Aether theories which are experimentally indistinguishable from SR.

[clj4]

It does mean that one may not claim that all aether theories are ruled out by experiment, and that one may not claim that the one-way speed of light is measurable in any coordinate-system independent way. If an aether theory is presented with nothing more than adhoc additions to SR, then you may criticize it for this.

Nonsense, you have been shown the opposite over 4 threads and more than 400 posts.

 

[Aether]

Really? What about the infinity of non-preferentail inertial frames in the Mansouri-Sexl theory? Last I checked , light speed was not isotropic in ANY of them, just in the preferentail frame. And they all are inertial...

Where in Mansouri-Sexl do they call a frame "inertial" that doesn't have an isotropic light speed?

Going around in circles again, Aether. Happy flying, make sure that you don't get dizzy. At the end of the flight, don't forget : aether theories are NOT indistinguishable from SR. The OWLS experiments and the theory behind them tell them apart. This is the point you "took off". This is the point where you also land.

No, this is me going around in circles again (I'm the one on the near-side holding the camera out the "window").

 

[clj4]

Where in Mansouri-Sexl do they call a frame "inertial" that doesn't have an isotropic light speed?

Re-read the Mansouri papers,you have them, you obviously missed it. And to think that I wasted hundreds of posts with you.

 

[Aether]

Where in Mansouri-Sexl do they call a frame "inertial" that doesn't have an isotropic light speed?

Re-read the Mansouri papers,you have them, you obviously missed it. And to think that I wasted hundreds of posts with you.

Quit stalling and answer the question.

 

[yogi]

I'm curious. Do you have a link, or something, about M-M apparatus in space?

Thanks

Sorry - I do not.. was hoping myself that someone would soon undertake to refine Olaf Romers techniques to establish some anisotropic error bars on the measurement of light speed when the Earth is approaching and receding from Jupiter. Shapiro has drawn some conclusions about the isotrophy of radar signals bounced off planets, but not everyone agrees with his interpretation of the data. Seems it would be feasible to place a mirror and precision clock on a deep space probe that is receding from the solar system and measure the two way and one way light travel times...

 

[Aether]

I'm curious. Do you have a link, or something, about M-M apparatus in space?

Thanks

Try this: http://lisa.jpl.nasa.gov/TECHNOLOGY/LISA_interfer.html

Seems it would be feasible to place a mirror and precision clock on a deep space probe that is receding from the solar system and measure the two way and one way light travel times...

This clock would have to be synchronized with some other clock; typically either by Einstein's procedure or by slow clock transport. This makes any one-way light travel time "measurement" coordinate-system dependent. It's less confusing to talk about the results of such an experiment in terms of the coordinate-system independent $$\alpha$$ parameter of Mansouri-Sexl theory.

 

[pervect]

Thanks for the links. I will study this fully, but I can see things are not right from the start. From “Why the Ether is Unobservable” dated November 21, 1999:



This opening paragraph is a bit controversial, suggesting that there is no proof of the ether, when there is real evidence to suggest that the detection of the ether is possible, the latest example being the Dewitte experiment.

There is absolutely nothing controversial about saying that the ether is unobservable from the perspective of mainstream science.

The fact that it is "controverisal" from your perspective says volumes about your perspective to anyone who is in the slightest bit familiar with mainstream physics.

The Dewitte experiments have failed the most important principle of science - reproducibility. Irreproducible results are worthless, and there have been many unsucessful attempts to reproduce the Dewitte results that you apparently cling to. Unless and until these results can be reliably and repeatably reproduced, they do not and cannot prove anything, except that experimenters can make mistakes, which any reasonable person already knows.

There have been some recent suggestions that, possibly, the Dewitte results MIGHT be able to be reproduced with a setup that involved deliberately putting gas into the interferometer. Frankly, I don't think that this is a very likely. It's the sort of "forlorn hope" that anyone who wants to be an ether theorist (for whatever personal reasons they may have for this desire) have to rest their hats on nowadays, as anything that's significantly more likely has already been ruled out by numerous experiments.

 

[clj4]

Quit stalling and answer the question.

This is not France, Joseph. Where you live you can order your servants.
Re-read your papers.

 

[Aether]

This is not France, Joseph. Where you live you can order your servants.
Re-read your papers.

