## On Signal Propagation Speed in Coaxial Cable

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### On Signal Propagation Speed in Coaxial Cable

Coaxial cable (or simply 'coax') technology was developed by English engineer and mathematician Oliver Heaviside, who patented the design in 1880. Everyone knows what a coax looks like, but here is a cutaway that requires no description.

With accurately controlled dimensions and materials, the cable has a uniform capacitance ($C$) and inductance $(L$) per unit length and hence a predictable impedance and signal loss/attenuation characteristics. It also has a predictable signal propagation speed along its length.

From the standard engineering textbook: TRANSMISSION LINES AND NETWORKS. INTERNATIONAL STUDENTS EDITION by Walter C. Johnson, 1963, the speed of signal propagation in coax is given by:

$\large v_p = \frac{1}{\sqrt{LC}}$ m/s,

where $C$ is the distributed capacitance per unit length in pF and $L$ is the distributed inductance per unit length in µH.

Note that as long as the cable is in a state of inertial movement, i.e. not accelerated,[1] $v_p$ is independent of the orientation of the cable, or whether it is coiled, looped, etc. The exact values of the distributed $L$ and $C$ depend on the proportional radial dimensions of the cable and the materials used.[2]

The most common dielectric materials used in coax are solid polyethylene and polyethylene foam, giving a speed of signal propagation $v_p$ ~ 2e8 m/s, i.e. about 2/3 of the speed of light. Does this mean that the signal speed in coax depends on the speed of light? Well, not quite. The speed of light in a vacuum depends on the permittivity and permeability of free space:

$c = \large \frac{1}{\sqrt{\epsilon_0 \mu_0}$ m/s.

Since $\epsilon_0, \, \mu_0$ represent the absolutely lowest possible values of permittivity and permeability obtainable in nature, it means that $c$ represents the highest possible propagation speed.

The capacitance ($C$) and inductance ($L$) of coax depend on the permittivity and permeability of the materials in the coax and it gives a similar equation for the propagation speed in coax

$\large v_p =\frac{1}{\sqrt{\epsilon \mu}$ m/s.

It is useful, but not required, to express the signal propagation speed of a specific type of coax as a fraction of the speed of light in vacuum. Is is the dimensionless velocity factor of the coax, i.e.

$\large v_f = v_p/c = \frac{\sqrt{\epsilon_0 \mu_0}}{\sqrt{\epsilon \mu}} = \frac{1}{\sqrt{\epsilon_r \mu_r}$,

where $\epsilon_r = \epsilon/\epsilon_0$ and $\mu_r=\mu/\mu_0$, the relative permittivity and permeability, each expressed as the ratio to the corresponding value for the vacuum.

Since the vacuum has the lowest possible values, it means the relative ratios must be larger than unity. The values for typical coax are $\epsilon_r = 2.25$ and $\mu_r = 1.00000037$. The latter is so close to one because coax materials are generally non-magnetic.

The reason for hammering these relations is that there exists a false perception that the propagation speed in coax is a function of the speed of light. It is not - it only depends on the dimensions and electromagnetic properties if the coax materials. It can be calculated and measured without bringing the speed of light into the equation.

The salient point of this post is that the propagation speed in coax can be used to measure the one-way speed of light, without depending on the one-way speed of light. This issue has been discussed in the Physics thread: One-way Speed of Light a proven postulate? It was successfully concluded (before diverging into humorous banter), but there were some "dissident voices" that argued that "Lincoln's test" actually only measures the two-way speed of light.

For this to be true, it would require that the capacitance and/or the inductance per meter length of a coax cable must be changing with orientation in space. Or with how fast the cable is moving relative to some inertial frame. Or differently stated, for a straight cable, its propagation speed must be different in the two directions. Quite absurd, because it would mean that its capacitance/inductance must be different if measured from the two ends respectively.

Jorrie

[1] Acceleration may deform the dielectric and conductor shapes and hence change the cable's characteristics.

[2] http://www.ittc.ku.edu/~jstiles/220/handouts/Capacitance%20of%20a%20Coaxial%20Transmission%20Line.pdf
and https://en.wikipedia.org/wiki/Inductance#Inductance_of_a_coaxial_line

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### Re: On Signal Propagation Speed in Coaxial Cable

Hi all,

If the cables are perpendicular to the direction of motion, then the One-Way signal velocity would be equal from either end to either end, and of course it would be slower than light speed.

But if one orients the cable to be parallel to the direction of motion, then the same issues arise as would in a Vacuum using light. If one orients a lamp equal distance between two mirrors moving in some direction such that the travel path for the light is parallel to the direction of motion, then light must take longer to reach the mirror in front because it is chasing said Mirror and the Velocity of Light is not additive to the Velocity of the Source of that Light.

The same but opposite effect take place in sending a signal toward the rear mirror because the rear mirror is coming towards the signal source and thus the travel path is shorter towards the rear mirror.

