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# Classical explanation for Fizeau & Sagnac

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The nonrelativistic calculation does not predict the result to arbitrary accuracy, and the difference can be measured for v<<c. v/c in this case is 10^-7. So we could be going several orders of magnitude faster and still be in the v<<c regime. 100x faster would mean ~10,000x increase in the effect.

Relativistic effect is only the difference between the classical result and the relativistic one. And for low speeds, this difference is very small, usually very hard to detect. This is the "trend", as we seen in the car going 100 km/hr example and Sagnac in air example.

So, in the same way we still use classical physics for cars, we can and should have a complete classical explanation for Sagnac and Fizeau. Do you agree?

I used underline and bold for you to see that basically you are saying the same as I said. Now you agree?

Anybody else? Please help us here to get over it.

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"this difference is very small, usually very hard to detect" is a watered-down claim from the original. It allows for exceptions, and thus negates any expectation that there must be a nonrelativistic explanation for any effect where v<<c.

Which means you still can't arbitrarily claim that there should be a nonrelativistic explanation for something. You can ask if there is one, but you can't demand it.

——————

To the question of the OP, any calculation that relies on c being invariant is a relativistic calculation, as that is a postulate of special relativity.

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"this difference is very small, usually very hard to detect" is a watered-down claim from the original. It allows for exceptions, and thus negates any expectation that there must be a nonrelativistic explanation for any effect where v<<c.

Which means you still can't arbitrarily claim that there should be a nonrelativistic explanation for something. You can ask if there is one, but you can't demand it.

My claim is not arbitrarily. It is based on the fact that we don't know any exception (big differences for v<<c and no GR effects) and, more important, on the fact that we have an excellent non-relativistic explanation for Sagnac effect in vacuum. You really think that for n>1 everything changes and a non-relativistic (non-Lorentzian) explanation is impossible?

... any calculation that relies on c being invariant is a relativistic calculation, as that is a postulate of special relativity.

This is a good point That's why I wrote "almost":

... A good explanation/theory of how light travels in transparent materials can and should cover this. I have such a theory and, as I said, this has almost nothing to do with relativity.

On the other hand, the fact that the speed of light in vacuum is constant, c, in one place (the lab) is not exclusively from relativity. It may be true also for aether theories. So, a theory based only on that is not necessarily "a relativistic calculation". However, I know that the constancy of c in our real lab is due to relativity, so let's use non-Lorentzian instead of non-relativistic.

Edited by DanMP
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On the other hand, the fact that the speed of light in vacuum is constant, c, in one place (the lab) is not exclusively from relativity. It may be true also for aether theories. So, a theory based only on that is not necessarily "a relativistic calculation". However, I know that the constancy of c in our real lab is due to relativity, so let's use non-Lorentzian instead of non-relativistic.

Do you have an example in mind? Because every aether theory I can think of has an absolute reference frame for measuring all speeds. If you don't have an absolute frame, what is the point of the aether?

IOW, the postulates of relativity would have been unnecessary if they were already part of standard physics.

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Do you have an example in mind? Because every aether theory I can think of has an absolute reference frame for measuring all speeds. If you don't have an absolute frame, what is the point of the aether?

IOW, the postulates of relativity would have been unnecessary if they were already part of standard physics.

...any calculation that relies on c being invariant is a relativistic calculation, as that is a postulate of special relativity.

First, the invariance of c is not a product of relativity. It was postulated based on experimental results. Confirmed, yes, but not the result of a relativistic (or any) calculation.

Lorentz transformations (used to explain Fizeau & Sagnac) are actively based on the above mentioned postulate, because 2 frames with the same speed for light in vacuum, c, are considered (in Fizeau exp.: the lab frame and the moving water frame). So here we do have a relativistic calculation.

If we consider only the lab frame, we don't really use the postulate that claim: "The speed of light in free space has the same value c in all inertial frames of reference.". We use only the fact, proved experimentally, that in the lab frame the speed of light in vacuum is c, in all directions. The lab may be in a special/preferred frame. The result is the same. So, this is not a relativistic calculation.

As I said, I know that the lab frame is not special, and the speed of light in free space has the same value c in all inertial frames of reference, but the explanation/calculation doesn't use/need that, so it is not a relativistic calculation.

To be entirely correct we can call it non-Lorentzian, as I proposed above.

By the way, how many theories based on postulates do we have? Are you happy with this kind of "solving" things?

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First, the invariance of c is not a product of relativity. It was postulated based on experimental results. Confirmed, yes, but not the result of a relativistic (or any) calculation.

It's a product of nature. But that was not recognized as such in pre-relativity physics, other than the trivial case of c being infinite. So it is part of relativity.