You have made an absurdly false claim about what's in the Mansouri-Sexl papers, so I demand that you answer my question. Otherwise, your claim is forfeit. So, quit stalling and answer the question.

 

[clj4]

You have made an absurdly false claim about what's in the Mansouri-Sexl papers, so I demand that you answer my question. Otherwise, your claim is forfeit. So, quit stalling and answer the question.

You asked for it, frenchie, here it is:

1. Read page 500 of the Mansouri paper at the bottom,
the definition of the preferred frame $$\Sigma$$.

2. Read the Tom Roberts page, you know, the one that you quoted so fondly when it supported your POV re: indistiguishability of "aether" theories from SR.

3. And read this:

https://www.physicsforums.com/showpost.php?p=755432&postcount=92

..your own words! Once in a while, under proper supervision you can even do simple calculations correctly. Not very often.

If you still don't get it go get another degree from Sorbonne in how to argue endlessly by cheating and by diversion.

 

[NoTime]

The Dewitte experiments have failed the most important principle of science - reproducibility. Irreproducible results are worthless, and there have been many unsucessful attempts to reproduce the Dewitte results that you apparently cling to. Unless and until these results can be reliably and repeatably reproduced, they do not and cannot prove anything, except that experimenters can make mistakes, which any reasonable person already knows.

I think this
http://prola.aps.org/abstract/PRD/v42/i2/p731_1?qid=6c4ab66eee46e0e8&...
was conceptually similar.

IIRC it used hydrogen-maser clocks separated by about 10miles of fiber optic cable. It produced much the same signal that Dewitte shows, but they only ran for a few days.

I'm inclined to think its a replication.
Didn't really have much use for Dewitte's ideas about it though.
Gotta say he was nice enough to send me his raw date though.

 

[Aether]

You asked for it, frenchie, here it is:

1. Read page 500 of the Mansouri paper at the bottom,
the definition of the preferred frame $$\Sigma$$.

2. Read the Tom Roberts page, you know, the one that you quoted so fondly when it supported your POV re: indistiguishability of "aether" theories from SR.

3. And read this:

https://www.physicsforums.com/showpost.php?p=755432&postcount=92

..your own words! Once in a while, under proper supervision you can even do simple calculations correctly. Not very often.

If you still don't get it go get another degree from Sorbonne in how to argue endlessly by cheating and by diversion.

I looked at your refs 1&3, but found nothing whatsoever suggesting that the one-way speed of light is anisotropic in any inertial frame; ref 2 is too non-specific. Please quote the actual passages that you are referring to. Also, please control your temper (and your paranoia); I don't want to see you banned from PF.

 

[clj4]

I looked at your refs 1&3, but found nothing whatsoever suggesting that the one-way speed of light is anisotropic in any inertial frame; ref 2 is too non-specific. Please quote the actual passages that you are referring to. Also, please control your temper (and your paranoia); I don't want to see you banned from PF.

Actually, you'd love to see me banned but is not going to happen as long as I expose your false claims. Can't you read your own posts? Your own calculations (which happen for once to be right)?
No? read again:

https://www.physicsforums.com/showpost.php?p=755432&postcount=92Still can't read?

Try this one:

C. Braxmaier, H. Müller, O. Pradl, J. Mlynek, A. Peters, and S. Schiller: "New Tests of Relativity Using a Cryogenic Optical Resonator", Phys. Rev. Lett. 88, 010401 (2002).

You can find it (together with a lot of others that say the same thing) here:

http://qom.physik.hu-berlin.de/

(under "Publications")

 

[Aether]

Actually, you'd love to see me banned but is not going to happen as long as I expose your false claims.

Can't you read your own posts? Your own calculations (which happen for once to be right)?
No? read again:

https://www.physicsforums.com/showpost.php?p=755432&postcount=92


Still can't read?

Try this one:

C. Braxmaier, H. Müller, O. Pradl, J. Mlynek, A. Peters, and S. Schiller: "New Tests of Relativity Using a Cryogenic Optical Resonator", Phys. Rev. Lett. 88, 010401 (2002).

You can find it (together with a lot of others that say the same thing) here:

http://qom.physik.hu-berlin.de/

(under "Ppublications")

Please quote the specific passages that support your claim, or your claim stands forfeit.

