Naked Science Forum
On the Lighter Side => New Theories => Topic started by: nilak on 07/11/2016 18:58:17
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In SR there is a convention which says no mater what direction you are traveling speed of light is the same. However the one way speed of light can't be measured.
There is a version I'm currently analyzing. It starts with a thought experiment. Presuming the speed of light is constant ( c ) is only in an absolute reference frame, the speed relative to an observer in motion relative to the absolute reference frame will not be the same. However the two way speed of light measured by any observer will be always c. The absolute frame of reference is probably because of a space structure like an aether. The only difference from the Lorentz Theory of Aether is that the matter is part of aether, and the aether is not homogenous and it can expand and contract. But the aether properties are not important for this thought experiment. I should be important to analyze the analogy with GR.
Let's suppose the point R is at rest relative to the space structure (SS) and the SS is homogenous (like in SR, no gravity involved). Next, there is a room in a ship, where we are trying to measure the speed of light. The clock that measures time is a photon that when the ship is at rest relative to R, it describes a circle with a radius r=1m. There laser that sends a light beam towards a mirror. We measure the time it takes to the beam to reach the mirror and come back by measuring how many cycles the photon clock makes.
n1 is the number of cycles when going forward, n2 is for the way back. nr is the number of cycles we get when at rest, when measuring the the beam to the mirrir and back.
If the ship travels towards the mirror at a velocity v, I get the following results. n1+n2=(1/gamma)*nr, where gamma is the Lorent factor. This means we don't have the whole picture of what is happening. The distance that separates the mirror and the laser needs to shorten for this to be consistent with real experiments. The room that contains the laser and the mirror being an atomic structure, something is happening that makes it get shrinked and need to be further analyzed. It must have something to so with the acceleration phase. In the meanwhile we can use the real results to correct the results.
Time needs to be corrected by applying Lorentz factor. That is for the both way speed of light, so we get the correction for the average speed of light. But n1 is not equal to n2. I've calculated:
n1=nr*1/2*sqrt((c+v)/(c-v)). n2=nr*1/2*sqrt((c-v)/c+v)).
These numbers (n1 and n2) are not very useful until we find the mechanics that expalains length contraction. If we correct the sqrt term we get n1=n2=nr/2 which might not be true. However these factors are not equal to each other but the length contraction should be. It's no reason for length contraction differences. Hence the correct number of cycles ( which translates to time measured) will not be the same on the oubound compared to the inbound beam travel.
For two observers traveling like in the twin paradox, the speed difference will be v, -v , and not c-v and c+v. On the both segments of the journey it should generate the same factor which is the Lorentz factor.
Following the idea, assuming there is a space contraction, if we could measure one way speed the photon clock will show the number of cycles for the beam travelling up to the mirror, nf=nr/2*1/(1-v/c) and for thw way back nb=nr/2*1/(1+v/c). nr is the cycle count at rest. For v=0, nf=nb=nr/2, for v close to c, nf goes tend to go to infinity, nb goes to zero.
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In SR there is a convention which says no mater what direction you are traveling speed of light is the same. However the one way speed of light can't be measured.
You can measure the speed of light one way with an atomic clock. There is a 14 ns difference between New York and San Francisco in direction. The rotation is similar to a straight line for the distance light has to travel. This as been verified with atomic clocks.
There is a version I'm currently analyzing. It starts with a thought experiment. Presuming the speed of light is constant ( c ) is only in an absolute reference frame, the speed relative to an observer in motion relative to the absolute reference frame will not be the same.
This is correct but the measuring device is confounded with the speed of light measurement.
However the two way speed of light measured by any observer will be always c.
Yes because the 14 ns are added in one direction and subtracted in the opposite direction.
We measure the time it takes to the beam to reach the mirror and come back by measuring how many cycles the photon clock makes.
During vector motion the clock photon and mirror photon are affected by the same angular motion. A photon clock will tick at the same rate at any angle during vector motion. This can be calculated in plane geometry using the finite speed of light.
. But the aether properties are not important for this thought experiment. I should be important to analyze the analogy with GR.
Unless the Aether is the light. GR and SR are always combined. GR can become insignificant in the furthest distances from macro mass where dilation is at a minimum. The Voyagers moving out from our solar system reduced there space dilation. The result was a quicker return of the signal which appeared as if the voyagers slowed down when in fact it was a clock tick rate increase. Simple Relativity.
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There is a version I'm currently analyzing. It starts with a thought experiment. Presuming the speed of light is constant ( c ) is only in an absolute reference frame, the speed relative to an observer in motion relative to the absolute reference frame will not be the same.
This is correct but the measuring device is confounded with the speed of light measurement.
Yes you are right. It may be wrong. It is like trying to measure a projectile with a twin one that is rotating like the photon clock. No mater how fast it moves you always get the same result. I think that regardless of what clock you use, the dilation factors will be the same.
. But the aether properties are not important for this thought experiment. I should be important to analyze the analogy with GR.
