Is spacetime independent of its universe?

[Fredrik]

... the block universe is a philosophical interpretation of the Lorentz transforms,...

I like your choice of words. I'm going to start using it, or some version of it. I'll probably say this: "The block universe interpretation and the ether interpretation are two different interpretations of the the same theory".

The former interpretation is preferred because of its simplicity. The latter is still interesting for pedagogical, philosophical and historical reasons. In particular, it's useful for someone who wants to understand interpretations of quantum mechanics to understand that even a classical theory can have two different interpretations.

Theories by definition make predictions about results of experiments. Interpretations by definition do not. This means that experiments can support or falsify a theory, but they can't favor an interpretation over another.

 

[Tosh5457]

Something is throwing me here.

No matter how fast one is going, relatively speaking, one is in the same universe as everyone (and everything) else. We're all going through the same spacetime, albeit at different velocities. You're in the same universe as I am and we both see the same space, light, and bikinis.

If what I've already said is wrong, it makes me believe the universe itself is an idea that has no absolute form. Because, regardless of different speeds of motion, if we are "trapped" in the same universe and going through the same "spacetime", how can time dilation make any sense? For time dilation to make sense, it's almost like we're altering the universe by virtue of our speeds through it.

WannabeNewton is in a spaceship (working on some huge equation that would take me 6,000 years to understand) and is going fast.

The Great One (Peter Donis) is in a spaceship (flexing his muscles) going very fast.

I'm in a spaceship (and throwing the ball for my golden) going very, very fast.

However, we're all in the same universe and we're all going through the same spacetime.

Unless our relative speeds are creating different universes (I'm sure I'm not saying this exactly right, but work with me), I don't see how the speeds matter.

Is spacetime independent of the universe in which it's understood?

I was wondering the same thing some weeks ago, but the thing is that I was only thinking in 3 dimensions. When you look at space-time, which has 4 dimensions, and you use the Minkowski distance, that distance doesn't change with velocities. There isn't contraction of lengths in space-time due to velocity, so yes it makes sense to speak about an Universe, as long as we refer to it as a 4-dimensional Universe.

 

[bobc2]

All of these experiments can be taken as experimental confirmation of LET: http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html

Why do you reference this? How do any of those experiments confirm LET? I think part of the problem is that you have never presented your understanding of what LET is, other than special relativity with ether. And you always imply that a theory that includes ether is incompatible with block universe. It is only incompatible with block universe if you include as a part of LET that the universe is strictly 3-dimensional evolving with time. I am quite skeptical of your ability to provide evidence of some mechanism that would be consistent with a 3-dimensional time-evolving universe. The original LET certainly did not, because the mechanism assumed at that time was not in agreement with special relativity as later presented by Einstein.

 

[ghwellsjr]

Originally, Fitzgerald, Lorentz, Poincare' and others presented papers that attempted to explain the special features of special relativity has resulting from electrical force transmission delays, etc. (the "Lorentz Aether Theory"--or LET). Rindler, in his textbook, does not go into the details of the theory, but dismisses it with the comment that the theory faded away into obscurity. However, some people seem to still affirm the theory, although, in spite of my recent literature searches, it still is not clear to me personally whether or what kind of modifications have been applied to overcome the original defects in the theory (e.g., if one rod, moving at relativistic speed, is shrunk due to absolute physical effects, and another rod at rest in the ether is not shrunk, then everyone would always be able to tell which one is shrunk--unlike Einstein's relativity, where each observer sees the other's rod as shrunk). I've not been successful in getting responses on this forum that would further clarify that point. I'm not claiming to have proved the theory to be invalid--just haven't found a convincing demonstration of it (since it is based on a physical mechanism, you should be able to validate the mechanism).

Notice the "E" in LET? That stands for ether which simply means a single absolute state in which light travels in all directions at c. Take all of SR and then ignore the second postulate and instead postulate that light travels at c only in a single reference frame and you have LET. Whether or not Lorentz actually formulated or believed in that particular form of LET, that's what we mean today when we speak of LET. It's identical to SR except that it assigns one Inertial Reference Frame (IRF) to be preferred, in the sense that nature operates physically on it, even though we cannot tell which IRF that is.

