Measuring c (split from Is foundational physics stuck?)

[DanMP]

On 11/15/2024 at 8:39 PM, swansont said:

Simple math is still math. Simulations are not magic.

 Yes, of course, but simple math/simulations are easier to master, as opposed to:

On 11/12/2024 at 5:21 PM, joigus said:

In the case of physics, foundational or not, students generally have to master sophisticated calculational tools in order to tackle the simplest problems of the most modern theories. 

 

 

On 11/15/2024 at 8:33 AM, Markus Hanke said:

How do you propose to reassess this? The numerical value of c is ...

I wrote "the invariance of c" for briefness. I meant "the invariance of the speed of light in vacuum" and I propose the following way to reassess that:

First, you must make a step back, forget/ignore Einstein's space-time and equations. Remember only the facts, like time dilation.

Then, you should observe that we measure the speed of light in vacuum using instruments made of atoms and molecules, held together by the electromagnetic force, a force that propagates (is transmitted) with exactly the same speed we need to measure.

Now, I propose a thought experiment, with light clocks:

(the same clocks we used to explain kinematic time dilation).

We take one light clock with the distance between mirrors 14.9896229 cm (29.9792458/2). Then we put it in a box, together with a measuring device for the speed of light, something like the Fizeau apparatus:

 

with the distance between the toothed wheel and the mirror 3 times larger: 3x14.9896229 cm (remember that this is a thought experiment ...).

Now we pump the air out of the box, creating a vacuum. The round trip from one mirror of the light clock to the other and back again will take the light pulse exactly 1 ns, in agreement with an atomic clock nearby. The light in the measuring device would need exactly 3 ns, 3 "ticks" of the light clock, to travel to the mirror and back, confirming that the speed of light in vacuum is 299,792,458 m/s, c.

Now we start to let air in the box. If we measure the speed of light, with the Fizeau apparatus in the box, using the time provided by the atomic clock nearby, the value gets smaller, but if we use the light clock next to it to measure the time, the speed of light remains c, regardless of air pressure/density. We can even insert water. It will take exactly 3 "ticks" of the clock situated in the same environment, for the beam of light to complete a round trip from the toothed wheel to the mirror and back.

So, the speed of light appears invariant when measured with instruments working based on exact same speed. Maybe the invariance of the speed of light in vacuum is a consequence not an enforced law ...

Furthermore, we notice that the light clock is "ticking" faster in vacuum than in air. We can clearly see this by adding an identical light clock that is kept all the time in vacuum. As we increase the air density in the first box, the respective clock "ticks" slower and slower (when compared with the one in vacuum).

This may suggest that an atomic clock situated at a high altitude (top of a mountain), where the air density is lower, is ticking faster than a sea level clock (as in gravitational time dilation) due to air density. Of course, this is not true, one reason being that there is no air inside the atoms of the atomic clock (the air is made of atoms and molecules, too big to get inside other atoms and molecules).

In Einstein's time, that would have been the end of the story (thought experiment), but now, more than 100 years later, we know that there is something called dark matter, something that is gravitationally attracted, forming roughly spherical halos around galaxies, exactly how a gas would do.

The fact that we cannot detect DM particles may mean that their mass/energy is very very small, so, in order to make more than 5 times the mass of ordinary matter, there should be in huuuuge numbers and slow moving (with small kinetic energy, "cold").

So, it is not impossible to exist a dark matter atmosphere around the Earth, made of particles small enough and plenty enough to fill the space inside atoms/molecules, and with densities decreasing from the sea level up ... 

 

If you want to learn more, read what I wrote in Speculations, in august 2018, and search the experimental tests I proposed in Physics forums, as DanMP, just before I was kicked out (not because I violated their strict rules, but because they learned about my theories posted in this forum ... By the way, this is another reason why foundational physics is stuck: the high level physicists tend to reject not only different ideas, but also uncomfortable questions and experimental test proposals).

[Mordred]

Lets start with a couple of statements Physicforum doesn't allow any form of speculation or any physics that isn't concordance or found in Peer reviewed literature. However that is irrelevant.

