Fields and ether

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3 minutes ago, swansont said:

Scare quotes have meaning where I come from, but it doesn't make "fix" the proper description of the introduction/use of the aether.

We thank you for the great contribution made in clarifying absolutely nothing we have been discussing, other than a first course in English. But we still thank you nontheless.

The two of you are amusing with your dislikes of my non-physics posts... but I completely understand.

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5 hours ago, studiot said:

Why is it necessary for all these oscillators to exist, even when they are not oscillating?
Why can they not pop up into place like ducks in a shooting gallery when they are needed.
And pop down again when they are no (ie the wave has passed their location) ?

Alternatively why can they not be laid like the railway tracks in the Wallace & Grommit movie,
directly infront of the travelling train or wave?
And pulled up again behind the train.

Dear studiot, for the first time I find a person who exposes justly the essentials in this subject. What you have written has mathematical expression in the following.

In dissertation format it would be a long and confusing paragraph. Then I prefer a dialogue format.

- Environment: The vacuum
- Theoretical context: Classical electrodynamics
- Starting point: The electromagnetic wave equation
- Highlight detail: In the propagation, the electric displacement works undulatory. That is, that operation fulfills some solution of the wave equation.
- Mathematically there is a complex exponential solution. For now let's not think about physics. Think only of mathematics.
- This solution may correspond to circular or elliptical polarization, with both components in transverse direction. It may also correspond to the case of a transversal component and a longitudinal component. Remember, momentarily we are not thinking about physics. Only in mathematics.

- Now we start thinking about physics.
- In the vacuum, the electric field E can not have a longitudinal component, since there is no free charge in the vacuum.
- Something prohibits that there is some type of linked charge in a vacuum, even if it is a type that has not been treated or known until today?
- Although it would be a very conditioned type of bound charge, its existence is not prohibited. It should meet conditions that we have not faced before, but existence is not prohibited.
- Any special condition that serves as an example? At each point the charge density should vary locally by alternating signs, with no charge movement in the direction of propagation, since the charge movement is conduction current and, in a vacuum, only the displacement current is allowed.
- Mathematically exist the complex exponential solution. Is there any field in classical electrodynamics that can, without conflicts, fulfill that solution without having both transverse components?
- Yes, the electric displacement.
$\vec{D} = \vec{P}+ \varepsilon_o \ \vec{E}$

- Could the vector P be transverse? Impossible. Polarization is a field that, in terms of local results, has collinear symmetry. To have collinear symmetry we need that there can be, in a finite region, two resultants that have the same module, they are on the same line and they have opposite senses corresponding to the opposite signs of the bound charges. In the case of the wave, two vectors P corresponding to different charging signs are in different half cycles. In case of being transverse vectors P, the collinear symmetry is impossible. Then the only possibility is that P is longitudinal.

- In the case of a plane wave, without circular or elliptical polarization, when the direction of propagation is the axis x , we can express the displacement in the following way.
$\vec{D} = \vec{x} \ P + \vec{y} \ \varepsilon_o \ E$
- The solution of the wave equation in that case has the following form.
$\vec{D} = \vec{x} \ \hat{D} \ cos\left(\omega t-kx) \right) + \vec{y} \ \varepsilon_o \ sin\left(\omega t-kx) \right)$
- And the modules meet the following condition.
\hat{D}=\hat{P}=\varepsilon_o \ \hat{E}
- In that solution, divergence of the electric displacement is not equal to zero. It is finite. Then there is a finite bound charge density in the region where the wave propagates. After the passage of the wave, when nothing propagates in the region, the bound charge density returns to zero. The road disappears after the passage of the train and, so that the train can travel, the road is formed only where the train is at each moment.
- The road does not travel. Locally, a piece of road is born at each point where the train has to pass. In other words, the bound charge does not travel. The infinitesimal bound charge that allows the propagation appears locally at each point. At each point the bound charge density is finite and varies sinusoidally, in the case of a sine wave.

Actually @studiot, the example you have given corresponds perfectly to a solution accepted by classical electrodynamics. Let to see how looks the divergence.