But you cannot attribute a physical mechanism exclusively to LET and not to SR. The Lorentz Transformation (LT) in SR requires that all the laws of physics transform according to LT. Maxwell's equations already did this prior to Einstein formulating SR. But other laws did not and they had to be modified to correctly reflect relativistic requirements. And once that's done, the physical mechanism that you want to attribute only to LET is also in SR. It's just that no one bothers to look in detail for a demonstration of it because it cannot be detected, just like the propagation of light cannot be detected.

The reason that SR is preferred over LET is that SR is simpler. It frees us of having to assign a candidate ether rest state, even if we believe the ether exists. The question for you is: do you agree that there is never a requirement to assign more than one IRF in any given scenario?

ghwellsjr, I get the impression that you have no understanding of LET, other than the fact that light waves appear in an absolute stationary medium known as the aether and that the Lorentz transformations are applied (thus, in your mind, making it equivalent to Einstein's special relativity). Lorentz at least presented a thoroughly developed derivation for a specific mechanism. I have a hunch that you could not describe or provide derivations for any such mechanism that would hold up today.

I thought I gave a pretty good explanation of my understanding of LET in the first paragraph you quoted of me. As such, your hunch is irrelevant. Please re-read my understanding. I believe it is pretty much the same as most everyone else's today. In other words, we don't care about the history of the evolving LET, we only care where it ended up.

As wikipedia puts it:

Today LET is often treated as some sort of "Lorentzian" or "neo-Lorentzian" interpretation of special relativity. The introduction of length contraction and time dilation for all phenomena in a "preferred" frame of reference, which plays the role of Lorentz's immobile aether, leads to the complete Lorentz transformation (see the Robertson-Mansouri-Sexl test theory as an example). Because of the same mathematical formalism it is not possible to distinguish between LET and SR by experiment.

At the end of your quote of mine, I asked you a question for which I'm still awaiting an answer: do you agree that there is never a requirement to assign more than one IRF in any given scenario?

 

[Dale]

Why do you reference this? How do any of those experiments confirm LET?

LET makes all of its experimental predictions using the Lorentz transforms. All of those expermients are consistent with the Lorentz transforms. Therefore all of those experiments can be taken as experimental confirmation of LET.

I think part of the problem is that you have never presented your understanding of what LET is, other than special relativity with ether. And you always imply that a theory that includes ether is incompatible with block universe. It is only incompatible with block universe if you include as a part of LET that the universe is strictly 3-dimensional evolving with time.

I don't know what you mean by "incompatible". They are philosophically different but experimentally identical. That is the point. It shows that the scientific method cannot distinguish betweeen two such philosophical propositions.

I am quite skeptical of your ability to provide evidence of some mechanism that would be consistent with a 3-dimensional time-evolving universe. The original LET certainly did not, because the mechanism assumed at that time was not in agreement with special relativity as later presented by Einstein.

As far as original LET vs. modern LET, as long as whatever flavor of LET you choose uses the Lorentz transform to make its experimental predictions then experimentally it is indistinguishable from the block universe.

 

[TheBC]

All of these experiments can be taken as experimental confirmation of LET: http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html

Experimental confirmation for LET ?

Your various compliants here are scientifically irrelevant.

This is really hilarious. C'mon Dalespam, seems to me you still don't understand the difference between mathematics and science. Einstein and Lorentz did understand the difference. Feynman did too: "... Physics is not mathematics, and mathematics is not physics. One helps the other. But you have to have some understanding of the connection of the words with the real world." At 45:42 in video http://www.youtube.com/watch?v=kd0xTfdt6qw

All that matters from a scientific perspective is whether or not a theory's predictions match experiment.

In other words, you still consider epicycles for in the planet's orbits a valid scientific alternative for experimental observations? I think you miss some essential issues in the evolution of physics.

LET's predictions do.

No.
1/ If LET is a valid alternative, where is your scientific proof the ether exists?
2/ If the (light carrying) ether exists, in LET a moving frame will 'measure' (f.ex. speed of light) only as a mathematical illusion, as explained in post 34. Do you consider this scientific experimental evidence for LET? I don't.