DM has little or nothing to do with the isotropy of the speed of light or its constancy. Both isotropy and constancy is a large part of Lorentz invariance tests. The tests you have above are far too behind the times of modern day tests of c constancy or Lorentz invariance. 

Those precision tests place the error margin at roughly 1 part in 10^15 for any error margin. That is well beyond the tests you have proposed. 

for example you second proposed test  takes what you have into far greater precision.

https://arxiv.org/abs/physics/0510169

here is the usage of stellar objects and time of flight

https://arxiv.org/pdf/2409.05838

we also use microwave interferometers, laser interferometers, rotating mirrors, to name a few other tests commonly done.

here are some Lorentz invariance constraints

https://arxiv.org/abs/2406.07140

here is one example using gravity waves

https://arxiv.org/abs/1906.05933

here is a small listing of modern methods

https://arxiv.org/abs/gr-qc/0502097

https://arxiv.org/pdf/1304.5795

model independent tests

https://arxiv.org/abs/1707.06367

tests done in space

New Test of Lorentz Invariance Using the MICROSCOPE Space Mission

https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.123.231102

 

All the above clearly show that we are constantly testing c and Lorentz invariance those tests never stop and were constantly seeking higher precision tests. So nothing you have suggested above is new or hasn't been thought of already. In point of detail Modern tests have far far greater precision than what you have above

Edited November 22 by Mordred

[swansont]

6 hours ago, DanMP said:

you should observe that we measure the speed of light in vacuum using instruments made of atoms and molecules, held together by the electromagnetic force, a force that propagates (is transmitted) with exactly the same speed we need to measure.

You can devise experiments that don’t rely on the value of c to determine c, so I’m not sure why this matters.

Quote

This may suggest that an atomic clock situated at a high altitude (top of a mountain), where the air density is lower, is ticking faster than a sea level clock (as in gravitational time dilation) due to air density.

Any clock able to discern gravitational time dilation has the atoms in a vacuum chamber, so this isn’t an issue. Further, you have multiple designs of clocks that would not have the same response to environmental perturbations, so they would not give a consistent shift if the result was from such a cause. And “maybe it’s air density” is not a rigorous objection without a model of how it should depend on air density.

[Eise]

... and you forget that the speed of light, funny as it sounds, is not about the speed of light: c is the maximum speed of causality, and as a consequence, all kinds of particles without rest mass, have that speed. At the moment, we only know of 2 phenomena that have exactly that speed: light and gravity.

Another way to see it, is that in spacetime the conversion factor of time to distance is c. Dependency of the speed of light in a medium is of no importance at all.

13 hours ago, DanMP said:

Maybe the invariance of the speed of light in vacuum is a consequence not an enforced law ...

So it is both. it is a consequence of the causal structure of spacetime, i.e. enforced by it.

[Markus Hanke]

I have little else to add to the above excellent replies, except perhaps this: on a fundamental level, ‘being in relative motion’ is not a physical property of an observer. Motion is merely a relationship between at least two chosen frames - meaning one can simultaneously be at motion wrt to one reference frame, and at rest wrt to another. It is therefore impossible for the laws of physics within a local frame to depend on relative motion, since this would create unresolvable paradoxes. Needless to say that no such thing has ever been observed.

So I stand by what I said earlier - the absence of physical paradoxes in our universe precludes any kind of violation of Lorentz invariance.

[KJW]

It's worth noting that it is possible in principle to measure the value of c by performing the Fizeau experiment and applying the relativistic velocity-addition formula.

 

Edited November 22 by KJW

[DanMP]

15 hours ago, Mordred said:

All the above clearly show that we are constantly testing c and Lorentz invariance those tests never stop and were constantly seeking higher precision tests. So nothing you have suggested above is new or hasn't been thought of already. In point of detail Modern tests have far far greater precision than what you have above

 You obviously didn't read/understand what I wrote. I presented a thought experiment (there is no actual Fizeau apparatus) aiming to show why the speed of light in vacuum is invariable, not to deny it.