$\nabla \cdot \vec{D} = \hat{D} \ k \ sin\left( \omega t - kx \right)$

Does that mean that some charge travels in a vacuum when the wave propagates? No charge needs to travel to produce that divergence. In the cities there are giant illuminated signs, which are panels populated by thousands of luminous cells, controlled by a programmable device. A program can achieve that the brightness of each cell varies sinusoidally, in the form corresponding to a wave function. You can program two colors, say blue and red. The first cell is initially dark. Then the blue light grows sinusoidally, reaches the maximum and decreases sinusoidally, until the cell becomes dark. Follow the sinusoidal stage of the red light, which does the same. All the cells are immobile on the board, but the program manages to see alternate blue and red areas traveling along the board. The effect is equivalent to colors in movement. At each point of the vacuum, the charge density varies sinusoidally. The signs of the charge do the same as the colors. The effect is equivalent to alternating zones with opposite charges traveling in the direction of propagation, although no infinitesimal or finite charge is actually moving.

- Although the charge does not really move, the effect is equivalent to moving charge, as happens with colors that look like moving sections with $\tfrac{1}{2} \ \lambda$ in blue and $\tfrac{1}{2} \ \lambda$ in red.

- The effects of the virtual movement of the charge density are equivalent to a virtual density of current in the direction of propagation, equal and opposite to the longitudinal component of $\dfrac{\partial \vec{D}}{\partial t}$ . This derivative is part of the Ampere-Maxwell law.

Ampere-Maxwell law $\rightarrow \ \ \ \vec{\nabla} \times \vec{H}=\vec{j}+ \dfrac{\partial \vec{D}}{\partial t}$ .

Finally $\vec{\nabla} \times \vec{H}$ it remains, in a net form, identical to the result obtained for the real solutions of the wave equation, which lack a longitudinal component.

Edited by quiet

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2 hours ago, swansont said:

Isn't that moot? The aether was dropped before QM, and was dropped because of SR. There's no overlap. The aether is a purely Newtonian classical physics issue, that was dropped pretty quickly after we had a good model of electromagnetism.

Was it though?

Quote

Photoelectric Effect – The Physics Hypertextbook

The photoelectric effect was first observed in 1887 by Heinrich Hertz during experiments with a spark gap generator (the earliest device that could be called a ...

But I did say we need to carefully distinguish between Relativity and Quantum effects.

Many mix them up in relation to this subject and its history.

Nobel winner Frank Wilczek has, of coursed re-introiduced an ether of his own in QFT.

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Why in a group of people interested in science prevails the spirit of dispute, instead of the spirit of understanding?

It gives the feeling, in many cases, of people who read the notes of others only to trace reprehensible phrases. In many cases, they cut sentences without having read or understood the context, to write a sour repudiation, very far from lucid discernment.

So we hope to advance every little bit more in the understanding of the topics that we like the most?

Let's take an example in my case, so as not to involve someone who does not want to be involved. Did someone take the task to read my first post carefully, understand the content cleanly, then go to the second post, do the same and, thus, get to my last post, to have a conceptual and contextual panorama representative of what I am exposing? If someone had done this work, no one would appear saying that my intention is to affirm the existence of the ether, nor would people appear writing pieces of history to, supposedly, help me understand why the ether is unnecessary. No one has seen that I took the task of putting mathematically the reason why neither the ether nor anything of that kind is necessary.

This thread is only one of the threads spoiled by the vocation of dispute, which replaces the vocation of analysis and understanding. I trust that after reflecting every person within himself, this unfortunate problem will disappear.

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This is an incredible discussion.  It's a shame that this topic is forbidden for some members.

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4 minutes ago, steveupson said:

This is an incredible discussion.  It's a shame that this topic is forbidden for some members.

Rubbish. Members are not forbidden. Unfounded baseless nonsense is. What’s a shame is that some members seem incapable of posting anything other than unfounded baseless nonsense.

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19 minutes ago, steveupson said:

This is an incredible discussion.  It's a shame that this topic is forbidden for some members.

Not forbidden to anyone. Of course, if someone wanted to hihack it with their pet theory, that would be against the rules.

31 minutes ago, quiet said:

Why in a group of people interested in science prevails the spirit of dispute,

Challenging is how science progresses.

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5 minutes ago, Strange said:

Challenging is how science progresses.

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5 hours ago, Romeo22 said:

The two of you are amusing with your dislikes of my non-physics posts... but I completely understand.

!

Moderator Note

Understand better. This is a science discussion forum, and this thread is in mainstream physics. It's not a matter of "dislike", but of meaningfulness.

