3D pose of clock in Hafele-Keating experiment

[sahil5d]

In the Hafele-Keating experiment (cesium clock on an airplane), is it important how the clock is posed, as in 3D xyz pose?

I have found no mention or discussion of the pose of the clock, which should be important, right? Specifically, the path of the cesium beam or the microwave beam inside the clock. Let's say the airplane velocity is in the +x direction. I would think there is a difference between the cesium beam or microwave beam

• also moving along the x axis,
• or along the y axis, or z axis,

because in the y or z, the beam literally is traversing a longer path to get to the other side (the famous v, sqrt(c^2 - v^2), c right triangle, not in a theoreticalinternalclock way but in a practicaltravelpath way).

Beam path
https://cdn.britannica.com/10/99010-004-E79A90B6/atomic-clock.jpg?s=1500x700&q=85

Pose of Mr. Clock
https://en.wikipedia.org/wiki/File:Hafele%E2%80%93Keating_experiment.jpg
https://en.wikipedia.org/wiki/File:HP_5061A_Cesium_Beam_Frequency_Standard.JPG
https://www.youtube.com/watch?v=gdRmCqylsME

[ftessier]

According to special relativity, length contraction and time dilation are orthogonal, so to speak. Both length $l$ contraction (along the relative velocity direction) AND time $t$ dilation is observed. Both are simply related through $\gamma$ (the product $l\times t$ is constant), but are otherwise independent. Hence orientation has no bearing on time dilation.

[HanDeBruijn]

It would be great if all of us could only agree upon a Static Euclidean Universe instead of the current one based upon General Relativity .

[RedshiftDrift]

These coordinate systems are all relative to Earth, for convenience. There's nothing 'absolute' about them.

Horizontal system
The horizontal, or altitude-azimuth, system is based on the position of the observer on Earth...

Equatorial system
The equatorial coordinate system is centered at Earth's center, but fixed relative to the celestial poles and the March equinox...

Ecliptic system
The fundamental plane is the plane of the Earth's orbit, called the ecliptic plane.

Galactic system
The galactic coordinate system uses the approximate plane of the Milky Way Galaxy as its fundamental plane. The Solar System is still the center of the coordinate system...

Supergalactic system
The supergalactic coordinate system corresponds to a fundamental plane that contains a higher than average number of local galaxies in the sky as seen from Earth.

In the animation, the camera follows 'Earth', then 'Voyager-1', etc... There is no 'absolute' reference frame.
The second animation gives a sense of motion relative to the matter we see (galaxies).

Astrophysicists talk about a Hubble flow relative to the CMB, but that is pure theoretical convenience since it cannot be measured. And since the CMB is tied to the matter that produces it, we're still using a relative coordinate system.

Even in a static Euclidean geometry, the origin of the coordinate system is an arbitrary choice.

[sahil5d]

I mean absolute as in a piece of length is the same piece of length in any coordinate system, and there isn't any stretching or squishing.

I'm also saying that shutting down the idea of absolute velocity and absolute position is wrong, because we can continue to define ever-better coordinate systems based on ever-larger centers of mass, and it is not impossible that at some point we find a largest possible center of mass. And it is not impossible that we establish a frame of stillness, such as with the latest measurements of the distant quasars, the Distant Quasar Rest Frame.

[HanDeBruijn]

@sahil5d .

absolute velocity and absolute position

You may appreciate section 1.2 Mean Rest Frame, in the book Origin of Inertia by Amitabha Ghosh.

[sahil5d]

@HanDeBruijn Yes. However I currently think the distant quasar dipole is a better candidate than the CMB dipole.
https://twitter.com/sahil5d/status/1665862086331875328.