This conversation is running in circles. You have already been corrected

Corrected? Wow, easy Dalespam,... you only gave your point of view, I gave mine.

and you are now aware of the fact that the block universe is a philosophical interpretation of the Lorentz transforms, and one which is not uniquely validated by experiment. You are also now aware that there are other interpretations of the Lorentz transforms, such as LET, which also are validated by all of the same experimental evidence.

Why should I 'now be aware' of this? Just because in your opinion you consider everything I say as being scientifically irrelevant, even Einstein's and Lorentz's quotes?

You may feel free to explain the block universe and describe why you think it is a philosophically superior interpretation. You may not present it as uniquely proven by experiment.

I still do not see why not. SR and ether theories are are very different scientific theories. If you consider these only different philosophical interpetations, then I guess for you science = philosophy. I can not accept that. And you should not either. I am flabbergasted you do not realize this yourself.
I try to discuss scientific issues and you consider them philosophy. You stick to mathematics and consider any scientific interpretation of a number as being philosophy. Do you mind I prefer to follow Einstein, Lorentz, Feynman etc. ?

 

[Dale]

seems to me you still don't understand the difference between mathematics and science.

I do understand the difference between mathematics and science: experiment. The problem is that you still don't understand the difference between philosophy and science: experiment.

Feynman did too: "... Physics is not mathematics, and mathematics is not physics. One helps the other. But you have to have some understanding of the connection of the words with the real world." At 45:42 in video http://www.youtube.com/watch?v=kd0xTfdt6qwIn other words, you still consider epicycles for in the planet's orbits a valid scientific alternative for experimental observations?

I agree completely with Feynman's quote.

It is interesting that you should use Feynman and planet's orbits as your example. Feynman was the one who taught me about the scientific value of not putting any philosophical interpretation on the equations. His specific example was the ancient Mayan calculation of planetary orbits which involved similar things to the western epicycles.

See: Especially from 3:11 on where he discusses how different Mayans may have interpreted the meaning of the numbers and how the modern approach is to not make any interpretation.

SR and ether theories are are very different scientific theories.

Then please identify any single experimental measurement where SR uses the Lorentz transform to predict one result and LET uses the Lorentz transform to predict a different result. If they don't differ experimentally then how will you use the scientific method to distinguish between these two supposedly "very different scientific theories"?

 

[TheBC]

Dalespam,
we are talking past each other. Waste of time. I quit. Please continue your mathematical discussions here, no doubt they will be of great value to potential relativity experts. Lots of fun.

 

[ghwellsjr]

Notice the "E" in LET? That stands for ether which simply means a single absolute state in which light travels in all directions at c. Take all of SR and then ignore the second postulate and instead postulate that light travels at c only in a single reference frame and you have LET. Whether or not Lorentz actually formulated or believed in that particular form of LET, that's what we mean today when we speak of LET. It's identical to SR except that it assigns one Inertial Reference Frame (IRF) to be preferred, in the sense that nature operates physically on it, even though we cannot tell which IRF that is.

But you cannot attribute a physical mechanism exclusively to LET and not to SR. The Lorentz Transformation (LT) in SR requires that all the laws of physics transform according to LT. Maxwell's equations already did this prior to Einstein formulating SR. But other laws did not and they had to be modified to correctly reflect relativistic requirements. And once that's done, the physical mechanism that you want to attribute only to LET is also in SR. It's just that no one bothers to look in detail for a demonstration of it because it cannot be detected, just like the propagation of light cannot be detected.

The reason that SR is preferred over LET is that SR is simpler. It frees us of having to assign a candidate ether rest state, even if we believe the ether exists. The question for you is: do you agree that there is never a requirement to assign more than one IRF in any given scenario?

LET is an awful attempt to mix dynamical ether effects in one frame and pure spatio-temporal 4D effects in another. I am flabbergasted you can take this serious...

Although you quoted my question, you also failed to answer it, at least not immediately.

I think maybe you did answer it in a later post (#34):

Your post #27:

if one rod, moving at relativistic speed, is shrunk due to absolute physical effects, and another rod at rest in the ether is not shrunk, then everyone would always be able to tell which one is shrunk--unlike Einstein's relativity, where each observer sees the other's rod as shrunk). I've not been successful in getting responses on this forum that would further clarify that point.

