[Centra (OP)]

I must clarify what I said about the Sagnac effect being inconsistent with Special Relativity. It's actually the experiment by Dufour and Prunier in which part of the apparatus was in rotation and part was stationary in the lab frame. That was the experiment I quoted earlier a couple times. Here's what they said about the regular Sagnac experiments.

1 The optical circuit, closed, is in its entirety fixed to the revolving disc. --
This is the well-known case of experiments of Sagnac. The two theories are here in agreement between them and in agreement with the experiment, with regard to the total shift of the 8 fringes recorded on the disc turning. However, the traditional theorist and the relativistic theorist are not in agreement between them on the distribution that they make, of the cause of the phenomenon, between the various components of the total course. But so that the physicist operator who makes the experiment has the possibility of choosing between these two theoretical interpretations, it would be necessary to take an experimental measurement directly of the speed of light on the platform in rotation, an operation which is obviously impossible to realize with the precision necessary, in the current state of the art.

[Bored chemist]

This may be shocking to some sensitive viewers, but Einstein did not originate E=mc2, just thought you should know in case you were under any illusions to that effect.

As I already said, it's the experiments that matter.

[Bored chemist]

That was a very shoddily executed experiment, and the facts that the atmosphere travels with the earth's rotating surface and that airplanes travel relative to air rendered it pointless.

The thing that actually measures time is in a vacuum chamber.
The clock doesn't know if there is air or not.

Your objection makes no sense.

For the experiment to be valid, there would need to be wind at the altitude of the planes blowing from East to West at a velocity of about 1000 mph relative to the surface of the earth, which there wasn't.

If your objection was valid, (and it's not) then you are still mistaken.
Locally, there was a wind traveling at about 1000 mph.
The air inside the plane was traveling.

You could also cite the experiment with the highly sensitive atomic clock in recent times where they found that raising the clock 33 cm caused a difference in the time rate due to gravity difference and also claimed to have confirmed that motion also affected time.

I strongly suspect that experiment is not showing that motion affects time, it's showing that gravity affects time.
It's probably better if you understand experiments before criticising them.

We don't know how vibrating atoms

And atom can't really vibrate.

Gravity and motion are two different things though

Nobody said they were the same, but they have both been shown to alter the rate of the passage of time.

We don't know why gravity affects time though, we don't know that it's due to curvature of spacetime, just that it does.

We don't know "why" gravity makes you fall down, but we know that it does and we know how to do the calculations.
It's the same with everything else- including time dilation.

[Bored chemist]

it would be necessary to take an experimental measurement directly of the speed of light on the platform in rotation, an operation which is obviously impossible to realize with the precision necessary, in the current state of the art.

That's the bit where they accept that their 1942 experiment isn't as good as it needs to be.

[Centra (OP)]

Quote from: Centra on Today at 10:02:24
"That was a very shoddily executed experiment, and the facts that the atmosphere travels with the earth's rotating surface and that airplanes travel relative to air rendered it pointless."

The thing that actually measures time is in a vacuum chamber.
The clock doesn't know if there is air or not.
Your objection makes no sense.

And what was causing the vacuum chambers to move? Were they in space moving by themselves or were they in planes moving in the air, which was itself moving with the earth? Your objection to my objection makes no sense.

Quote from: Centra on Today at 10:02:24
"For the experiment to be valid, there would need to be wind at the altitude of the planes blowing from East to West at a velocity of about 1000 mph relative to the surface of the earth, which there wasn't."

If your objection was valid, (and it's not) then you are still mistaken.
Locally, there was a wind traveling at about 1000 mph.
The air inside the plane was traveling.

Oh, the air inside the plane was moving at 1000 mph? I find that difficult to believe.

Quote from: Centra on Today at 10:02:24
"You could also cite the experiment with the highly sensitive atomic clock in recent times where they found that raising the clock 33 cm caused a difference in the time rate due to gravity difference and also claimed to have confirmed that motion also affected time."

I strongly suspect that experiment is not showing that motion affects time, it's showing that gravity affects time.
It's probably better if you understand experiments before criticising them.

I addressed the motion part of the experiment later in the post, stating that they made the cesium atoms vibrate to simulate motion. It's probably better if you understand posts before criticising them.