 

[clj4]

Please quote the specific passages that support your claim, or your claim stands forfeit.

https://www.physicsforums.com/showpost.php?p=755432&postcount=92

Is this a french thing when you loose an argument you declare victory? Even when you defeat yourself? See here:

https://www.physicsforums.com/showpost.php?p=755432&postcount=92

 

[Aether]

https://www.physicsforums.com/showpost.php?p=755432&postcount=92

Is this a french thing when you loose an argument you declare victory? Even when you defeat yourself? See here:

https://www.physicsforums.com/showpost.php?p=755432&postcount=92

There isn't anything in this post that supports your claim. I can't figure out what's confusing you unless you quote the specific passage to which you are referring.

 

[JustinLevy]

Fine, we are done. There was never any discussion about non-inertial frames. The discussion was (see the title of the thread) about the separation beween Mansouri-Sexl theories and SR. In the MS thory, there is an infinite number of iINERTIAL frames in which light speed is not isotropic.

We are not done because you are still not understanding.

Are you defining an inertial frame as a frame in which a freely moving object has a constant velocity (that is, the frame agrees with Newtons First Law)? This is the only way I can see anyone calling the frames of MS theory \"inertial frames\".

First of all, note that is not the relativistic definition of an inertial frame.

But if you wish to use that definition, so be it.
You have admitted that there are coordinate systems in which light speed is not isotropic. Good, it appears we are now in agreement that the speed of light is not a coordinate system independent quantity.

So that answers one of my questions and leaves this one:

-Experiments do NOT restrict what coordinate systems we can describe the universe with, because the physical laws can be stated as tensor equations which are true in any coordinate system. Do you agree? I hope so.


The point you are missing is that these one way light experiments only measure the one way speed of light IN INERTIAL FRAMES (defined by the first postulate of SR ... not the second one as Aether claims ... and not with what Clj4 is apparrently using as a definition of inertial frames). The experiments cannot say more about the one-way speed of light than this because it is a coordinate system dependent quantity. The experiments agree with SR beautifully, so the one-way speed of light is constant and isotropic IN INERTIAL FRAMES.

 

[yogi]

Try this: http://lisa.jpl.nasa.gov/TECHNOLOGY/LISA_interfer.html

This clock would have to be synchronized with some other clock; typically either by Einstein's procedure or by slow clock transport. This makes any one-way light travel time "measurement" coordinate-system dependent. It's less confusing to talk about the results of such an experiment in terms of the coordinate-system independent $$\alpha$$ parameter of Mansouri-Sexl theory.

If the intent of the experiment is not to measure light speed, but rather to detect a "difference" between the time of arrival of a signal sent from Earth and recorded by a distant clock and the synchronization time to which the distant clock would be set using Einstein's convention, then the need for a coordinate system is obviated.

 

[Aether]

The point you are missing is that these one way light experiments only measure the one way speed of light IN INERTIAL FRAMES (defined by the first postulate of SR ... not the second one as Aether claims ... and not with what Clj4 is apparrently using as a definition of inertial frames). The experiments cannot say more about the one-way speed of light than this because it is a coordinate system dependent quantity. The experiments agree with SR beautifully, so the one-way speed of light is constant and isotropic IN INERTIAL FRAMES.

Correct, inertial frames are defined by the first postulate of SR and not the second.

 

[Aether]

If the intent of the experiment is not to measure light speed, but rather to detect a "difference" between the time of arrival of a signal sent from Earth and recorded by a distant clock and the synchronization time to which the distant clock would be set using Einstein's convention, then the need for a coordinate system is obviated.

You have a first clock t1 on the Earth, and a second clock t2 on a spacecraft traveling along a hyperbolic escape trajectory. You synchronize these two clocks using Einstein's convention. You "measure" the travel time of a light signal traveling from t1 to t2 which has to be t2-t1=(x2-x1)/c_0 if the clocks are syncrhonized by Einstein's convention. Is there something else to the experiment?

I put "measure" in quotations because this isn't really a true measurement as it is dependent on the coordinate system established by the chosen clock synchronization method.

 

[clj4]

We are not done because you are still not understanding.

Are you defining an inertial frame as a frame in which a freely moving object has a constant velocity (that is, the frame agrees with Newtons First Law)? This is the only way I can see anyone calling the frames of MS theory \"inertial frames\".

First of all, note that is not the relativistic definition of an inertial frame.

