SR, LET, FTL & Causality Violation

[TrickyDicky]

What I mean (for some reason DaleSpam deleted his answer to my last post) is that I think stglyde is referring to the observed doppler dipole that is observed by COBE and WMAP and the fact that according to current mainstream knowledge this doppler shift would not be expected to be observed in the cosmological comoving frame, how is that doppler shift related to the last scattering surface source that is supposed to be taken care of by the fact the CMB photons are redshifted to microwave wavelengths?, seems to me a different altogether issue than what stglyde is referring to.

 

[PeterDonis]

the observed doppler dipole that is observed by COBE and WMAP and the fact that according to current mainstream knowledge this doppler shift would not be expected to be observed in the cosmological comoving frame

Yes (meaning the dipole, not the shift as a whole).

how is that doppler shift related to the last scattering surface source that is supposed to be taken care of by the fact the CMB photons are redshifted to microwave wavelengths?, seems to me a different altogether issue than what stglyde is referring to.

Because the process of the universe becoming transparent to photons took place homogeneously and isotropically throughout the universe. The "last scattering surface" marks the place (and time) where that process happened, and the CMB photons are the photons that have been traveling freely since the last scattering.

Put another way, in the "comoving" frame the process of "last scattering" took place at the same time everywhere (more precisely, since the process was not instantaneous, it started and ended at the same times everywhere). So the CMB photons coming from every direction have been traveling freely for (on average) the same amount of time. Since their redshift depends on how long they have been traveling freely (because it depends on how much the universe has expanded since they were emitted), the redshift will be (on average) isotropic in the "comoving" frame. In other words, no dipole is equivalent to saying that the "comoving" frame is the frame in which the last scattering was isotropic.

 

[TrickyDicky]

Hi, Peter, always glad to read your knowledgeable answers.

Yes (meaning the dipole, not the shift as a whole).

Sure, that was my meaning too, the dipole anisotropy from the Doppler shift of the background radiation due to the Earth's motion wrt the CMB frame as we both know.

In other words, no dipole is equivalent to saying that the "comoving" frame is the frame in which the last scattering was isotropic.

Oh, I think there's been some sort of misunderstanding. The dipole has nothing to do with the last scattering, it only reflects the relative motion of the Earth wrt CMB comoving frame.
I was merely trying to clarify that IMO the discussion in this thread was not related to the redshift of the CMB photons due to the cooling expansion, but that when stglyde talks about isotropy (he probably made a bad choice of words) he is not referring to the last scattering surface isotropy that is observed in the CMB maps after the dipole and the local sources have been cleaned off, but to the fact that an observer comoving with the CMB is not supposed to observe any dipole.
I thought Dalespam was mixing these and that's why i pointed it out.

 

[Dale]

for some reason DaleSpam deleted his answer to my last post

Sorry, I just decided I didn't want to get sidetracked and start a new chain of arguments.

 

[PeterDonis]

The dipole has nothing to do with the last scattering, it only reflects the relative motion of the Earth wrt CMB comoving frame.

Yes, but the fact that the CMB is isotropic in the comoving frame is due to the fact that the surface of last scattering is a surface of constant comoving time. And *that* fact is due to the fact that the process of "last scattering" occurred homogeneously and isotropically throughout the universe, which is a *physical* property of that process, and therefore of the surface in spacetime on which it took place. So the dipole we observe *is* connected to the actual physical process of last scattering.

I thought Dalespam was mixing these and that's why i pointed it out.

If he was, he was justified, IMO, because as I just noted, the two are connected. The CMB is not isotropic in the comoving frame by magic; it's that way *because* of a particular physical process that produced the CMB, and that process started at the surface of last scattering.

 

[TrickyDicky]

Yes, but the fact that the CMB is isotropic in the comoving frame is due to the fact that the surface of last scattering is a surface of constant comoving time. And *that* fact is due to the fact that the process of "last scattering" occurred homogeneously and isotropically throughout the universe, which is a *physical* property of that process, and therefore of the surface in spacetime on which it took place. So the dipole we observe *is* connected to the actual physical process of last scattering.



If he was, he was justified, IMO, because as I just noted, the two are connected. The CMB is not isotropic in the comoving frame by magic; it's that way *because* of a particular physical process that produced the CMB, and that process started at the surface of last scattering.

