SR, LET, FTL & Causality Violation

[stglyde]

@stglyde, I know you defined it in the Beyond forum thread. But just for clarity, could you (since you are the OP) please state the definition of LET we are using in this thread? Is LET a Poincare invariant set of laws stated in a particular Lorentz inertial frame?

You seem to be saying that LET is just a temporary way of looking at SR without thinking hard about the essence of LET. Like simply thinking "In LET, the aether frame is one particular inertial frame." Then full stop. I've been thinking about your mode of thinking the past two days and wondering if you merely do it because you don't want to think further. I wonder if this is what LET as thought by all other physicists too or only your way of thinking? Can others verify?

 

[PeterDonis]

The question is not of their equivalence, of which I am not disputing. Rather, I am speaking of their ability to co-vary with respect to motions relative to the aether. If the former increases by 1 part in a billion, then so should the other.

I'm still confused. Are you saying that LET *is* consistent with the equivalence of inertial and gravitational mass? Or that it isn't? Or are you not sure?

 

[PeterDonis]

But philosophy makes difference in the domain where theory breaks down and you have to make adjustments to it. In case of LET and SR it would be when you bring gravity into the picture.

Are you saying that there is an extension of LET that covers gravity, as GR is an extension of SR that covers gravity, but which gives different predictions than GR? Can you elaborate?

You seem to be saying that LET is just a temporary way of looking at SR without thinking hard about the essence of LET.

The "essence of LET", if it's anything more than just a "way of looking at SR", is up to the proponents of LET to define. For example, see the question I just asked zonde above. If LET is more than just an "interpretation", it has to make different predictions than the "standard" theories (SR and GR) at some point. That means somebody has to work out an LET theory that makes such predictions. Is there such a theory? I haven't seen one, but if there is one, feel free to give references.

 

[Dale]

For LET to be even thinkable. The aether must be consistent and ponderable. But can the aether really do such?

I assume that by the word "ponderable" you mean "experimentally detectable". If that is the case, then by your criteria LET is not even thinkable.

So what kind of aether is it or what must it be composed of for LET to be even acceptable by physicists?

To be acceptable by physicists it simply needs to match experimental results. In every experiment done so far, every aether which is experimentally different from no aether fails to match experimental results. So the only kind of aether which remains acceptable to physicists is the one that is experimentally identical to no aether.

 

[stglyde]

I'm confused. If LET shares the same transform as SR then what about this:

"About v = (V + dv) - (V - dv) = 2dv = 0.866c

Note that the aetherial speed V factored out."

As DaleSpam pointed out, this is not the correct velocity addition law. If LET uses the same transform as SR does, then it uses the same velocity addition law as SR does. That means you can't cancel out the V in the above.

V is a symbol for velocity it is not a formula. Let's say you have
three speeds V1, V2, v.

V2 > V1 > v


Object A is V1, object B is V2. Assume object A is our baseline
so,


v = V2 - V1


and therefore,


V2 = V1 + v


Where is your problem?

Also, you're talking a lot about "actual" or "real" things that can never "actually" or "really" be measured; for example:



Which can't be determined because we can't know which frame is the aether frame. So what's the point of talking about it? SR accounts for all our observations without having to even worry about the fact that we can never figure out what our "actual" state of motion is.

Perhaps SRists are like the Midieval Clerics who refused to look into Galileo's telescope because they already knew what the would see. BUT! to most rational people the CMB is the background of the aether see the references provided below in post to Dalespam. So, contrary to your proclimation one can do so if they so choose.

 

[stglyde]

"Change of heart" is overstated. I would make a minor adjustment to language. SR has relativity of simultaneity, LET has relativity of local simultaneity. They both come from the Lorentz transform.

I have said so myself several times.

No we don't know that. That is purely speculation/assumption. Since we cannot measure the velocity of any frame wrt the aether we cannot know that the CMBR is at rest wrt the aether.

Please find a mainstream science reference where a GR analyst states that their reason for using the CMBR as a reference frame is because it is Lorentz's aether frame. Otherwise don't make such a claim.