[budrap00]

It would be even better if we dismissed the atavistic cultural concept of a Universe as unphysical. The question of whether the Universe is Riemmanian or Euclidean is akin to discussing the number of angels that can dance on the head of a pin - it is a metaphysical argument without scientific meaning. Bud

…

On Sat, Jul 1, 2023 at 8:35 AM Han de Bruijn ***@***.***> wrote: It would be great if we all can agree upon a Static *Euclidean* Universe instead of the current one based upon General Relativity <#78> . — Reply to this email directly, view it on GitHub <#82 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BAIWF7G7LN7RTVAOTXTPRDTXOAKRFANCNFSM6AAAAAAZXXZRNY> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.*** com>

[RedshiftDrift]

Actually no, the geometry can be known by measuring distances and angles.

We measure distances that add up along a certain direction, and the sum of the angles of a triangle is 180 degrees. So the Euclidean geometry is appropriate to describe distances.

[budrap00]

Hi Louis, You missed the point. It is in the context of the simultaneously existing Universe that lies at the base of all modern cosmological systems that the question of which geometry has no meaning. That Universe is falsified under standard physics by the observed scale of the Cosmos and the max light speed limitation. There is not and cannot be such an entity as the simultaneous Universe and therefore discussing its geometry is scientifically meaningless. As far as observations within the observable Cosmos go, Euclidean geometry does appear quite adequate. The interesting question here is whether this indicates a flat physical spacetime geometry or merely a relational spacetime with no inherent physical characteristics. I don't think the two cases are distinguishable. Regards, Bud

…

On Sat, Jul 1, 2023 at 10:07 AM Louis Marmet ***@***.***> wrote: Actually no, the geometry can be known by measuring distances and angles. We measure distances that add up along a certain direction, and the sum of the angles of a triangle is 180 degrees. So the Euclidean geometry is appropriate to describe distances. — Reply to this email directly, view it on GitHub <#82 (reply in thread)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BAIWF7GPBUQ4EYVIIWE3CO3XOAVKNANCNFSM6AAAAAAZXXZRNY> . You are receiving this because you commented.Message ID: ***@***.***>

[RedshiftDrift]

Your first paragraph is the metaphysics of cosmology, which is not what my comment was about.

I agree that the two cases you describe in the second paragraphs are indistinguishable. In that case one is free to use either one or the other description. I pick Euclidean geometry because I am more familiar with it.

[budrap00]

My original comment dismissed the commonly held concept of a Universe as falsified by standard physics and cosmological observations, and therefore the question of the geometry of the Universe is rendered scientifically meaningless metaphysics.

You objected that you could measure the geometry, although you only implied but did not state "of the Universe". So what is your point exactly? Is the geometry of the Universe a scientifically meaningful concept or just metaphysics?

[sahil5d]

@marmetl forgive me if this has been asked before, but what are your thoughts on P. Marmet's https://www.newtonphysics.on.ca/michelson/?

During the last century, the Michelson-Morley equations have been used without realizing that two essential fundamental phenomena are missing in the Michelson-Morley demonstration. We show that the velocity of the mirror must be taken into account to calculate the angle of reflection of light. Using the Huygens principle, we see that the angle of reflection of light on a moving mirror is a function of the velocity of the mirror. This has been ignored in the Michelson-Morley calculation. Also, due to the transverse direction of the moving frame, light does not enter in the instrument at 90 degrees as assumed in the Michelson-Morley experiment. We acknowledge that, the basic idea suggested by Michelson-Morley to test the variance of space-time, using a comparison between the times taken by light to travel in the parallel direction with respect to a transverse direction is very attractive. However, we show here that the usual predictions are not valid, because of those two classical secondary phenomena, which have not been taken into account. When these overlooked phenomena are taken into account, we see that a null result, in the Michelson-Morley experiment, is the natural consequence, resulting from the assumption of an absolute frame of reference and Galilean transformations. On the contrary, a shift of the interference fringes would be required in order to support Einstein’s relativity. Therefore, for the last century, the relativity theory has been based on a misleading calculation.

These two concerns

• the angle of reflection of light on a moving mirror is a function of the velocity of the mirror
• light does not enter in the instrument at 90 degrees

make a lot of sense to me.

[Francois-Zinserling]

@sahil5d I am not sure of your question but I will give it a go.