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Question....While accepting that the old luminiferous ether was invalidated by Michelson and Morley, could the spacetime of GR possibly be inferred as an ether?

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15 minutes ago, beecee said:

Question....While accepting that the old luminiferous ether was invalidated by Michelson and Morley, could the spacetime of GR possibly be inferred as an ether?

Again, depends what you mean by the word “ether”. Einstein used it to describe spacetime. Wilczek used it to describe quantum fields. You could call the atmosphere “the ether” if you wanted (close to its original meaning).

I think, given the history, such uses just serve to confuse (and, perhaps, cause unnecessary antagonism).

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34 minutes ago, beecee said:

Question....While accepting that the old luminiferous ether was invalidated by Michelson and Morley, could the spacetime of GR possibly be inferred as an ether?

I was thinking yes, it is possible, but can see an objection to the use of the term, as Strange points out. I don't personally have any objection as the luminiferous aether of Newton has been clearly ruled out. Whatever it is cannot be fixed to any frame we would readily recognize...including any inertial frame.

Edited by J.C.MacSwell

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Your original post, Quiet, asked for REASONS to dismiss ( and also to keep ) the notion of the aether.
You have been given plenty of reasons, and some of those developed historically.

At first we had a model which relied on commonly held assumptions of what a wave needs to propagate.
With J C Maxwell's and A Einstein's work, we were able to get rid of these 'assumptions' and simplify the model.
And this new model has worked exceedingly well.

Are you now saying you wish to discuss something else concerning the aether ?

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1 hour ago, Strange said:

I think, given the history, such uses just serve to confuse (and, perhaps, cause unnecessary antagonism).

1 hour ago, J.C.MacSwell said:

I was thinking yes, it is possible, but can see an objection to the use of the term, as Strange points out. I don't personally have any objection as the luminiferous aether of Newton has been clearly ruled out. Whatever it is cannot be fixed to any frame we would readily recognize...including any inertial frame.

Just something that I have been going to ask for a while....

"Einstein is generally credited with eliminating the need for the aether. However, as documented in the book “Einstein and the Ether”, from 1916 until his death he believed in the aether in some form. In these years, he used the terms “relativistic ether” and “physical space” to convey this idea.  For example, in 1934 he wrote “Physical space and the ether are different terms for the same thing; fields are physical states of space.”

The standard model is a field theory where all fundamental particles are considered “excitations” of their respective fields. For example, there is an electron field, a muon field and a Higgs field. Do these fields physically exist in spacetime? If so, can they be described physically and collectively described as a relativistic aether?

The recent detection of gravitational waves (GWs) has elevated this discussion because one model says that GWs are waves of gravitons propagating at the speed of light through the empty void of space. The competing model advanced by D. B. Blair et al is that GWs are “ripples in the curvature of spacetime which propagate in a very stiff elastic medium. Spacetime has a characteristic impedance of c3/G.” This is describing the physical properties of spacetime encountered by GWs as an elastic medium with a tremendously large impedance.  The word “aether” is not used by Blair, but perhaps the elastic properties of spacetime, the multiple fields of the standard model, and the vacuum fluctuations or quantum field theory should be lumped together into the collective term “relativistic aether”. Is space an empty void which messenger particles propagate through or does space have physical properties which justify the term “relativistic aether” and call for further analysis?"

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Any comments? I'm not perturbed one way or the other in actual fact, and do not see it as causing a problem.

This paper may also be open to some comment...again, I'm unable to see any problem one way or the other....

Space, Time and Aether

Received Date: September 25, 2016;

Abstract:

At the end of the nineteenth century a luminiferous aether was considered necessary to explain electromagnetic interactions and the propagation of light waves. As this aether could not be detected it was disregarded and mathematical theories were developed to explain physical interactions without reference to the aether. Now, over a century later, it is generally acknowledged that a major part of the universe consists of Dark Energy. This article considers that dark energy could be the same entity as the elusive luminiferous aether and looks at implications for time, space and gravity. The conclusion is that results can be obtained by this method that are equivalent to those obtained according to Einstein’s theories

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And I find this interesting.........................

extract:

"In 1920 Einstein said about ether corresponding with classical ether. But in his paper in 1924, named “Concerning the Aether”, Einstein explained the “aether of general relativity” is not absolute, because matter is influenced by the aether, just as matter influences the structure of the aether.