How about 855 of them? Samples like:

http://arxiv.org/PS_cache/arxiv/pdf/1011/1011.6466v2.pdf
http://arxiv.org/PS_cache/arxiv/pdf/1004/1004.2901v1.pdf
http://arxiv.org/PS_cache/arxiv/pdf/0808/0808.2673v1.pdf


http://arxiv.org/PS_cache/arxiv/pdf/0806/0806.1731v2.pdf


"One usually analyzes the change in resonator frequency as a function of the Poynting vector direction with respect to the velocity of the lab in some preferred frame, typically chosen to be the cosmic microwave background."


http://arxiv.org/PS_cache/arxiv/pdf/0812/0812.1050v2.pdf


"We now turn to the evolution of the sigma-model in a cosmological background. It is usually assumed in the literature that the the preferred frame coincides with the cosmological rest frame"

I would also still like to see a reference that shows that LET does not use the relativistic velocity addition formula.

Another interesting tidbit LR does not have length contraction for 'empty space', only for moving sources and matter. Thus the Bell spaceship issue is readily explained by this. But, I see no problem with this.

I showed the math above. If you disagree then please post your work.

That math is based upon what? Where are the measurements to be evaluated? It's back to the firecracker issue. I'm sorry that you cannot tell the difference between perception, a.k.a.
'determined' states and actual ones.

In LET, if something is always a tachyon relative to its emitter then it is always possible to find an emitter from which it will go backwards in time in the aether, and violate causality. Conversely, if something is a tachyon only wrt to the aether then it is always possible to find a local frame in which it goes backwards in time, but it will not violate causality.

Not so. First, BY DEFINITION! FTL is outside the specified domain of LET. This is like trying to use the Lorentz transform for v > c. There are no real solutions. This tells you something critical,
you need an description (equations) for these conditions. It's not in LET or SR and thus trying to describe behavior based on those is folly.

 

[PeterDonis]

Not so. First, BY DEFINITION! FTL is outside the specified domain of LET. This is like trying to use the Lorentz transform for v > c. There are no real solutions.

You're mis-stating the limitations here. You can't use Lorentz transformations to transform spacelike vectors to timelike vectors or vice versa. And the Lorentz gamma factor is imaginary for v > c. But neither of these things prevent us from treating tachyons theoretically. All they mean is that tachyons must have spacelike worldlines in all frames, and that there is no such thing as the "rest frame" of a tachyon. This in no way puts tachyons "outside the specified domain" of SR (or LET, at least to the extent that LET makes the same predictions as SR).

 

[atyy]

You're mis-stating the limitations here. You can't use Lorentz transformations to transform spacelike vectors to timelike vectors or vice versa. And the Lorentz gamma factor is imaginary for v > c. But neither of these things prevent us from treating tachyons theoretically. All they mean is that tachyons must have spacelike worldlines in all frames, and that there is no such thing as the "rest frame" of a tachyon. This in no way puts tachyons "outside the specified domain" of SR (or LET, at least to the extent that LET makes the same predictions as SR).

One of the things I'm not sure of is whether LET (defined as a set of Poincare invariant dynamics in a particular Lorentz inertial frame) has SR tachyons. I think of LET as say Maxwell's equations in old fashioned E and B fields, ie. a set of dynamical equations. But how does one formulate dynamical equations for tachyons? I don't think "tachyonic" wave equations give the same thing as SR particle tachyons.

 

[Aether]

Perhaps SRists are like the Midieval Clerics who refused to look into Galileo's telescope because they already knew what the would see.

LETists don't have any better telescopes than do the SRists. Both would have to look into a GRists telescope if they wanted to understand things like the CMB for example.

BUT! to most rational people the CMB is the background of the aether see the references provided below in post to Dalespam. So, contrary to your proclimation one can do so if they so choose.

You need to use GR if you want to understand the CMB. The CMB is not "the aether". The CMB is a field of photons that were last scattered about 300,000 yrs after the big bang.

 

[atyy]

Some people do refer to the CMB as "aether". In Smoot's lecture, he says "One application that Peebles laid out was entitled “The Aether Drift Experiment” in which one could use the CMB (zero net momentum of the radiation frame) as a reference to measure one’s motion relative to the natural frame to describe the Big Bang expansion of the universe." Or more prosaically by Lineweaver: "The CMB gives all the inhabitants of the Universe a special common rest frame with respect to which all velocities can be measured - the comoving frame in which the observers see no CMB dipole. People who enjoy special relativity but not general relativity often baulk at this concept." However, the CMB is not the aether of LET (defined as Poincare invariant dynamics stated in a particular inertial frame), neither is it the aether of Ted Jacobson's Einstein-Aether theory.

