Through what medium does EM propagate in empty space?

[turbo]

Through what medium does EM propagate in "empty" space?

Einstein stated in his Leyden address (1926, I think) that an EM ether was mandatory for the transmission of EM waves through "empty" space. He was unable to reconcile this with the dynamical gravitational ether that had to exist to make GR work, so he proposed an EM ether that had NO sensible properties. In other words, it could not possibly be subject to polarization, densification, or any other measurable variation, unlike all the other fields known to exist. This concept seems a little silly, since fields are known to exhibit variations and the variations must be explainable via physical laws.

Is there anybody here that is willing to contemplate that the quantum vacuum might be this EM field - the palette upon which the Universe is written?

 

[SpaceTiger]

Is there anybody here that is willing to contemplate that the quantum vacuum might be this EM field - the palette upon which the Universe is written?

You mean that the quantum vacuum would be the ether? This sounds more like a question for the Quantum Physics forum. As far as I know, the universe is still etherless, but someone more knowledgeable in QFT might be able to give you a better answer.

 

[Chronos]

In my opinion, Einstein was pointing out the futility of positing an 'ether' with any physically quantifiable qualities. I interpret that as meaning it's irrelevant. I also think it's OK to disagree on that.

 

[turbo]

You mean that the quantum vacuum would be the ether? This sounds more like a question for the Quantum Physics forum. As far as I know, the universe is still etherless, but someone more knowledgeable in QFT might be able to give you a better answer.

Yes. The quantum vacuum consists of a field of virtual particles that pop in and out of existence continuously and exist for such brief periods of time that it completely satisfies Einstein's requirement that it have no sensible properties, such as motion.

From this paper on the ether:
http://redshift.vif.com/JournalFiles/V08NO3PDF/V08N3GRF.PDF

According to the general theory of relativity space without ether is unthinkable; for in such space there not only would be no propagation of light, but also no possibility of existence for standards of measuring rods and clocks, nor therefore any space-time intervals in the
physical sense.

that now it appears that space will have to be regarded as a primary thing and that matter is derived from it, so to speak, as a secondary result. Space is now having its revenge, so to speak, and is eating up matter.

In this new concept, the constant mass of matter
disappeared. The ether alone, and not matter anymore, was inertial. Only the ether opposed to a resistance to motion, thus one could say: there was no matter, there were only holes in the ether.

 

[selfAdjoint]

These quotations show that Einstein and Poincre thought that what extends and supports radiation was the spacetime geometry, sometimes called the metric field. Neither man had anything to do with the quantum vacuum. Not that it isn't correct that the quantum vacuum supports radiation! But it isn't an ether in the nineteenth century sense, a medium in which the light waves wave.

 

[Berislav]

But it isn't an ether in the nineteenth century sense, a medium in which the light waves wave.

Yes. The quantum vacuum has "wave-like" properties, itself. So by the 19th century idea it too would require some sort of ether.

 

[turbo]

These quotations show that Einstein and Poincre thought that what extends and supports radiation was the spacetime geometry, sometimes called the metric field. Neither man had anything to do with the quantum vacuum.

Perhaps not by that name, but what we have come to understand as the quantum vacuum serves the purpose admirably. Einstein himself said that without a transmissive medium ("ether" in the parlance of the day) light could not propagate through space. Lest we multiply entities unnecessarily, it would behoove us to examine the vacuum's role in the transmission of EM. As a neutral sea of virtual particles, it provides a baseline against which fluctuations can be expressed - a medium through which waves can be transmitted.

Not that it isn't correct that the quantum vacuum supports radiation! But it isn't an ether in the nineteenth century sense, a medium in which the light waves wave.

Why not? And if not, how can we describe the propagation of light through a vacuum? Must we resort to some corpuscular theory that reduces photons to little points of energy hurtling through "empty" space, heedless of the sea of virtual particles all around them?

What is the concordance view on the transmission of EM through the vacuum?

 

[selfAdjoint]

Why not? And if not, how can we describe the propagation of light through a vacuum? Must we resort to some corpuscular theory that reduces photons to little points of energy hurtling through "empty" space, heedless of the sea of virtual particles all around them?

What is the concordance view on the transmission of EM through the vacuum

Virtual Photons, taking zero time en route as experienced by themselves and therefore unable to interact. Photons are not corpuscles.

 

[turbo]

In my opinion, Einstein was pointing out the futility of positing an 'ether' with any physically quantifiable qualities. I interpret that as meaning it's irrelevant. I also think it's OK to disagree on that.

I don't think it's irrelevant. I think that the quantum vacuum (consisting of particle/antiparticle pairs that last for minimal times, in accordance with the Heisenberg uncertainty principle) can provide the Machian ether that Einstein envisioned without being "sensible" as a fixed background.

In later years (early 1950s) Dirac also made a case for the existence of an ether.

http://home.tiscali.nl/physis/HistoricPaper/Dirac/Dirac1951b.pdf

 

[turbo]

Virtual Photons, taking zero time en route as experienced by themselves and therefore unable to interact. Photons are not corpuscles.

Now I'm confused. If EM propagates as waves, not corpuscular entities traveling through empty space, how does EM propagate? Without a transmissive medium, waves go nowhere.

 

[Chronos]

Light waves do not obey the rules of classical mechanics. Maxwell's equations work perfectly without ascribing any properties to a 'transmissive media'. I think it is fair to say a media devoid of any physically quantifiable properties is the same as saying it is nonexistent [an occams razor thing]. I also think this is the point of Einstein's Leiden address. He was trying to put the issue in perspective and coax his audience into relinquishing their traditionally cherised concepts.