 

The title of this thread is wrong/misleading. It should be: "A thought experiment meant to show that c invariance and gravitational time dilation are caused by a dark matter atmosphere". Being now in the speculation forum, I can be less subtle.

Let's try again. In a box we have an imaginary device that is sending a pulse of light towards a mirror and receives the pulse reflected by the mirror. In vacuum, the total time from emission to detection is exactly 3 nanoseconds (as explained in the first post). The light clock is "ticking" exactly 3 times. The atomic clock situated on the same table agrees. 

Now, we introduce a gas in the box, a gas that is not detectable (like DM), but makes the light travel slower, exactly as any known gas would do. The light clock would still tick exactly 3 times (3 ns) for a round trip of the light pulse in the measuring device, so,  for the people in the box, the speed of light in what they think is vacuum, is invariant.

The atomic clock would measure more than 3 ns, and everybody is wondering why the speed of light in what they thought is vacuum, is decreasing. Not knowing about the DM gas, they declare that the space is warped, and this is what GR pretends to happen in the regions where in fact light is traveling slower due to the increase density of the DM gas.

In real life, the atomic clock is also affected by the DM gas, because, being made of extremely tiny particles, the DM gas cannot be contained. So, if you measure the speed of light in "vacuum" at the sea level, you get c, but only if the clock is also at the sea level, at the same DM gas density. If the clock you use is on a mountain top, at lower DM gas density, you obtain a value lower than c for the sea level speed of light in "vacuum". 

 

14 hours ago, swansont said:

You can devise experiments that don’t rely on the value of c to determine c, so I’m not sure why this matters.

You know any thing or device that can be used to measure the time and is not made of parts held together by a force that is transmitted similar with the light in vacuum? Even if you know one (the muon?), how can you be sure that the proposed DM gas has no influence?

14 hours ago, swansont said:

And “maybe it’s air density” is not a rigorous objection without a model of how it should depend on air density.

 You obviously didn't read what I actually wrote:

21 hours ago, DanMP said:

This may suggest that an atomic clock situated at a high altitude (top of a mountain), where the air density is lower, is ticking faster than a sea level clock (as in gravitational time dilation) due to air density. Of course, this is not true, one reason being that there is no air inside the atoms of the atomic clock (the air is made of atoms and molecules, too big to get inside other atoms and molecules).

Read what I underlined. I wrote that it's not true and I presented one reason (there are more). So, your comment, although good and interesting (thanks), was uncalled for.

 

7 hours ago, Eise said:

At the moment, we only know of 2 phenomena that have exactly that speed: light and gravity.

So, the electromagnetic force acts/propagates slower than light in vacuum? 

 

6 hours ago, Markus Hanke said:

Motion is merely a relationship between at least two chosen frames - meaning one can simultaneously be at motion wrt to one reference frame, and at rest wrt to another.

Ok, but you should notice that in real life there are  preferred frames. See the Hafele-Keating experiment. The relevant frame there is exactly the DM atmosphere I'm proposing. It is a kind of aether, but one that not only agrees with Lorentz transformation, time dilation, and so on, but is also explaining them. Follow the link to my theory I provided.

 

I'm pretty sure that no one searched the experimental test I offered/mentioned, so here they are:

Thread 'Suggestion for 2 more GR tests' https://www.physicsforums.com/threads/suggestion-for-2-more-gr-tests.1056055/

Thread 'Time dilation in a planet-moon system' https://www.physicsforums.com/threads/time-dilation-in-a-planet-moon-system.1053613/

https://www.physicsforums.com/threads/is-there-an-atomic-clock-experiment-on-the-moon-testing-relativity.1053545/

Edited November 22 by DanMP

[Mordred]

Well then the thought experiment in essence has already been performed if you look through I  provided you would find improved yet equivalent style experiments.

Or did you not notice for an example the experiment done in space and quite frankly if you do a Google search you would find related equivalence principle experiment done on the moon.