 

[Aether]

The comoving frame in which all observers see a homogeneous and isotropic universe could also be considered as such a universal landmark frame. So, which one is "the aether" frame? Neither one really, but in the transition to GR some of the sterile concepts of SR get relaxed.

 

[PeterDonis]

One of the things I'm not sure of is whether LET (defined as a set of Poincare invariant dynamics in a particular Lorentz inertial frame) has SR tachyons. I think of LET as say Maxwell's equations in old fashioned E and B fields, ie. a set of dynamical equations. But how does one formulate dynamical equations for tachyons? I don't think "tachyonic" wave equations give the same thing as SR particle tachyons.

The Usenet Physics FAQ has a useful (if brief) discussion:

http://www.desy.de/user/projects/Physics/ParticleAndNuclear/tachyons.html

It talks about "tachyonic" solutions of the Klein-Gordon equation (which is a sort of analogue to Maxwell's equations for a spin-zero particle), and concludes:

"The bottom line is that you can't use tachyons to send information faster than the speed of light from one place to another. Doing so would require creating a message encoded some way in a localized tachyon field, and sending it off at superluminal speed toward the intended receiver. But as we have seen you can't have it both ways: localized tachyon disturbances are subluminal and superluminal disturbances are nonlocal."

 

[ghwellsjr]

The following inside the quotes is statements made by ghwellsjr. Since Dalespam, PeterDonis shares the same views as ghwellsjr, then please address them as well.

In "your inertial frame", meaning in a frame in which you are at rest, you are not experiencing length contraction (or time dilation) and that is the reason why everything is normal to you. It would be just like if you happened to be at rest in the one and only aether frame, wouldn't it?

In LET YES, you are experiencing distortions of time & space. He explicitly talks about this as the 'local frame', try actually reading his paper:

http://www.dwc.knaw.nl/DL/publications/PU00014148.pdf


What seem to fail to grasp is you're Dirac's fish in this case... As said, you can pretend your frame is the aether rest frame for the convenience of computing offset into other moving systems SINCE only delta or relativie velocities matter to these computations. This is why we use the ECI and GR analyst use the CMBR as preferred baselines.

Are you saying that you know the rest state of the aether and that's why you can say that we can only pretend our frame is the aether rest frame? Otherwise, how do you know our frame is not the actual aether rest frame? And if you don't know, then how do you know what offset or delta or relative velocities to use?

BTW: what is Dirac's fish and what is ECI?

But those other people traveling with respect to you, and therefore with respect to the aether (if you want to think of it this way), will be experiencing length contraction and time dilation but they won't know it because their rulers are contracted along the direction of motion and their clocks are running slow. Now when they view you, still while in your rest frame, they will measure you to be length contracted and time dilated.

You do seem to love seeing is somehow believing. Any magician wants an audience filled with people like you.

I never realized that making measurements was such an unscientific thing to do.

One way to help understand this is to consider what happens when they approach you and pass right by you. If you had identical spaceships, you could each measure the length of other one by seeing how long it takes the front of each spaceship to traverse the distance from the front of the other one to its rear. Since you are at rest with respect to the chosen frame, you are not experiencing length contraction or time dilation so the time according to your clock that it takes the other ship to pass you multiplied by its speed gives you its length.

But both can certainly be distorted. This is the crux of the pole in the barn paradox case. There are no such paradoxes in LET. What is physically real is based solely upon thec total velocity of each object wrt to the local background. There length in the direction of mation and the tick rastes of their clocks. This way it sucked to be A in that tachyon duel :). He NEVER HAD A CHANCE!

So you call making measurements with rulers and clocks a distortion? There are also no such paradoxes in SR if you stick with one frame. Paradoxes come from using distances and times for one object from one frame of reference and distances and times for another object from a different Frame of Reference and combining them.