Quote from: Centra on Today at 10:02:24
"We don't know how vibrating atoms
And atom can't really vibrate.

That would be the part right there.

Quote from: Centra on Today at 10:02:24
"Gravity and motion are two different things though"

Nobody said they were the same, but they have both been shown to alter the rate of the passage of time.

I disagree.

Quote from: Centra on Today at 10:02:24
"We don't know why gravity affects time though, we don't know that it's due to curvature of spacetime, just that it does."

We don't know "why" gravity makes you fall down, but we know that it does and we know how to do the calculations.
It's the same with everything else- including time dilation.

How did you know how to do the calculations, wasn't it from Einstein's theories? Like I said, we don't know that motion affects time the way he said at all and if gravity does affect time, we don't know that it's for the reason Einstein said, so how can it validate his theory? Maybe his calculations just match the actual observed time dilation by coincidence. There are articles showing that the same results can be obtained using classic theory and not involving the speed of light at all. Making a theory that has the same results as other existing theories does not make that theory valid.

See this page for a quick summary of the problems with Einstein time dilation http://www.alternativephysics.org/book/TimeDilation.htm

[Centra (OP)]

Quote from: Centra on Today at 10:31:38
"it would be necessary to take an experimental measurement directly of the speed of light on the platform in rotation, an operation which is obviously impossible to realize with the precision necessary, in the current state of the art."

That's the bit where they accept that their 1942 experiment isn't as good as it needs to be.

Only problem is, they weren't talking about the experiment whose results contradicted Special Relativity, that was the next section. They were talking about the regular Sagnac effect there.

[Origin]

How did you know how to do the calculations, wasn't it from Einstein's theories?

Among others.

Like I said, we don't know that motion affects time the way he said

Sure we do, haven't you been paying attention?  Experimentation agrees with the theory.

and if gravity does affect time, we don't know that it's for the reason Einstein said, so how can it validate his theory?

Haven't you been paying attention?  Experimentation agrees with the theory.

Maybe his calculations just match the actual observed time dilation by coincidence.

Pretty mind boggling coincidence!  All experiments just happen to agree, over and over?  GPS just happens to work every time I use it?  Boy is that a lucky coincidence.

There are articles showing that the same results can be obtained using classic theory and not involving the speed of light at all.

See this page for a quick summary of the problems with Einstein time dilation http://www.alternativephysics.org/book/TimeDilation.htm

Oh great, the crank is going to start parading out the crank websites.  There as some swell websites about bigfoot or lizard aliens running the government you might also be interested in...

[Centra (OP)]

More about Olinto De Pretto and E=mc2. The only difference is he used "v" instead of "c" to represent the speed of light and he didn't put the "E" in front. He even went further and gave the formula for obtaining the caloric value, mv2/8338.

On 23 November 1903 a memoir by Dr. Olinto De Pretto entitled "Hypothesis of the ether in the life of the universe" was presented by Count Almerico Da Schio to the Royal Veneto Institute of Sciences, Letters and Arts (which later appeared in February 1904 in the Proceedings of the same Institute, Volume LXIII, Part II, pp. 439-500).

In the third paragraph of this paper, entitled "Energy of the ether and latent energy in matter" (see the following Chapter IX), we find formulated not only the same relationship hypothesized by Einstein between mass and energy, but also its 'correct' interpretation physics, which is expressed through the following words:

"The matter of any body contains in itself a sum of energy represented by the entire mass of the body, which moves all united and en bloc in space, with the same speed as the individual particles. [...] The formula mv 2 gives us the living force and the formula mv 2/8338 gives us, expressed in calories, this energy. Given therefore m = 1 and v equal to 300 million meters [per second], which would be the speed of light, also allowed for the ether, everyone will be able to see that you get a quantity of calories represented by 10794 followed by 9 zeros and that is over ten million million "(pp. 458-459).

[Kryptid]

That was a very shoddily executed experiment, and the facts that the atmosphere travels with the earth's rotating surface and that airplanes travel relative to air rendered it pointless.

Why?

The earth did not rotate beneath the planes as if they were in space, it pulled/pushed them with it in the atmosphere. For the experiment to be valid, there would need to be wind at the altitude of the planes blowing from East to West at a velocity of about 1000 mph relative to the surface of the earth, which there wasn't.