Maxwell and Newton equations have no time components in them. They work well for static charges and masses, and by each having sufficient time to set up a surrounding (static) field, we can observe effects like 'instant action at a distance'.

But when things start moving the situation changes. Rapidly so for charges (because of relative strength and also relative velocities of the interactions) but less noticeable for masses. Electrodynamics have done advanced research on this, because it is so easily observable and testable. Not only for velocity but even also for acceleration.
Not so much for gravity. We are still stuck with Newton because GR is slow on popping out usable solutions.

Retarded potential considers propagation time from the source to the observer, so it tries to account for the 'instant action at a distance' which logically cannot be correct but in gravity still somehow seem to work. Even in the case of gravity sun-to-earth there is an 8 minute retardation. Yet the earth is attracted not to where the sun was 8 minutes ago, but it is attracted to exactly where the sun is NOW. This seems like Newton is correct but we know causally it cannot be.

So the logic conclusion is that there must be a secondary effect based on velocity (lateral - sideways velocity, not radial inward or outward). This velocity component is very well observed in electrodynamics, and this is being logically pushed in gravity.
Yes, the velocity component caters exactly for the anomaly, but if there were no velocity there would be no anomaly. So I don't see a problem with solving it that way.

You are right. Photons are not attraction of charged bodies. Even quantum physics have not solved this yet, not even with virtual particles. The actual mechanism of charge attraction or repulsion is still unknown.

[sahil5d]

I still don't get the distinction you said there is between "gravity moves at the speed of light" and "the surrounding field gets updated at the speed of light". What distinction is there?

the 'instant action at a distance' which logically cannot be correct but in gravity still somehow seem to work.

it is attracted to exactly where the sun is NOW. This seems like Newton is correct but we know causally it cannot be.

Those assertions might not necessarily be true. Anchoring on a belief that "no changes can happen faster than c" might be wrong.

I hypothesize that photons and electrons (informally, "things") may be able to move from point to point in a volume no faster than c, but acceleration vector changes at all points in the volume could happen, instantly.

there must be a secondary effect based on velocity (lateral - sideways velocity, not radial inward or outward). This velocity component is very well observed in electrodynamics

That may be possible, sure. A velocity-dependent term might exist in an expression for instantaneous gravitational attraction. But that is not proof of "the surrounding field gets updated at the speed of light".

[Francois-Zinserling]

"gravity moves at the speed of light" and "the surrounding field gets updated at the speed of light". What distinction is there?

The distinction is that we cannot really say gravity moves at the speed of light, because when mass is there, gravity is already there. There is no way to say it isn't, because if you can see it (light) you can already feel it (gravity). Then it might appear that gravity is instant, but it isn't.

But by saying the field gets updated at the speed of light, e.g. when a mass moves, we are saying gravity gets updated or 'changes' at the speed of light. It all works out fine with 'c' as the limiter.
So e.g. a gravitational wave is the wave of the changes in gravity. d(gravity)/dx, or d(gravity)/dt depending if you are measuring over distance or over time. Either way, this wave moves at the speed of light.
No need for any superluminal speeds or spooky actions.

[sahil5d]

So e.g. a gravitational wave is the wave of the changes in gravity. d(gravity)/dx, or d(gravity)/dt depending if you are measuring over distance or over time. Either way, this wave moves at the speed of light.

I still challenge that. There is the issue of unstable circular orbits, which is excused by another effect "damping". And according to the Wikipedia page on the [gravity field gets updated at c] model, "The attraction toward an object moving with a steady velocity is towards its instantaneous position with no delay, for both gravity and electric charge." So the entire model could be frivolous!

No need for any superluminal speeds or spooky actions.

I disagree. There is a need for a model of [instantaneous gravitational attraction], which is that the [gravity field gets updated at c] model may be unnecessary and wrong, because practically and theoretically, attraction is to instantaneous position. I think we should take a hint from Feynman's half-retarded and half-advanced theory.