That is the One-Way Speed of Light differential in path lengths from center to ends for Light.

The return path lengths for Bounced light is opposite and thus, from the center point of view, a signal sent from center to ends and back again will be simultaneous on arrival. That is the Two-Way sum of a single path and both front going and rear going signals will have equal path lengths and equal travel timing.

It's already a given that the Cable version will be slower than a Light Version and it will be a constant delay adjusted by Speed of Light Limitations.

Jorrie wrote:For this to be true, it would require that the capacitance and/or the inductance per meter length of a coax cable must be changing with orientation in space.

Wrong. You must include the fact that propagation speed through a cable is subject to the same limitations as Light through a Vacuum.

One cannot cheat the One-Way and Two-Way limitations of Light Speed. Thus the signal via Light to Mirrors or Cable to an electrical echo transponder would suffer the exact same path Length effects, but with an extra added delay if using Cables vs Mirrors.

Thus the One-Way vs Two-Way signal travel times in a Cable can not cheat the Travel distance involved any more than one can with using just Mirrors and Light.

To say the cable lengths are constant is just the same as saying that the distance between a center Lamp and its end Mirrors are a constant. We only care about Path Length Propagation Times. Even in a Cable, the signal path length going against the direction of motion is not the same path length as in the direction opposite of Motion.

Why?

Even in a copper cable, which is mostly just space anyway between it composite atoms etc, you still can't go faster than Light Speed. Given some exotic type of Copper has conductance equal to propagation Speeds as that of Light and a Vacuum, you can't cheat mother nature.

Thus replace the Cables with Mirrors and Light for Highest possible Speeds and we just see the Two-Way Speed of Light is being measured.. in the thread Jorrie has Referenced.

The only way I can be wrong is if the Velocity of Light actually can be added to the Velocity of the Source of that Light, which of course would give us FTL Light.. lol.

The illusion that a Cable has somehow a more constant internal path length than the rigid distance between a Lamp and a Mirror is where this fallacy becomes manifested.

Best Regards,
Dave :^)

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### Re: On Signal Propagation Speed in Coaxial Cable

Dave_Oblad » 20 Feb 2017, 20:42 wrote:
Jorrie wrote:For this to be true, it would require that the capacitance and/or the inductance per meter length of a coax cable must be changing with orientation in space.

Wrong. You must include the fact that propagation speed through a cable is subject to the same limitations as Light through a Vacuum.

Wrong. Capacitance for one has nothing to do with the speed of light limitations. Your idea means that the distributed capacitance of a coax changes when it is orientated lengthwise parallel or lengthwise orthogonal to its direction of inertial movement. If it was so, it would have been very easy to detect absolute movement! Sadly, it isn't possible.[1]

Dave_O wrote:Even in a copper cable, which is mostly just space anyway between it composite atoms etc, you still can't go faster than Light Speed.

Ah, I was waiting for this one, because it should finally pull the plug on your argument. Tune Lincoln's two cables the way he prescribed, so that the signals arrive simultaneously on his scope. Now consider the lab moving at significant v/c relative to your "absolute space". Take one cable's midpoint away parallel to the movement and the other one's midpoint orthogonal to the movement. Note that the signals still arrive simultaneously at the scope (as Michelson & Morley experimentally discovered first, with hundreds of experiments confirming it afterwards).

This would require that the cables drag your "absolute space" along inside them, in the empty space between the atoms. How else could the signals still arrive simultaneously on your scope? Perhaps by Lorentz's physical contraction? You know, all those scary stuff that the cable and your ruler both physically contract in the direction of movement, so that you cannot detect the physical contraction in one of your cables...[2]

If you cannot solve this, the only logical conclusion is that the signal propagation speed is the same in all directions, irrespective of the orientation of the cables in free space or of any relative inertial movement - relative to an "absolute frame" or whatever.

And remember, this thread is about the propagation speed of signals in a coax, not about the speed of light. I think I have decoupled the two successfully in the OP.

Jorrie

[1] Actually, it is not sad, but fortunate for engineering. Could you imagine the engineering chaos if we had to consider, from nanosecond to nanosecond, how the one-way signal delay times (especially digital signals) would change, depending on how the cables/conductors were oriented relative to our planet's movement through the "absolute space"? ;)

[2] Remember, even Michelson & Morley realized that according to the prevailing aether theory at the time, there should be a difference in propagation times for the two arms. And they could not explain the null result.

PS: Dave, I appeal to you as an engineer, to not keep on spreading these false perceptions. It is OK to question the standard theory, but is not a good idea to make questionable statements, as authoritatively as you do, on any professional forum.

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### Re: On Signal Propagation Speed in Coaxial Cable

Hi Jorrie,

On my side: I only need the premise that the Velocity of Light is not additive to the velocity of the source of that light.