Yes, I understand that ultimate causal connection, I was merely saying that for the purposes of the discussion of this thread the exact specific mechanism of production of the isotropy of the CMB is not reallly relavant, the fact it is isotropic is the relevant one rather than the specific mechanism for discussing how the dipole observed reflects (is more directly connected) to the relative motion of the Earth wrt to a rest comoving frame, the frame at which the "cosmologic fluid" or the galactic Hubble flow or whatever one wants to call it is at rest in the FRW coordinates and the possibility that this rest frame reflects what the OP calls a Lorentz eather frame.
I know this coordinates are arbitrarily chosen, but I think this thread is ultimately about the "happy coincidence" that in this arbitrary choice (historically made by Robertson in the 30s) a microwave radiation pervading all space was found in 1964. I tend to think too that there is something physical behind this coincidence rather than considering it a "magical coincidence"

 

[Q-reeus]

I know this coordinates are arbitrarily chosen, but I think this thread is ultimately about the "happy coincidence" that in this arbitrary choice (historically made by Robertson in the 30s) a microwave radiation pervading all space was found in 1964. I tend to think too that there is something physical behind this coincidence rather than considering it a "magical coincidence"

Rather partial myself to the notion of CMBR as arbiter of an infinity of 'local' LET rest frames. This is a long thread and I got just far enough looking back to see that the OP apparently believes in a single 'absolute' LET rest frame, which cannot be reconciled with an expanding cosmos. I like to use the familiar (2+1)D analogue of expanding balloon with dots all over it. No single dot could be taken as marker of any 'absolute' rest frame, but if stationary wrt the local balloon surface, anyone could be taken to mark the 'local rest frame'. I guess most here would agree that applied to the 4D real-world case, that is how an LET 'rest frame' is to be taken?

 

[TrickyDicky]

Rather partial myself to the notion of CMBR as arbiter of an infinity of 'local' LET rest frames. This is a long thread and I got just far enough looking back to see that the OP apparently believes in a single 'absolute' LET rest frame, which cannot be reconciled with an expanding cosmos. I like to use the familiar (2+1)D analogue of expanding balloon with dots all over it. No single dot could be taken as marker of any 'absolute' rest frame, but if stationary wrt the local balloon surface, anyone could be taken to mark the 'local rest frame'. I guess most here would agree that applied to the 4D real-world case, that is how an LET 'rest frame' is to be taken?

We all agree about that ,I think, and indeed I can see no easy way to reconcile it, so that could be licitly used as an argument against the OP claim, but the fact is no one until your post did.
I was commenting firstly a rather trivial question about mixing arguments in an IMO unfair way in view of what was being discussed, and in my last post I was simply expressing my curiosity about an apparent coincidence, in no way saying the OP's claim about existence of an absolute rest frame is right (if that is what he is claiming).

 

[Q-reeus]

I was commenting firstly a rather trivial question about mixing arguments in an IMO unfair way in view of what was being discussed, and in my last post I was simply expressing my curiosity about an apparent coincidence, in no way saying the OP's claim about existence of an absolute rest frame is right (if that is what he is claiming).

Yes, sorry TrickyDicky if I came across as undermining your point - not at all. Agreed about OP's likely position re dipole anisotropy. Just thought I'd throw in my idea of what LET rest frame could mean in a FLRW or somesuch universe. Took a risk of repeating someone else's entry on that - but it is a looooong thread.

 

[TrickyDicky]

Just thought I'd throw in my idea of what LET rest frame could mean in a FLRW or somesuch universe.

I fully agree with that, and I don't exactly know why nobody mentioned it, it would have saved many complicated or irrelevant arguments if someone had said: look, that kind of absolute frame directly contradicts expansion so there's no need to go on talking about it, period.
I guess it was because apparently it was being discussed in the restricted domain of SR, thus the justified insistence of atty and peterdonis on the OP's formal definition of LET. But when Dalespam introduced cosmological considerations I think things got a bit muddled.

 

[Dale]

But when Dalespam introduced cosmological considerations I think things got a bit muddled.

I didn't introduce it, and I agree that it is muddled, which is why I don't want to argue this line.

 

[PeterDonis]

Yes, I understand that ultimate causal connection, I was merely saying that for the purposes of the discussion of this thread the exact specific mechanism of production of the isotropy of the CMB is not reallly relavant, the fact it is isotropic is the relevant one rather than the specific mechanism for discussing how the dipole observed reflects (is more directly connected) to the relative motion of the Earth wrt to a rest comoving frame, the frame at which the "cosmologic fluid" or the galactic Hubble flow or whatever one wants to call it is at rest in the FRW coordinates and the possibility that this rest frame reflects what the OP calls a Lorentz eather frame.

The specific mechanism is not really relevant, but the fact that there *is* a physical mechanism involved certainly is.