Let me clarify then. Only the rod moving wrt the aether is shrunk, but if that rod were to measure the length of the stationary rod then it would still measure the aether rod to be shrunk. I.e. Even though the ontological state is asymmetric (one contracted the other not) the measurable state is symmetric (both measure other contracted).

I am shocked by what you write here. What you write here boils down to: only the rod moving wrt the aether is shrunk, and the moving observer only measures the aether rod shrunk... For the moving observer the aether rod 'is' not shrunk, but he measures it as shrunk.

Your analysis makes me think of optical illusion, but instead of an optical illusion it's is a mathematical illusion: the rod has a certain length but you only measure it differently. Here your measurement does not give any experimental evidence at all, not even for the not shrunken rod. similar for the time dilation.

Correct me if I'm wrong, but it appears that you believe that it is possible to distinguish between being at rest in one Inertial Reference Frame (IRF) and in motion in another IRF where the two IRF's are related by the Lorentz Transformation.

 

[Dale]

I quit.

Very well. Should you ever try to think about an experiment that can distinguish between LET and the block universe then I will be glad to discuss that with you.

Please continue your mathematical discussions here

And please continue your philosophical discussions elsewhere.

 

[TheBC]

Very well. Should you ever try to think about an experiment that can distinguish between LET and the block universe then I will be glad to discuss that with you.

And please continue your philosophical discussions elsewhere.

I cannot follow your reasoning. Correct me if I am wrong, but you are the one considering ether (LET) a valid SR alternative, hence you first have to give me an experiment/observation/measurement of (any specific aspect of) the ether.

If you consider an ether but can not detect one, then you are into philosphy, not me.

Again, I'm afraid we are really talking past each other at a very basic level... ;-)

 

[Fredrik]

I cannot follow your reasoning. Correct me if I am wrong, but you are the one considering ether (LET) a valid SR alternative, hence you first have to give me an experiment/observation/measurement of (any specific aspect of) the ether.

If you consider an ether but can not detect one, then you are into philosphy, not me.

Again, I'm afraid we are really talking past each other at a very basic level... ;-)

I think DaleSpam has made it clear that he doesn't consider LET an alternative to SR. He considers LET and "the block universe" two different interpretations of SR. So LET is an alternative to the block universe interpretation, but not an alternative to SR. As I said earlier...

Theories by definition make predictions about results of experiments. Interpretations by definition do not. This means that experiments can support or falsify a theory, but they can't favor an interpretation over another.

 

[DrGreg]

I cannot follow your reasoning. Correct me if I am wrong, but you are the one considering ether (LET) a valid SR alternative, hence you first have to give me an experiment/observation/measurement of (any specific aspect of) the ether.

When Einstein first considered SR a valid alternative to ether (LET), did he (or anyone else) first have to give an experiment/observation/measurement to favour SR over LET? No such experiment has ever been found.

You can reject LET on grounds of aesthetics (Occam's razor) or philosophy. I certainly do and my impression is that almost everybody else does too. But you can't reject it on grounds of mathematical logic or experimental evidence, because the logic is correct and nobody has found any experiment to disprove one interpretation while confirming the other.

If you consider an ether but can not detect one, then you are into philosphy, not me.

Note that LET says that the ether can't be detected, so any experiment that fails to detect it is compatible with the theory!

 

[bobc2]

I cannot follow your reasoning. Correct me if I am wrong, but you are the one considering ether (LET) a valid SR alternative, hence you first have to give me an experiment/observation/measurement of (any specific aspect of) the ether.

If you consider an ether but can not detect one, then you are into philosphy, not me.

Again, I'm afraid we are really talking past each other at a very basic level... ;-)

TheBC, I must admit that you have a reasonable point here. There is nothing in special relativity that implies an aether. In fact any theory involving ether requires a mechanism to account for such things as length contraction. But the only mechanism that has ever been advanced in a LET theory applies in one direction only—in direct contradiction to special relativity which results in observer A (at rest relative to observer B) finding that observer B’s length is contracted, while observer B finds observer A’s length to be contracted. With a LET mechanism, both observers find B to be contracted if A is at rest in ether. Now, some will claim that is irrelevant since modern LET applies the Lorentz transform in both directions, the same as special relativity.