On your side: You should have suggested that the ramp-up coil synchronizations of the LHC would be problematic if One-Way speeds were an issue.

That would have stumped me and required me to dig into the design of the LHC for rather exotic specs that are probably not publicly available.

But just out of curiosity, do you believe the time for light to travel from source to mirror is the same as the return trip, given the test is in motion parallel to the direction of the light path?

Best Regards,
Dave :^)

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### Re: On Signal Propagation Speed in Coaxial Cable

Hi Dave,

Dave_Oblad » 21 Feb 2017, 08:09 wrote:On my side: I only need the premise that the Velocity of Light is not additive to the velocity of the source of that light.

It does not help if you misinterpret what that premise means. It means if I measure the speed of the source in my inertial frame and I measure the speed of light coming from it in my inertial frame, the two speeds cannot be additive, because I always get c, irrespective of any relative movement between me and the source.

This contradicts your premise that the one-way speed differs from the two-way average speed.

But just out of curiosity, do you believe the time for light to travel from source to mirror is the same as the return trip, given the test is in motion parallel to the direction of the light path?

Absolutely! I obviously use the standard definitions of space and time, as per SR.

Dave, again, the topic is not the speed of light, but the speed of signal propagation in coax cable. Please consider the engineering issues that I mentioned.

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### Re: On Signal Propagation Speed in Coaxial Cable

Hi Jorrie,

My premise would be:
Assume a test could be rigged such that a ship Traveling at .5c were to approach a satellite and upon crossing a trip point, both ship and satellite were to set off a flash simultaneously, one Green the other Blue. Further ahead about 300,000 Kilometers away a finish line is setup with sensors for Blue and Green flashes from the starting line. The premise is that both flashes that emanated from the starting line simultaneously would arrive at the finish line simultaneously. Thus meaning that the ship, having an advantage of already being at .5c did not give any advantage to the speed of the light flash it gave off.

Thus: One can not add the speed of light to the speed of the source of that light. It's that simple. Doesn't need to be complicated with frames, synced clocks and observers spread all over the place.

I'll call that the "Non-Additive" principle.

If we can agree on this one simple Fact then the next part must also be true.

Given this setup:

Two way measurement device

Obviously the flash lamp emits a pulse passing through the bottom sensor tripping a start timer. The flash bounces off the mirror ahead and returns to trip the upper sensor and stop the timer. Knowing the distance to the mirror and the duration of the lapse time, we compute the velocity of light as 300,000 Kilometers per second. I assume we can agree thus far, given the device is stationary.

Now we set the device at an inertial velocity of 0.5c with the mirror towards the front in the direction of travel. Two things will happen. Since the device is rigid, it will shorten by a dilation factor. Also the clock will slow by the same dilation factor. Thus we will see no difference in the readout for the Two-Way lapse time.

However, we now know the beam path to the mirror is longer than the return path because the light going to the mirror is chasing the mirror and the return path is shorter because the final sensor is coming towards the beam and meeting it early. The sum of the two paths create a round trip time that is still consistence in timing and we see no difference in the total lapse time.

This, of course, is what's meant by the Two-Way speed of light.

Are we in agreement so far?

But given the "Non_Additive" principle, we must agree that the lower beam/flash path is longer than the return beam/flash path and thus they can not be equal in path lengths and thus they can not be equal in flight duration's.

So far I have said nothing that should raise any eyebrows from Novice to Expert.

This brings us to the "Speed of Stick".

It's been suggested by many novices that if one had a solid long stick of near zero mass/weight.. that one could push/pull the end of the stick and it would simultaneously push/pull at the other end for an observer, thus transferring information at FTL speed.

Of course this is patently false.

The pressure wave up the stick can not exceed the speed of light. Also, because the atomic structure of the stick behaves like a bunch of springs, the compression wave along the stick will be far slower than light speed.

Since I see the compression wave must transfer information from atom to atom across the intervening space between atoms, then it should be safe to assume the same issue would apply to path length duration's as seen in the Two-Way Device shown above.

We are simply replacing the beams with sticks. The pressure information going in the direction of the device would have a longer internal path length than the pressure information traversing the internal return path length. It's all about the fact that the stick is mostly Space-Time gaps between Atoms (and inside the Atoms) and is thus subject to the same limitations as the original Two-Way beam device.

Thus, if I replaced the Light Beams in the Two-Way device with Sticks, it would make no difference. The Space-Time path length inside the Sticks would be longer for the lower (send) stick than the upper (return) stick for the EXACT same reason as with using Light Beams.

Just because the sticks are equal in length, doesn't imply the internal Space-Time paths are equal for information passing through them.

If you can see this on the Atomic Level, then it should be equally obvious that Electrical Cables would suffer the same effect. The internal Atomic Space-Time path lengths are only equal.. when they are perpendicular to the direction of Travel.