So don't tell me the effort I took is uncalled for or does the simple detail experiments are constantly being performed in dozens of different methodologies elude you.

 

Edited November 22 by Mordred

[DanMP]

1 hour ago, Mordred said:

Or did you not notice for an example the experiment done in space and quite frankly if you do a Google search you would find related equivalence principle experiment done on the moon.

So don't tell me the effort I took is uncalled for or does the simple detail experiments are constantly being performed in dozens of different methodologies elude you.

I really appreciate you and your effort to find and offer links to interesting papers regarding relativity, but after following at least 3 of them, I realized that you didn't notice the requirment to prove/disprove my DM gas theory. We need to measure the time in a very high orbit, in a place where the Hill sphere of the instrument/satellite is large enough, because otherwise the instrument/satellite cannot have it's own DM atmosphere. If/when the instrument/satellite has it's own DM atmosphere, the kinematic time dilation dissappears, because the instrument becomes static in relation with the DM atmosphere surrounding it. That's it. It is a simple, powerful experiment, and it was never done. When there is no own DM atmosphere, there is absolutely no reason to disagree with GR.

As for the Moon and other distant celestial bodies, like stars, we only have indirect measurements, redshift observations, and the redshift is caused by many different things, besides kinematic time dilation. It is impossible to exactly tell how much of it is from kinematic time dilation. Also, the observations are flawed by the fact that we obtained our data considering the kinematic time dilation as existent. And, when the data disagree with our theory, we usually add a peculiar velocity ...

[Mordred]

DM doesn't interact with the electromagnetic spectrum so doesn't interfere with photons 

That's well known so how would it affect c in regards to any test using photons ?

In rhst regards any far field test using stellar objects would have intervening DM and we do not see any evidence of scattering due to DM.

So any link I included using any methodology of far field stellar object examination is also testing any intervening DM.

Believe me I wish DM would scatter or influence photon path it would be far easier to detect 

 

Edited November 22 by Mordred

[swansont]

6 hours ago, DanMP said:

Ok, but you should notice that in real life there are  preferred frames. See the Hafele-Keating experiment.

H-K does not show a preferred inertial frame

6 hours ago, DanMP said:

You know any thing or device that can be used to measure the time and is not made of parts held together by a force that is transmitted similar with the light in vacuum? Even if you know one (the muon?), how can you be sure that the proposed DM gas has no influence?

Now it’s my turn to say you didn’t read/understand what I wrote. 

 

6 hours ago, DanMP said:

Read what I underlined. I wrote that it's not true and I presented one reason (there are more). So, your comment, although good and interesting (thanks), was uncalled for.

Air not being inside atoms only eliminates one possible effect, because atmospheric pressure does, in fact, affect some atomic clocks. But it does not correlate with gravitational time dilation. My point still stands: you need to be able to quantify the effect, rather than give a hand-wave.

Quote

Now, we introduce a gas in the box, a gas that is not detectable (like DM), but makes the light travel slower

How does it slow light if there is no E-M interaction?

[DanMP]

6 hours ago, Mordred said:

DM doesn't interact with the electromagnetic spectrum so doesn't interfere with photons 

That's well known so how would it affect c in regards to any test using photons ?

In rhst regards any far field test using stellar objects would have intervening DM and we do not see any evidence of scattering due to DM.

So any link I included using any methodology of far field stellar object examination is also testing any intervening DM.

Believe me I wish DM would scatter or influence photon path it would be far easier to detect 

If you read what I wrote 6 years ago, you understand how. In short, I proposed  that light, actually the photons, travel through both ordinary and dark matter, by quasi-absorptions quickly followed by re-emissions. DM particles never really absorb photons, so the tiny delay of each such interaction is the only effect (in fact this causes one more, a refraction, responsible for gravitational lensing). I initially used this idea for ordinary matter, successfuly explaining (with math and all) the Fizeau experiment and the Sagnac effect. You should read what I wrote 6 years ago ...