Now they are doing the same thing with respect to you but remember this will all be considered from the same frame where their ship is length contracted and their clocks are running slow. Now when they are at the front of your spaceship, they note the time on their clock (just like you are doing). Then some time later, when they reach the rear of your ship, they make another note of the time on their clock. Since their clock is running slow, they will get a smaller value than they otherwise would and when they do the division, they conclude that it is your spaceship that is length contracted. See how this works? All in a single arbitrarily chosen inertial frame.

This is where SR & LET's domsins overlap. It takes T I M E for signals to go from one point in space to any other. ThustThe coordinate offsets are related by the same transformations. Thus the observed as in 'determined' behavior AS SEEN! is descibed by those equations. But, in Lorentzian Relativity (LR) seeing is just that, seeing, and not actual reality. Thus there are no possibility of symmetry or paradoxes or time reversals or meeting oneself by FTL travel. Time's arrow is 'actually' never affected by any speed.

There's no time delay in the measurement I described. There's also no need for either observer to establish any Frame of Reference or adhere to any developed theory such as LET or SR when making the measurement. There's no transformations, no coordinates, no offsets. Just measure how long it takes each ship to pass the other. They both get the same answer, even though one of them is stationary in the aether rest frame and one of them isn't (although they don't need to know that).

So even though they are the ones that are length contracted, they still think you are the one that is length contracted. Every measurement that you make of them, they will make of you, even though they are the ones that are "really" experiencing length contraction and time dilation, so it's impossible to tell who really is at rest with respect to the aether.

I think you need a better understanding Lorentz's version. To master an opponent you
must know thine enemy. Therefore understand the underpinning of both SR and LR. Just FYI superluminal (sL) velocities are allowed in both LR and LR BUT! if it happens both are moot on describing its behavior. LR has a patheway for extension which I cannot see for SR. Given the observance of Chererov radiation in media the LR extension has some basis in observation behavior.

Do you agree that Lorentz and others before Einstein believed that light traveled at c only in the aether rest state? Do you agree that they could not identify the aether rest state? Do you agree that they believed that any actual inertial state that they were in was definitely not the aether rest state?

 

[Dale]

How about 855 of them?

One that actually makes the point and is mainstream would be sufficient. Not one of these references actually demonstrates that some GR analyst states that their reason for using the CMBR as a reference frame is because it is Lorentz's aether frame.

http://arxiv.org/PS_cache/arxiv/pdf/1011/1011.6466v2.pdf

Is about Einstein-aether (gravitational aether) theory, not LET (luminiferous aether).

http://arxiv.org/PS_cache/arxiv/pdf/1004/1004.2901v1.pdf

Not published in a mainstream journal, and is about a gravitational aether, not a luminiferous aether.

http://arxiv.org/PS_cache/arxiv/pdf/0808/0808.2673v1.pdf

Explicitly looking for Lorentz-violating terms incompatible with LET.

http://arxiv.org/PS_cache/arxiv/pdf/0806/0806.1731v2.pdf

Only aether theories it mentions are Lorentz-violating.

http://arxiv.org/PS_cache/arxiv/pdf/0812/0812.1050v2.pdf

Is about sigma-model aether, not LET.

That math is based upon what? Where are the measurements to be evaluated?

That results were in the aether frame. The tachyon went backwards in time in the aether frame as determined by the Lorentz transform and as determined by the relativistic velocity addition formula.

Not so. First, BY DEFINITION! FTL is outside the specified domain of LET.

Interesting. Then why did you start this thread.

This is like trying to use the Lorentz transform for v > c. There are no real solutions. This tells you something critical,
you need an description (equations) for these conditions. It's not in LET or SR and thus trying to describe behavior based on those is folly.

Let's carry your logic one step further. You also cannot use the Lorentz transform for v=c. So, does that imply that light is outside of the specified domain of LET and SR?

 

[Dale]

However, the CMB is not the aether of LET (defined as Poincare invariant dynamics stated in a particular inertial frame), neither is it the aether of Ted Jacobson's Einstein-Aether theory.

Exactly! And that is the point I specifically challenged him on.

 

[harrylin]

I assume that by the word "ponderable" you mean "experimentally detectable". If that is the case, then by your criteria LET is not even thinkable.