I know this coordinates are arbitrarily chosen, but I think this thread is ultimately about the "happy coincidence" that in this arbitrary choice (historically made by Robertson in the 30s) a microwave radiation pervading all space was found in 1964. I tend to think too that there is something physical behind this coincidence rather than considering it a "magical coincidence"

The coordinates aren't really "arbitrarily" chosen; they're chosen based on the physical assumption that the universe is homogeneous and isotropic. It's true that when that assumption was first made, there wasn't a lot of data either way, but the data has steadily accumulated to support the assumption; the discovery of the CMBR was one such piece of data (and now, of course, the CMBR is telling us how accurate the assumption is--about one part in 10^5). So I agree that there is definitely something physical behind the "coincidence".

the OP apparently believes in a single 'absolute' LET rest frame, which cannot be reconciled with an expanding cosmos. I like to use the familiar (2+1)D analogue of expanding balloon with dots all over it. No single dot could be taken as marker of any 'absolute' rest frame, but if stationary wrt the local balloon surface, anyone could be taken to mark the 'local rest frame'.

You make a good point and I agree with your description, but I'm not sure how much it would add to the arguments already made against the idea of an "LET aether" in this thread. (The possibility of the CMBR's rest frame being the "aether" frame only came up fairly late in the thread, which may be why no one had yet hit on the argument you pose.) Anyone who believes in LET has already accepted the fact that they have to pick out one particular frame and call it "absolute rest", even though there is nothing that physically picks out that frame from all the others. So an LET theorist would just say that yes, you're right, I can't take the "comoving" frame (the rest frame of the CMBR) as the "aether frame" as it stands because that frame is not a single inertial frame (objects "at rest" in this frame are moving away from each other); but that just means there is some *particular* comoving observer whose current rest frame happens to be the aether frame--we just don't know which one.

Of course, *which* comoving observer happens to be "at rest" in the aether will *change* with time, as you note; but given the number of highly implausible things the LET theorist already believes in, what's one more? (Sounds like the LET theorist must have read Lewis Carroll, and likes to believe six impossible things before breakfast.)

guess most here would agree that applied to the 4D real-world case, that is how an LET 'rest frame' is to be taken?

No, most here would say that the idea of an "LET rest frame" is not valid in the first place.

 

[TrickyDicky]

The coordinates aren't really "arbitrarily" chosen; they're chosen based on the physical assumption that the universe is homogeneous and isotropic.

Which is a reasonable assumption and explains why and how they were chosen by Robertson, but I was referring to the accepted fact that there is nothing "absolute" about taking these coordinates to fix a comoving rest frame where observers see the CMB without the dipole anisotropy, they are merely "preferred" for practical reasons and the above mentioned assumptions, so in that sense they are arbitrary coordinates, or do you have reasons to think they are the only possible coordinates or that they are special and unique in some other way? I don't think so, that would put you in an equally or more awkward position than the "LET theorists".

 

[PeterDonis]

Which is a reasonable assumption and explains why and how they were chosen by Robertson, but I was referring to the accepted fact that there is nothing "absolute" about taking these coordinates to fix a comoving rest frame where observers see the CMB without the dipole anisotropy, they are merely "preferred" for practical reasons and the above mentioned assumptions, so in that sense they are arbitrary coordinates

Ah, I see, yes, with this meaning of "arbitrary" they are arbitrary; nothing requires us to describe the universe using "comoving" coordinates, it just looks simpler provided that the universe actually is homogeneous and isotropic, which it is to a good approximation, and the appearance of the CMB reflects that.

 

[Q-reeus]

No, most here would say that the idea of an "LET rest frame" is not valid in the first place.

Sure but I meant 'how it could make sense assuming it is predictively equivalent to SR'. Maybe this should be in a new thread, but here goes. Have been tossing around an heretical idea for a while re detecting an LET rest frame - which amounts to saying it could falsify SR. Vacuum polarization. When electric field strength reaches a critical value E_crit ~ 1.3*10¹⁶v/cm, QED predicts the vacuum undergoes 'dielectric breakdown' with copious production of electron-positron pairs (see e.g. http://arxiv.org/abs/0706.4363, eqn's (1) & (2)). These move under the action of the applied E to create a current. Creating the requisite enormous field intensity in the lab frame is still way beyond current technology, but as gedanken experiment that's not an issue.