 

[turbo]

Light waves do not obey the rules of classical mechanics. Maxwell's equations work perfectly without ascribing any properties to a 'transmissive media'. I think it is fair to say a media devoid of any physically quantifiable properties is the same as saying it is nonexistent [an occams razor thing]. I also think this is the point of Einstein's Leiden address. He was trying to put the issue in perspective and coax his audience into relinquishing their traditionally cherised concepts.

Please read the address carefully. Einstein was not denouncing the ether - he was announcing his embrace of it and defining its role in physics, with historical references to its role in earlier physical models. He had come to realize that GR demanded the existence of an ether, else the properties of rotation and acceleration could not exist, except as Machian action-at-a-distance, which he would not accept. GR demanded that rotation and acceleration be expressed as changes relative to a LOCAL frame - the ether.

http://www.geocities.com/antonioferrigno/ether.html

To deny the ether is ultimately to assume that empty space has no physical qualities whatever.

The fundamental facts of mechanics do not harmonize with this view. For the mechanical behaviour of a corporeal system hovering freely in empty space depends not only on relative positions (distances) and relative velocities, but also on its state of rotation, which physically may be taken as a characteristic not appertaining to the system in itself.

In order to be able to look upon the rotation of the system, at least formally, as something real, Newton objectivises space.

Since he classes his absolute space together with real things, for him rotation relative to an absolute space is also something real. Newton might no less well have called his absolute space "Ether"; what is essential is merely that besides observable objects, another thing, which is not perceptible, must be looked upon as real, to enable acceleration or rotation to be looked upon as something real.

It is true that Mach tried to avoid having to accept as real something which is not observable by endeavouring to substitute in mechanics a mean acceleration with reference to the totality of the masses in the universe in place of an acceleration with reference to absolute space. But inertial resistance opposed to relative acceleration of distant masses presupposes action at a distance; and as the modern physicist does not believe that he may accept this action at a distance, he comes back once more, if he follows Mach, to the ether, which has to serve as medium for the effects of inertia. But this conception of the ether to which we are led by Mach's way of thinking differs essentially from the ether as conceived by Newton, by Fresnel, and by Lorentz. Mach's ether not only conditions the behaviour of inert masses, but is also conditioned in its state by them.

Mach's idea finds its full development in the ether of the general theory of relativity.

As for my original question, regarding the nature of the transmissive medium through which EM propagates in "empty" space :

Recapitulating, we may say that according to the general theory of relativity space is endowed with physical qualities; in this sense, therefore, there exists an ether.

According to the general theory of relativity space without ether is unthinkable; for in such space there not only would be no propagation of light, but also no possibility of existence for standards of space and time (measuring-rods and clocks), nor therefore any space-time intervals in the physical sense. But this ether may not be thought of as endowed with the quality characteristic of ponderable media, as consisting of parts which may be tracked through time.

The idea of motion may not be applied to it.

Einstein did not, as many imagine, kill the notion of an all-pervasive ether. To the contrary, he embraced the concept, stripped it to its bare essentials, and attempted to use it to unify gravitation and electromagnetism. He failed to accomplish this, but I firmly believe he was on the right track.

To get back to the original question: what is the nature of the transmissive medium through which EM propagates?

 

[selfAdjoint]

Yes, and his ether was the dynamic metric field of spacetime gemoetry. He spent the rest of his life trying to tweak that metric field so it would support EM, but he died before fully achieving that. I don't see what his opinion forces on us today.

It is clear that EM by itself, while perfectly usable within its proper energy/scale envelope, cannot predict the detailed spectra or behavior of charged particles such as electrons. There are further effective theories: Dirac's. QED. and the Standard Model, which do that much more accurately. So trying to unify "light waves" with gravity at this late date is like putting elliptical epicycles into Ptolemy.

 

[turbo]

Yes, and his ether was the dynamic metric field of spacetime gemoetry. He spent the rest of his life trying to tweak that metric field so it would support EM, but he died before fully achieving that. I don't see what his opinion forces on us today.

His opinion forces nothing on us; however it might be wise to reconsider his opinion periodically, especially in the light of things that came to be better-understood later.

The properties of the vacuum were poorly understood when Einstein was at his most productive, and Einstein was not too fond of quantum theory anyway. Today (and for some time actually) we have demonstrable proof that the quantum vacuum exists (Casimir effect, Lamb effect, etc). It is the baseline of our universe, and as such, it is practically insensible. It is pervasive and universal, and Sakharov believed that interaction of matter with this vacuum field endowed the matter with mass, inertia, and gravitation. Does not this sound suspiciously like the Machian ether described by Einstein in his Leyden address?

Again, does the quantum vacuum act as a transmissive medium for EM waves? If not, what is the nature of the field upon which EM waves travel in "empty" space?

 

[selfAdjoint]

His opinion forces nothing on us; however it might be wise to reconsider his opinion periodically, especially in the light of things that came to be better-understood later.

The properties of the vacuum were poorly understood when Einstein was at his most productive, and Einstein was not too fond of quantum theory anyway. Today (and for some time actually) we have demonstrable proof that the quantum vacuum exists (Casimir effect, Lamb effect, etc). It is the baseline of our universe, and as such, it is practically insensible. It is pervasive and universal, and Sakharov believed that interaction of matter with this vacuum field endowed the matter with mass, inertia, and gravitation. Does not this sound suspiciously like the Machian ether described by Einstein in his Leyden address?

Again, does the quantum vacuum act as a transmissive medium for EM waves? If not, what is the nature of the field upon which EM waves travel in "empty" space?