Also, while "superluminal" is a somewhat fair description, it's not like a thing is moving like a photon is moving. It's more like an instant state change at all points in the volume. And "spooky"? Well, ok, but it's happening everywhere, so amend that to spooky action between all distances, or better yet, exceedingly normal action in the whole volume.

[RedshiftDrift]

> have you seen Hossenfelder's ... video on LIGO?

Wow, she's so "zen" in that video! I agree with most of what she says. When one looks carefully at "gravitational wave detection" experiments, a lot can be wrong in the interpretation of the signals since many other physical effects can explain similar detections.

I do not doubt that the gravitational wave detections are real

1. I do not doubt that the gravitational wave detector has produced signals. But I have doubts about what caused these signals. That's actually what Sabine says later in the video, see 4. below.

These deformations happen because Einstein's theory of general relativity tells us that space and time are not rigid but react to the presence of matter.

2. I agree that GR can be interpreted that way, and that's how mathematics describes gravitational effects. But I apart from describing "variable space-time" there is another way to explain relativistic effects as an effect on matter, including rulers and clocks. The mathematical equations to describe relativistic effects are the same (as long as no discontinuity exists in the equations!) and so gravitational waves should also arise from the "variable ruler-clock" interpretation, see point 2. here. But if gravitational waves can exist, it doesn't mean we have detected them.

'the curve in the famous light curve' was not found by using analysis algorithm but partly done by eye and hand tuned for pedagogical purposes.

3. I agree that's a problem. It is worrisome that the oscillating curve of increasing frequency can also be explained by the energy released by the sudden absorption of a particle in a mirror of the interferometer.

we don't have confirmation that the signals that LIGO detects are of astrophysical origin](https://youtu.be/WWTvNlfkvoI?t=376) (and also here)

4. We have that confirmation now. So * if * GWs are detected, they travel at the speed of light. But signals from astrophysical origin other than gravitational waves could also trigger the LIGO detector. These types of signals (image below) are rather generic and are observed in many experiments.

The LIGO website explains "LIGO’s sensitivity to gravitational waves will be limited by the quantum nature of light at high frequencies between about 200 Hz and 10,000 Hz and by Brownian motion in the suspensions and test masses at frequencies from 10 Hz ~ 200 Hz." Therefore only signals at 200 Hz appear with their full amplitude, and any other frequency is necessarily attenuated by the detector. The signal amplitude should therefore peak at 200 Hz and have a smaller amplitude at other frequencies. And that's exactly what is seen on the data.

I indicated the period of a 200 Hz signal on the figure, right at the frequency of the expected best response of the detector. So a prediction based on the detector response explains the data without any gravitational wave.

we are waiting for independent confirmation, this one missed the mark

5. Good point. The words 'prediction', 'postdiction' and 'independent confirmation' are very loosely used by the LIGO collaboration.

they do not really know what their detector detects. They just throw away data that don't look like they want it to look

6. And that's the main argument against GW detection. The last sentence can also mean 'they keep data that look like they want it to look', or 'cherry picking'. Four years later, I still agree 100% with Sabine.

Other problems mentioned on Hossenfelder's blog are also of concerns. Example: "In April this year, LIGO started the third observation run (O3) after an upgrade that increased the detection sensitivity by about 40% over the previous run. Many physicists hoped the new observations would bring clarity with more neutron-star events that have electromagnetic counterparts, but that hasn’t happened."

[RedshiftDrift]

Where in the manuscript?

Implicit in previous work, see Refs. 12, 13, 14, 19

Not pertinent? The focus here is the angle of reflection of light on a moving mirror in an absolute stillness frame.

There is no way to detect an "absolute stillness frame", all experiments done so far show Galilean invarience. So if a theory predicts something else, it is in disagreement with experiments.

[RedshiftDrift]

Those are two distinct claims:

1. these experiments prove there is no absolute stillness frame, and
2. so we all must think that space is stretching and squishing.