Note that then also Newton's mechanics (which is based on his "absolute space" postulate) is "not even thinkable"

To be acceptable by physicists it simply needs to match experimental results. In every experiment done so far, every aether which is experimentally different from no aether fails to match experimental results. So the only kind of aether which remains acceptable to physicists is the one that is experimentally identical to no aether.

Not really: without an ether and nothing to replace that concept (so that "empty space" is truly empty), there is nothing to control the properties of space - not even the speed of light. When he realized that simple fact (surprisingly that took him many years), Einstein made it the topic of an inauguration speech and he discussed it in several articles.

 

[harrylin]

Are you saying that there is an extension of LET that covers gravity, as GR is an extension of SR that covers gravity, but which gives different predictions than GR? [..] If LET is more than just an "interpretation", it has to make different predictions than the "standard" theories (SR and GR) at some point. That means somebody has to work out an LET theory that makes such predictions. Is there such a theory? I haven't seen one, but if there is one, feel free to give references.

Then perhaps Schmeltzer's GLET may be interesting to some people here. I think that his generic paper about it has not been published in a relevant journal (you can find it in Arxiv or on his web site); however, the following related paper (which regretfully is too technical for me) has been published in Foundations of Physics:
http://arxiv.org/abs/arXiv:0908.0591
Note: to see what the paper is really about, one should read its Introduction

 

[PeterDonis]

Then perhaps Schmeltzer's GLET may be interesting to some people here.

AFAICT from skimming the paper, this theory makes the same predictions regarding gravity as GR does; it just derives them by a different route. Also, I'm not sure whether this is actually an "LET" type theory; the paper does use the term "preferred frame" to describe the "unobservable" flat background spacetime that is used, but I'm not sure the theory actually requires that one particular "slicing" of the flat Minkowski background into space and time (i.e., one particular "frame") is privileged over all others as an "aether" frame. The theory may only require that the flat background is Minkowski, but still allow all inertial frames to be equivalent as ways of looking at that flat background.

 

[PeterDonis]

Not really: without an ether and nothing to replace that concept (so that "empty space" is truly empty), there is nothing to control the properties of space - not even the speed of light. When he realized that simple fact (surprisingly that took him many years), Einstein made it the topic of an inauguration speech and he discussed it in several articles.

This is a different use of the term "aether"; it's what DaleSpam referred to as "Einstein aether" or "gravitational aether" a couple of posts back. The LET use of the term "aether" is more than just saying there has to be "something" to control the properties of spacetime; it is saying that one particular slicing of that "something" into space and time, i.e., one particular "frame", is the "true" one.

 

[stglyde]

There's no time delay in the measurement I described. There's also no need for either observer to establish any Frame of Reference or adhere to any developed theory such as LET or SR when making the measurement. There's no transformations, no coordinates, no offsets. Just measure how long it takes each ship to pass the other. They both get the same answer, even though one of them is stationary in the aether rest frame and one of them isn't (although they don't need to know that).

Are you saying that regardless of whether one can detect the aether rest frame or not, the results are the same with each of the ship in relative motion measuring time dilation and length contraction in the other ship.. or would everything change if there was a way to detect the aether rest frame (just for sake of discussion).. meaning one of the ship would establish physical time (since it could determine it is the one at rest with respect to the aether) and the other apparent time (because it knows it is in motion with respect to the aether hence is the one contracted or time dilated)? How then would the results differ to the case when they couldn't detect the aether rest frame? What do you think PeterDonis, Dalespam and others?

 

[stglyde]

One that actually makes the point and is mainstream would be sufficient. Not one of these references actually demonstrates that some GR analyst states that their reason for using the CMBR as a reference frame is because it is Lorentz's aether frame.

I think the term 'preferred frame' for a universal background frame. Does anyone 'say' Lorentz aether frame? No, but there IS only one proposed physical medium called aether. GR-aether, Lorentz aether lumniferous aether are all just names for the very same thing.

Is about Einstein-aether (gravitational aether) theory, not LET (luminiferous aether).

Not published in a mainstream journal, and is about a gravitational aether, not a luminiferous aether.

Explicitly looking for Lorentz-violating terms incompatible with LET.

Only aether theories it mentions are Lorentz-violating.