So the only similarity of this relativistic aether concept with the classical aether models lies in the presence of physical properties in space. Therefore, Einstein’s use of the word “aether” found little support in the scientific community, and played no role in the continuing development of modern physics"

Edited by beecee

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1 hour ago, MigL said:

Are you now saying you wish to discuss something else concerning the aether ?

If you have read my posts carefully at this thread, you will have understood that I have never tried to argue in favor of the ether. And you will have noticed that mathematically I have argued against, because the vacuum is polarizable and the polarization fulfills everything that can be asked of a substrate.

I do not try to discuss something outside the main thread. And I have already mathematically shown the minimum to give a framework to the subject.

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1 hour ago, quiet said:

If you have read my posts carefully at this thread, you will have understood that I have never tried to argue in favor of the ether. And you will have noticed that mathematically I have argued against, because the vacuum is polarizable and the polarization fulfills everything that can be asked of a substrate.

I do not try to discuss something outside the main thread. And I have already mathematically shown the minimum to give a framework to the subject.

You were asked to confirm thst you were referring to the luminiferous aether, and I may have missed the response. Is that what we’re discussing? (It’s what I was assuming)

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11 hours ago, swansont said:

You were asked to confirm thst you were referring to the luminiferous aether, and I may have missed the response. Is that what we’re discussing? (It’s what I was assuming)

I don't know how clear was my initial post for who read that I have wrote. For me can mean something and for other person can mean something very different. Now I will try to improve the expression.

I have reasons, physical and mathematical, to reject the idea of ether. Mathematical reasons are exposed in this thread.

I have reasons but, anyway, I am interested in all kinds of arguments. Why? Because I am a teacher. There are a little number of boys and girls really interested in this issue, and they are very intelligent, and they present many valuable arguments. I am trying  to collect in the forum powerful arguments of all kinds, that can prepare me to manage better classroom arguments.

When I started the thread, I ignore that it can generate passioned discussion and fighting. And I ignore that I will  need to fight too for achieve that people read my posts with a bit of attention, in a way that avoid missunderstanding. I don't wrote, in no paragraph, that I am in favor of the ether hypotheses. But some persons have believed the inverse idea.

Anyway, here was generated a very interesting development of the main issue. And I am greatful for this.

Edited by quiet

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1 hour ago, quiet said:

I don't know how clear was my initial post for who read that I have wrote. For me can mean something and for other person can mean something very different. Now I will try to improve the expression.

It is interesting that you still haven’t answered the question.

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1 hour ago, quiet said:

I don't know how clear was my initial post for who read that I have wrote. For me can mean something and for other person can mean something very different. Now I will try to improve the expression.

I have reasons, physical and mathematical, to reject the idea of ether. Mathematical reasons are exposed in this thread.

I have reasons but, anyway, I am interested in all kinds of arguments. Why? Because I am a teacher. There are a little number of boys and girls really interested in this issue, and they are very intelligent, and they present many valuable arguments. I am trying  to collect in the forum powerful arguments of all kinds, that can prepare me to manage better classroom arguments.

When I started the thread, I ignore that it can generate passioned discussion and fighting. And I ignore that I will  need to fight too for achieve that people read my posts with a bit of attention, in a way that avoid missunderstanding. I don't wrote, in no paragraph, that I am in favor of the ether hypotheses. But some persons have believed the inverse idea.

Anyway, here was generated a very interesting development of the main issue. And I am greatful for this.

So there never was a hidden agenda.  +1

However the question of the word ether deserves clarification since it has enjoyed many meanings (not unconnected) over the millenia.

The modern word ether comes to us (English) from the ancient Greek aither meaning the upper air.
It was a substance believed to occupy space beyond the moon and cotnain the planets and stars.

It entered Old English as edder and Old French as ether.

It then moved on to Middle English as aether but now came to mean
The region of clear space above the clouds.

Passing on to modern English the diphthong was dropped and the word came to be ether.

Because Greek, Norse and Saxon and Christian heaven's were located in this reagion the word etherial came to be associated with things heavenly/spiritual and of tenuous substance.

This was the view of Newton and Descartes - not an all pervading ether but a medium to support the transmission of light rays. Their theories were not wave theories.

Later scientists (Fresnel) proposed a 'lumineferous aether' (note the old spelling returning) as a specific change to an all pervading immaterial substance to support wave motion, when Young's wave theory had become ascendant.