First Einstein and now Sakharov! You can't build physics by cherry-picking quotations from famous dead men. The quantum vacuum as it exists in actual physics is the ground state of a quantum field. In order to talk about gravitation and quantum vacuum meaningfully you have to quantize gravitation. When you have done that come back and we'll talk about whether the quantum vacuum you derive from your quantized gravity theory does or does not support EM in such a way as to be sensibly called an ether.

 

[turbo]

First Einstein and now Sakharov! You can't build physics by cherry-picking quotations from famous dead men.

I think you would find it very difficult to do real physics without studying the problems that have stumped the great minds. Understanding and breaking down these problems lead to paradigm shifts. It is called epistemology, and Einstein was a great fan of that process. Case in point: Mach's concept that inertia arose from a body's acceleration relative to the entirety of the universe. Einstein's distaste for this action-at-a-distance concept was central to his view that the ether is real and local.

The quantum vacuum as it exists in actual physics is the ground state of a quantum field. In order to talk about gravitation and quantum vacuum meaningfully you have to quantize gravitation. When you have done that come back and we'll talk about whether the quantum vacuum you derive from your quantized gravity theory does or does not support EM in such a way as to be sensibly called an ether.

I think that it is a bit much to demand that I develop a full-blown theory of quantum gravity before you will condescend to answer a simple question:

Through what transmissive medium does EM propagate in "empty" space?

Let's start there.

 

[selfAdjoint]

Through what transmissive medium does EM propagate in "empty" space?

Assuming that the teachings of QED and the electroweak theory survive the quantization of gravity, light is carried by real photons, which do not interact with the quantum vacuum. The photons are not corpuscles as you well know, and it is disingenuous to suggest they are. They may on occasion be observed as plane waves when traveling from one star to another. But those are not waves that change the state of any circumambient medium.

 

[Chronos]

I think the point is lost in semantics. The quantum vacuum does have properties, specifically, it produces measurable effects in the presence of matter [e.g., casimir effect]. But it does not exhibit properties consistent with those of a transmissive media in classical mechanics. There is nothing suggesting the quantum vacuum interacts with EM fields. Thus the contextual meaning of this statement by Einstein:

"...we may say that according to the general theory of relativity space is endowed with physical qualities; in this sense, therefore, there exists an ether..."

But, the more important point Einstein made is, IMO:

"... But this ether may not be thought of as endowed with the quality characteristic of ponderable media..."

Which is to say, IMO, it is not endowed with any of the properties typical of a classical transmissive media [e.g., viscosity, mass, rigidity, etc.] Does that make any sense?

Hence, the central argument of the great ether controversy is, does empty space behave consistent with classical mechanics? Einstein's answer is no.

 

[wolram]

by Cronos, Which is to say, IMO, it is not endowed with any of the properties typical of a classical transmissive media [e.g., viscosity, mass, rigidity, etc.] Does that make any sense?

I think people do give the medium properties, i remember Marcus told me that
ST rings like a bell, How else can gravity waves propagate?

 

[selfAdjoint]

Casimir, at least, thought of the virtual particles as having wave lengths; that was how he worked out his "effect".

 

[turbo]

Casimir, at least, thought of the virtual particles as having wave lengths; that was how he worked out his "effect".

Yes, that is key to the concept of supression of the EM wavelengths that demonstrated the reality of the energy of the vacuum.

Again, through what media does EM propagate through "empty" space? It there is no field ("ether", in the case of Einstein's 1920 Leyden address),there can be no propagation of EM waves through space. This is not a trick question, boys and girls! Is there an answer that is acceptible by adherents of the concordance model?

 

[Chronos]

What properties of your 'ether' contribute to the propogation of EM waves? Would you agree the only relevant properties are what is usually called permissivity and permeability? How do those relate to your concept of a 'transmissive medium'? Perhaps a quantified definition of what constitutes a 'transmissive medium' would clarify matters.

 

[turbo]

What properties of your 'ether' contribute to the propogation of EM waves? Would you agree the only relevant properties are what is usually called permissivity and permeability? How do those relate to your concept of a 'transmissive medium'? Perhaps a quantified definition of what constitutes a 'transmissive medium' would clarify matters.

I already have a very concrete concept of what that transmisive medium is, and why it behaves the way it does, and if I explain it here, this thread will be locked and the discussion will stop.

I ask again, to all the adherents of the standard model:

Please explain how EM traverses "empty" space. If, like Einstein, you believe that EM waves need a medium through which to propagate, please describe the medium. If you believe that EM waves can propagate without a medium, please explain your reasoning.

 

[selfAdjoint]

We've all done that and you just ignore us and repeat your question. Maybe you don't want to hear the answer?

 

[SpaceTiger]

If there is no field ("ether", in the case of Einstein's 1920 Leyden address),there can be no propagation of EM waves through space.

EM waves without an ether?! That's like...like...the universe without a creator!

Don't force your preconceived notions on the universe. You can make a theory that predicts an ether, but it will have to conform to the experimental limits already in place.

 

[turbo]

EM waves without an ether?! That's like...like...the universe without a creator!

Don't force your preconceived notions on the universe. You can make a theory that predicts an ether, but it will have to conform to the experimental limits already in place.

Einstein called it an ether - you can call it an EM field or whatever you like, but can EM waves propagate in the absence of a field?

 

[turbo]

We've all done that and you just ignore us and repeat your question. Maybe you don't want to hear the answer?

I think your most succinct answer (correct me if I'm wrong) was:

...light is carried by real photons, which do not interact with the quantum vacuum.

I have seen no research to back up that assertion. In fact, if the Scharnhorst effect is real, light MUST interact with the EM field of the quantum vacuum.