But if you wish to use that definition, so be it.
You have admitted that there are coordinate systems in which light speed is not isotropic. Good, it appears we are now in agreement that the speed of light is not a coordinate system independent quantity.

So that answers one of my questions and leaves this one:

-Experiments do NOT restrict what coordinate systems we can describe the universe with, because the physical laws can be stated as tensor equations which are true in any coordinate system. Do you agree? I hope so.


The point you are missing is that these one way light experiments only measure the one way speed of light IN INERTIAL FRAMES (defined by the first postulate of SR ... not the second one as Aether claims ... and not with what Clj4 is apparrently using as a definition of inertial frames). The experiments cannot say more about the one-way speed of light than this because it is a coordinate system dependent quantity. The experiments agree with SR beautifully, so the one-way speed of light is constant and isotropic IN INERTIAL FRAMES.

Looks like you like to beat things to death. I told you already, the whole discussion has always been in the framework of inertial frames.
This is what the 11 papers talk about, this is what the 400+ posts talk about.
You seem to be very hung up on the tensorial formalism of SR/GR. None of the authors of the 11 papers uses this formalism (i.e. what you call "coordinate independent"). This doesn't make the papers any less valid as Aether would like us to believe it.
1.The experimental part is of these 11 papers (and mounting) is valid.

2. The theoretical part (though it does not use the tensor formalism) is valid.

3. Probably if the authors knew about the fixation you have with the tensor formalism they could recast their papers in this notation and get a fresh paper :-) For the time being they appear uniterested in doing so.

4. Therefore all the 11 the papers (and mounting) are valid and yes, "so the one-way speed of light is constant and isotropic IN INERTIAL FRAMES."

 

[Aether]

"so the one-way speed of light is constant and isotropic IN INERTIAL FRAMES."

Correct. What is your definition of an "inertial frame"?

 

[clj4]

Correct. What is your definition of an "inertial frame"?

Read the 11 papers, they'll set you straight.

 

[Aether]

Read the 11 papers, they'll set you straight.

Wrong answer.

Here's some info on inertial frames:
http://plato.stanford.edu/entries/spacetime-iframes/#2

It may seem surprising that, after this insightful analysis of the concept of inertial frame and its role in electrodynamics, Einstein should have turned almost immediately to call that concept into question. But he had a compelling combination of physical and philosophical motives to do so. On the physical side, he realized (along with many others) that special relativity would require some fundamental revision of the Newtonian theory of gravity. On the philosophical side, he became convinced, largely by his reading of Mach (1883), that the central role of inertial frames was an “epistemological defect” that special relativity shared with Newtonian mechanics. (Einstein 1916, pp. 112-113.) Only relative motions are observable, yet both of these theories purport to identify a privileged state of motion and use it to explain observable effects (such as centrifugal forces). Coordinate systems are not observable, yet both of these theories assign a fundamental physical role to certain kinds of coordinate system, namely, the inertial systems. In either theory, inertial coordinates are distinguished from all others, and the laws of physics are said to hold only relative to inertial coordinate systems. In an epistemologically sophisticated theory, both of these problems would be solved at once: the new theory would only refer to what is observable, which is relative motion; it would admit arbitrary coordinate systems, instead of confining itself to a special class of system. Why, after all, should any genuine physical phenomenon depend on the choice of coordinate system?

 

[clj4]

Wrong answer.

Here's some info on inertial frames:
http://plato.stanford.edu/entries/spacetime-iframes/#2

Duh, this is the intro to GR. This is how the tensor formalism gets introduced. Stick to philosophy, Aether, experimental physics is not for you.

 

[yogi]

You have a first clock t1 on the Earth, and a second clock t2 on a spacecraft traveling along a hyperbolic escape trajectory. You synchronize these two clocks using Einstein's convention. You "measure" the travel time of a light signal traveling from t1 to t2 which has to be t2-t1=(x2-x1)/c_0 if the clocks are syncrhonized by Einstein's convention. Is there something else to the experiment?

I put "measure" in quotations because this isn't really a true measurement as it is dependent on the coordinate system established by the chosen clock synchronization method.