For 1) experiments prove neither [there is an absolute stillness frame] nor [there is no absolute stillness frame].
The situation is that there is no need for an absolute stillness frame to explain experimental results. (@ftessier Special Relativity (SR) and General Relativity (GR) are compatible with an absolute inertial frame of reference but have no need for one because the physics is the same in all inertial frames. There is therefore no empirical way to determine which frame of reference is 'special'.)
Therefore, the choice of one or the other is a metaphysical/mathematical decision for which science offers no guidance.

For 2) "stretching and squishing" of space and time is a model among many others. One can also use a model where matter/light changes its properties when it is accelerated (similar to {but not exactly like} the explanation you give for the muon). Hilton Ratcliffe was one of many scientists who discussed that in one of his books (I forget which one...) In principle, both special relativity (SR) and general relativity (GR) can be rewritten so that space and time are not squished and stretched. This is how Einstein initially developed SR, but for GR the equations were getting a bit complicated and the mathematics had already been developed to address the problem with 'coordinate transformations'. So 'squishing and stretching' 'space and time' became the convenient way to calculate things. The language to explain 'coordinate transformations' mirrors the type of mathematical transformations that are used in SR and GR.

However the language/mathematics does not necessarily reflect the physical process. We have discussed this earlier: using $\sqrt{-1}$ in equations does not mean that $i$ has a physical reality. For SR and GR, 'coordinate transformations' are pure mathematical convenience, and as discussed in earlier posts there is currently no experiment that distinguish between [space/time stretching/squishing] and [acceleration-modified physical properties], so the choice of one or the other is again a metaphysical/mathematical decision for which science offers no guidance.

[ftessier]

Special Relativity (SR) and General Relativity (GR) are compatible with an absolute inertial frame of reference but have no need for one because the physics is the same in all inertial frames. There is therefore no empirical way to determine which frame of reference is 'special'.

You express my thoughts so much more clearly! Thank you. By "notion of an absolute rest frame", I meant one that can be distinguished, which then implies that the physics is different in that frame.

[sahil5d]

Great, we agree on 2).

For 1), I still disagree. For example, there are choices of frames that are wrong, such as trying to center a coordinate system at the muon coming in hot at .98c.
Given there are choices that are wrong, and some more wrong than others, we can work the other way. There are more sensible coordinate system centers than others.

[ftessier]

Why is it wrong? What is more sensible? What do you mean by wrong and sensible? I don't get it.

[HanDeBruijn]

@marmetl.
See Wikipedia: an Inertial frame of reference is a sensible notion in Special Relativity but it's not so easy in General Relativity. Please stop mixing up the two relativity theories! GR hardly bears any resemblance to SR! That's also the reason why your [ For 2) "stretching and squishing" of space and time ] section doesn't make much sense to me.

[RedshiftDrift]

Physicists are still trying to find empirical evidence of an absolute frame of reference. Experiments that are thousands of times more sensitive than Rømer's, Michelson-Morley's, Vessot's, Hafele-Heating's, etc. have been performed since then (C.f. Michael Tobar, Jun Ye, André Clairon, André Luiten, Peter Wolf, Giorgio Santarelli, etc.) and have produced no detection so far.

Since these modern experiments are all published in the scientific litterature, @sahil5d why do people in this group always go back to the primitive historical experiments made decades and centuries ago?

It's like trying to build a supersonic airplane from the Wright brothers' drawings...
Or design an email server based on training homing pigeons...

[sahil5d]

Funny comparisons but not what's happening here. Also, that kind of criticism is often made by faster-than-light-expanding-space-standard-model cosmology against light fatigue/tired light/photon hubbling cosmology, so I think you've seen cases where there really are deep errors.

Here's my point. There is an unobjectionable stupidity to centering a frame of reference on a muon coming into the atmosphere at .98c. There are frame centers that are worse than others, and therefore there are some better than others. And the best possible frame is 0 position as the center of mass of the system, and 0 speed as the speed at which objects have the least energy.