I am not trying to be disengenuous or abtuse, as you have suggested. Is there is an EM field suffusing all of space through which EM waves can propagate, and if so, what is the nature of that field? Can that field be subject to densification, rarification, polarization, etc? What are the properties of the field through which EM propagates in "empty" space?

 

[Chronos]

It is not enough to assert a transmissive medium is required for EM waves without quantifying the relevant properties. According to accepted theory, the only relevant properties are P&P, as already mentioned. Those properties bear no resemblance to the 19th century concept of an 'ether'. Furthermore, Einstein stated his version of 'ether' was "not endowed with the quality characteristic of a ponderable media." Which is the basis of my objection to this argument:

... Can that field be subject to densification, rarification, polarization, etc? ...

Does that not appear to conflict with Einstein's comment?

 

[Nereid]

We've had some discussions, here in PF's own S&GR, on similar topics.

A couple of links (not directly pertinent): Tom's "Aether theories indistinguishable from ..." thread; Reshma's "Ether Drag Theory" (this has a lengthy 'discussion' of a certain Albert's 1920 address).

 

[PhilipF]

A vibrating point extended through space geometrically constitutes a wave . Since vibrating points i.e. electrons are the source of EM radiation. You don't need a medium, all you need is for the vibrating point to be extended by its relative motion through space or by the expansion of space itself .This would also explain why there is a fixed speed in a vacuum since the wave is in a sense not 'pushed' out from its source but rather 'pulled' at a fixed rate . As the photon/EM wave has a different relation to time than matter does (ie no time passes for it ) this is consistent with the notion that it is in a sense standing still in time while the space in which it exists is drawing out giving it its characteristic wave form .

 

[Nereid]

Am moving this to Quantum Physics. Other than that the 'astronomical' or 'cosmological' domain may be where some of the (important) tests of concepts, theories, and ideas related to the OP are conducted, I feel the content of this thread has far more to do with quantum physics than GA&C (as ST pointed out, very early on).

 

[selfAdjoint]

have seen no research to back up that assertion. In fact, if the Scharnhorst effect is real, light MUST interact with the EM field of the quantum vacuum.

I apologize, I did not know about the Scharnhorst effect. The photon does interact with the quantum vacuum by sometimes creating virtual electron-positron pairs. After their brief candle is out it procedes as a photon till it creates another pair. It cannot create real ones because that would violate conservation of energy and momentum, but it can create virtual ones, "off the mass shell". No names, no pack drill.

But far from supporting the radiation this quantum process slows it down! It is precisely the point of Scharnhorst's theory that by intervening with plates a la Casimir we can cause fewer of these transitions and hence increase the speed of the photon above ordinarily measured c. So invoking Scharnhorst, and the active QED vacuum generally, as a "modern ether" is exactly in the wrong direction.

 

[member 11137]

Now I'm confused. If EM propagates as waves, not corpuscular entities traveling through empty space, how does EM propagate? Without a transmissive medium, waves go nowhere.

Think at the ocean and at some waves propagating at the surface of it; it is not always the water that moves, but the ondulation of the surface going up and down without any lateral motion that give us the sensation of a "propagation". Can we not imagine a similar picture for EM waves and vacuum? Or going further can we not imagine that infinitesimal variations of the metric are only giving us the illusion that something is propagating ?

 

[turbo]

I apologize, I did not know about the Scharnhorst effect. The photon does interact with the quantum vacuum by sometimes creating virtual electron-positron pairs. After their brief candle is out it procedes as a photon till it creates another pair. It cannot create real ones because that would violate conservation of energy and momentum, but it can create virtual ones, "off the mass shell". No names, no pack drill.

Do not apologize. Nobody can be familiar with all the research done by everyone in physics. In fact, I had been trying to determine the optical properties of the quantum vacuum for nearly a year when one of the most prominent researchers in that field tipped me off to the Scharnhorst effect in an email. I was coming at this from the viewpoint of an optician and was not as familiar with the theoretical/experimental work in quantum physics as I could have been.

But far from supporting the radiation this quantum process slows it down! It is precisely the point of Scharnhorst's theory that by intervening with plates a la Casimir we can cause fewer of these transitions and hence increase the speed of the photon above ordinarily measured c. So invoking Scharnhorst, and the active QED vacuum generally, as a "modern ether" is exactly in the wrong direction.

No, it's exactly the right direction for my purposes. Now let's think through the implications of this: If the Sharnhorst effect is real, and the quantum vacuum is the dynamical gravitational ether envisioned by Einstein, we have something to work with. The gravitational densification/polarization of the vacuum field would cause an increase in these reactions, resulting in a slowing of the propagation speed of light, while rarification/relaxation of this field would result in faster propagation of light (a la the Scharnhorst effect between the plates of a Casimir device). This is a real mechanical explanation of "gravitational lensing" that makes sense in classical optics.

I am trained as an optician and have been studying the quantum vacuum field as if it were a refractive medium. If the Scharnhorst effect is confirmed, then the quantum vacuum is definitely a refractive medium, and optical effects will give us powerful probes into the qualities of the vacuum fields around galaxies and clusters.

 

[selfAdjoint]

The gravitational densification/polarization of the vacuum field would cause an increase in these reactions, resulting in a slowing of the propagation speed of light, while rarification/relaxation of this field would result in faster propagation of light (a la the Scharnhorst effect between the plates of a Casimir device)

Quantum polarization is not densification. The optical consequences of the Scharnhorst effect were shown by Visser to be unobservable. The quantum vacuum as a medium does nothing but resist and slow the photon, it did not create it and does not support its momentum.

 

[turbo]

Quantum polarization is not densification. The optical consequences of the Scharnhorst effect were shown by Visser to be unobservable. The quantum vacuum as a medium does nothing but resist and slow the photon, it did not create it and does not support its momentum.