Please explain why that would be necessary.

[Centra (OP)]

That was a very shoddily executed experiment, and the facts that the atmosphere travels with the earth's rotating surface and that airplanes travel relative to air rendered it pointless.

Why?

The earth did not rotate beneath the planes as if they were in space, it pulled/pushed them with it in the atmosphere. For the experiment to be valid, there would need to be wind at the altitude of the planes blowing from East to West at a velocity of about 1000 mph relative to the surface of the earth, which there wasn't.

Please explain why that would be necessary.

I misinterpreted what they were trying to do. The air wouldn't matter because it was just the rotation of the earth itself that they were concerned with, it would have been the same if they could drive vehicles around the earth. 

About the experiment being shoddily executed, this quote is one thing I read that gave me that idea.

3 Conclusions
The HK experiment has been reproduced by recalculating the predicted values using flight data provided in [HK-3] using the formulas described in [HK-1] and [HK-4], and compared with expected values provided with HK in their paper in [HK-1] and actual observations in [HK-2]. It is expected that the values re-calculated using theory model matches with the HK predicted ones, as presented in [HK-2] and [HK-5], within the limit of the approximation applied, but that is not the case for both general and simplified models.

Passing to the observed values, the figures provided by HK in their paper significantly change from the preliminary ones in [HK-3] to the final ones in [HK-2] without any clarification of the type of consolidation made in the data post-processing. The reason could be due to a wrong use of the model expressions or their flight parameters, which are not fully released by HK, and/or to insufficient experiment data accuracy, which did not consider external effects (e.g. environmental) influencing the measurements.

As final conclusion, it is noted that
1. the accuracy of the clocks used for the experiment, namely the rms of their measured times both on ground and in flight, looks of the same order of magnitude of the effect to be measured. That raises doubts on the possibility of using any type of result for the purpose of the experiment’s objectives;

2. overall all analysed data, either predicted, recalculated and observed, are within the same order of magnitude (tenths of nsecs for Eastward case and hundreds of nsecs for Westward case), but the residual differences as significantly high (up to 40%), meaning that the accuracy of the experimental measurements was not good enough for providing a conclusive answer to the objective of validating the SR/GR model as the only one valid for time shift.

Hafele-Keating Experiment Reassessed
Gianni Casonato

[Bored chemist]

And what was causing the vacuum chambers to move?

The stuff in the chamber doesn't know, so it can't make any difference.
That's why your objection makes no sense.

Oh, the air inside the plane was moving at 1000 mph? I find that difficult to believe.

The equator spins at about 1000 mph.
If the air in the planes wasn't moving at something like that speed then the wings would get ripped off.

You could also cite the experiment with the highly sensitive atomic clock in recent times where they found that raising the clock 33 cm caused a difference in the time rate due to gravity difference and also claimed to have confirmed that motion also affected time. The problem there is that their "motion" was in fact making the cesium atoms vibrate, which is not the same as simply moving the clock around. We don't know how vibrating atoms effects a cesium clock's operation.

Are you talking about the experiment wiki cites?

"In 2010, Chou et al. performed tests in which both gravitational and velocity effects were measured at velocities and gravitational potentials much smaller than those used in the mountain-valley experiments of the 1970s. It was possible to confirm velocity time dilation at the 10⁻¹⁶ level at speeds below 36 km/h. Also, gravitational time dilation was measured from a difference in elevation between two clocks of only 33 cm (13 in).[27][28]"

[Bored chemist]

I disagree.

People who disagree with reality get called lots of things, but "scientist" isn't one of them.

How did you know how to do the calculations, wasn't it from Einstein's theories?

As you said, Einstein wasn't the only one to derive that formula.

Like I said, we don't know that motion affects time the way he said at all and if gravity does affect time,

Yes we do.
Because we checked.

Maybe his calculations just match the actual observed time dilation by coincidence

Every single time it has ever been tested, to a precision of a part in millions of millions?

How small a straw are you prepared to clutch at?

There are articles showing that the same results can be obtained using classic theory and not involving the speed of light at all.

Prove it.

[Bored chemist]

I misinterpreted what they were trying to do.