But, then all you have is special relativity with ether arbitrarily thrown in. And no further basis is provided other than Poincare’s assertion that there must be an ether for light to wave in.

Contrast that with Paul Davies’s presentation that shows block universe as a direct manifestation of the Lorentz transformations. Once the Lorentz transformations are proven experimentally, then the block universe follows as a direct result of the transformations.

LET (neither the mechanism nor the ether) certainly does not manifest itself as a direct result of Lorentz transformations in this manner. That’s why most physicists (including Einstein) referred to LET as an “Ad Hoc” theory (something made up just to fit this purpose).

 

[TheBC]

When Einstein first considered SR a valid alternative to ether (LET), did he (or anyone else) first have to give an experiment/observation/measurement to favour SR over LET? No such experiment has ever been found.

What is this for skew logic? SR shows ether is not necessary. If you can not give any observation/measurement of any specific aspect of ether or enything else, then it is not an option.

You can reject LET on grounds of aesthetics (Occam's razor) or philosophy. I certainly do and my impression is that almost everybody else does too. But you can't reject it on grounds of mathematical logic or experimental evidence, because the logic is correct and nobody has found any experiment to disprove one interpretation while confirming the other.

Note that LET says that the ether can't be detected, so any experiment that fails to detect it is compatible with the theory!

So you have a theory that considers anything that can not be measured/detected as a valid interpretation? Hilarious.
If you can not detect ether it is scientifically irrelevant, non existent. Philosophy.
SR is 4D block spacetime. You cannot cut that part. What else would be SR? Just mathematics and everything else is philosophical interpretation? Again, then science = philosophy. That's when I quit.

 

[Fredrik]

If you can not detect ether it is scientifically irrelevant,

Everyone agrees with this part.

SR is 4D block spacetime.

"The block universe" (not to be confused with Minkowski spacetime) is just an interpretation too. A special relativistic theory is defined by the mathematical definitions of things like Minkowski spacetime and proper time, and some correspondence rules that tell us how to interpret the mathematics as predictions about results of experiments. Special relativity is the framework in which special relativistic theories is defined.

An interpretation of a theory is an attempt to state explicitly what the theory is suggesting about what reality is really like. LET may have started as a "theory" (something that can be used to make predictions), but the proper way to view it today is as an interpretation of SR. This is what DaleSpam is doing.

The block universe interpretation is (roughly) the idea that reality is like a 4-dimensional "painting" that's already finished. An object's entire existence is just a bunch of lines in that painting, and the idea of a "now" (objective or subjective) is an illusion.

People usually associate this idea with SR, but pre-relativistic classical theories can be interpreted this way as well.

You cannot cut that part. What else would be SR? Just mathematics and everything else is philosophical interpretation? Again, then science = philosophy. That's when I quit.

No one is saying that "science=philosophy".

 

[DrGreg]

SR shows ether is not necessary. If you can not give any observation/measurement of any specific aspect of ether or enything else, then it is not an option.

Just because something isn't necessary doesn't prove it doesn't exist.

Perhaps you missed the part where I said I reject LET. But the reason I reject it isn't mathematical logic or experiment, as there is no evidence from either of those. Lack of evidence isn't evidence of a lack. Ultimately I reject it because I don't like it and I like Einstein's interpretation much better.

 

[ghwellsjr]

So you have a theory that considers anything that can not be measured/detected as a valid interpretation? Hilarious.

Special Relativity is a theory that has something that cannot be measured/detected--the propagation of light being c in any Inertial Reference Frame (IRF), just like LET which only claims that light propagates at c only in one IRF. If SR is consistent with anything that can be measured/detected then it affirms LET, doesn't it?

Or did you think that there was a way to measure/detect the propagation of light apart from postulating/defining/assuming/stipulating that it is c in any IRF?

 

[ash64449]

Ultimately I reject it because I don't like it and I like Einstein's interpretation much better.

you cannot reject because you do not like it. If LET makes prediction different from that of SR,we need to conduct experiment and need to look whose prediction nature follows. And then only we can reject a theory.