Is about sigma-model aether, not LET.

That results were in the aether frame. The tachyon went backwards in time in the aether frame as determined by the Lorentz transform and as determined by the relativistic velocity addition formula.


Let's carry your logic one step further. You also cannot use the Lorentz transform for v=c. So, does that imply that light is outside of the specified domain of LET and SR?

It is the basis FOR these. Go look up the titles of the papers.

The CMB is certainly not the aether, it can however, by its very nature and composition illuminates that frame. No? And why?

 

[Dale]

I think the term 'preferred frame' for a universal background frame.

A frame may be "preferred" for many reasons. It could be preferred because the laws of physics are measurably different in that frame (a Lorentz violation), it could be preferred simply because computations are easier in it, or it could be preferred because it is Lorentz's aether. Simply saying the words "prefered frame" doesn't imply the LET aether.

Does anyone 'say' Lorentz aether frame? No, but there IS only one proposed physical medium called aether. GR-aether, Lorentz aether lumniferous aether are all just names for the very same thing.

No, they are not. They have different experimental predictions, therefore they are patently not the very same thing.

The CMB is certainly not the aether, it can however, by its very nature and composition illuminates that frame. No? And why?

No. By the nature of LET you can never test the supposition that the CMB is at rest wrt the aether.

 

[stglyde]

Are you saying that you know the rest state of the aether and that's why you can say that we can only pretend our frame is the aether rest frame? Otherwise, how do you know our frame is not the actual aether rest frame? And if you don't know, then how do you know what offset or delta or relative velocities to use?

First and foremost there is no global rest state for aether any more than there is for Eath's oceans or atmosphere. There is however always localized equalibrium but how large that region is completely depends on gradients in the region. But, if you 'assume' that your time and rulers are 'at rest' you assume they are not distorted. You have just normalized your system conceptually to the rest frrame state of the aether. Your definition of meter and second matched the aether's rest frame. IT NOT!, and your clocks and rulers are distorted by its motion
but you can certainly created a self consistent view which mimics the aether's actual rest frame. SR/GR call these 'proper' time & length.

BTW: what is Dirac's fish and what is ECI?

ECI -> Earth Centered Inertial look up the term

Dirac compared us to fish in the ocean. Since the ocean is such a natural element of the fishes enviorment the fish ignores and doesn't consider it.

So you call making measurements with rulers and clocks a distortion? There are also no such paradoxes in SR if you stick with one frame. Paradoxes come from using distances and times for one object from one frame of reference and distances and times for another object from a different Frame of Reference and combining them.

How do you measure a high speed object?

There's no time delay in the measurement I described. There's also no need for either observer to establish any Frame of Reference or adhere to any developed theory such as LET or SR when making the measurement. There's no transformations, no coordinates, no offsets. Just measure how long it takes each ship to pass the other. They both get the same answer, even though one of them is stationary in the aether rest frame and one of them isn't (although they don't need to know that).

And how exactly does one do that?

 

[ghwellsjr]

There's no time delay in the measurement I described. There's also no need for either observer to establish any Frame of Reference or adhere to any developed theory such as LET or SR when making the measurement. There's no transformations, no coordinates, no offsets. Just measure how long it takes each ship to pass the other. They both get the same answer, even though one of them is stationary in the aether rest frame and one of them isn't (although they don't need to know that).

Are you saying that regardless of whether one can detect the aether rest frame or not, the results are the same with each of the ship in relative motion measuring time dilation and length contraction in the other ship.. or would everything change if there was a way to detect the aether rest frame (just for sake of discussion).. meaning one of the ship would establish physical time (since it could determine it is the one at rest with respect to the aether) and the other apparent time (because it knows it is in motion with respect to the aether hence is the one contracted or time dilated)? How then would the results differ to the case when they couldn't detect the aether rest frame? What do you think PeterDonis, Dalespam and others?

I'm saying if there exists an aether rest state and if one observer is stationary in it (whether or not he believes he is) and if another observer is moving with respect to the aether (whether or not he believes he is), all measurements that each one makes will be identical. Each one will measure the same length contraction and time dilation in the other one to the same degree and none in themselves. That's the way our world is. It's the principle of relativity.