Suppose then we have say a very long length of fully evacuated straight coax line. Inner line is held at a high potential wrt outer coax tube; and we fancifully assume it could yield some reasonable fraction say 0.5 E_crit at the inner line surface. In an SR setting it matters not if an observer, moving parallel to the coax axis at some large fraction of c sees a transverse E >> E_crit - if there no breakdown in the lab frame, none can be occurring in the observer's frame either. There is of course a large transverse B field present in that frame, but a B field has no influence on initiating breakdown - it could only modify the flow of an existing breakdown current.

But what is the viewpoint in LET setting. If our original setup corresponds to the 'true' LET rest frame, and we now propel the coax setup to the same relative speed as before - but now relative to 'the rest frame', can it now be said that an E >> E_crit in LET rest frame doesn't matter? That is surely inconsistent with the notion that the vacuum should not distinguish between an E field generated by a source at rest or moving (as before, the added B field is irrelevant re initiating breakdown). In other words, LET scenario predicts breakdown occurring because coax motion is wrt rest frame. Put in another way - the vacuum 'knows' what is the true rest frame when breakdown is imminent. OK, throwing it over to the pros - what is wrong with this argument?

 

[PeterDonis]

Put in another way - the vacuum 'knows' what is the true rest frame when breakdown is imminent. OK, throwing it over to the pros - what is wrong with this argument?

The rest frame is determined by the rest frame of the apparatus that is producing the E field, not the vacuum. If we launch the field generator on a rocket and accelerate it to near the speed of light, relative to the lab, it's still the E field in the rest frame of the field generator, not the lab, that determines when "breakdown" occurs (so we, in the lab, will see breakdown occur at a much *higher* value of E, because of the relative motion). So the vacuum doesn't pick out a particular rest frame.

 

[Q-reeus]

The rest frame is determined by the rest frame of the apparatus that is producing the E field, not the vacuum. If we launch the field generator on a rocket and accelerate it to near the speed of light, relative to the lab, it's still the E field in the rest frame of the field generator, not the lab, that determines when "breakdown" occurs (so we, in the lab, will see breakdown occur at a much *higher* value of E, because of the relative motion). So the vacuum doesn't pick out a particular rest frame.

That is partly a restatement of the SR situation in my middle paragraph in #255, but omits two things which imo are critical to the argument. There is one additional consideration I omitted there - duration. As eq'n (2) in the reference shows, the applied E must be sustained for a minimum time for breakdown to be appreciable. Take say an atom of Uranium with a large nucleus and near critical field E field there in it's rest frame. Whizzing by at near light speed, the transverse E field may be much higher than Ecrit, but it matters not either in SR setting (your argument), or in LET setting owing to the briefness of E field duration. This is why I specified a very long coax - make it as long as one likes so that even at v -> c the transverse E is sustained uniformly for sufficient time.
You will have to explain then why, in LET perspective, it should matter that E is owing to static or moving source. In reference to the second consideration recall here that unlike a ponderable dielectric medium where your argument re higher observer dependent breakdown strength makes sense [i.e. dielectric say is moving relative to the transverse B field in that frame such that there is an offset against the transverse E in that frame], the vacuum is supposed to exhibit the same properties at any speed. Certainly in SR! And, if my argument has merit, mostly in LET.

 

[PeterDonis]

As eq'n (2) in the reference shows, the applied E must be sustained for a minimum time for breakdown to be appreciable. Take say an atom of Uranium with a large nucleus and near critical field E field there in it's rest frame. Whizzing by at near light speed, the transverse E field may be much higher than Ecrit, but it matters not either in SR setting (your argument), or in LET setting owing to the briefness of E field duration.

Since we are talking about a breakdown of the vacuum, the Uranium nucleus is irrelevant. The "breakdown" the paper is talking about is a production of electron-positron pairs from *vacuum*--i.e., in a region where there is *no* matter present. (However, that does *not* mean there is "nothing" present--see further comments at the end of this post.)

This is why I specified a very long coax - make it as long as one likes so that even at v -> c the transverse E is sustained uniformly for sufficient time.

Do you mean you are trying to sustain a transverse E field in the lab frame even though the power source that the field generator uses is moving at v -> c relative to the lab frame? You do realize that electricity does not travel down the coax at infinite speed, right? It travels at the speed of light. So as the generator moves away, it will be impossible for the electricity from the coax to travel back down it fast enough to sustain the E field.

In any case, when I talked about a "field generator", I was not talking about the energy source; I was talking about the actual apparatus that *produces* the electric field: the Van De Graff generator or whatever it is. What I am saying is that the rest frame of that apparatus is what determines the "rest frame" with respect to which the E field has to reach E_crit for breakdown to occur. It doesn't matter how you feed power to the apparatus. And you can't take such an apparatus and somehow pipe its output via a coax cable to somewhere else; that doesn't make sense, because its output is the E field, directly; it's not something that somehow gets turned into the E field.

