If there is no Ether how can we talk about light being a wave?

[Eyesaw]

Originally posted by ahrkron
Because there are many situations in which the gravitational field is so close to a flat metric (i.e., what you call "non gravity") that the effect of the curvature is extremely small compared to the SR effects.

Pretty much all experimental science works this way: you care for the main effects first, neglecting other things that produce small deviations, and verify that your theory accounts for what you can measure.

You never can take into account all minute distorsions due to all imaginable effects, but that is ok because they usually introduce deviations that are smaller than your experimental precision. Think of any theory with which you are comfortable. Say, thermodynamics. Does it take into account electromagnetic fields? QCD effects? Cosmic rays? radiation pressure? background radioactivity? no, but even when all of these effects are always present, the theory is still valid since it has been proven that the only important quantities are Volume, Pressure and Tempreature (how? by varying these quantities and observing if their correlation with experiment is consistent throughout many experiments, regardless of the values of all the other quantities).

I think Maxwell's equations point out that the speed of light
in vacuum is related to the permitivitty and permeability of the vacuum, and Einstein used his equations to arrive at the constancy of speed of light postulate in SR, no? I would think that permitivitty and permeability are descriptions only
valid for a medium, which for the vacuum was termed the luminiferous ether at the time, so if that is how one obtains the speed of
light as constant, how does Einstein get a constant c without
a medium?

And if in GR, one of the properties of space-time (which is for all purposes a light-speed determining medium except by name), curvature, is dependent on the presence of matter, how can we be sure that space-time can have any properties at all without matter? In SR's imaginary universe without matter then, light may not move at all or it could move at an infinite velocity- who knows? Surely it would depend on the permittivity and permeability of space in that case, anyhow, and if those were 0, can the speed of light still be c?

Basically, I don't think it's appropriate to consider a flat space-time to have any permitivitty and permeability properties since SR denies the existence of a light-carrying medium in its postulate of the constancy of c. The historical relevance of SR was supposed to be its elimination of the necessity for a luminiferous ether, so I'd like to see the correct version of SR right now- one in which the constancy of speed of light was derived without the permittivity and permeability of the vacuum. Anyone who thinks GR is reduced to SR in flat-spacetime has the obligation to
produce Einstein's secret derivation of the constancy of c without Maxwell's equations.

Since I don't believe such a derivation exists, the speed of light in a vacuum then depends on the permitivvity and permeability of the vacuum and can not be a constant if the permittivitty and permeability of the vacuum are variable properties.

 

[Peterdevis]

the speed of light then depends on the permitivvity and permeability of space and is not really a constant if those properties of space were not constant.

I think you' re right here. Permitivvity and permeability are dependend of the "medium" light is traveling. The permitivity of glass is quite different of that of vacuüm. So the speed of light is variable.
Nevertheless, this is no problem for GR. Because the fundation of GR is the (einstein)Equivalence principle:"In small enough regions of spacetime, ALL laws of physics reduce to those of special relativity, it is IMPOSSIBLE to detect the existence of a gravitational field"
This mean that , no matter in which coördinate system we are, the result of measering permitivvity and permeability of a "medium" must be the same and the speed of light is constant for that medium.

so what is your problem?

 

[Eyesaw]

Originally posted by Peterdevis
I think you' re right here. Permitivvity and permeability are dependend of the "medium" light is traveling. The permitivity of glass is quite different of that of vacuüm. So the speed of light is variable.
Nevertheless, this is no problem for GR. Because the fundation of GR is the (einstein)Equivalence principle:"In small enough regions of spacetime, ALL laws of physics reduce to those of special relativity, it is IMPOSSIBLE to detect the existence of a gravitational field"
This mean that , no matter in which coördinate system we are, the result of measering permitivvity and permeability of a "medium" must be the same and the speed of light is constant for that medium.

so what is your problem?

My problem is that the c in Maxwell's equation depended on a
medium, which for the vacuum was called the luminiferous ether
in the 19th century. Since SR eliminated the ether, it becomes inconsistent to use Maxwell's equation to derive the speed of light, which Einstein did in SR.

 

[Peterdevis]

My problem is that the c in Maxwell's equation depended on a
medium, which for the vacuum was called the luminiferous ether
in the 19th

It is not because maxwell believed in an ether, that there must be an ether too derive Maxwell's equations.
An theory is independent of the scientist, what maxwell, einstein, Newton... thinks of a theory is not important. But the ability of prediction is what a theory makes usefull.