Why?
Is it because you do not know what you are talking about?

[Centra (OP)]

Are you talking about the experiment wiki cites?

"In 2010, Chou et al. performed tests in which both gravitational and velocity effects were measured at velocities and gravitational potentials much smaller than those used in the mountain-valley experiments of the 1970s. It was possible to confirm velocity time dilation at the 10−16 level at speeds below 36 km/h. Also, gravitational time dilation was measured from a difference in elevation between two clocks of only 33 cm (13 in).[27][28]"

Yeah, I guess it might be valid, I viewed the pdf of the experiments and the motion time dilation part does match the predicted curve very well. Anyway, I'm not saying everything about relativity theory is wrong, but it can also be arrived at by classical methods, it's not hard to find articles about it.

My theory in this thread is just about how the thought experiments I've seen don't seem to actually make sense as showing real light velocity situations.

From what I've read, about the Sagnac effect and other experiments, light maintains constant speed relative the the lab frame, which is really the earth frame, more specifically the center of earth frame. It appears that light has constant velocity relative to the largest mass in the vicinity of its emission, the earth instead of the turntable and rotating light source in Sagnac experiments, for instance. That's what was concluded in the book "Challenging Modern Physics: Questioning Einstein's Relativity Theories". You can't download the whole book for free but you can read much of in Google Books.

 All those light experiments like Sagnac and Michelson always are explainable by light speed being constant in relation to the at rest center of the earth. I guess they consider it at rest because it rotates so slowly in comparison to the surface. But what I said about light speed being constant in relation to the largest mass near where it's emitted might also explain stellar aberration. The light from the stars is constant relative to those stars, being very massive. Obviously it has to be constant relative to something, and it's not aether, but it could be the largest mass in the vicinity of its emission.

 I say "vicinity" because the light sources in the Sagnac type experiments were not part of the lab or earth frame, being on the rotating turntable, and yet the light they emitted behaved as if it had been emitted in the stationary lab frame. It didn't behave like it was in a different inertial frame with its own constant light speed, it acted like it was part of the lab frame. How could that happen unless the constant speed is relative to the largest mass, the earth, which the lab frame is also part of? So that's a little different than what Einstein postulated. His postulates would predict that the light emitted and received in the turntable frame would be constant relative to the turntable, not the lab/earth, a separate "stationary" frame.

[Bored chemist]

Are you talking about the experiment wiki cites?

"In 2010, Chou et al. performed tests in which both gravitational and velocity effects were measured at velocities and gravitational potentials much smaller than those used in the mountain-valley experiments of the 1970s. It was possible to confirm velocity time dilation at the 10−16 level at speeds below 36 km/h. Also, gravitational time dilation was measured from a difference in elevation between two clocks of only 33 cm (13 in).[27][28]"

Yeah, I guess it might be valid,

So, do you understand that the experiment which refers to 33cm is a verification (of enormous precision) of the effect of gravity on the rate of passage of time?
(And do you understand that the experiment is northing to do with movement? That's a different experiment)

[Bored chemist]

Anyway, I'm not saying everything about relativity theory is wrong, but it can also be arrived at by classical methods, it's not hard to find articles about it.

Then please do so.

[Bored chemist]

My theory in this thread is just about how the thought experiments I've seen don't seem to actually make sense as showing real light velocity situations.

We have shown that you do not understand them.
Is it any wonder that they "don't seem to actually make sense"?

[Halc]

it would be necessary to take an experimental measurement directly of the speed of light on the platform in rotation, an operation which is obviously impossible to realize with the precision necessary, in the current state of the art.

That's the bit where they accept that their 1942 experiment isn't as good as it needs to be.

Just a note: No instrument is accurate enough. They're talking about measuring the one-way speed of light, which cannot be done at all, per Galilean relativity theory coupled with Maxwell's equations. On the other hand, measuring the value of c can be done (and had been done at the time of the writing of the above quote) on a rotating platform.

Just to clarify; do you mean this article? (Obviously, the original is in French)
http://www.conspiracyoflight.com/pdf/Dufour_and_Prunier-On_the_Fringe_Movement_Registered_on_a_Platform_in_Uniform_Motion_%281942%29.pdf
The French version's here but it's paywalled anyway.