What I propose is to start with two widely separated clocks T1 and T2 - both at rest wrt each other, and far removed from the influence of Earth or other masses. We send a signal from T1 at 1pm and it is reflected off a mirror attached to T2 and returns to T1 at 3pm - so by Einstein's convention we now know we should set set T2 to 2pm + augmented by how much time has elapsed on T2 since the signal was reflected by the mirror (In other words we transmit information to T2 after T1 receives the reflected signal at 3pm) We have now synchronized T2. Now at 7 pm as read on T1 and we send a 2nd pulse toward T2. It should arrive at T2 when T2 reads 8 pm. If it does not, we have an indication that something is wrong.

 

[JustinLevy]

Looks like you like to beat things to death. I told you already, the whole discussion has always been in the framework of inertial frames.

No, the discussion has brought up the non-inertial frames described by the fairly general MS transformations many times.

...and yes, \"so the one-way speed of light is constant and isotropic IN INERTIAL FRAMES.\"

Good, you are finally admitting that a qualification is necessary for that statement.

And given that statement, I assume you will now admit this previous statement of yours is incorrect:

What about the infinity of non-preferentail inertial frames in the Mansouri-Sexl theory? Last I checked , light speed was not isotropic in ANY of them, just in the preferentail frame. And they all are inertial...

The MS transformations are fairly general and can be used as a test theory for experiments to constrain what transformations relate inertial frames. This does not mean all MS transformations yield inertial frames. Also, it does not mean experiment \'disproves\' all the MS transformations that are not lorentz transformations, for experiment cannot disprove a coordinate system (all coordinate systems can be used). It ONLY means that experiment restrict the transformations to be lorentz transformations for INERTIAL FRAMES.

Do you agree with all of this?
If so, we can finally lay this to rest.

 

[JustinLevy]

It\'s less confusing to talk about the results of such an experiment in terms of the coordinate-system independent \\alpha parameter of Mansouri-Sexl theory.

Now you are making the same errors you complained about Clj4 making.

None of the Mansouri-Sexl transformations parameters are coordinate independent. Therefore experiment cannot constrain them in general. Experiment can only constrain their values for relating INERTIAL FRAMES.

 

[Aether]

Now you are making the same errors you complained about Clj4 making.

None of the Mansouri-Sexl transformations parameters are coordinate independent. Therefore experiment cannot constrain them in general. Experiment can only constrain their values for relating INERTIAL FRAMES.

It is my understanding that the $$\epsilon$$ parameter selects the coordinate system, and can't be constrained by experiment; but the $$\alpha$$, $$\beta$$, and $$\delta$$ parameters are coordinate-system independent parameters that can be constrained by experiment. Do you have a copy of the Mansouri-Sexl papers? I can make them available for download if you don't already have them.

 

[clj4]

The MS transformations are fairly general and can be used as a test theory for experiments to constrain what transformations relate inertial frames.

Correct, no one said anything different

This does not mean all MS transformations yield inertial frames.

No one said this , you seem to be on your way of constructing a strawman.

Also, it does not mean experiment \'disproves\' all the MS transformations that are not lorentz transformations, for experiment cannot disprove a coordinate system (all coordinate systems can be used).

This sentence does not parse.

It ONLY means that experiment restrict the transformations to be lorentz transformations for INERTIAL FRAMES.

Now your strawman is complete. This was the starting point, the middle point and the endpoint of the whole discussion. Have you read any of the 11 papers I listed? This is evident in all of them.

 

[clj4]

Good, you are finally admitting that a qualification is necessary for that statement.

Looks like you keep repeating the same obvious stuff. You keep ignoring the fact that the framework of the discussion has always been the inertial frames of SR. Why do you keep beating the poor strawman? Leave it alone.

And given that statement, I assume you will now admit this previous statement of yours is incorrect:

Originally Posted by clj4
What about the infinity of non-preferentail inertial frames in the Mansouri-Sexl theory? Last I checked , light speed was not isotropic in ANY of them, just in the preferentail frame. And they all are inertial...