 

[DrGreg]

you cannot reject because you do not like it.

But LET is only an interpretation of a theory. I'm not rejecting any theory. I don't like the interpretation and prefer Einstein's interpretation of the same theory. It doesn't matter whether I reject it or not because both interpretations are fully compatible with experiment. And it's not a permanent rejection. If anybody found any evidence that the LET interpretation was superior to Einstein's, I'd change my mind.

In fact "reject" is too strong a word. I really mean "dismiss as irrelevant for me".

If LET makes prediction different from that of SR...

It doesn't, at least not for anything you can measure experimentally.

 

[Dale]

Again, I'm afraid we are really talking past each other at a very basic level... ;-)

I agree. However, others such as Fredrik and DrGreg clearly understand my posts, so I don't think that the communication breakdown is on my end.

I cannot follow your reasoning. Correct me if I am wrong, but you are the one considering ether (LET) a valid SR alternative

As Frederik mentione LET is not an alternative to SR, it is an interpretation of SR, just like the block universe is another interpretation of SR. Do you understand the difference between an "alternative theory" and an "interpretation of a theory"?

hence you first have to give me an experiment/observation/measurement of (any specific aspect of) the ether.

According to LET things moving through the aether length contract and time dilate such that the transformation between inertial frames is given by the Lorentz transform. Therefore all of these experiments can be taken as experimental confirmation of LET: http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html

Furthermore, my only claim is that no experiment is possible which favors the block universe interpretation of SR over the LET interpretation of SR. This claim can be proven mathematically by the simple fact that both interpretations use the Lorentz transforms to make all of their experimental predictions, therefore since they use the same equations they make the same predictions. If you dispute that claim then on what grounds do you dispute it?

 

[Dale]

SR is 4D block spacetime. You cannot cut that part. What else would be SR? Just mathematics and everything else is philosophical interpretation?

SR (the theory, not any interpretations of the theory) consists of the Lorentz transforms and a set of rules about how the terms in the equations correspond to experimental results. For example, there is a rule (called the Einstein synchronization convention) about how to take a set of standard clocks and rods and use light signals to synchronize them such that the values on the clocks and the rods correspond to the variables in the Lorentz transform. That is SR.

Whenever you take that and go beyond it to claim "reality is a 4D block universe" or "reality is a 3D universe with a Lorentzian aether" then you are doing philosophy. Note the use of the philosophical term "reality", which is a strong indication that the following statements are philosophical, not scientific.

 

[Dale]

you cannot reject because you do not like it.

You cannot reject a theory because you do not like it. But LET is not a theory, it is an interpretation of a theory. You can reject or accept interpretations for any reason or no reason at all, and you can change which interpretation you use at will.

My personal recommendation is to learn all of the interpretations of any theory you use, and use whichever interpretation is most practical for the scenario at hand. With SR, I tend to use LET for relativistic Doppler problems, and block universe for everything else.

Do you understand the difference between a theory and an interpretation of a theory?

 

[bobc2]

Therefore all of these experiments can be taken as experimental confirmation of LET: http://www.edu-observatory.org/physics-faq/Relativity/SR/experiments.html

These experiments confirm special relativity. I challenge the assertion that LET is an interpretation of special relativity. LET theory does not apply the Lorentz transformations symmetrically. The object moving with respect to ether is always the contracted object in LET theory. This contradicts special relativity. So far as I am aware, no one has ever cited a paper that derives a mechanism for relativistic contraction that is applied symmetrically.

That may be why Rindler wrote in his special relativity textbook that LET has faded into oblivion and why DrGreg and others dismiss LET.

 

[TheBC]

These experiments confirm special relativity. I challenge the assertion that LET is an interpretation of special relativity. LET theory does not apply the Lorentz transformations symmetrically. The object moving with respect to ether is always the contracted object in LET theory. This contradicts special relativity. So far as I am aware, no one has ever cited a paper that derives a mechanism for relativistic contraction that is applied symmetrically.

That may be why Rindler wrote in his special relativity textbook that LET has faded into oblivion and why DrGreg and others dismiss LET.