Lorentz transformations (used to explain Fizeau & Sagnac) are actively based on the above mentioned postulate, because 2 frames with the same speed for light in vacuum, c, are considered (in Fizeau exp.: the lab frame and the moving water frame). So here we do have a relativistic calculation.

If we consider only the lab frame, we don't really use the postulate that claim: "The speed of light in free space has the same value c in all inertial frames of reference.". We use only the fact, proved experimentally, that in the lab frame the speed of light in vacuum is c, in all directions. The lab may be in a special/preferred frame. The result is the same. So, this is not a relativistic calculation.

That's an interesting claim, considering that Fizeau is considered one of the tests that helped disprove the aether, owing to the prediction of additive velocities. The water is moving in the experiment, and in two different directions, so this claim of one frame is nonsense.

https://en.wikipedia.org/wiki/Fizeau_interferometer

https://en.wikipedia.org/wiki/Fizeau_experiment

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That's an interesting claim, considering that Fizeau is considered one of the tests that helped disprove the aether, owing to the prediction of additive velocities. The water is moving in the experiment, and in two different directions, so this claim of one frame is nonsense.

Ok, Fizeau in one frame was not posted (yet), so please refer to Sagnac explanation in vacuum posted by imatfaal.

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Ok, Fizeau in one frame was not posted (yet), so please refer to Sagnac explanation in vacuum posted by imatfaal.

AFAIK the Sagnac effect in general does not make this same distinction between relativistic and pre-relativistic physics, even though there are two directions for the light travel. It's consistent with the earth being in a fixed aether; the inconsistency with other experiments are what discredit the aether idea, since they show that we can't be at rest with respect to it.

As my point was that v<<c is not an automatic criterion for requiring relativity, and the Fizeau experiment is an example of this, my point is made. I did not claim that all phenomena with v<<c are relativistic.

However, if the Sagnac experiment is carried out with optical fiber (or any medium), then it incorporates the velocity addition formulas and requires relativity to explain this, just as in the Fizeau experiment.

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AFAIK the Sagnac effect in general does not make this same distinction between relativistic and pre-relativistic physics, even though there are two directions for the light travel. It's consistent with the earth being in a fixed aether

...

However, if the Sagnac experiment is carried out with optical fiber (or any medium), then it incorporates the velocity addition formulas and requires relativity to explain this, just as in the Fizeau experiment.

I wrote from the very beginning (and repeated many many times):

Fizeau experiment and Sagnac effect are explained completely and correctly only using special relativity (Lorentz transformations) ...

As I wrote here, Sagnac effect is explained in a classical way only when light is travelling through vacuum or air. When the refractive index is greater than 1, SR is used.

I also wrote:

Relativistic effect is only the difference between the classical result and the relativistic one. And for low speeds, this difference is very small, usually very hard to detect. This is the "trend", as we seen in the car going 100 km/hr example and Sagnac in air example.

So, in the same way we still use classical physics for cars, we can and should have a complete classical explanation for Sagnac and Fizeau. Do you agree?

You never agreed. You said:

"this difference is very small, usually very hard to detect" is a watered-down claim from the original. It allows for exceptions, and thus negates any expectation that there must be a nonrelativistic explanation for any effect where v<<c.

Which means you still can't arbitrarily claim that there should be a nonrelativistic explanation for something. You can ask if there is one, but you can't demand it.

I replied:

My claim is not arbitrarily. It is based on the fact that we don't know any exception (big differences [between classical and relativistic results] for v<<c and no GR effects) and, more important, on the fact that we have an excellent non-relativistic explanation for Sagnac effect in vacuum. You really think that for n>1 everything changes and a non-relativistic (non-Lorentzian) explanation is impossible?

You never answered. Please answer.

I also need an answer to this:

By the way, how many theories based on postulates do we have? Are you happy with this kind of "solving" things?

Edited by DanMP
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I wrote from the very beginning (and repeated many many times):

I also wrote:

You never agreed. You said:

I replied:

You never answered. Please answer.

I never agreed with the one statement because I don't agree with it. We don't have a completely classical explanation for Sagnac and Fizeau, since we don't have a completely classical explanation for Fizeau.

As for the other, it's a straw man of what I have been saying. I saw no reason to defend a straw man. If you read what I have repeatedly said, you wouldn't need me to answer. I said that v<<c is not automatically a guarantee that a non-relativistic explanation exists. Saying that a non-relativistic explanation is impossible is not a faithful restatement — it's a twisting of the statement into saying something else. So no, I don't really think that, and never said or implied it.

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You don't seem to be willing to understand.

Sure you can use Newtonian physics where There is miniscule relativistic effects. However it will not be as accurate.

For example there is a measurable time dilation experiment where two clocks were a measly 12" apart.