Let me try one more time, in slightly different words : in their papers, in their OWN writing, MS use the premise that light speed is isotropic in ONE ARBITRARY frame (the one that they call "preferential"). In ALL the OTHER frames, light speed is NOT isotropic. This is exactly what you quoted me saying above. Are you quibbling about not adding the qualifier "inertial"? Isn't that obvious enough? If not, then please look up the exact statement in paper I, page 505:

"One easily sees that this modified velocity addition theorem (4.2) does not exclude superlight velocities (duh!) and in fact it does predict unisotropic (sic!) light propagation IN ALL FRAMES EXCEPT $$\Sigma$$"

From the Gagnon paper, bottom of page 38:

"...we consider a theory (GGT) which postulates the existence of a preferred or absolute frame of reference in which light propagates isotropically at a fixed speed. IN ALL OTHER reference frames the one way speed of light depends on the state of motion of an observer wrt the preferred reference frame"

I much prefer discussing math and experiments than splitting hairs over philosophy of science. So, if you have anything that can be quantified mathematically, Justin, let's see it. Enough pose and hair splitting.

 

[Aether]

Let me try one more time, in slightly different words : in their papers, in their OWN writing, MS use the premise that light speed is isotropic in ONE ARBITRARY frame (the one that they call "preferential"). In ALL the OTHER frames, light speed is NOT isotropic. This is exactly what you quoted me saying above. Are you quibbling about not adding the qualifier "inertial"? Isn't that obvious enough? If not, then please look up the exact statement in paper I, page 505:

"One easily sees that this modified velocity addition theorem (4.2) does not exclude superlight velocities (duh!) and in fact it does predict unisotropic (sic!) light propagation IN ALL FRAMES EXCEPT $$\Sigma$$"

The preferential frame $$\Sigma$$ is an inertial frame, and all of the others where light speed is anisotropic are not inertial frames. Are you disputing this, or are we just misunderstanding each other in some way?

 

[clj4]

The preferential frame $$\Sigma$$ is an inertial frame, and all of the others where light speed is anisotropic are not inertial frames.

Can you prove the above statement? With math, not with prose.

 

[clj4]

We are not done because you are still not understanding.

Are you defining an inertial frame as a frame in which a freely moving object has a constant velocity (that is, the frame agrees with Newtons First Law)? This is the only way I can see anyone calling the frames of MS theory \"inertial frames\".

First of all, note that is not the relativistic definition of an inertial frame.

But if you wish to use that definition, so be it.
You have admitted that there are coordinate systems in which light speed is not isotropic. Good, it appears we are now in agreement that the speed of light is not a coordinate system independent quantity.

So that answers one of my questions and leaves this one:

-Experiments do NOT restrict what coordinate systems we can describe the universe with, because the physical laws can be stated as tensor equations which are true in any coordinate system. Do you agree? I hope so.The point you are missing is that these one way light experiments only measure the one way speed of light IN INERTIAL FRAMES (defined by the first postulate of SR ... not the second one as Aether claims ... and not with what Clj4 is apparrently using as a definition of inertial frames). The experiments cannot say more about the one-way speed of light than this because it is a coordinate system dependent quantity. The experiments agree with SR beautifully, so the one-way speed of light is constant and isotropic IN INERTIAL FRAMES.

So the new argument (that you now share with Aether) is that all the other frames in MS are not inertial (i.e. with the exception of the preferred frame).
I will ask you the same I asked Aether: prove it. With math, not with prose. You two guys can work together on this proof.

 

[Aether]

The preferential frame $$\Sigma$$ is an inertial frame, and all of the others where light speed is anisotropic are not inertial frames.

Can you prove the above statement? With math, not with prose.

See http://www.mathpages.com/home/kmath386/kmath386.htm" reference for the supporting math:

The problem here, as in almost the entire literature on this subject, is the invalid extrapolation from Newton’s first law to all of Newton’s laws...It seems most reasonable to reserve the expression “inertial coordinate system” to those systems of space and time coordinates in terms of which inertia is homogeneous and isotropic, because this is sufficient to unambiguously define a unique reference frame for each state of motion. On this basis, the definition of inertial coordinate systems given in all existing modern textbooks (at least all I have seen) is wrong. (I restrict this to “modern” texts, because clearly Galileo, Newton, and the other 17th century originators of modern physics understood the need for inertial isotropy, but this understanding seems to have been lost in the intervening centuries.

Inertia is not isotropic in a frame where speeds are not isotropic, so if we "reserve the expression “inertial coordinate system” to those systems of space and time coordinates in terms of which inertia is homogeneous and isotropic", then:

The preferential frame $$\Sigma$$ is an inertial frame, and all of the others where light speed is anisotropic are not inertial frames.

Do you understand and accept the need for inertial isotropy as part of the definition of "inertial frame"?