 

4 hours ago, swansont said:

H-K does not show a preferred inertial frame

Maybe, but the Earth centered non-rotating frame is the one we usually choose (although the clocks at rest in the dragged frame would be the fastest ... while rotating - with respect to distant stars - and having centripetal acceleration ...).

 

5 hours ago, swansont said:

Now it’s my turn to say you didn’t read/understand what I wrote. 

Ok, I admit I didn't quite understand, so please elaborate. Also, my questions, even seemingly unrelated, still stand.

 

5 hours ago, swansont said:

How does it slow light if there is no E-M interaction?

See the beginning of this post.

[Mordred]

1 hour ago, DanMP said:

If you read what I wrote 6 years ago, you understand how. In short, I proposed  that light, actually the photons, travel through both ordinary and dark matter, by quasi-absorptions quickly followed by re-emissions. DM particles never really absorb photons, so the tiny delay of each such interaction is the only effect (in fact this causes one more, a refraction, responsible for gravitational lensing). I initially used this idea for ordinary matter, successfuly explaining (with math and all) the Fizeau experiment and the Sagnac effect. You should read what I wrote 6 years ago ..

So what is known as  scattering which is detectable using spectography. 

So as scatterring events are detectable why do we not see any evidence of such scatterrings?

We can certainly measure such events with regards to photons and regular matter why do we not see any such events with photons and DM ?

Photon scattering events are readily detectable 

Did you forget photons only travel at c ina vacuum when photons travel through some medium such as ordinary matter ie plasma the propagation speed is no longer c ?

That is precisely why photons only travel at c in a vacuum.

9 hours ago, Mordred said:

 

In rhst regards any far field test using stellar objects would have intervening DM and we do not see any evidence of scattering due to DM.

 

 

See previous comment I already mentioned scatterings.

For the record I do in actuality perform spectographic research its part of my professional formal training and a large part of my internships directly involved studying spectroscopic data. This is also true with @swansont as the same physics applies with neutron interferometry which I know @swansont has professionaly been involved with.

Specifically Braggs law, Moseley law, Shells law,  which you learn that there is a frequency dependency on scattering angles  as well as the medium refractive index.

Scatterrings are very distinctive from redshift just an FYI.

You might also note I included related articles above which involve such scatterrings with ordinary matter.

Edited November 23 by Mordred

[Eise]

17 hours ago, DanMP said:

So, the electromagnetic force acts/propagates slower than light in vacuum? 

Eh? Does it help when I say 'electromagnetic radiation' instead of 'light'? No idea why you think that.

Edited November 23 by Eise

[Markus Hanke]

17 hours ago, DanMP said:

You know any thing or device that can be used to measure the time and is not made of parts held together by a force that is transmitted similar with the light in vacuum?

Any unstable elementary particle. For that matter also all hadrons, since the strong interaction behaves nothing like electromagnetism.

17 hours ago, DanMP said:

how can you be sure that the proposed DM gas has no influence?

No one can be sure of such a thing, given that the very notion of “DM particle” is itself speculative. What we can state though is that the statistical decay rate of unstable elementary particles (irrespective which ones) has never been been observed to depend on external circumstances. It seems to be an intrinsic property of those particles.

And that’s part of the problem with this idea - all types of clocks, irrespective of their internal mechanisms and composition (or lack thereof), display precisely the same time dilation under the same circumstances. The amount of kinematic time dilation is solely a function of relative velocity. On the other hand, we know that DM, if it exists, cannot be evenly distributed - it must be more dense in some regions than in others in order to match observations, so we’d see differing time dilation effects in different regions/directions, which we don’t.

Honestly, I don’t see how you could make this work at all - your DM particle would need to interact with all types of other particles in exactly the same way, and the interaction could not even depend on the density of the gaseous medium. This seems highly implausible, and appears to be incompatible with the Standard Model.