I have been a Professional Electronics Engineer for 40 years and I understand cable dynamics very well.

I've only been learning Real Physics for about 5 years as a hobby. So I am somewhere between Novice and Expert in that subject. Even though I tend to be rather lazy in the Math department, Physics is very Logical and makes perfect sense. Even Quantum Physics.. which I'm starting to dabble in.

That's why I have a great deal of trouble in understanding why You, or Don, don't see the Logic in my observations as I have presented above. This is not some personal Theory.. it is plain simple Novice level Logical Physics.

If one replaces the Cables with Light Flashes, then it is completely obvious that the Experimental setup from the OP is measuring the Two-Way Speed of Light.

I have no Authority in the subject beyond basic Junior Physics. But even at that level, the Logic as presented above should be completely obvious to anyone at or above my level. A Cable or a Stick is mostly Space-Time between, and inside, Atoms. Thus my argument must be well grounded in simple Physics.

This is the best I can do and I'm low on spare time.

Highest Regards,
Dave :^)

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### Re: On Signal Propagation Speed in Coaxial Cable

Dave, I'm sad to say that your whole post is completely physically incorrect, but we have been through that enough times, so I'm not going refute every false claim again.

You are even wrong on the "speed of stick" - the speed of sound in the stick does not depend on the speed of light, it is just limited to the value 'c', as observed in the inertial frame of the stick.

If one do not understand the principles of inertial frames, this may not make sense, but nature does not care if we understand or not - it works as it works.

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### Re: On Signal Propagation Speed in Coaxial Cable

BurtJordaan » February 21st, 2017, 7:42 am wrote:It does not help if you misinterpret what that premise means. It means if I measure the speed of the source in my inertial frame and I measure the speed of light coming from it in my inertial frame, the two speeds cannot be additive, because I always get c, irrespective of any relative movement between me and the source.

This contradicts your premise that the one-way speed differs from the two-way average speed.

Dave,

Do you agree with Burt's first paragraph above?

Dave_Oblad wrote:But given the "Non_Additive" principle, we must agree that the lower beam/flash path is longer than the return beam/flash path and thus they can not be equal in path lengths and thus they can not be equal in flight duration's.

But they can be equal in speed.
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### Re: On Signal Propagation Speed in Coaxial Cable

Hi Positor,

Jorrie's statement is true, But it's an Apples and Grapes debate. The Speed of Light is an absolute Distance in a period of Time. You can't make it go faster by adding it to the speed of the source.

Here is the only valid test I know of:
Go completely stationary relative to the CMB. Have two clocks synced in the Center of a Rig. Move those two clocks apart at the same rate in opposite directions to their pre-measured ends, equal distance from the center. Make them rigid with the frame. Now you can apply speed to the rig and because they co-exist in the same frame, they will stay in sync. Both clocks are tied to flash sensors. The front sensor picks up a remote flash ahead and marks its event time. The rear second sensor picks up the same flash and marks its event time.

Both times can then be transmitted as simple numerical data, by any means, to some computer that computes the delay differential time for the single same flash and stores it for later. Now we do the same for a flash coming from the rear.

Logically, if the rig was moving at 0.5c forward then the distance the flash had to travel between the front Sensor to the rear Sensor is cut in half. Like wise, a flash from the rear, after registering at the rear Sensor, has to chase the front Sensor to register on its clock. That path length will be longer and thus will register as a longer measured period when all the recorded times are compared (tomorrow) by the computer.

This isn't Relativity (Apples). It's pure Logic (Grapes). But from the Rigs point of view, the lapse time for light going from front to rear is shorter than the lapse time for light going from rear to front. I don't care that the clocks are equally dilated slower or the rig is dilated shorter as a whole. It plain simple common logical sense. Don't even need any Math, common sense will do just fine.

The (A) to (B) path length is Shorter than the (B) to (A) Path length. Thus transit Times are different and that's the One-Way Speed of Light issue in a nut shell. No Magic, No Observers, No outside Clocks, Just plain simple Logic.

Now, My personal issue with the OP is this:

Space-Time is not like the air inside a Spaceship. You don't ever isolate yourself from it. It permeates Everything, inside and out. The Space-Time Outside your Spaceship is identical to the Space-Time Inside your Spaceship is identical to the Space-Time inside of You, and your stick, and your cables.

Proof: The Clock outside and attached to the Ships hull, and the Clock inside the Ship on the wall, and the Clock on Your wrist, and your Biological Clocks, will all be Dilated the exact same amount. They all share the same Frame as Relativists like to put it. This is because Space-Time is everywhere, even between the Atoms and Particles.

Signal transit time though Matter is always slower than Light by some constant and I have no objection to this.

But the One-Way issues I have are still present in Matter because such Matter is Permeated with Space-Time.