References please...

 

[selfAdjoint]

References please...

This is the slides from a talk Visser gave in Brazil. Warning - it's postscript.

www.physics.wustl.edu/~visser/Analog/casimir-rio.ps[/URL]

 

[turbo]

Quantum polarization is not densification. The optical consequences of the Scharnhorst effect were shown by Visser to be unobservable. The quantum vacuum as a medium does nothing but resist and slow the photon, it did not create it and does not support its momentum.

If the quantum vacuum is densified by the presence of large masses, we might expect EM to move more slowly near massive bodies and faster in less-dense domains. This could be the explanation for the unexplained sunward acceleration of the Pioneer probes. They are moving along nicely on they original trajectories, but since they are traveling though less and less dense regions of vacuum, EM from them gets to Earth a little faster than we might expect, leading us to believe that they are slowing down.

 

[selfAdjoint]

If the quantum vacuum is densified by the presence of large masses, we might expect EM to move more slowly near massive bodies and faster in less-dense domains. This could be the explanation for the unexplained sunward acceleration of the Pioneer probes. They are moving along nicely on they original trajectories, but since they are traveling though less and less dense regions of vacuum, EM from them gets to Earth a little faster than we might expect, leading us to believe that they are slowing down.

Your ideas of scale are all off. The vacuum isn't more or less dense except at submicroscopic distances near charged bodies like electrons. which polarize it.

 

[turbo]

Your ideas of scale are all off. The vacuum isn't more or less dense except at submicroscopic distances near charged bodies like electrons. which polarize it.

I don't think my ideas of scale are "off". In Einstein's Leyden address, he expressed the opinion that the ether (the vacuum) is dynamical. It does not simply sit there as a background on which the universe is played out, but is affected by the matter embedded in it.

It is true that Mach tried to avoid having to accept as real something which is not observable by endeavouring to substitute in mechanics a mean acceleration with reference to the totality of the masses in the universe in place of an acceleration with reference to absolute space. But inertial resistance opposed to relative acceleration of distant masses presupposes action at a distance; and as the modern physicist does not believe that he may accept this action at a distance, he comes back once more, if he follows Mach, to the ether, which has to serve as medium for the effects of inertia. But this conception of the ether to which we are led by Mach's way of thinking differs essentially from the ether as conceived by Newton, by Fresnel, and by Lorentz. Mach's ether not only conditions the behaviour of inert masses, but is also conditioned in its state by them.

Mach's idea finds its full development in the ether of the general theory of relativity.

There is a possible mechanism by which the particle-antiparticle pairs of the vacuum can be polarized and densified, and that mechanism will be put to the test at CERN, as soon as they can make and contain experimentally-useful quantities of neutral anti-hydrogen. That test (a critical part of the Athena project) is to measure the gravitational infall rate of antihydrogen and compare it to the gravitational infall rate of hydrogen. It has been assumed but never proven that these infall rates are equivalent. The problem is that all previous measurements have involved charged antiparticles, and the electromagnetic effects absolutely swamp any detectable gravitational effects.

 

[selfAdjoint]

You evidently won't be persuaded by any modern science, you continually revert to what Einstein said in the 1920's, which to my mind has no force at all. and you interpret everything according to your preconceptions. I am through with this discussion.

 

[turbo]

You evidently won't be persuaded by any modern science, you continually revert to what Einstein said in the 1920's, which to my mind has no force at all. and you interpret everything according to your preconceptions. I am through with this discussion.

I refer to Einstein's Leyden address because in it he puts his view of the "ether" in historical context. He was convinced that GR was incomplete and that he had to explain the interaction of matter with the vacuum before he could unite gravity with the fundamental forces. It is a critical concept.

Have you read this paper? Is this modern enough?

http://arxiv.org/PS_cache/hep-th/pdf/9810/9810221.pdf

Relativistic quantum field theory can be understood as having emerged, historically, from a combination of special relativity and quantum mechanics, but as its very fathers have always been very aware it is not a synthesis of these two theories. In standard relativistic quantum field theory, space-time is considered as a fixed arena in which the physical processes take place. The characteristics of the propagation of light are considered as classical input to the theory. This entails the view that there exists a single universal vacuum velocity of light c. However, starting in the early 1950’s [1] research in quantum electrodynamics (QED) has revealed that higher conceptional sophistication in discussing the propagation of light in a vacuum is required. This more advanced insight derives from studies of QED vacua which have been modified by means of external conditions [background fields (electromagnetic, gravitational), finite temperature (heatbath), boundary conditions]. These modified vacua can be explored by studying the behaviour of particles immersed into the vacuum. One particular method, which is of special conceptional significance, consist in the investigation of the propagation of photons (light) in the vacuum modified by external conditions. The characteristics of the propagation of light then describe certain aspects of the vacuum structure. As a result, it has been found that
modified QED vacua are complicated dispersive media which exhibit almost every phenomenon which is well known from ordinary condensed matter media in this respect. This is a quantum effect which is caused by the phenomenon
of vacuum polarization.

Extrapolating from this work and others relating to the behavior of light in modified vacua, we may expect to see observable effects in the manner in which EM propagates through the vacuum. If the vacuum exhibits gravitational dynamic behaviour as Einstein's Machian ether demands, the optical effects of EM traversing vacua of different densities should be apparent. We may discover that we do not need lots of dark matter to explain excess cluster lensing. We may have a solution to the Pioneer acceleration riddle.

 

[Nereid]

That test (a critical part of the Athena project) is to measure the gravitational infall rate of antihydrogen and compare it to the gravitational infall rate of hydrogen. It has been assumed but never proven that these infall rates are equivalent.