Interesting that conspiracyoflight would pick up this Dufour and Prunier (D&P) article. It certainly wasn't first posted there.
The site is a religious science-denial site, and no paper makes its way in there unless it is fallacious. It became an interesting homework assignment to find your field of study and point out the mistakes made by each of the articles in the chosen field. This article is no exception, despite the fact that it agrees that the Sagnac effect does not contradict relativity:

[case] 1 The optical circuit, closed, is in its entirety fixed to the revolving disc.
This is the well-known case of experiments of Sagnac. The two theories are here in agreement between them and in agreement with the experiment, with regard to the total shift of the 8 fringes recorded on the disc turning

This is an important clue that the mistake is not with the calculations made for the rotating part of the experiment, but by the fixed part, as shown in the diagram on page 10 where the beams exit the plate and detour to the ceiling for a while, to come down at the opposing mirror.

Centra, I didn't see your reply right away.

As Sagnac experiments have established, Sagnac effect does not conform to Special Relativity predictions

Interesting that the very paper you quote says quite the opposite just a few lines above the part you quoted. See the quote just above.

In reality, relativity theory adds almost nothing to the classic calculation of the effect. In order for relativity theory to be invoked, you need to spin the device at relativistic speeds and then let various theories compete for descriptions of how the rotating device must deform at those speeds. But ring interferrometers work today detecting the slightest rotation, such that they are commonly found in say video game controllers.
So relativity doesn't come into play at all, but Galilean physics must still be followed, and D&P fail to do even this.

I can't quote the equations as seen in the pdf, because they use symbols which can't be copy/pasted, they come out as squares, but I'm sure you can find the article if you feel the need to see them.

[case] 2 Part of optical circuit  is fixed to the revolving disc, the other part of the optical circuit remains fixed compared to the laboratory. –   

Under these conditions, which are those of our experiments, the shift of the fringes is due obviously to the optical course fixed to the revolving disc. We will calculate the values which return to us according to the two theories. In the experiments made in accordance with assembly of figure 6, the area included in the sector having for base the light path trained FDEOKJ and for top of the path the center C of rotation of the platform had as an algebraic full value (because the surface of the small basic triangle base ED in this figure must be counted as negative), A' = 1777 cm2 approximately, while the area of that of the same sector based light path FDEOKJ and whose top is the item 0 where the observer is pulled by the disc, had as an algebraic full value:
A = 169 cm2 approximately

By introducing these numerical values into the expression of the fringe shifts δ, one finds with λ= 0.56 um, for the two directions of rotation and for an angular velocity of 1 turn/sec,
    δ = (16-A') / eλ = 0.053 in fringes (according to the classical theory)
    δ = (16-A') / eλ = 0.005 in fringes (according to the relativistic theory);
                                   
that is to say a value that is approximately ten times smaller, according to this last theory than according to the preceding one.
The relativistic theory thus seems to be in complete dissention with the classical theory and also with the result provided by this experiment.
...

Concerning the part in blue:
The symbols are right here on the site, so you don't even need tex. The paper says (absurdly):
    δ = (16-A') / eλ = 0.053 in fringes (according to the classical theory)
    δ = (16-A') / eλ = 0.005 in fringes (according to the relativistic theory);

This makes no sense. Two identical equations yield completely different values. So maybe there's a translation error. I think the lower equation meant to say A=..., not A'=...,

I see A'=1777 cm² in one place and A=169 cm² elsewhere, but relativity doesn't suggest that the polygon in question is a tenth the area that the classical theory says, so they're using a different polygons, and then mistakenly not making corrections for the non-rotating part of the light path. Apparently D&P regard the ceiling to be rotating in classic theory but not in relativity theory. Ouch...

OK, so they're deliberately using different polygons, which is legal, but then the time between mirrors J and F needs to be accounted for, and they assume it is the same in both directions, which is not true in the deliberately obfuscating frame in which they choose to frame what's going on. See the bold in the quote below, taken from the prior page:

III. - Interpretation of the experimental results.
Let us point out initially the elements of the theories that we will apply here. Theclassical theory supposes, as one knows, that for the observer linked (fixed) to the disc,the speed of the light in a point of the revolving disc differs from the speed C of the lightin the laboratory, in a quantity equal to + /- v, if v represents in value the absolute projection of the linear velocity of the disk at the point considered on the platform, theelement of the path considered.