So in the OP as presented here, if one removes the natural transit delay constants of Signals through Matter and make such delays as short as possible, such as using Light Speed, then the Setup given can only measure the Two-Way Speed of Light. This should be utterly and completely Obvious.

Ie: The flash of light hitting the front sensor sets off an instantaneous flash and the Trigger Flash races the Triggered Flash, arriving at the center simultaneously to be registered. Rats.. it's a Tie. But the Trigger Flash continues on to the second sensor and it sends BACK a Triggered Flash Response. Thus, we are measuring Center to End and End to Center again.

That can only be the constant (c) because it is the sums of a Two-Way travel path. So if Don claims the experiment measures the Two-Way path as being (c) then I have no doubt. But the setup, as given, can not measure the One-Way Speed of Light. I have no Problem with the cables introducing a constant Transit Delay, but when you remove or null those two Transit cable Delays, you come full circle to measuring the Two-Way Speed of Light again.

Positor wrote:But they can be equal in speed.

Of course the two beams are equal in speed, it's (c). It's the path lengths that create the difference. And it's the Space-Time path lengths "inside the cables" that is being ignored previously. Can't be ignored, it's part of our Reality.

To possibly suggest that the two beams (Source to Mirror) and (Mirror to Final) have the same transit times with different path lengths means the two beams are not Moving at the same speed. Obviously, one beam would have to be going FTL to make them equal transit delays. That doesn't work in my book or anyone's book for that matter.

Experts don't intimidate me. Even Einstein, who helped formulate Quantum Mechanics, objected to some parts and presented a Debate called the EPR paradox. Much later, it became feasible to do the suggested experiment and what do you know???

Einstein was Wrong.

Don't misunderstand me, Einstein is my most favorite and admired Thinker in the World.

Anyway, I have no more time to waste on this thread. I've made my point as clearly as possible without resorting to any deliberate obfuscations. Obfuscation is a tool I refuse to employ.

Best Regards All,
Dave :^)

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### Re: On Signal Propagation Speed in Coaxial Cable

Positor » 22 Feb 2017, 17:04 wrote:
BurtJordaan » February 21st, 2017, 7:42 am wrote:It does not help if you misinterpret what that premise means. It means if I measure the speed of the source in my inertial frame and I measure the speed of light coming from it in my inertial frame, the two speeds cannot be additive, because I always get c, irrespective of any relative movement between me and the source.

Dave,

Do you agree with Burt's first paragraph above?

Dave_O wrote:The Speed of Light is an absolute Distance in a period of Time. You can't make it go faster by adding it to the speed of the source.

Positor, Dave_O is one of the unmovable 'absolute framers' and it is generally futile to try and convince them of the scientific reality of spacetime. What we have to do here is to ensure that the 'scientific public' does not get confused by their ideas and misinterpretations, despite the intuitive appeal that such ideas may have.

A case at point is the misconception that inside the molecules and atoms of a coax cable, there is some portion of the propagation of EM signals that travel at "c" relative to "some aether". The modern scientific view, stated very simply, is that the signals propagate in a probabilistic (quantum) way between microscopic parts of the material, to which we can only ascribe an average speed of signal propagation in the cable. This speed is determined solely by electro-mechanical properties of the cable, as described in the OP.

That propagation rate is independent of the orientation, or any relative movement of the cable in free space. And this includes motion relative to the CMB rest (comoving) frame. It is actually not very hard to measure such propagation speed and show that it is at least isotropic (the same in all directions) and does not change throughout the day, the month or the year - as the lab and Earth find themselves moving at different velocities relative to "space at large".

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### Re: On Signal Propagation Speed in Coaxial Cable

Hi all,

Good post Jorrie.. really!

I went on the Net to read all I could on One-Way vs Two-Way light speed. In every single case they talk about the speed of the light being possibly different dependent on direction through Space.

The Actual Speed of the Light isn't the problem. It's all about path lengths.

Given: I place (A) 1000 meters in front of me and (B) 2000 meters in front of me.. and I shoot a flash at them. The flash will be seen by (A) before (B). In the Two-Way Device I showed earlier, both beams to and from the mirror are at light speed. It's a nice constant speed. But the Path Lengths of the Light are different if the device is in motion as showed.

If those guys want to squabble about variable light speeds then so be it, that holds little interest with me. My argument is based solely on Path Lengths and not the Speed of the Light itself.

Why does no one get this?

How about the Speed of Snails?

If I had a snail that crawled at a constant speed of 1 foot per minute and a start/finish line with a wall 1 foot in front of the snail, then it will take the snail 1 minute from start/finish line to reach the wall and one minute to return to the start/finish line. Obviously.. two minutes for a round trip.

But if I moved the <start/finish line> and the wall ahead of the snail at 1/2 foot per minute, it will take the poor snail much longer to reach the wall because it is chasing the wall. Conversely, the snails return trip will be very short because the <start/finish line> is coming towards the snail at 1/2 foot per minute. The whole two way trip will still take the snail two minutes but the going and returning path lengths are not going to be equal.