This is what I referred to in my post #34,last paragraph:

If LET is a melting pot of 4D spacetime and 3D aether space, then LET is simply an awful attempt to mix dynamical ether effects in one frame and pure 4D spatio-temporal 4D effects in another. It would mean that in one frame one has to accept that the origin of contraction and dilation is dynamical, and in the other frame the cause is not dynamical but pure spatio-temporal. Two different causes in one theory that has the intention to show how all laws are physical equal in all frames.

Can this be considered a valid interpretation for SR?

 

[Dale]

These experiments confirm special relativity.

Yes, the experiments confirm SR and LET is an interpretation of SR. An experiment which confirms a theory can be taken as evidence for any or all of its interpretations.

I challenge the assertion that LET is an interpretation of special relativity. LET theory does not apply the Lorentz transformations symmetrically. The object moving with respect to ether is always the contracted object in LET theory. This contradicts special relativity.

Contradicts? In what way? Not experimentally, which is what makes it an interpretation.

 

[Dale]

This is what I referred to in my post #34,last paragraph:

Can this be considered a valid interpretation for SR?

Yes.

 

[bobc2]

Yes, the experiments confirm SR and LET is an interpretation of SR. An experiment which confirms a theory can be taken as evidence for any or all of its interpretations.

Contradicts? In what way? Not experimentally, which is what makes it an interpretation.

Yes. Contradicts. Notice in the Minkowski Space-Time sketch below that Einstein's special relativity applies the Lorentz transformation between blue and red symmetrically. The LET theory applies the theory in one direction for an object at rest with respect to ether and another object in motion relative to ether. So, the space-time diagram would not look the same.

Even though you never know if an object is at rest with respect to the ether, the transformation would still not be applied symmetrically. The object moving faster relative to the ether is still more contracted than the slower moving object.

Now, if you assert that I'm just resurrecting the old LET, then my response is that your new LET is nothing more than special relativity with a postulate that there is an ether. However, in that case, you cannot maintain that LET is an interpretation of special relativity, because special relativity in no way implies an ether.

However, special relativity certainly implies a 4-dimensional space-time universe.

 

[ash64449]

You cannot reject a theory because you do not like it. But LET is not a theory, it is an interpretation of a theory. You can reject or accept interpretations for any reason or no reason at all, and you can change which interpretation you use at will.

But only one interpretation can be correct or only accepted by nature. I know we can explain data in many ways.but nature follows only one of those interpretations. So we need to look for more predictions made by those two different interpretation and look whether they make different predictions. If we find it,then check which one nature follows. So You cannot reject interpretation at your will. Only by more and more expreiment we can reject it.

My personal recommendation is to learn all of the interpretations of any theory you use, and use whichever interpretation is most practical for the scenario at hand. With SR, I tend to use LET for relativistic Doppler problems, and block universe for everything else.

And wherever we go,try to find different predictions made by those interpretation,and if we failed to do find,it is more likely that both interpretations are one and the same.

Do you understand the difference between a theory and an interpretation of a theory?

Of course,I know.

 

[DrGreg]

So we need to look for more predictions made by those two different interpretation and look whether they make different predictions.

But we have looked and there are none.

I don't mean there might be some but we haven't found any yet. I mean that we have proved mathematically that both interpretations always make exactly the same predictions about any raw measurements that you could make in an experiment.

The two interpretations do differ over things that you calculate from the raw measurements but can never measure directly, such as "time dilation".* But those are internal details of the interpretation that are never visible on the outside.

But only one interpretation can be correct or only accepted by nature. I know we can explain data in many ways.but nature follows only one of those interpretations.

That's just your belief. It's not a fact. Nature doesn't understand any interpretations, it just does what it does.

_____

*In case anyone finds this confusing, I don't mean the sort of cumulative clock difference that occurs in the twins paradox, which is experimentally measurable without any theory. I mean an instantaneous comparison of clock rates, which depends on coordinates and synchronisation conventions, which can only be calculated within the context of a particular theory or interpretation.

 

[Dale]

Yes. Contradicts. Notice in the Minkowski Space-Time sketch below that Einstein's special relativity applies the Lorentz transformation between blue and red symmetrically. The LET theory applies the theory in one direction for an object at rest with respect to ether and another object in motion relative to ether. So, the space-time diagram would not look the same.