You will have to explain then why, in LET perspective, it should matter that E is owing to static or moving source.

I don't have to explain anything relative to LET, since I don't think it's a correct interpretation of the physics anyway.

In reference to the second consideration recall here that unlike a ponderable dielectric medium where your argument re higher observer dependent breakdown strength makes sense, the vacuum is supposed to exhibit the same properties at any speed. Certainly in SR!

The vacuum *does* exhibit the same properties at any speed. What exhibits properties that are "speed dependent" (if you insist on looking at everything from a single inertial frame) is the E field generator, as I explained above; what E field strength you observe it to be generating when electron-positron pairs start to appear will depend on its state of motion relative to you.

Also, saying that the electron-positron pairs come "from the vacuum" is really a misstatement; the pairs are being produced from the energy that is being pumped into the E field generator from some power source. The phrase "from vacuum" is used only because there is no other matter already present in the region where the pairs are produced; but there is not "nothing" present either, because the field is there, and the energy that produced it had to come from somewhere.

 

[Q-reeus]

Since we are talking about a breakdown of the vacuum, the Uranium nucleus is irrelevant. The "breakdown" the paper is talking about is a production of electron-positron pairs from *vacuum*--i.e., in a region where there is *no* matter present.

You seem not aware of the spontaneous beta-decay arguments re supercritical nucleii (nucleii not yet created, but the theory is long established)

Originally Posted by Q-reeus:
"This is why I specified a very long coax - make it as long as one likes so that even at v -> c the transverse E is sustained uniformly for sufficient time."

Do you mean you are trying to sustain a transverse E field in the lab frame even though the power source that the field generator uses is moving at v -> c relative to the lab frame? You do realize that electricity does not travel down the coax at infinite speed, right? It travels at the speed of light. So as the generator moves away, it will be impossible for the electricity from the coax to travel back down it fast enough to sustain the E field.

Where did this all come from?! A gedanken experiment for pete's sake! Did I once say the power source (and it need only be a voltage source really) was moving wrt the coax? Or ultrarelativistic speeds were needed? Coax is primarily a capacitor acting as source of transverse E. So we can simply charge it up in lab frame, and rather than sustained breakdown, we observe for the moving coax (can be moving at moderately relativistic speed) a precipitous decline in E concommitant with onset of breakdown. Or whatever - this is a standard type thought experiment and we don't have to worry about grease, nuts and bolts etc.

In any case, when I talked about a "field generator", I was not talking about the energy source; I was talking about the actual apparatus that *produces* the electric field: the Van De Graff generator or whatever it is. What I am saying is that the rest frame of that apparatus is what determines the "rest frame" with respect to which the E field has to reach E_crit for breakdown to occur. It doesn't matter how you feed power to the apparatus. And you can't take such an apparatus and somehow pipe its output via a coax cable to somewhere else; that doesn't make sense, because its output is the E field, directly; it's not something that somehow gets turned into the E field.

Peter - please go back and slowly re-read #255, then #257. You appear to have totally misunderstood my argument - your passage above has nothing to do with anything I wrote and you are arguing against a phantom. You do realize for instance as per previous comments that the coax is not taken as a power source per se, but simply a tubular capacitor? That was not made ultra clear enough in #255!? How did you figure it becomes a power-lead?

Originally Posted by Q-reeus: "You will have to explain then why, in LET perspective, it should matter that E is owing to static or moving source."

I don't have to explain anything relative to LET, since I don't think it's a correct interpretation of the physics anyway.

And I'm not claiming this LET-trumps-SR argument is necessarily true, but imo it does deserve a properly targeted response.

Originally Posted by Q-reeus:
"In reference to the second consideration recall here that unlike a ponderable dielectric medium where your argument re higher observer dependent breakdown strength makes sense, the vacuum is supposed to exhibit the same properties at any speed. Certainly in SR!"

The vacuum *does* exhibit the same properties at any speed. What exhibits properties that are "speed dependent" (if you insist on looking at everything from a single inertial frame)...

I obviously didn't in #255 - where again is the issue?

...is the E field generator, as I explained above; what E field strength you observe it to be generating when electron-positron pairs start to appear will depend on its state of motion relative to you.

Once you cotton-on the coax is a *capacitor* until breakdown occurs, (and so what if an on-board generator sustains or not the breakdown current thereafter) I think this extraneous issue will thankfully also evaporate.