If it were possible to determine the absolute aether rest state, then both LET and SR would have to be discarded and who knows how things would be different? Both LET and SR share the same first postulate, the principle of relativity, but they have a different second postulate. LET's second postulate is that light travels at c only in a single aether rest state whereas SR's second postulate is that light travels at c in any rest state you choose. It is not possible to prove one of these postulates over the other. The choice is philosophical and a matter of convenience. However, in my opinion, if you believe in a single absolute aether rest state for philosophical reasons, I would still recommend SR as a matter of convenience.

 

[stglyde]

I'm saying if there exists an aether rest state and if one observer is stationary in it (whether or not he believes he is) and if another observer is moving with respect to the aether (whether or not he believes he is), all measurements that each one makes will be identical. Each one will measure the same length contraction and time dilation in the other one to the same degree and none in themselves. That's the way our world is. It's the principle of relativity.

You were saying above that if it were possible to determine the absolute aether rest state, then both LET and SR would still be compatible.

Yet you wrote in first sentence below that "If it were possible to determine the absolute aether rest state, then both LET and SR would have to be discarded.."

You gave conflicting accounts. So which of them do you really mean?

If it were possible to determine the absolute aether rest state, then both LET and SR would have to be discarded and who knows how things would be different? Both LET and SR share the same first postulate, the principle of relativity, but they have a different second postulate. LET's second postulate is that light travels at c only in a single aether rest state whereas SR's second postulate is that light travels at c in any rest state you choose. It is not possible to prove one of these postulates over the other. The choice is philosophical and a matter of convenience. However, in my opinion, if you believe in a single absolute aether rest state for philosophical reasons, I would still recommend SR as a matter of convenience.

 

[ghwellsjr]

You were saying above that if it were possible to determine the absolute aether rest state, then both LET and SR would still be compatible.

Where did I say that?

 

[stglyde]

Where did I say that?

You wrote the first paragraph ending with "It's the principle of relativity" which I assume is SR.

"I'm saying if there exists an aether rest state and if one observer is stationary in it (whether or not he believes he is) and if another observer is moving with respect to the aether (whether or not he believes he is), all measurements that each one makes will be identical. Each one will measure the same length contraction and time dilation in the other one to the same degree and none in themselves. That's the way our world is. It's the principle of relativity."

In other words. If there exists an aether rest state. They would still (as you said) "measure the same length contraction and time dilation in the other one to the same degree and none in themselves".

Hmm... perhaps I misunderstood what you wrote. What I meant was what if the aether rest state was "actually detected". So they would no longer measure the same length contraction and time dilation in the other one to the same degree and none in themselves?

 

[PeterDonis]

or would everything change if there was a way to detect the aether rest frame (just for sake of discussion)..

I don't see how to answer this question, since it makes two assumptions that I can't see how to deal with:

(1) It assumes an imaginary world in which the results of key experiments, such as the MMX, are different than they are in reality, but without specifying *how* they are different; for example "detecting the aether rest frame" would require a non-null result for the MMX, but *what* non-null result? Without some kind of constraint anything we say is just idle speculation.

(2) It assumes some kind of physical model that makes sense of the imaginary world, but without specifying that physical model; for example, what are the physical implications of a non-null result for the MMX? Without some kind of model to work from, we can't make any real predictions, and anything we say is just idle speculation.

In short, I don't think your question is well-defined, and making it well-defined seems like a lot of work.

 

[PeterDonis]

But, if you 'assume' that your time and rulers are 'at rest' you assume they are not distorted. You have just normalized your system conceptually to the rest frrame state of the aether. Your definition of meter and second matched the aether's rest frame.

How do you come to this conclusion? I don't have to make any such assumptions to make measurements. All I have to "assume" is that I can assign coordinates to events in my vicinity such that those coordinates approximate, to the level of accuracy I need, a local Lorentz frame. But I put "assume" in scare-quotes because as soon as I start to make measurements, I can test the assumption: do my measurements behave as they should for a local Lorentz frame given the coordinate assignments I make? If the answer is yes (which it is, to a good approximation), then I have all I need to do physics. No assumptions about lack of "distortion" or anything else come into it, certainly not assumptions about how my coordinates relate to any "aether".