OK, the spacetime diagram would not look the same. I assume that you mean that in LET the only "real" spacetime diagram is the one in the aether frame. If so then I agree. But the spacetime diagram is a calculation tool, not an experimental outcome. In the aether frame the spacetime diagram is the same for the block universe and LET and all experimental outcomes can be calculated in that one frame and all experimental outcomes will agree between the two interpretations. So the contradiction is not experimental.

you cannot maintain that LET is an interpretation of special relativity, because special relativity in no way implies an ether.

Of course SR in no way implies an ether. Theories never imply their interpretations. If they were implied then they would be consequences of the theory, not interpretations.

However, special relativity certainly implies a 4-dimensional space-time universe.

It certainly does not. The existence of a second interpretation proves that. If the block universe were implied then there could be no other interpretation.

 

[Dale]

So we need to look for more predictions made by those two different interpretation and look whether they make different predictions.

If they make different predictions then they are different theories, not different interpretations. By definition two interpretations make ALL of the same predictions.

So You cannot reject interpretation at your will. Only by more and more expreiment we can reject it.

There is never any possible experiment which distinguishes two interpretations, by definition. So you cannot use "more and more experiment" as a criterion for rejecting. Since both interpretations are equally valid experimentally the choice between them is entirely a matter of personal preference.

 

[ghwellsjr]

I have redrawn your Loedel diagram as a conventional Inertial Reference Frame (IRF) to show how the red observer comes to the conclusions that you describe in your Loedel diagram. In my diagram, both observers are moving at 0.5c in opposite directions which gives them a relative speed of 0.8c and a gamma factor of 1.667 and an inverse gamma factor of 0.6. I am using one foot per nanosecond as the speed of light:

The thin red lines represent three radar measurements that the red observer makes which he calculates to have been applied all at the same time. Recall that a radar measurement is assumed to have been applied at the midpoint in time between when the radar signal was sent and when it was received and the distance measured is one half the difference in those two times multiplied by the speed of light. So the three distance measurements are 8, 5.5 and 4 feet in the order that the signals are sent (and the opposite order that their reflections are received). I have drawn in a green line that connects red's time at which red calculates that all these measurements were made with the distant events at which those measurements were calculated to have "happened".

Red calculates that the length of blue's rod is 8-5.5=2.5 feet.
Red calculates that the length of his own rod is 4 feet (his last measurement).
Red calculates that Blue's clock was at 6 nanoseconds when his own clock was at 10 nanoseconds (this is what the green line shows).

All of these calculations are based on red's assumption that the time that it takes for each radar signal to hit its target is the same as the time it takes for the reflection to return--identical to Einstein's synchronization convention. Note that red cannot tell the coordinate times that are assigned by this IRF. In fact, we could transform this IRF into the IRF in which red is at rest and then his assumption would match his rest IRF and his calculations would match the coordinate times and distances.

I could also show similar radar measurements for blue and they would be mirror images of red's with identical calculations.

I take issue with the comments in your drawing that the each observer can see the other ones time dilation and length contraction.

For example, you state:

When the red guy is at his worldline event with his clock reading t₂ [10 nSec], he (red) sees blue's clock reading t₁ [6 nSec].

This is false. The red guy doesn't see blue's clock reading 6 nSec until his own clock reads 18 nSec and only then is he able to make the calculation that I described earlier that allows him to conclude that blue's clock was at 6 nSec when his was at 10 nSec based on his assumption regarding the speed of light.

 

[TheBC]

As Frederik mentione LET is not an alternative to SR, it is an interpretation of SR, just like the block universe is another interpretation of SR. Do you understand the difference between an "alternative theory" and an "interpretation of a theory"?

LET = Lorentz Ether Theory

 

[TheBC]

Yes.

In LET in one frame the origin of contraction and dilation is dynamical, and in the other frame the cause is not dynamical but pure spatio-temporal. Two different causes in one theory/interpretation that has the intention to show how all laws are physical equal in all frames.

In LET there is a built-in asymmetry that's not present in SR at all. How can LET then be a valid 'interpretation'?
Block universe does not have any asymmetry...