Also, saying that the electron-positron pairs come "from the vacuum" is really a misstatement; the pairs are being produced from the energy that is being pumped into the E field generator from some power source. The phrase "from vacuum" is used only because there is no other matter already present in the region where the pairs are produced; but there is not "nothing" present either, because the field is there, and the energy that produced it had to come from somewhere.

It's not called vacuum breakdown for nothing. Let's not keep getting bogged down in irrelevancies. Of course energy is supplied etc - can you point to me suggesting otherwise?

 

[PeterDonis]

You seem not aware of the spontaneous beta-decay arguments re supercritical nucleii (nucleii not yet created, but the theory is long established)

I'm aware of them, but that's a different phenomenon from "vacuum breakdown". Which phenomenon do you want to talk about?

Where did this all come from?! A gedanken experiment for pete's sake! <much further comment snipped>

I am trying to understand the scenario you are describing, but it's difficult because you are not describing it clearly. Let me try to describe, clearly, the scenario I have been understanding you to describe, and then you can tell me if my description matches the scenario you were trying to describe.

There is some object which produces an electromagnetic field. Call it the "source". In the rest frame of that object, the EM field produced appears as a pure electric field, E. In *that* frame, the field strength that induces breakdown (i.e., the production of electron-positron pairs when no other matter is present) is given by the formula in the paper you quoted for the "critical" field, E_crit.

In a frame in which the source is moving, the EM field it produces will no longer be a pure electric field; it will have both electric and magnetic parts, E and B. The E part will not be the same as it is in the source's rest frame (in the particular case you were describing, motion parallel to the E field, E will be larger in the moving frame).

So if we are in the moving frame (i.e., we are moving relative to the source), the E field *we* observe when breakdown occurs will be different than E_crit. But that's because we are moving relative to the source; it has nothing to do with any preferred frame picked out by the vacuum.

And I'm not claiming this LET-trumps-SR argument is necessarily true, but imo it does deserve a properly targeted response.

First the term "LET" needs to be properly defined so we know what to respond to. The OP has been requested a number of times to do that but hasn't.

 

[Q-reeus]

Originally Posted by Q-reeus:
"You seem not aware of the spontaneous beta-decay arguments re supercritical nucleii (nucleii not yet created, but the theory is long established)"

I'm aware of them, but that's a different phenomenon from "vacuum breakdown". Which phenomenon do you want to talk about?

Actually 'spontaneous positron emission' was probably closer to the correct terminolgy, but anyway the issue here is whether vacuum breakdown can be explained in SR setting the same as in LET setting. So just forget atoms! Moral was sustained E is needed for significant vacuum breakdown.

I am trying to understand the scenario you are describing, but it's difficult because you are not describing it clearly. Let me try to describe, clearly, the scenario I have been understanding you to describe, and then you can tell me if my description matches the scenario you were trying to describe.

There is some object which produces an electromagnetic field. Call it the "source". In the rest frame of that object, the EM field produced appears as a pure electric field, E. In *that* frame, the field strength that induces breakdown (i.e., the production of electron-positron pairs when no other matter is present) is given by the formula in the paper you quoted for the "critical" field, E_crit.

Fair summary so far - although I specified E transverse to any subsequent relative motion is what matters.

In a frame in which the source is moving, the EM field it produces will no longer be a pure electric field; it will have both electric and magnetic parts, E and B. The E part will not be the same as it is in the source's rest frame (in the particular case you were describing, motion parallel to the E field, E will be larger in the moving frame).

WRONG! I specified, as per above, motion is parallel to axis of coaxial capacitor, and therefore normal to applied E. Hence SR transformation for transverse E component is relevant. Longitudinal E never exists, and anyway such would be unaffected by relative motion.

So if we are in the moving frame (i.e., we are moving relative to the source), the E field *we* observe when breakdown occurs will be different than E_crit. But that's because we are moving relative to the source; it has nothing to do with any preferred frame picked out by the vacuum.

If the E is transverse, yes, and this circular discussion brings me back to the points made in the second paragraph in #255, and last paragraph of #257. You have simply repeated the standard SR perspective of which we both agree on.

First the term "LET" needs to be properly defined so we know what to respond to. The OP has been requested a number of times to do that but hasn't.