So where we need an ether to derive Maxwell's equations?

 

[protonman]

Originally posted by Eyesaw
The whole notion of an ether was incorporated into Maxwell's
equations for EM waves. Hence the equations for propogation
are wave equations and their propogation speed only dependent
on the permitivitty and permeability of the medium. Without a medium, there can be no waves so you won't have Maxwell's equations- you'd have Einstein's Undiscoverable Equations.

Eyesaw is making a very good point and the responses to his question have not really addressed the issue. I think the answer is that the medium that light travel through is space. For example, if light bends in the presense of a gravitational field it must be moving through something that has the ability to bend.

 

[russ_watters]

Originally posted by Peterdevis
I think you' re right here. Permitivvity and permeability are dependend of the "medium" light is traveling. The permitivity of glass is quite different of that of vacuüm. So the speed of light is variable.

Light transmission through glass happens via absorption, delay, re-emission of the photons, making it appear to travel more slowly when you observe it macroscopically. Light always travels at C.

As said before, the fact that space-time has physical properties does not make it a classical "ether."

what maxwell, einstein, Newton... thinks of a theory is not important.

Except insofar as they wrote their theories of course!

I think the answer is that the medium that light travel through is space. For example, if light bends in the presense of a gravitational field it must be moving through something that has the ability to bend.

That is quite true, protonman, but it does not make space a classical ether.

 

[Eyesaw]

Originally posted by Peterdevis
It is not because maxwell believed in an ether, that there must be an ether too derive Maxwell's equations.
An theory is independent of the scientist, what maxwell, einstein, Newton... thinks of a theory is not important. But the ability of prediction is what a theory makes usefull.

So where we need an ether to derive Maxwell's equations?

Well, Maxwell's equations for EM radiation are wave equations,
so they need a medium since waves don't exist as far everyday
observations go, independent of a medium. To derive Maxwell's
equations without an ether then would require one to show
that the vacuum is completely empty, else one can always assume
a medium that is just too small to be observed.

Since this can never be done, it's more economical to assume light, if it is a wave, requires like every observable wave phenomenon,
a medium for propogation. So you need an ether to derive Maxwell's equations.

An alternative would be to consider light as particles, in which case you would have to explain why their velocity is not source dependent like other ballistic particles.

Einstein did neither so his postulate of a constant c in SR then has neither physical nor mathematical basis since he disposed of the ether.

 

[Nereid]

Eyesaw wrote: *SNIP
Since this can never be done, it's more economical to assume light, if it is a wave, requires like every observable wave phenomenon, a medium for propogation. So you need an ether to derive Maxwell's equations.

An alternative would be to consider light as particles, in which case you would have to explain why their velocity is not source dependent like other ballistic particles.

So, here's some of what's been observed about light:
- double-slit experiment -> "wave-particle duality", well accounted for by quantum mechanics
- photoelectric effect -> light as photons
- gravitational bending and Shapiro time delay -> predicted and well accounted for by GR.

In summary, all observations match predictions of the theories.

If your view of 'waves' requires they need a medium for propogation, then either 'light is not a wave', or 'your view of the nature of waves is incomplete' (or both).

If your view of 'ballistic particles' requires that their velocity is source dependent, then either 'light is not a ballistic particle', or 'your view of the nature of ballistic particles is incomplete' (or both).

 

[quantumdude]

Originally posted by Eyesaw
Well, Maxwell's equations for EM radiation are wave equations,
so they need a medium since waves don't exist as far everyday
observations go, independent of a medium.

Why not? What substrate is implied by Maxwell's equations?

To derive Maxwell's
equations without an ether then would require one to show
that the vacuum is completely empty, else one can always assume
a medium that is just too small to be observed.

"Too small"?

The light that we see from the sun travels 93 million miles to Earth! In what sense is this supposed medium "too small"?

Since this can never be done, it's more economical to assume light, if it is a wave, requires like every observable wave phenomenon,
a medium for propogation. So you need an ether to derive Maxwell's equations.

Why is it more economical to add an assumption?

An alternative would be to consider light as particles, in which case you would have to explain why their velocity is not source dependent like other ballistic particles.

We do consider light as particles, when the intensity of the radiation is sufficiently weak. But why do we have to explain why the velocity of those particles is not source dependent? That is like demanding an explanation of why the charge of an electron has the value that it does.

Einstein did neither so his postulate of a constant c in SR then has neither physical nor mathematical basis since he disposed of the ether.