Other than to test the Standard Model, and pick up on anything that looks interesting, do you know if these experiments will have the sensitivity (etc) to test various non-mainstream 'EM propogation through vaccua' models/theories/ideas (e.g. LQG)?

Extrapolating from this work and others relating to the behavior of light in modified vacua, we may expect to see observable effects in the manner in which EM propagates through the vacuum.

Such as? To what extent have these been quantified?

If the vacuum exhibits gravitational dynamic behaviour as Einstein's Machian ether demands, the optical effects of EM traversing vacua of different densities should be apparent.

How? To what extent? Why haven't these been detected so far?

We may discover that we do not need lots of dark matter to explain excess cluster lensing.

Is this an example? Or does 'galactic DM' and 'cosmological DM' get swept up here too?

We may have a solution to the Pioneer acceleration riddle.

Indeed.

However, it sure would be nice if something specific could be predicted ahead of time (akin to Garth and SCC, re GPB)!

 

[turbo]

However, it sure would be nice if something specific could be predicted ahead of time (akin to Garth and SCC, re GPB)!

You want predictions relating to observable effects of vacuum polarization/densification? Here is a list I made some time ago.

1) Testing the Gravitational Mass of Matter vs. Antimatter

The Athena Project is designed to produce experimentally usable quantities of anti-hydrogen. One experiment is of particular interest – the measurement of the gravitational mass-equivalence of matter vs. antimatter. In my model, the quantum vacuum is polarized due to a differential in the gravitational infall rates of matter vs. antimatter. Particle-antiparticle pairs of the vacuum preferentially arise in the orientation that requires the least amount of energy, and if antiparticles are more strongly attracted to nearby mass than their partner particles, we have a mechanism by which the quantum vacuum (Einstein's gravitational ether) is polarized. The Polarized ZPE model is falsifiable by this mass-equivalence experiment, for without this gravitational mass differential, I cannot conceive of a simple universal mechanism by which the gravitational ether can interact with embedded masses.

2) Testing for the Existence of ZPE Field Polarization in Earth Orbit

I propose adding an experiment to an Earth-orbiting platform to test the strength of the Casimir effect in various orientations. Using a conventional Casimir device with parallel conducting plates, the device should be oriented with the plates parallel to an imaginary line drawn from the orbiter to earth. A second data run should be made with the conducting plates oriented perpendicular to that line. Each data run should consist of a large enough number of orbits to allow the effects of ZPE field fluxes caused by the Sun and the Moon to be extracted and compared. The Polarized ZPE field model predicts measurable differences in Casimir force as the device traverses gradients in the ZPE field caused by these massive bodies. Subject to instrument sensitivity, the Polarized ZPE model is falsifiable by this test.

3) Measuring the Speed of Light in a Casimir “Vacuum”

Casimir devices produce ZPE fields that are slightly under the local ground state by using very small gaps to physically suppress the appearance of some frequencies of the ZPE spectrum. This suppressed field is somewhat below the local ZPE ground state, although it is by no means a true quantum vacuum. I propose an experiment using interferometry to compare the speed of light across a Casimir gap to that of a beam crossing an equivalent vacuum with no ZPE suppression. The Polarized ZPE model’s concept that the speed of light is dependent on the density of the ZPE field through which is propagates is falsifiable by this test. GR’s invariable speed of light in a vacuum is also falsifiable by this test. (Note: A ZPE researcher kindly pointed out to me that this effect had already been predicted by Klaus Scharnhorst in 1990. My newness to the field has resulted in several such surprises, though I find it encouraging to have deduced a concept only to find that someone else has come to the same conclusion, often through another line of reasoning.)

4) WMAP Anisotropies Resulting from Motion Relative to the Vacuum Fields

WMAP's first year data contains interesting anisotropies. The dipole anisotropy is oriented with respect to our galaxy, and there are several strong multipole anisotropies. These anisotropies are due to our motion relative to the vacuum. Contributory motions include the passage of the MW through the vacuum (responsible for the large dipole anisotropy), the rotation of our spiral arm, the motion of the Sun through the spiral arm, and the motion of the Earth (and the WMAP probe at L2) around the Sun. When WMAP's second year is finally released, I predict that the dipole anisotropy and larger-scale anisotropies will be consistent with the first year data. The smaller anisotropies will not overlay properly, and when studied, they will be seen as artifacts of the WMAP probe's motion relative to the reference frame of the vacuum field. An antenna oriented in the direction of the probe's motion will sense a higher temperature, and one oriented toward the rear will sense a lower temperature. Even the very smallest anisotropies cover vast areas when projected to cosmological distances, as in the CMB. These vast areas cannot have conspired to change from one year to the next. If these small-scale anisotropies have not changed from WMAP1 to WMAP2, my ZPE model is falsified. If they have changed, the CMB is local, not cosmological.

5) Frequency-dependent Effects of the ZPE Fields on Light

Light propagating through ZPE fields should exhibit effects that are frequency-dependent. High frequency, short wavelength EM will be found to interact more strongly with the ZPE fields and will be slowed more than low-frequency, long wavelength EM. Observationally, the light curve of a distant astronomical source like a supernova should exhibit a stretched light-curve, with the low frequency EM arriving sooner on average than the high frequency EM. The spectra of long-lived objects of steady luminosity will appear normal, and frequency-dependent arrival times will not be measurable. The spectra and luminosity curves of objects that exhibit rapid changes in luminosity will be spread by the interactions of the EM with the ZPE fields. Perhaps the best objects to study for confirmation of this effect are gamma-ray bursters. Their light curves should exhibit a spectral smear in which long wavelength "forerunner" EM precedes gamma rays by an amount proportional to the distance from the source to Earth and the density of the ZPE fields traversed on that path.