[RedshiftDrift]

The center of mass of a muon is centered on the muon and moves with it. Why would that be a "stupid frame of reference"?

(That's the same question @ftessier is asking above.)

[sahil5d]

@marmetl @ftessier Because it's stupid to establish 0 velocity at the muon, and then say the whole atmosphere is moving into it at .98c.

[ftessier]

I don't understand why this is "stupid". The alternative is writing physical laws that are only valid for you (the observer), but no one else. By the same token, would it not also be "stupid" to pick the Earth frame as the reference, instead of the Sun?

[budrap00]

Louis, I'm in full agreement with everything you've said here except this: "... so the choice of one or the other is again a metaphysical/mathematical decision for which science offers no guidance." From a calculational standpoint that is certainly true but from an empirical perspective there is absolutely no evidence supporting the existence of a causally interacting spacetime so science should reject such an interpretation until there is empirical evidence for spacetime 's existence. Frameworks and coordinate systems are useful calculational tools but they don't necessarily describe anything more than relationships. All physical relationships have physical causes but a successful calculation does not necessarily describe the underlying cause. See Ptolemy and the wavefunction of QM. The fact that physicists are still searching for an absolute frame is indicative of the mathematicist predilection for ignoring repeated negative empirical results while clinging to unnecessary metaphysical/mathematical constructs. The situation begs the question, how many negative results are enough? Why is anyone getting paid to search for things that considerable empirical evidence says are not there? How can science move forward if it's stuck in a negative feedback loop?

…

On Thu, Jul 6, 2023, 11:27 Louis Marmet ***@***.***> wrote: Physicists are still trying to find empirical evidence of an absolute frame of reference. Experiments that are *thousands of times* more sensitive than Rømer's, Michelson-Morley's, Vessot's, Hafele-Heating's, etc. have been performed since then (C.f. Michael Tobar, Jun Ye, André Clairon, André Luiten, Peter Wolf, Giorgio Santarelli, etc.) and have produced no detection so far. Since these modern experiments are all published in the scientific litterature, @sahil5d <https://github.com/sahil5d> why do people in this group always go back to the primitive historical experiments made decades and centuries ago? It's like trying to build a supersonic airplane from the Wright brothers' drawings... Or design an email server based on training homing pigeons... — Reply to this email directly, view it on GitHub <#82 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/BAIWF7AAESFZ4M3DJZVNPQ3XO3KOFANCNFSM6AAAAAAZXXZRNY> . You are receiving this because you commented.Message ID: ***@***.***>

[RedshiftDrift]

I meant this from a calculational standpoint. Quantitative models make predictions that are verified experimentally.

A quantitative model can be interpreted in numerous ways, "the existence of a causally interacting spacetime" is only one interpretation of many. Empirical tests do not distinguish between different interpretations of the same quantitative model. So I agree with what you wrote.

how many negative results are enough?

I have to clarify what I mean by "no result so far". There are two types of negative results:

1. The experimentalists mentioned above work with actual signals that provide results sensitive to the speed of light. As they improve the accuracy of their experiments, they find no deviation from quantitative models when other conditions are varied, i.e. the measured speed of light does not change when the measuring device is moved to another inertial frame of reference. They detect the signals but don't detect any change, so they have "no result so far" showing deviations from relativity-theory calculations. I believe it is good to continue such precision experiments because that's how physics moves forward (e.g. when planetary orbits were found to deviate from circles...)
2. Experimentalists trying to detect e.g. "dark matter" have never seen a signal of any sort. They build various sensors but are "in the dark" about how that could work. They have "no results so far" showing a signal that can be linked to "dark matter". I would say that three failures at 95% confidence (i.e. "nothing to see here" with $&gt;5\sigma$ statistical significance) are enough to abandon the hypothesis (which already happened years ago with "dark matter"). However, the answer to your question becomes non-scientific when the money is flowing and the experimentalist has a mortgage to pay ;-) It's like sitting in front of a slot machine - it's hard to quit when you have invested so much and might hit big on the very next try!