No, SR has both. Its mathematical basis follows from the (very well tested) Maxwell equations. Its physical basis follows from all the experiments that have been done to corroborate it.

 

[Phobos]

Mentor note:
This past page or two has been getting back on track to a decent discussion. If the nonsense of the first 5 pages starts again, then this topic is over.

 

[Nereid]

Originally posted by pelastration
Nereid,

have you even seen this quote of Maxwell?

"In speaking of the Energy of the field, however, I wish to be understood literally. All energy is the same as mechanical energy, whether it exists in the form of motion or in that of elasticity, or in any other form. The energy in electromagnetic phenomena is mechanical energy."
--- JAMES CLERK MAXWELL

I found that on a website of Joseph Newman, never found other oringinal references. But it fits in my ideas about multi-layered spacetime where membrane friction creates all other interactions.

AFAIK, Maxwell died before the results of the Michelson-Morley experiment were published (and he died even before M&M began their experiment?) So we cannot know how he would have felt, or what he would have thought, had he lived another few or 20 years. Certainly, Maxwell died before quantum weirdness was discovered.

As others have said here, we're on a journey, learning new things all the time ... finding new things doesn't diminish the great contributions of past giants, but neither would they wish us to stay stuck with only what they found.

 

[GRQC]

A question which was posed earlier, and I think needs re-iterating, is why do we need an ether? There is this prevailing notion from some posters that the universe must behave as Newtonian physics predicts, and that "fanciful" theories such as quantum mechanics and relativity theory must be incorrect because they contradict classical Newtonian intuition -- despite the fact that Newtonian physics is a limiting case in both theories.

Perhaps those calling for proof of why they should believe modern theories should in turn tell us why Newtonian physics is expected to be the ultimate theory.

 

[russ_watters]

Originally posted by GRQC
Perhaps those calling for proof of why they should believe modern theories should in turn tell us why Newtonian physics is expected to be the ultimate theory.

Its pretty simple: Newtonian physics 'makes sense.' A wave without a medium in which to propagate? Absurd!

That the coolest thing about QM: pretty much everything in the entire theory contradicts classical interpretations of how the world 'should work.' Its bizarre. Rediculous. Illogical. But with so much clear and incontrovertible evidence that the bizarre is for real, we have no choice but to change our view of how the world 'should work,' not look for a reason why QM could be wrong.

 

[protonman]

That is quite true, protonman, but it does not make space a classical ether. [/B]

Why not? It seems logical to consider space as the medium of propagation of light. Yes, not in the classical sense of an ether that can serve as an absolute reference frame but none the less a medium of propagation.

In addition, it may simply be the case that the medium of propagation has not been searched for properly. In any experiment there are assumptions. If the wrong ones are made the outcome will be incorrect or at least inconclusive.

 

[protonman]

Originally posted by Eyesaw
Well, Maxwell's equations for EM radiation are wave equations,
so they need a medium since waves don't exist as far everyday
observations go, independent of a medium. To derive Maxwell's
equations without an ether then would require one to show
that the vacuum is completely empty, else one can always assume
a medium that is just too small to be observed.

Since this can never be done, it's more economical to assume light, if it is a wave, requires like every observable wave phenomenon,
a medium for propogation. So you need an ether to derive Maxwell's equations.

An alternative would be to consider light as particles, in which case you would have to explain why their velocity is not source dependent like other ballistic particles.

Einstein did neither so his postulate of a constant c in SR then has neither physical nor mathematical basis since he disposed of the ether.

This is excellent work. What you are doing is here is a breath of fresh air. Another related question to raise is that if SR is incorrect how do you explain all the phenomena that have been explained using SR? For example, Pion decay experiements.

 

[protonman]

Originally posted by Nereid
So, here's some of what's been observed about light:
- double-slit experiment -> "wave-particle duality", well accounted for by quantum mechanics
- photoelectric effect -> light as photons
- gravitational bending and Shapiro time delay -> predicted and well accounted for by GR.

In summary, all observations match predictions of the theories.

If your view of 'waves' requires they need a medium for propogation, then either 'light is not a wave', or 'your view of the nature of waves is incomplete' (or both).

If your view of 'ballistic particles' requires that their velocity is source dependent, then either 'light is not a ballistic particle', or 'your view of the nature of ballistic particles is incomplete' (or both).

So basically when new evidence doesn't fit your previous definitions and rules just change the them.