Besides, since even quite ordinary clocks on quite ordinary energy levels are easily seen to exhibit time dilation, why do we not detect the DM particle in our accelerators, which detect interactions with many orders of magnitude higher precision? It’s completely implausible that all our precision and high-energy detection experiments have come up empty-handed, whereas at the same time the DM gas interacts strongly enough with (eg) a simple satellite clock to give it a substantial time dilation.

[DanMP]

10 hours ago, Mordred said:

what is known as  scattering

Quasi (or failed) absorption immediately followed by re-emission is not scattering. The definition of scattering is: "the process whereby a beam of waves or particles is dispersed by collisions or similar interactions". There are no collisions ... and the change in direction at re-emission is very limited, because the time between quasi-absorptions and re-emissions is too short. Normal matter, as opposed to DM, can form atoms and molecules, structures able to use (actually absorb) the photons if the photon energy is the one needed by the electron to "jump" to a higher energy level. So, the time between quasi-absorptions and re-emissions is longer, giving the time for the electron to move around (Bohr model) and emit in other directions than the original. The time needed to "decide" if the photon can be used depend on its energy, therefore light/photons travel at different speeds in transparent materials and the refraction is energy/frequency dependent.

 

6 hours ago, Markus Hanke said:

we know that DM, if it exists, cannot be evenly distributed - it must be more dense in some regions than in others in order to match observations, so we’d see differing time dilation effects in different regions/directions, which we don’t.

DM gas atmosphere, like any atmosphere, is denser near the massive object it surrounds (like stars, planets, black holes) and, going upward, gets less dense. The  gravitational time dilation is therefore greater near the massive object and smaller as we go up. No contradiction with reality.

6 hours ago, Markus Hanke said:

all types of clocks, irrespective of their internal mechanisms and composition (or lack thereof), display precisely the same time dilation under the same circumstances.

They are all equally affected. Please read my explanations for the invariance of the speed of light in vacuum posted 6 years ago. I really have not enough time to write/explain everything again. When I'll have time, I'll try to cover/explain what I didn't.

[Mordred]

No such thing as a quasi or failed absortion. Nice try the rest is nothing more than random hand waving assertions based on WAG guess work. You have two types of scattering and all particle based interactions are described by scatterings  inelastic and elastic. No scattering equals no particle to particle interaction.

Scatterrings involve particles not just atoms see Feymann diagrams those interactions are also scattering events and detectable.

When particles collide in a cyclotron those are scattering events 

Edited November 23 by Mordred

[swansont]

2 hours ago, Mordred said:

No such thing as a quasi or failed absortion.

There are absorptions to virtual states which accounts for light slowing down in a medium, but that presupposes a composite system like an atom, so there are real absorptions possible as well, and an electromagnetic interaction.

3 hours ago, DanMP said:

DM gas atmosphere, like any atmosphere, is denser near the massive object it surrounds (like stars, planets, black holes) and, going upward, gets less dense. The  gravitational time dilation is therefore greater near the massive object and smaller as we go up. No contradiction with reality.

With gas molecules you have the ability to shed energy in inelastic scattering. Where’s the evidence a similar distribution in DM?

What’s the formula for the distribution?

 

[Mordred]

41 minutes ago, swansont said:

There are absorptions to virtual states which accounts for light slowing down in a medium, but that presupposes a composite system like an atom, so there are real absorptions possible as well, and an electromagnetic interaction.

 

Yes but there is still no such thing as a quasi absorption not to my knowledge. Absorptions  I can accept quasi-absorptions not so much lol. However irrelevant as absorption still amounts to light slowing down and absorptions still requires DM to interact with photons.

 

 

[swansont]

2 hours ago, Mordred said:

Yes but there is still no such thing as a quasi absorption not to my knowledge. Absorptions  I can accept quasi-absorptions not so much lol.

No, but that might just be an issue of imprecise terminology 

2 hours ago, Mordred said:

However irrelevant as absorption still amounts to light slowing down and absorptions still requires DM to interact with photons.

Yes, and this is the crux of the problem

[Mordred]

9 minutes ago, swansont said:

No, but that might just be an issue of imprecise terminology 

Yes, and this is the crux of the problem

Agreed the one way light can however be used to detect DM hasn't been mentioned yet.  Though c is still invariant  nor is light interacting with DM.