The debate is not about variable snail speed (or Light Speed).. it's everything about path lengths.

Now.. if that is settled and clear..

I am merely suggesting the path lengths inside the cables are not equal in the experiment Don suggested that started this all. If you remove the constant delay in signals over wire for both wires, then we come full circle to the fact that the experiment is measuring, or summing, the Two-Way path lengths from center to back end and return to center.. and both path lengths "individually" can't be equal to each other.. if the experiment is in motion as defined.

I accept the Relativity aspect. If clocks slow down, and biological aging slows down, all due to velocity.. then so would the signal propagation time through the wires also slow down.. the same as everything else in that frame.

So once again, if you could take the signal delay (due to Matter interactions) out of the cables then the experiment won't even start until the test photon is half way to the center. From there it's a Two-Way test.

Now.. add a constant delay to both wires and it doesn't change this simple fact.

Yes, I am a Relativity Absolutist. But that has nothing to do with the Logic we observe in this problem.

Best wishes all,
Dave :^)

Ps. I just completed my current project tonight at 2:30 AM. One more Project and I retire.. yippee!

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### Re: On Signal Propagation Speed in Coaxial Cable

Dave,

I would be interested in any comments you may have on the following:

BurtJordaan » February 23rd, 2017, 4:46 am wrote:A case at point is the misconception that inside the molecules and atoms of a coax cable, there is some portion of the propagation of EM signals that travel at "c" relative to "some aether". The modern scientific view, stated very simply, is that the signals propagate in a probabilistic (quantum) way between microscopic parts of the material, to which we can only ascribe an average speed of signal propagation in the cable. This speed is determined solely by electro-mechanical properties of the cable, as described in the OP.

Jorrie has said that the signal propagates at about 2/3 of the speed of light.
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### Re: On Signal Propagation Speed in Coaxial Cable

Hi Positor,

One needs to be a bit familiar with the Standard Model.

Wiki wrote:Technically, quantum field theory provides the mathematical framework for the Standard Model, in which a Lagrangian controls the dynamics and kinematics of the theory. Each kind of particle is described in terms of a dynamical field that pervades space-time. The construction of the Standard Model proceeds following the modern method of constructing most field theories: by first postulating a set of symmetries of the system, and then by writing down the most general renormalizable Lagrangian from its particle (field) content that observes these symmetries.

Quantum Field Theory is the Quantum Analogy of the Standard Model.

Within atomic nuclei, is a constant exchange of force carriers or mediators as shown below:

Forces within Nature by the Standard Model

None of these Force Carriers can exceed Light Speed of course.

But all are subject to path lengths when Matter is in motion. In a circular fashion, such force exchanges are the Two-Way paths as described by my Snail Analogy. Though the Snail moves at a constant 1 foot per minute, the forward and return path is always 2 feet. Thus the cycle time for the Snail is always 2 minutes, even if the confinement is moving at 1/2 foot per minute, the Path Length, per leg length of each 1/2 of the trip, is variable.. but the sum is an averaged Constant.

But note in the chart that the Force Carrier for Electromagnetics is the Photon (Light).

Jorrie wrote:..speed is determined solely by electro-mechanical properties of the cable

Jorrie is absolutely correct in describing the flow of Electrons through a Cable is slowed by Quantum Probabilities. Thus the Speed of Voltage Pressure is very fast (but not Light Speed) but the actual travel duration of any individual Electron could take hours to go just a few inches.

Wiki wrote:The drift velocity deals with the average velocity of a particle, such as an electron, due to an electric field. In general, an electron will propagate randomly in a conductor at the Fermi velocity. Free electrons in a conductor follow a random path. Without the presence of an electric field, the electrons have no net velocity. When a DC voltage is applied, the electron drift velocity will increase in speed proportionally to the strength of the electric field. The drift velocity is on the order of millimeters per hour.

Back on track: The Force Carrier for electro-mechanical interactions is the Photon and the intervening space between Atomic Parts is Space-Time. I've already stressed that one can not divorce themselves from Space-Time. Space-Time is not an atmosphere that moves with you.. you always move through it. It permeates everything, including the Gaps between Particles.

Thus, Current Flow is the sum of both Space-Time Photon Mediation and Quantum Probabilities. Since Electron mediation is by Photons and Photons do travel through the intervening Space-Time and the direction is determined by Voltage Pressure.. then such Photon Travel is subject to the same path length issues regarding Direction of Motion and Light Speed limitation.

Thus, a Stationary Cable has equal Space-Time Path Lengths from opposing ends to the Center. But put that cable in motion parallel to a straight line direction, then the Space-Time Path Lengths from opposing ends to the physical Center are no longer equal in Space-Time travel Length, due to the Speed of Light Constant, and thus would manifest non-equal propagation delays between the two halves of a cable relative to the Center, when it is in motion as described.

