect tests confirm the special relativity is a very accurate set-up.

[Jeremy0922]

But special relativity has been proven to be consistent with nature over and over again. Both direct and indirect tests confirm the special relativity is a very accurate set-up.

 

 

Certainly, Some experimental results seem to fit to some deduction from SR, but SR is not the unique theory to explain them. For example, the acceleration of a charged particle in a synchrotron, decreases with the increase of velocity of the particle. according to SR, the reason is the mass of the particle increase with the increase of its velocity. But we could find a other idea to understand this experiment result, if the electric force acting on the charged particle relates to the velocity, and decreases with it, then the phenomena could be explained.

That is, Coulombic force might relate to not only the distant between the two charged particles, but also the velocities of them. I think this idea is worth to be considered.

[imatfaal]

I think it is GR that predicts the increase in mass. I seem to remember that the radiation given off by an accelerated charged particle is a limiting factor as well (ie the increasing energy goes into producing synchrotron radiation not into increasing velocity).

[D H]

The image given by relativity theory is only a phantasm, but not an actual description for real phenomena, because the observation method selected by Einstein has obvious error for moving object.

So, SR and its consequences need us to rethink.

Just because you do not like or do not understand a concept does not mean that that that concept is wrong. It might just mean that you are wrong.

 

Which, by the way, is exactly what is going on here.

 

 

 

[Jeremy0922]

I think it is GR that predicts the increase in mass. I seem to remember that the radiation given off by an accelerated charged particle is a limiting factor as well (ie the increasing energy goes into producing synchrotron radiation not into increasing velocity).

 

 

Yes, electromagnetic radiation is an important limiting factor to be considered.

[D H]

I think it is GR that predicts the increase in mass.

No, it doesn't.