This was again a narrowing down of the, term tightening up the specification as both experimental and mathematical knowledge improved/increased.

At this time Chemistry was developing and first a substance, then a class of substances, was discovered which is very volatile so quickly evaporates and dissipates into the air.
They called this ether and later, ethers following the old idea of insubstantiality.

Other scientists developed several ether models (eg Maxwell) in the late 19 century when the study of light really got going.

Most of these facts are recorded in the links I have already provided.

So there you have it, quiet.

This is why anyone using the term needs to be carefully spelled out when used and why many responders have asked exactly what 'ether' you mean.

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1 hour ago, studiot said:

So there ...

For classroom, and for improve my cultural panorama, your contribution is valuable (and beautyful). Thak you very much.

---------

Respect to Maxwell himself. Have Maxwell believed until the tomb in the neccesity of a substantial medium that allow the electromagnetic propagation?

Maxwell begin using his mechanical model and, in last stage of his research, he have discarded that model and keep only the set of equations, wich include the electric displacement. Have Maxwell ignored the conflictive situation between the rigidity and the evanescent density are needed to formulate the phenomenon in ether terms? Can a person who have created such delicate, datailed and versatile mechanical model ignore the bugs of it?

Edited by quiet

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1 hour ago, quiet said:

For classroom, and for improve my cultural panorama, your contribution is valuable (and beautyful). Thak you very much.

---------

Respect to Maxwell himself. Have Maxwell believed until the tomb in the neccesity of a substantial medium that allow the electromagnetic propagation?

Maxwell begin using his mechanical model and, in last stage of his research, he have discarded that model and keep only the set of equations, wich include the electric displacement. Have Maxwell ignored the conflictive situation between the rigidity and the evanescent density are needed to formulate the phenomenon in ether terms? Can a person who have created such delicate, datailed and versatile mechanical model ignore the bugs of it?

Maxwell was unfortunate in several ways.

Last month I was doing a guided tour of the city where he was born and became a university lecturer.

But they sacked him.

Which is why he went to Edinburgh.

There he did his best and most famous work.

Unfortunately he died young, before he could finish his works.

There are many aspects you need to know including Helmholtz paper.

One other important English word is imponderable.

This meant and still means scientifically without inertia (mass).
Ponderable is with inertia.

The mid 19 century hymns introduced it to mean unthinkable or unknowable and this has come to be it modern popular meaning.

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4 hours ago, quiet said:

I don't know how clear was my initial post for who read that I have wrote. For me can mean something and for other person can mean something very different. Now I will try to improve the expression.

I have reasons, physical and mathematical, to reject the idea of ether. Mathematical reasons are exposed in this thread.

The question was which aether? The one proposed hundreds of years ago and eliminated in 1905 (the luminiferous aether), or subsequent introductions? They aren't the same.

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26 minutes ago, studiot said:

Maxwell was unfortunate in several ways.

Last month I was doing a guided tour of the city where he was born and became a university lecturer.

But they sacked him.

Which is why he went to Edinburgh.

There he did his best and most famous work.

Unfortunately he died young, before he could finish his works.

There are many aspects you need to know including Helmholtz paper.

One other important English word is imponderable.

This meant and still means scientifically without inertia (mass).
Ponderable is with inertia.

The mid 19 century hymns introduced it to mean unthinkable or unknowable and this has come to be it modern popular meaning.

Can you elaborate on this? When was that?

He was born in Edinburgh, correct?

Apologies if that is OT.

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42 minutes ago, studiot said:

Maxwell was unfortunate in several ways...

So we do not know Maxwell's inner conviction a little before his 48 years. We only know that at one stage of the investigation he decided to abandon the mechanical model.
---------
Imponderable. Thanks for bringing this word. In Spanish it also exists, it is written the same and means the same. The texts in Spanish also apply to the ether that adjective. Now that you have explained the use in English, with the annexes and in the context of physics, I will be able to improve the expression in the future. Thank you.

16 minutes ago, swansont said:

The question was which aether? The one proposed hundreds of years ago and eliminated in 1905 (the luminiferous aether), or subsequent introductions? They aren't the same.

The one proposed hundreds of years ago and eliminated in 1905.

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2 minutes ago, quiet said:

The one proposed hundreds of years ago and eliminated in 1905.

Thank you

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