OK, so they've invented an observer that they've for some reason put on the disk (at location O, or 'S' on the picture on page 10, at the beam splitter at the bottom of the disk) despite the fact that no observation/measurement takes place there. Legal, but now they're using effectively an inertial frame for O in which the entire laboratory is moving. Do they always take account for this?  Of course not!
Also, note the contemptuous tone of D&P towards Mr Langevin. They want this not to work. These guys are trolling!

We will use as the relativistic theory of these phenomena,that given by Mr. Langevin [2] in 1921 and recalled by him more recently [3]. In thisform of interpretation, the observer is pulled by the moving disc and is supposed to adopt a central time t which is that reported by the Galilean observer in which the center 0 is chosen on the platform as motionless. (Let us notice while passing that this selected center 0 is not necessarily the center C of rotation of the platform, but that it is an unspecified point, arbitrarily chosen on the disc.) The form which takes the fundamental invariant ds² implies an anisotropy in light propagation of which the speed varies with direction between C + ωr and C - ωr with the first order of approximation in ω. In these expressions, ω is the angular velocity of rotation of the platform, r is the distance from center 0 arbitrarily chosen, at the point of passage, on the disc, of the light ray considered. Mr. Largevin finds thus that duration dt of light course of length dl is given for a direction of circulation of the light by expression: dt = dl/C + 2ω dA/C²
where dA is the area of a triangle with base dl and top selected arbitrary center 0. While integrating along the finished light course fixed to the revolving disc, and by taking account of the other direction of propagation, one can deduce the value from the displacement of the fringes ascribable to the course considered.

I want to note here that no consideration is made for the fact that the ceiling is moving at some velocity to the left in the frame of O in which they're doing their computations. Zero mention of this.
Light from point J takes longer to get to F than does light from F to J, just like in the frame of a train platform, light takes longer to go from tail to nose than it does to go from nose to tail. There's simply a different distance that needs to be traveled, and they don't account for this difference in their computation of δ.

I'm not even a physicist and I can see the errors in this description. Surely this paper was at some point peer reviewed, and ultimately discarded, which is why it today can only be found on denial sites like conspiracyoflight.

Also note: Relativity theory was never invoked. It was all Galilean relativity that was used. No contradiction. Lorentz factors, dilation etc. These factors would need to be addressed with very fast rotation, but not for this.

Mr Halc, so would you like to rephrase your statement that my words were "tosh"?

I would. Your words are deliberately but not particularly exceptionally tosh. You deniers need some new material.

This may be shocking to some sensitive viewers, but Einstein did not originate E=mc2, just thought you should know in case you were under any illusions to that effect.

Despite the pop association he has with that equation, it is indeed well known that he didn't originate it.It seems your beef with relativity is a personal one against Einstein, not necessarily against his theory. Now why is that? How is this comment otherwise relevant to the discussion?

[Bored chemist]

On the other hand, measuring the value of c can be (and has been) done in a rotating platform.

It almost always is. The platform is called the Earth.
It's a pity Centra can't accept this simple fact.

They're talking about measuring the one-way speed of light, which cannot be done at all

Again, I know that (and posted a video about it) , but Centra is ... not so well informed.

[Centra (OP)]

Are you talking about the experiment wiki cites?

"In 2010, Chou et al. performed tests in which both gravitational and velocity effects were measured at velocities and gravitational potentials much smaller than those used in the mountain-valley experiments of the 1970s. It was possible to confirm velocity time dilation at the 10−16 level at speeds below 36 km/h. Also, gravitational time dilation was measured from a difference in elevation between two clocks of only 33 cm (13 in).[27][28]"

Yeah, I guess it might be valid,

So, do you understand that the experiment which refers to 33cm is a verification (of enormous precision) of the effect of gravity on the rate of passage of time?
(And do you understand that the experiment is northing to do with movement? That's a different experiment)

They did both experiments in the same article so I don't know what your point is. Yeah, apparently gravity and motion effect time, but Relativity isn't the only thing that provides an explanation for the results.