Yes the effect is extremely small but nonetheless it is present.

As far as theories based on postulates. Well most theories start out as postulates then the math is developed, then experimental evidence is gathered to see if they are correct. If the evidence doesn't show then the postulates are shown to be wrong.

Happens more often than people realize.

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As far as theories based on postulates. Well most theories start out as postulates then the math is developed, then experimental evidence is gathered to see if they are correct. If the evidence doesn't show then the postulates are shown to be wrong.

So, instead of using QM/QPh or my simple explanation (see here), I may write a postulate stating something like that: "All our instruments are made of atoms, and they compensate any apparent change in light/interaction speed, giving the same result for the speed of light in vacuum: c ".

This would cover also the other Einstein postulate, because all the atoms in the same frame are affected in the same way, so they will not notice any difference within the frame. Time dilation, length contraction, etc. affect all the atoms in the frame in the same way. (Now you have the reason why - and you can understand how - "time" affects everything in a frame, not only clocks, you can see beyond mathematics).

And Mordred, my postulate being in agreement with Einstein's postulates, the maths may remain the same, giving the same validity to such a theory. Do you agree?

So Swansont, after 37 posts, you agree at least that it is possible to have a non-relativistic explanation for Fizeau & Sagnac?

Edited by DanMP
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So Swansont, after 37 posts, you agree at least that it is possible to have a non-relativistic explanation for Fizeau & Sagnac?

I answered this already. Were you not paying attention? Fizeau does not have a non-relativistic explanation, while Sagnac does as long as it's in free space.

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Why would you think I would agree with you. You have yet to show any math to show how you can account for these experiments via Newtonian physics at the same degree of accuracy as those covered by relativity.

If you honestly believe you can change a physicists mind about something without applying math and experimentation your deluding yourself.

Measuring equipment doesn't compensate for measurements that are non linear. In particular the equipment used in those experiments.

Your postulates is incorrect

Edited by Mordred
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I answered this already.

If this

... Saying that a non-relativistic explanation is impossible is not a faithful restatement — it's a twisting of the statement into saying something else. So no, I don't really think that, and never said or implied it.

is your answer, it's not very clear, that's why I asked again.

Anyway, if you think it is possible, why are you not interested in such a theory? It may offer a better explanation on how light travels through transparent materials. Or it can test current theories (on how light travels through transparent materials) ...

If you honestly believe you can change a physicists mind about something without applying math and experimentation your deluding yourself.

Who said I don't have experiments able to prove my theory? See here. There are more.

Your postulates is incorrect

Why exactly?

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If this

is your answer, it's not very clear, that's why I asked again.

Anyway, if you think it is possible, why are you not interested in such a theory? It may offer a better explanation on how light travels through transparent materials. Or it can test current theories (on how light travels through transparent materials) ...

Because all of physics is tied together; no one part stands alone.

Sagnac has a non-relativistic explanation, consistent with the earth being at rest with respect to an aether. But other experiments show this cannot be the case — we would have to be moving through an aether according to stellar aberration — so we can conclude than the aether does not exist. Thus, we know that the non-relativistic explanation for Sagnac is wrong. Even if it gives the right answer, that's purely accidental.

Why would I be interested in a model which is demonstrably wrong? If it's wrong, it can't offer a better explanation. We know it will fail horribly for some experiments.

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Why exactly?

Look at the equipment setup in the Fizou experiments. The equipment itself doesn't suffer from relativistic influence. Neither does the equipment in the Sagnac experiments. Or rather the experimentor is in the same frame of reference as the equipment.

Looks like your still having trouble with frames of reference.

If you have two observers Alice and Bob. Each with their own clock calibrated to each other.

Alice being stationary for simplicity. Bob being inertial.

Alice looks at her clock sees nothing out of the ordinary, when she looks at Bob's clock she sees the time dilation.

However Bob looks at his clock sees nothing but when he looks at Alice's clock he sees the same dilation.

In the Fizeou and Sacnac experiments the observer is in the same reference frame as the equipment.

Edited by Mordred
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Because all of physics is tied together; no one part stands alone.

Sagnac has a non-relativistic explanation, consistent with the earth being at rest with respect to an aether. But other experiments show this cannot be the case — we would have to be moving through an aether according to stellar aberration — so we can conclude than the aether does not exist. Thus, we know that the non-relativistic explanation for Sagnac is wrong. Even if it gives the right answer, that's purely accidental.

Why would I be interested in a model which is demonstrably wrong? If it's wrong, it can't offer a better explanation. We know it will fail horribly for some experiments.

Ok, then again, non-Lorentzian, not non-relativistic, although the fact that the speed of light in vacuum in one frame is c, is not due to a relativistic calculation. If you want a calculation for it, then why not Maxwell calculation?