 

[turbo]

That test (a critical part of the Athena project) is to measure the gravitational infall rate of antihydrogen and compare it to the gravitational infall rate of hydrogen. It has been assumed but never proven that these infall rates are equivalent.

Other than to test the Standard Model, and pick up on anything that looks interesting, do you know if these experiments will have the sensitivity (etc) to test various non-mainstream 'EM propogation through vaccua' models/theories/ideas (e.g. LQG)?

The Athena project is not going to test EM propagation rates, to my knowledge. The mass-equivalence experiment is absolutely critical to our understanding of gravitation, however, since it will employ neutral antihydrogen, which will make it possible to screen for EM effects and accurately measure gravitational effects on antimatter for the first time.

Extrapolating from this work and others relating to the behavior of light in modified vacua, we may expect to see observable effects in the manner in which EM propagates through the vacuum.

Such as? To what extent have these been quantified?

If my quantum vacuum=ether model is correct, the quantification of the effects of EM propagation through vacua of varying density has already been accomplished by the Pioneer telemetry studies. The puzzling sunward acceleration is not real - we interpret the shorter-than expected EM return times as if the probes are slowing because we believe that EM travels at the same speed through all vacua. If the Scharnhorst effect is real, this rule about the absolute nature of the speed of light is wrong, and we should consider that the Pioneer probes are traversing vacua that are less polarized and densified than we experience near Earth, and EM can traverse those vacua more quickly than here.

If the vacuum exhibits gravitational dynamic behaviour as Einstein's Machian ether demands, the optical effects of EM traversing vacua of different densities should be apparent.

How? To what extent? Why haven't these been detected so far?

Perhaps they have been detected, but have been misinterpreted. If you believe that "empty" space is truly empty, and that the vacuum cannot interact with matter and EM, you might look at strong cluster lensing, and decide that we are only seeing a tiny fraction of the mass in the cluster. You probably would not consider that the vacuum could be gravitationally densified or that EM waves encountering these fields could be refracted by them. You would simply refer back to Einstein's curved space-time model and infer lots of missing mass.

Is this an example? Or does 'galactic DM' and 'cosmological DM' get swept up here too?

If there is a dynamic gravitational ether comprised of the fields of the quantum vacuum, the simple inverse square relationship that works so well for simple systems like the Solar system may not apply very well at galactic and cluster scales. If mass, gravitation, and inertia are emergent (arising from matter's interaction with the vacuum) and not fundamental, the effects (cluster binding, excess cluster lensing, flat galactic rotation curves) that prompt the invocation of dark matter may be explainable by other means. I do not expect that it will be clean and easy to quantify gravitational forces with a dynamic vacuum field, but I believe that it is the only way that gravitation is going to be compatible with quantum theory.

 

[Chronos]

It still has a steep hill to climb:

Quantum Foam and Quantum Gravity Phenomenology
http://www.arxiv.org/abs/gr-qc/0405078

Modern tests of Lorentz invariance
http://www.arxiv.org/abs/gr-qc/0502097

Probing spacetime foam with extragalactic sources
http://www.arxiv.org/abs/gr-qc/0508121

Shortly after the original Scharnhorst paper, several papers quickly followed that raised objections. Unfortunately, they are not freely available.

John Baez said:

"However, further theoretical investigations have shown that once again there is no possibility of FTL communication using this [Scharnhorst] effect."

http://math.ucr.edu/home/baez/physics/Relativity/SpeedOfLight/FTL.html#12

 

[turbo]

You may wish to trace this thread re the Scharnhorst effect.

http://www.lns.cornell.edu/spr/1998-12/msg0013670.html

 

[Jonny_trigonometry]

when I think of the quantum vacuum, I get this picture of a bunch of em waves going all directions, frequencies, and present at every point with an overall energy-density (all frequencies have different energy densities). They mostly all cancel each other due to superposition, but every once and a while, like a chaotic system, there will be an emergant pattern that moves through due to the mutual seemingly serindipitous cooperation of all needed waves to make the emergant structure (ie, a photon). Later, if you view where the photon came from, then it's not so serindipitous when you see it was caused by an interaction of matter at some other point in space.

I think of matter waves in this way too, because a wave group is composed of an infinate number of superposed wavelegths, and I just imagine the same picture, only with matter waves, and the same properties result like in a chaotic dynamical system. This is what suits me as an answer to particles that pop out of nowhere and then disappear (emergant property of the chaotic dynamical system of matter waves).

So I would say that the quantum vacuum is in a way, an aether made of both matter and EM waves in a chaotic system of interaction.

 

[Nereid]

You want predictions relating to observable effects of vacuum polarization/densification? Here is a list I made some time ago.

1) Testing the Gravitational Mass of Matter vs. Antimatter

The Athena Project is designed to produce experimentally usable quantities of anti-hydrogen. One experiment is of particular interest – the measurement of the gravitational mass-equivalence of matter vs. antimatter. In my model, the quantum vacuum is polarized due to a differential in the gravitational infall rates of matter vs. antimatter. Particle-antiparticle pairs of the vacuum preferentially arise in the orientation that requires the least amount of energy, and if antiparticles are more strongly attracted to nearby mass than their partner particles, we have a mechanism by which the quantum vacuum (Einstein's gravitational ether) is polarized. The Polarized ZPE model is falsifiable by this mass-equivalence experiment, for without this gravitational mass differential, I cannot conceive of a simple universal mechanism by which the gravitational ether can interact with embedded masses.

Quantification (even OOM levels would do fine)?