Thus, if one removed the probabilistic delays from both cable halves, we see the only thing left is Photon Travel Time Though Space-Time, which is direction sensitive due to Speed of Light restraints.

Thus, if we removed said Quantum Probabilistic Delays, then the cable can be replaced with a photon signal at Light Speed.

Thus, the tripped sensor would form a race condition between the Triggered Photon and Original Photon with both arriving at the center point simultaneously. The time difference between Triggered Photon and Original Photon would be Zero.

Thus, the test really starts from the Center at zero time differential between the original and triggered photons.

Thus, the Test really measures the final leg of Center to trailing End and trailing End back to Center again.

Thus, this is a Two-Way length measurement and will always read as the Speed of Light being the sum of both Path Lengths (Center to End) and the return path (End to Center).

Thus, cables can't measure the One-Way Speed of Light, even when you put the equal Quantum Delay Constants back into both Cables. The cables may measure to be equal in length but the embedded Space-Time path lengths are not equal when in motion along the axis of the cable!

One-Way Path Lengths will be motion direction sensitive due to Speed of Light Limitations through Space-Time.

Too much use of the word "Thus" perhaps? ;)

I hope this has made my stance perfectly clear to all interested parties.

Best wishes all,
Dave :^)

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### Re: On Signal Propagation Speed in Coaxial Cable

Dave_Oblad » 25 Feb 2017, 00:19 wrote:Jorrie is absolutely correct in describing the flow of Electrons through a Cable is slowed by Quantum Probabilities. Thus the Speed of Voltage Pressure is very fast (but not Light Speed) but the actual travel duration of any individual Electron could take hours to go just a few inches.

Dave, you are an engineer and should know that I described signal propagation and not electron flow.

IMO, you could spend your time better than vigorously trying to prop up a dead horse. ;)

You have still not answered one of early questions on how on earth the timing in our systems would have worked if the signal propagation delays in cables depended upon their orientation relative to the universe. And please do not tell me that the propagation delay of those signals are two-way - they are exactly half of the two-way propagation delay, if the cable is inertial.

Even the observable effect that in accelerated frames, the one-way propagation delay is not half of the two-way propagation delay, and is not the same in all directions, exactly as SR predicts it to be, supports this fact.

It should be case closed, but sadly on this forum, it rarely happens.

BurtJordaan
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### Re: On Signal Propagation Speed in Coaxial Cable

Hi Jorrie,

To your specific question, it doesn't matter what the delay is in a cable as long as long as it is consistent. If I am reading the duration between pulses on an electric circuit and two pulses are separated by 5 Nanoseconds, then it doesn't matter if the cable delay has a massive constant 500 Milliseconds. When it is displayed on my scope, the duration between the two pulses will still be exactly 5 Nanoseconds apart, obviously.

But when it comes to Two-Way Control Systems then issues may arise. Take a worst case example of a Robot being controlled on Mars from here. If the Robot is heading towards a cliff and it takes an hour for the video/photo to reach me and another hour to tell the Robot to stop, then by that time the Robot may have gone over the cliff. Obviously, we are not that stupid and have designed various protocols to avoid such a scenario.

But I mentioned you should challenge me on hyper sensitive Control Systems here on Earth, such as the LHC. If I were to design such a system for Acceleration Timing, each super conductor around the Ring would have to be triggered by the preceding Ring(s) following a pre-planned uploaded schedule for the Acceleration desired. You would have one hell of a time triggering all the Super Conductors from a central location considering the velocity of the particles are eventually traveling near Light Speed.

The fact such sequencing has to be timed so precisely means remote control is impossible from a central location. Much like the Robot/Mars issues. The timing of packets traveling around the LHC loop 1000's of times per second (domino fashion) would pay little heed to something changing as slowing as the rotation (or orientation) of the Earth.

How about Radar? Or the Radar Guns the police use? Oh wait.. Those are all Two Way measurements.. never mind.

I thought about our GPS system being sensitive to my issues, but as it turns out, any such issues are worked out in learned advance and uploaded by the transmission of a Timing Almanac to each Satellite every 24 hours that schedules time shift adjustments way in advanced of needing such. Up to 60 days can be stored in the event of contact loss with Earth.

I'm between Projects at the moment, so I have some spare time finally to interact on this site. My next Project starts when the lab completes my prototype (waiting for parts) and I have to get started on the Software side of my new Design. After that I'm expecting to retire as soon as I can get my replacement trained. I'm so looking forward to having maximum leisure time. Or rather.. time I can spent on my own current interests as I choose.

Best Regards,
Dave :^)

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### Re: On Signal Propagation Speed in Coaxial Cable

Hi Dave, yea, it's good to be retired - the relativity of time suddenly makes a lot more sense!