 

[quantumdude]

Originally posted by protonman
So basically when new evidence doesn't fit your previous definitions and rules just change the them.

Exactly. It's the best anyone can do.

 

[protonman]

Why not? What substrate is implied by Maxwell's equations?

What is a wave?

 

[quantumdude]

Originally posted by protonman
What is a wave?

A wave is any traveling, periodic disturbance in a physical field.

My turn: What substrate is implied by Maxwell's equations?

 

[protonman]

We do consider light as particles, when the intensity of the radiation is sufficiently weak. But why do we have to explain why the velocity of those particles is not source dependent? That is like demanding an explanation of why the charge of an electron has the value that it does.

If you people were ever called to debate your views with those who know logic you would be laughed out of town.

Think about your attempt parallel reason. The reason you would have to explain why light is source independent is because everything else we know that is a particle is source dependent. You comparison to explaining the charge of an electron is completely off the mark.

This is what I have been saying all along. There are no more great thinkers. Just regurgitations.

 

[quantumdude]

Originally posted by protonboy
If you people were ever called to debate your views with those who know logic you would be laughed out of town.

Perhaps you wouldn't mind posting some actual logic then.

Think about your attempt parallel reason.

I did. Both questions get to the heart of the matter, which is that the universe is not known a priori. We don't have the answer to either question for that reason. It's a pity that you still don't understand that simple point, as I have elucidated it to you several times now.

The reason you would have to explain why light is source independent is because everything else we know that is a particle is source dependent. You comparison to explaining the charge of an electron is completely off the mark.

Everything else we know of that is a particle satisfies the exact same velocity addition law that light does. We cannot explain why that particular velocity addition law holds, any more than we can explain why the electron has the charge that it does.

This is what I have been saying all along. There are no more great thinkers. Just regurgitations.

Look in the mirror, protonboy.

 

[quantumdude]

Oh yes, one more thing:

What substrate is implied by Maxwell's equations?

 

[Zero]

Ummmm. Yeah...


If I am sidetracking something, let me know. What evidence is there for "ether"? Can somebody answer that for me?

 

[protonman]

That will be enough of that.

--Tom

 

[Zero]

Can someone give me a POLITE answer?

 

[protonman]

I did. Both questions get to the heart of the matter, which is that the universe is not known a priori. We don't have the answer to either question for that reason. It's a pity that you still don't understand that simple point, as I have elucidated it to you several times now.

What do you mean by the universe anyway?

 

[protonman]

Originally posted by protonman
That will be enough of that.

--Tom

Okey Dokey Tom!

 

[quantumdude]

Originally posted by protonman
What do you mean by the universe anyway?

By "the universe" I mean "the totality of material existence".

OK, that's 2 of yours I answered. It's only fair that I get one now.

What substrate is implied by Maxwell's equations?

 

[protonman]

Originally posted by Tom
By "the universe" I mean "the totality of material existence".

OK, that's 2 of yours I answered. It's only fair that I get one now.

What substrate is implied by Maxwell's equations?

I know something a priori about material existence.

 

[Zero]

What substrate is implied by Maxwell's equations?

Ooh, call on me, Teach!

 

[quantumdude]

Originally posted by protonboy
I know something a priori about material existence.

LMAO, you keep talking about what you know, and yet you never actually put any of this knowledge on display so the rest of us can review it. What's the matter, are you scared?

Tell me, what do you know a priori about material existence?

edit: You can start by filling me in on what substrate is implied by Maxwell's equations!

 

[GRQC]

Originally posted by protonman
I know something a priori about material existence.

Do you know everything about material existence, a priori? If so, I'm really impressed. Are you saying you've never been wrong about an assumption or belief before?

 

[Peterdevis]

This becomes again a meaningless discussion.
I suggest that protonman answer this question:

What substrate is implied by Maxwell's equations?

And the others wait with replying until he has answered

 

[protonman]

Originally posted by Tom
Tell me, what do you know a priori about material existence?
[/i]

Thanks for falling right into my trap. There are reasons why I don't give everything right away and you have not figured it out.

All material phenomena are produced.

 

[quantumdude]

Originally posted by protonman
Thanks for falling right into my trap. There are reasons why I don't give everything right away and you have not figured it out.

Oh, I figured it out all right. The reason you don't say what you think or why is that you are nothing but hot air and you have nothing of substance to say.

Prove me wrong!

All material phenomena are produced.

Produced by _________?