2) Testing for the Existence of ZPE Field Polarization in Earth Orbit

I propose adding an experiment to an Earth-orbiting platform to test the strength of the Casimir effect in various orientations. Using a conventional Casimir device with parallel conducting plates, the device should be oriented with the plates parallel to an imaginary line drawn from the orbiter to earth. A second data run should be made with the conducting plates oriented perpendicular to that line. Each data run should consist of a large enough number of orbits to allow the effects of ZPE field fluxes caused by the Sun and the Moon to be extracted and compared. The Polarized ZPE field model predicts measurable differences in Casimir force as the device traverses gradients in the ZPE field caused by these massive bodies. Subject to instrument sensitivity, the Polarized ZPE model is falsifiable by this test.

But if there were a null result, how could that rule out your ideas? I mean, you've proposed nothing quantitative (or did I miss it?), so a null result gets you nowhere (except, perhaps, a request for a repeat, way out in an Oort orbit, with sensitivity increased by 10^5 (or maybe way inside Mercury's orbit?).

3) Measuring the Speed of Light in a Casimir “Vacuum”

Casimir devices produce ZPE fields that are slightly under the local ground state by using very small gaps to physically suppress the appearance of some frequencies of the ZPE spectrum. This suppressed field is somewhat below the local ZPE ground state, although it is by no means a true quantum vacuum. I propose an experiment using interferometry to compare the speed of light across a Casimir gap to that of a beam crossing an equivalent vacuum with no ZPE suppression. The Polarized ZPE model’s concept that the speed of light is dependent on the density of the ZPE field through which is propagates is falsifiable by this test. GR’s invariable speed of light in a vacuum is also falsifiable by this test. (Note: A ZPE researcher kindly pointed out to me that this effect had already been predicted by Klaus Scharnhorst in 1990. My newness to the field has resulted in several such surprises, though I find it encouraging to have deduced a concept only to find that someone else has come to the same conclusion, often through another line of reasoning.)

OK, but again, without at least an OOM quantification, doing such an experiment tells you nothing, right?

4) WMAP Anisotropies Resulting from Motion Relative to the Vacuum Fields

WMAP's first year data contains interesting anisotropies. The dipole anisotropy is oriented with respect to our galaxy, and there are several strong multipole anisotropies. These anisotropies are due to our motion relative to the vacuum. Contributory motions include the passage of the MW through the vacuum (responsible for the large dipole anisotropy), the rotation of our spiral arm, the motion of the Sun through the spiral arm, and the motion of the Earth (and the WMAP probe at L2) around the Sun. When WMAP's second year is finally released, I predict that the dipole anisotropy and larger-scale anisotropies will be consistent with the first year data. The smaller anisotropies will not overlay properly, and when studied, they will be seen as artifacts of the WMAP probe's motion relative to the reference frame of the vacuum field. An antenna oriented in the direction of the probe's motion will sense a higher temperature, and one oriented toward the rear will sense a lower temperature. Even the very smallest anisotropies cover vast areas when projected to cosmological distances, as in the CMB. These vast areas cannot have conspired to change from one year to the next. If these small-scale anisotropies have not changed from WMAP1 to WMAP2, my ZPE model is falsified. If they have changed, the CMB is local, not cosmological.

You've said this before too ... but at what quantitative levels? How much 'relative motion' will produce how much 'not overlay properly'?

5) Frequency-dependent Effects of the ZPE Fields on Light

Light propagating through ZPE fields should exhibit effects that are frequency-dependent. High frequency, short wavelength EM will be found to interact more strongly with the ZPE fields and will be slowed more than low-frequency, long wavelength EM. Observationally, the light curve of a distant astronomical source like a supernova should exhibit a stretched light-curve, with the low frequency EM arriving sooner on average than the high frequency EM. The spectra of long-lived objects of steady luminosity will appear normal, and frequency-dependent arrival times will not be measurable. The spectra and luminosity curves of objects that exhibit rapid changes in luminosity will be spread by the interactions of the EM with the ZPE fields. Perhaps the best objects to study for confirmation of this effect are gamma-ray bursters. Their light curves should exhibit a spectral smear in which long wavelength "forerunner" EM precedes gamma rays by an amount proportional to the distance from the source to Earth and the density of the ZPE fields traversed on that path.

Same comment - what size is the effect you predict? Within an OOM of what the best experimental setup we could construct today would detect? Or 10^100 OOM smaller than this best? Something in between??

 

[reilly]

All this is way above my pay grade. However, it struck me as odd that Einstein, who destroyed the 19th cenury aether, would subsequently ressurect it. So, I looked all this up in Einstein's bio by Abdus Salaam. He says that in Einstein's inaugural address in Leiden, Oct 27, 1920, that the word aether meant the gravitational field: "The aether of the general theory of relativity is a medium without mechanical and kinematic properties, but which codetermines mechanical and electromagnetic events." Without access to the entire paper, I must admit to being clueless as to what that quote means.

But I do know that in his wonderful Relativity, The Special and General Theory Einstein discusses the well-known problems of the aether, and concludes that there ain't none. Much more detail about the history of the demise of the aether is provided by Max Born in his excellent book Einstein's Theory of Relativity.

It makes intuitive sense that the quantum vacuum has physical effects. But, it seems to me, there is a severe computational issue: because the vacuum must be Lorentz invariant, then the vacuum either has zero energy -- in the small and in the large, -- or infinite energy -- a flat radiation spectrum. Maybe, with the addition of, gravitation, the appropriate spatial energy can be made finite -- non-inertial frames and all that. Maybe even chaotic propreties as jonny trig suggests above.

Regards,
Reilly Atkinson

(My apologies if I have written what others have already said. I haven't read all the posts.)