Via gravitational lensing and its relation to mass luminosity.

Edited November 23 by Mordred

[swansont]

18 hours ago, DanMP said:

Ok, I admit I didn't quite understand, so please elaborate. Also, my questions, even seemingly unrelated, still stand.

If I measure the speed of light with the spinning mirror method, there’s nothing in that apparatus that relies on the speed of light being what it is, or on the interactions happening at c. The mirror spins at some speed, whose value is not critical to the experiment. Everything else is static. If c changed, nothing about the apparatus is affected

[KJW]

It's worth noting that if the shift in frequency is directly proportional to the frequency (if the ratio of frequencies is independent of the frequency), then the redshift is a time dilation. If the shift in frequency is directly proportional to the frequency, then any amplitude modulation of the signal will also have its frequency shifted in direct proportion to its frequency, and therefore the rate of any mechanical clock will appear to be similarly altered. By contrast, if the redshift is due to an energy loss without time dilation (e.g., Compton scattering), then the shift in frequency will not be directly proportional to the frequency.

 

[Markus Hanke]

16 hours ago, DanMP said:

The  gravitational time dilation is therefore greater near the massive object and smaller as we go up. No contradiction with reality.

I thought we were discussing kinematic time dilation for the time being, which is what my comment was aiming at. For example, the kinematic component of time dilation between a satellite clock and an Earth clock is solely due to relative velocity, and not a function of how high up the satellite is.

This is my main point - kinematic time dilation is solely a function of relative velocity (ie it doesn’t matter where and when the experiment is performed), whereas the density of your proposed DM gas is at a minimum a function of position and time. So I don’t see how you can meaningfully relate these two.

16 hours ago, DanMP said:

They are all equally affected.

I understand that that’s the idea, but I don’t see how any particle/field can interact with all the other fundamental particles and their interactions just so that any macroscopic composition of them is equally affected by time dilation. There’s no conceivable mechanism that can achieve this at below-GUT energies, since the fundamental interactions all function differently according to their own symmetry groups and coupling constants. 

[DanMP]

19 hours ago, swansont said:

No, but that might just be an issue of imprecise terminology 

Exactly (thanks), I just tried to describe what is happening. 

22 hours ago, swansont said:

There are absorptions to virtual states which accounts for light slowing down in a medium, but that presupposes a composite system like an atom, so there are real absorptions possible as well, and an electromagnetic interaction

I know it sounds silly, but I consider the DM particle as a very stable "system". When a photon gets in, the particle/ system becomes unstable and promptly "spits" the photon out. Don't ask me how, because it's like asking Koch when he just discovered bacteria about its DNA. Take it as a definition of my model. Let experimental tests I proposed to decide if the model is good. 

19 hours ago, swansont said:

If I measure the speed of light with the spinning mirror method, there’s nothing in that apparatus that relies on the speed of light being what it is, or on the interactions happening at c. The mirror spins at some speed, whose value is not critical to the experiment. Everything else is static. If c changed, nothing about the apparatus is affected

You need a clock to measure the mirror speed. So it's not much different than the Fizeau apparatus in the opening post. 

 

9 hours ago, Markus Hanke said:

This is my main point - kinematic time dilation is solely a function of relative velocity (ie it doesn’t matter where and when the experiment is performed), whereas the density of your proposed DM gas is at a minimum a function of position and time. So I don’t see how you can meaningfully relate these two.

You obviously didn't read what I wrote 6 years ago. I explained/proposed that, in the Hafele-Keating type experiments, kinematic time dilation is caused by the movement of the clock through Earth’s DM gas atmosphere, the reason being easy to explain with a light clock (the original use of the light clock). So, in very high orbit, where the instrument/clock can be surrounded by its own, comoving, DM atmosphere, there is no movement of the clock trough DM gas, hence no kinematic time dilation. Simply to detect but/and never attempted.