The kernel issue re LET is that vacuum breakdown, determined in an assumed LET rest frame, will by the moving capacitor argument given, be different - specifically less in any other LET lab frame where capacitor is stationary. In other words, in principle one could determine the 'true' rest frame by tests of breakdown strength at various velocities. As I have repeated before and do so again, to avoid that conclusion and square with SR, it has to be shown how LET vacuum could somehow distinguish between an E source that is static or moving wrt lab frame. I don't think anything beyond that is required re defining LET. The fact that in SR, transverse E breakdown strength is *not* a function of velocity is a statement that vacuum polarization has some very strange linkage to the source of transverse E (E aint just E) it seems to me.

 

[Dale]

AFAIK the vacuum polarization in QED is a rank-2 tensor, so it is guaranteed to transform correctly.

 

[stglyde]

True. But the source of the CMB is the surface of last scattering, not the aether. So again, the fact that it is measured to be isotropic provides no evidence about the velocity wrt the aether.

I encourage you to work through the math. According to LET, what would a detector measure for the radiation in each direction along the x and y axes for the case where the surface of last scattering and the detector are both moving at v=0 and both moving at v=.6c wrt the aether?

I don't know how to say again what I have repeatedly told to you. The CMB IS light and Lorentz's position (as was Einstein's) is that light IS isotropic c. For Lorentz this is because,the properties of the aether, namely its coefficient of compressibility (u) and density z deterimes this speed:

c = Sqrt(1/uz)

For Einstein it just a given that it is such for 'empty space'

OK then, do the math I suggested above and prove me wrong.

There are no surfaces of last scattering there is only the universal CMB field. That we see and measure to be universal and uniform and smooth to at least five decimal places. IF you are moving wrt to this sea of photons you WILL! measure a Doppler, period, end of story. From the Lorentzian model this identifies the aether background.


PeterDonis and others. Please describe in your own words where I got wrong because I may be stuck with DaleSpam particular language or chain of reasoning. Thanks.

 

[stglyde]

But you still haven't said what LET is. Even without going beyond the standard model, there are many concepts including the http://www.tu-harburg.de/rzt/rzt/it/Ether.html, the http://www.nobelprize.org/nobel_prizes/physics/laureates/2006/smoot_lecture.pdf, or the quantum vacuum which have been called "aethers" because they have some relationship to Lorentz's. That is not contested (by me). However, to have a good discussion of the similarities and differences between these different things, we need a sharp definition of LET, and give each of these aethers different names. For example, if one includes that the aether of LET is undetectable, then we can straightaway say that the CMB as a preferred frame does not have that property, since it is detectable. So could we please have your precise definition of LET, along the lines suggested by D H?

Which came first, Lorentz's version or Eistein's? And again. Lorentz NEVER! claimed the aether itself is undetectable he simply say that trying to determine one's speed within it
cannot be done using TWL path processes. But, he never proposed that his aether was anything but 'the aether'.

GR's equations are expressly hydrodynamical in nature. Einstein and others realize this and the implication should be obvious to any thinking being. But again, since GR encompasses SR and SR encompasses 'luminiferous' behavior there is NO! separate aethers except perhaps, in the concepts of 'your' mind.

 

[Dale]

I don't know how to say again what I have repeatedly told to you.

It doesn't matter how you say it, what you are saying is wrong. This isn't a miscommunication, just an incorrect idea.

The CMB IS light and Lorentz's position (as was Einstein's) is that light IS isotropic c.

Do you agree or disagree with the following statements:
1) in LET the speed of light IS isotropic only in the aether frame
2) in LET the speed of light is MEASURED to be isotropic in all frames

That we see and measure to be universal and uniform and smooth to at least five decimal places. IF you are moving wrt to this sea of photons you WILL! measure a Doppler, period, end of story.

Yes, I agree.

From the Lorentzian model this identifies the aether background.

No, it doesn't. Prove your point with math. Use the Lorentz transform to show that LET requires that if a given configuration of photons is measured to be isotropic then it must be at rest wrt the aether. I.e. that it is impossible to measure isotropic photons while moving relative to the aether in LET.

 

[Aether]

...the OP apparently believes in a single 'absolute' LET rest frame, which cannot be reconciled with an expanding cosmos. I like to use the familiar (2+1)D analogue of expanding balloon with dots all over it. No single dot could be taken as marker of any 'absolute' rest frame, but if stationary wrt the local balloon surface, anyone could be taken to mark the 'local rest frame'. I guess most here would agree that applied to the 4D real-world case, that is how an LET 'rest frame' is to be taken?

LET is exactly the same physical theory as is the standard formulation of SR, but it uses a different coordinate system. Both LET and SR are similarly limited to application within small space-time regions.