 

[stglyde]

A frame may be "preferred" for many reasons. It could be preferred because the laws of physics are measurably different in that frame (a Lorentz violation), it could be preferred simply because computations are easier in it, or it could be preferred because it is Lorentz's aether. Simply saying the words "prefered frame" doesn't imply the LET aether.

No, they are not. They have different experimental predictions, therefore they are patently not the very same thing.

No. By the nature of LET you can never test the supposition that the CMB is at rest wrt the aether.

For Lorentz, there was only one frame in which light was isotropic c.

Thus, since the CMB IS light, and universally uniform, the rest frame for Lorentz's aether would be uniquely the one with no discernable Doppler. Agree?

As for Einstein view it matches Lorentz's, he writes,


"... and also introduce another postulate, which is
only apparently irreconcilable with the former,
namely, that light is always propagated in empty
space with a definite velocity c which IS independent
of the state of motion of the emitting body"


Note he does not use the word 'determined' or 'measured' but IS...!


He later states,


"Any ray of light moves in the “stationary” system of
co-ordinates with the DETERMINED velocity c, whether the
ray be emitted by a stationary or by a moving body."


We note here he is also very specific and uses the word 'determined'
NOT IS! when talking about a relative stationary system.

 

[atyy]

@stglyde, DaleSpam is right. The CMB is not any aether of LET. The CMB is also not predicted by SR. So both LET and SR are wrong when it comes to the CMB.

 

[stglyde]

@stglyde, DaleSpam is right. The CMB is not any aether of LET. The CMB is also not predicted by SR. So both LET and SR are wrong when it comes to the CMB.

But since the CMB IS light, and universally uniform, the rest frame for Lorentz's aether would be uniquely the one with no discernable Doppler. No? If no, why not?

As for Einstein view it matches Lorentz's, he writes,


"... and also introduce another postulate, which is
only apparently irreconcilable with the former,
namely, that light is always propagated in empty
space with a definite velocity c which IS independent
of the state of motion of the emitting body"


Note he does not use the word 'determined' or 'measured' but IS...!


He later states,


"Any ray of light moves in the “stationary” system of
co-ordinates with the DETERMINED velocity c, whether the
ray be emitted by a stationary or by a moving body."


We note here he is also very specific and uses the word 'determined'
NOT IS! when talking about a relative stationary system.

 

[stglyde]

I don't see how to answer this question, since it makes two assumptions that I can't see how to deal with:

(1) It assumes an imaginary world in which the results of key experiments, such as the MMX, are different than they are in reality, but without specifying *how* they are different; for example "detecting the aether rest frame" would require a non-null result for the MMX, but *what* non-null result? Without some kind of constraint anything we say is just idle speculation.

(2) It assumes some kind of physical model that makes sense of the imaginary world, but without specifying that physical model; for example, what are the physical implications of a non-null result for the MMX? Without some kind of model to work from, we can't make any real predictions, and anything we say is just idle speculation.

In short, I don't think your question is well-defined, and making it well-defined seems like a lot of work.

There is something I can't understand fully. Why can't the aether being detected not live side by side with relativity? For example. If two ships in inertial motion with respect to each other measure each others' time slowing down and length contraction. We can say that this occur with respect to each other. So even if they each can detect the aether rest frame. They are not using it to time or sychronize each other... or their inertial frames are not with respect to the aether rest frame. But with respect to each other. So they should still experience time dilation and length contraction in default mode unless they synchronize to the aether rest frame in which their results would be different.

 

[atyy]

But since the CMB IS light, and universally uniform, the rest frame for Lorentz's aether would be uniquely the one with no discernable Doppler. No? If no, why not?

Before we go on, you must define LET.

 

[stglyde]

Before we go on, you must define LET.

LET means Lorentz Ether Theory.. or the Theory of Ethers by Lorentz. But if you would insist of your definition of LET as special relativity in a particular Lorentz inertial frame and then full stop. Note it's only your definition as you see fit. Also in the real world. Minkowski space is replaced by curved differential manifold in GR.. so SR and LET are not even large scale but only valid in very tiny local region. Some even thought of adding GR to LET. This means your definition of LET is not universal but only your own (and a few others).