Your proposition may have interesting side-effects on pulse repetition frequency (prf) and pulse period (pp) if the signals in cables were traveling at different speeds in different directions, but I haven't given that much thought. Fortunately, signals do not travel at different speeds in different directions - what a mess it would have been if they did!

What I did give some thought on before, is that if a GPS device had to take into account from which direction (relative to the distant stars) the different signals arrive, the math for GPS on our devices would not have given the precise answers that we get. Of course the device doesn't (and can't), but fortunately it "knows" that the speed of the signals are 'c' from all directions and that the difference in time-stamps from multiple satellites can be accurately converted to distances for triangulation purposes.

On your Almanac argument: the satellite does not know where the receiver will be, so it cannot compensate for that. Do you realize the problems if your receiver had to compensate for directional differences in signal speed due to the signal's orientation relative to Earth's velocity vector through the distant stars? Essentially, your position would have required this knowledge. Lucky us that you are wrong! ;)

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### Re: On Signal Propagation Speed in Coaxial Cable

Hi Jorrie,

Jorrie wrote:Lucky us that you are wrong!

I wish you would stop drawing such a conclusion until I've had a chance to defend myself.

You already know that when a transmitter is moving away or towards a receiver that the receiver can not detect the received signal at a tight specific frequency due to Doppler Shifting.

Thus, when a GPS receiver tries to fetch the data from a Satellite, it can't expect it to be at a specific carrier frequency. Each satellite has a unique frequency it transmits at and that frequency has a unique Doppler Shift.

If one didn't include Doppler shift issues.. then a Receiver would not be able to find the Satellite at a precise frequency. Ordinarily, if the Receiver could tune in a wider band to include Doppler shifts and then.. only accepted the position and time of the Satellite.. then the receiver only knows it lies somewhere on a circle painted with a big fat brush. When it receives from 3 Satellites, it can do triangulation and know where the 3 fat circles overlap, but the area of overlaps can be hundreds of feet due to the unknown widths of the various circle perimeters.

This is shown in the image below as the upper overlapping circles used for Triangulation. Each colored Circle is the information that a receiver fetches from a different satellite. From a single circle, one only knows they are located on the circumference of that circle. But these circles have an unknown line thickness that define an unknown area. That's not good enough.

GPS Triangulation

Your position could be almost anywhere within the Center White Triangle (in the upper set of circles) given the width of any perimeter is an unknown.

The width of each circle perimeter creates an unknown error band. So it is not enough to simply place yourself at the center of the overlapping circles, since the bandwidth of the circles introduces an unknown error.

To make this more precise, we must next reduce the width of the overlapping circle bands.

This is done by corrections using the Doppler Shift knowledge gained from knowing how far off frequency the receiver had to be tuned to lock into the satellites transmission frequency.. in order to collect its Position and its Clock Data and to provide extra correction to the transit delay timing.

This information then provides the receiver with more precise points of overlap and thus produces a far more accurate indication of where the center (your relative position) is actually located.

This is shown in the lower half of the image (above) as refined overlapping circles adjusted by Doppler Shift consideration. Now your position in the center white triangle of the lower circle set is greatly refined.

Just knowing where the satellites are and what their clock time is, is not good enough. You also need to know if they are coming towards you or away from you (etc), to accurately know its true distance (path length) from you at a given time.

And this is because everything, you and the satellites, are all in continuous Motion.

As a Relativist would say, none of the players share the same Frame. So Doppler correction is critical for decent accuracy in determining any real distances.

Have you seen all the Patent applications of those trying to provide the most efficient Math Algorithms to accomplish this final Doppler Refinement for GPS receivers?

So am I still wrong?

Regards,
Dave :^)

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### Re: On Signal Propagation Speed in Coaxial Cable

Hi Dave, you are right and wrong. Yes, GPS Doppler shift is measured and used in the signal processing, but it is not there for the sole purpose of making the position determination more accurate, just easier/faster and it yields more utility.

https://www.e-education.psu.edu/geog862/node/1786 wrote:Doppler information has broad applications in signal processing. It can be used to discriminate between the signals from various GPS satellites, to determine integer ambiguities in kinematic surveying, as a help in the detection of cycle slips, and as an additional independent observable for autonomous point positioning. But perhaps the most important application of Doppler data is the determination of the range rate between a receiver and a satellite. Range rate is a term used to mean the rate at which the range between a satellite and a receiver changes over a particular period of time.

The main method of (one way) distance measurement between receiver and satellite remains the time difference between transmission time and reception time, divided by the one-way speed of light, c. Doppler shift gives range rate, which together with the accurate knowledge of the satellite's speed, can give the receiver's speed on Earth. Out of it also comes a signal that can synchronize the receiver clock to GPS time.

My issue is that you are so doggedly trying to prop up the dead horse of an absolute frame for light, that you may lose sight of the real physics. GPS would not have worked if you were right!

;)

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