And forget aether. It's not about aether vs.relativity. It's about the fact that a calculation is not relativistic only because it uses c as the speed of light in vacuum in the lab frame. It agrees with relativity but is not a relativistic calculation!

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Ok, then again, non-Lorentzian, not non-relativistic, although the fact that the speed of light in vacuum in one frame is c, is not due to a relativistic calculation. If you want a calculation for it, then why not Maxwell calculation?

And forget aether. It's not about aether vs.relativity. It's about the fact that a calculation is not relativistic only because it uses c as the speed of light in vacuum in the lab frame. It agrees with relativity but is not a relativistic calculation!

If it uses the velocity addition formula of relativity it's relativistic.

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If it uses the velocity addition formula of relativity it's relativistic.

Non-Lorentzian means that it not uses Lorentz transformation, as in Sagnac effect in vacuum.

In the Fizeou and Sacnac experiments the observer is in the same reference frame as the equipment.

Yes, but the water/cable moves.

Mordred, to understand "my postulate" you have to go back in the linked thread, or to wait until I decide to post the full "story". I'm not sure that I will post it in "scienceforums.net", since I didn't get any positive feedback in a month, and in this thread I had to explain again and again the same thing and no one seem to understand, care or agree with anything.

Edited by DanMP
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Non-Lorentzian means that it not uses Lorentz transformation, as in Sagnac effect in vacuum.

So what? Did you miss where I said that the Sagnac effect in vacuum has a non-relativistic solution? (Three times now, I think, in the few posts I've dealt with Sagnac)

What is your point?

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So what? Did you miss where I said that the Sagnac effect in vacuum has a non-relativistic solution? (Three times now, I think, in the few posts I've dealt with Sagnac)

What is your point?

Ok, it seems that we both misunderstood. I believed that you consider the Sagnac effect in vacuum explanation relativistic just because it relies on the fact that the speed of light in vacuum in the lab is c. [in fact you wrote (#27): "any calculation that relies on c being invariant is a relativistic calculation, as that is a postulate of special relativity".] That's why I tried to explain that the fact that the speed of light in vacuum in the lab is c, is not necessarily from relativity, not a relativistic calculation, but a result of experiments and of Maxwell equations, and that the explanation does not use the fact that c is constant in all inertial frames.

You, on the other hand, believed that I rely on aether, although I wrote many times that I'm not, that I know that the speed of light in vacuum in the real lab is c due to relativity (that's why I proposed to use non-Lorentzian instead of non-relativistic). You seem to ignore that and for some reason wrote the stupid (sorry) conclusion below:

Sagnac has a non-relativistic explanation, consistent with the earth being at rest with respect to an aether. But other experiments show this cannot be the case — we would have to be moving through an aether according to stellar aberration — so we can conclude than the aether does not exist. Thus, we know that the non-relativistic explanation for Sagnac is wrong. Even if it gives the right answer, that's purely accidental.

Why would I be interested in a model which is demonstrably wrong? If it's wrong, it can't offer a better explanation. We know it will fail horribly for some experiments.

So, again, forget aether! My point is that we can have good non-Lorentzian explanations for Fizeau and Sagnac. And if we can, we should be interested in such an explanation for a better understanding on how light travels through transparent materials. Do you understand/agree now?

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So, again, forget aether! My point is that we can have good non-Lorentzian explanations for Fizeau and Sagnac. And if we can, we should be interested in such an explanation for a better understanding on how light travels through transparent materials. Do you understand/agree now?

How do you arrive at the proper velocity addition formula in a Lorentzian-free fashion? I'd like to see a derivation.

And how is light traveling through transparent materials relevant to Sagnac in free space?

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I don't care about your postulates I'm answering your errors in the posts here. I also read your other threads.

My replies still stand
Relativity uses the Lorentzian transformations. So how do you propose to use non Lorentzian but still use relativity?
In a statement earlier This thread you stated the equipment compensates.
Being made up of atoms etc.

Explain how the Fizeou and Sagnac equipment compensate? That was what I was replying to earlier.
Ps the Maxwell equations you mentioned earlier also uses the Lorentz transformation rules.

Edited by Mordred
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This would cover also the other Einstein postulate, because all the atoms in the same frame are affected in the same way, so they will not notice any difference within the frame. Time dilation, length contraction, etc. affect all the atoms in the frame in the same way. (Now you have the reason why - and you can understand how - "time" affects everything in a frame, not only clocks, you can see beyond mathematics).

And Mordred, my postulate being in agreement with Einstein's postulates, the maths may remain the same, giving the same validity to such a theory. Do you agree?

see above

Edited by Mordred

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