If the OP really does, as you say, "believes in a single 'absolute' LET rest frame...", then the simple existence of gravity here on Earth would be enough to falsify that belief; just as it is entirely sufficient to falsify the standard formulation of SR itself if/when the theory is applied to any suitably large space-time region.

 

[Aether]

stglyde,
You can't properly apply LET to the CMB any more than someone else could properly apply the standard formulation of SR to a simple problem involving gravity here on earth.

GR is the proper tool for dealing with gravity and the CMB, and GR let's you choose any coordinate system that you want.

 

[PeterDonis]

WRONG! I specified, as per above, motion is parallel to axis of coaxial capacitor, and therefore normal to applied E. Hence SR transformation for transverse E component is relevant. Longitudinal E never exists, and anyway such would be unaffected by relative motion.

Ah, sorry, I should have said E perpendicular to the direction of motion, not parallel.

If the E is transverse, yes, and this circular discussion brings me back to the points made in the second paragraph in #255, and last paragraph of #257. You have simply repeated the standard SR perspective of which we both agree on.

Ok, good, that means we at least agree on what standard SR says.

The kernel issue re LET is that vacuum breakdown, determined in an assumed LET rest frame, will by the moving capacitor argument given, be different - specifically less in any other LET lab frame where capacitor is stationary.

Now we get into the question of what, exactly, the term "LET" means. The standard usage of that term (or what most of us thought the standard usage was until it started getting thrown around in this thread) is a theory that makes exactly the same experimental predictions as SR, but interprets them differently. So "LET" by this definition would *not* predict any behavior different than SR; it would predict that the breakdown threshold is determined by the E field in the rest frame of the source. This "LET" would just attribute that to the fact that, even though the source is moving relative to the aether, the field it generates is moving with it, so they both get transformed the same way and the experimental results are the same as SR predicts.

If there is some other "LET" that makes different predictions, the onus is on whoever is propounding such a theory to explain how it makes those predictions.

The fact that in SR, transverse E breakdown strength is *not* a function of velocity is a statement that vacuum polarization has some very strange linkage to the source of transverse E (E aint just E) it seems to me.

No, it's a statement that the "breakdown" phenomenon is produced by pumping energy into the EM field until there is enough of it to produce electron-positron pairs, and the critical field threshold is determined in the rest frame of the source. I really don't see what is so mysterious about this.

 

[kmarinas86]

In the spirit of the title of this thread "SR, LET, FTL & Causality Violation" I would just like to say that it would far easier to adapt FTL with LET than with SR. A Lorentzian ether can easily be amended with one or more other types of transformation that are not Lorentzian (i.e. not based on \sqrt{1-v^2/c^2}) which coexist in the same "absolute space" (different than the "deformable electron" model). Relativity, on the other hand, presents a paradox as it would require some kind of wormhole or other way to "skip" space, if you will, or require that neutrinos didn't really originate with the STL muons but that somehow STL muons entrained itself with a pre-existing FTL substance not a part of the muons themselves and that the FTL substance rolled into FTL neutrinos as a result (as the light speed barrier according to SR cannot be breached from either side), all while at the same time still having the observed change in mass giving rise to the necessity of the neutrino hypothesis in the first place (so you would have to have another (but STL) particle or a strange alternate type of light-like energy traveling at c being emitted from the muon in addition to the FTL neutrino, yet somehow having the same energy!). In LET modified with additional transformations, you neither have to skip space through some other dimension nor require that something is already residing in the experiment moving faster than the speed of light, as things would be able to traverse the light speed barrier rather than be stuck on one side of it.

 

[stglyde]

It doesn't matter how you say it, what you are saying is wrong. This isn't a miscommunication, just an incorrect idea.

Do you agree or disagree with the following statements:
1) in LET the speed of light IS isotropic only in the aether frame
2) in LET the speed of light is MEASURED to be isotropic in all frames

Agree.

No, it doesn't. Prove your point with math. Use the Lorentz transform to show that LET requires that if a given configuration of photons is measured to be isotropic then it must be at rest wrt the aether. I.e. that it is impossible to measure isotropic photons while moving relative to the aether in LET.

If #1 & #2 are true the LT is irrelevant to the issue. If #1 is true and the CMB is universal, uniform, and isotropic it can only meet that condition, according TO Lorentz's model, due to the local aether properties. This is what makes #1 true according to the medium model.
Therefore the only state that can, in the aether model, result in a universal uniform (a.k.a. observable isotropic) radiation field IS the rest frame. All others because of the motion relative to the field produces a distinctive measurable Doppler. The LT have no place in this logic.