Unless the Aether is the light. GR and SR are always combined. GR can become insignificant in the furthest distances from macro mass where dilation is at a minimum. The Voyagers moving out from our solar system reduced there space dilation. The result was a quicker return of the signal which appeared as if the voyagers slowed down when in fact it was a clock tick rate increase. Simple Relativity.
Yes, they are important, but I wanted to simplify the experiment. I omitted the room structure in which the experiment is done. That is because adding that would require complicated detailed about what space or the aether is and and how it affects the atomic structure and distances between atoms. I asumed that the space contracts by the Lorentz transform.
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I asumed that the space contracts by the Lorentz transform.
SR is a visual transformation only. Nothing physically contracts in SR.
Its only in GR where space dilates to have equivalence with SR. Interesting that the geometry of the finite speed of light and dilation are both equally affected by c to confound the measurement of the speed of light.
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The 1-way speed of light cannot be measured directly since the observer can only be present at the emission or detection, but not both. The reflection event when part of the 2-way/round-trip measurement requires clock synchronization, which is only relative for an inertial frame at a specific speed.
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The 1-way speed of light cannot be measured directly since the observer can only be present at the emission or detection, but not both
I suspect this to possibly be incorrect. Einstein suggested atomic clocks can measure the one way speed of light. c+v and c-v of the Earth's rotational speed.
The reflection event when part of the 2-way/round-trip measurement requires clock synchronization, which is only relative for an inertial frame at a specific speed.
Inertial vector speed causes the reflection to be different from perpendicular. The different angle for light causes a longer distance for light to travel. This increase in distance slows the clock tick rate. Pythagoras and Lorentz are the same value for contraction.
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The 1-way speed of light cannot be measured directly since the observer can only be present at the emission or detection, but not both
I suspect this to possibly be incorrect. Einstein suggested atomic clocks can measure the one way speed of light. c+v and c-v of the Earth's rotational speed.
This is exactly what experimental results confirmed. Do you have a reference showing Einstein predicted that ?
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During vector motion the clock photon and mirror photon are affected by the same angular motion. A photon clock will tick at the same rate at any angle during vector motion. This can be calculated in plane geometry using the finite speed of light.
That is the starting point of my concept. That mirror clock measures time exactly as any atomic clock we use measures it.
The paper below is the proof that an absolute space or an aether exists.
"It is clear therefore that GPS technology very easily demonstrates that light speed is not constant and hence that the light speed invariance postulate which leads to the Lorentz Transformation and special relativity is invalid. This significant finding has profound implications for modern physics and metrology where light speed constancy is a foundation tenet. Moreover this light speed variability indicates the existence of a preferred frame, the search for which interestingly was the original objective of the Michelson-Morley experiment.
In order to confirm this preferred frame detection, the GPS clocks were utilized in a modified Michelson-Morley experiment where the clocks replaced the interferometer. The clocks measured light travel times along the arms of the apparatus and revealed ether drift arising from the Earth’s rotation. This direct determination of the light travel times rendered the measurement essentially immune to the second-order length contraction phenomenon which negates the fringe shift in the conventional Michelson-Morley experiments. The GPS technique did not require actual time measurement but utilized light travel time that is directly available from the CCIR clock synchronization algorithm. The modified experiment succeeded in detecting ether drift for rotational motion while the majority of other Michelson-Morley-type experiments are considered to have produced null results. In the approximately inertial frame of the experiment, special relativity is directly applicable and predicts a zero time-of-flight difference between equal orthogonal arms and hence a null result [2]."
http://cdn.intechopen.com/pdfs-wm/39778.pdf
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That is the starting point of my concept. That mirror clock measures time exactly as any atomic clock we use measures it.
The most festinating part is mechanical clocks follow atomic clocks.
The paper below is the proof that an absolute space or an aether exists.
While I agree a medium exists proof is in the eye of the beholder. Neither you nor I are the beholder of science. Mathematicians consider math is the mechanical reason for relativity and need no process. To many pure mathematicians and not enough engineers in physics to reproduce relativity mechanically. You appear to have an engineering spirit.
"It is clear therefore that GPS technology very easily demonstrates that light speed is not constant and hence that the light speed invariance postulate which leads to the Lorentz Transformation and special relativity is invalid.
This statement is just proof the author does not understand SR. I can explain why clocks tick at different rates by just using plain geometry. The speed of light is constant when you follow the postulate light being independent of the source. What that means is there is no perpendicular path for light with velocity.
Here is main streams mechanical solution: The clock contracts so the ability to stay perpendicular remains for all velocities. The problem with that is if the clock contracted and the speed of light remained the same the clock would tick faster with greater speed through space due to the shorter distance between mirrors in the clock. Like I said most are mathematicians not mechanical engineers.
Here is the plain geometry light being independent of the source: Lets use the simple half speed of light compared to a rest state observed position. The photon leaves its starting position as a sphere. When the signal reaches the mirror to be reflected the vector angle from the starting point to the finish point was 30 degrees. The observer at rest viewed the light at a 30 degree angle from perpendicular. So we can draw a 30,60,90 triangle where the actual travel distance for light was the hypotenuse. So that angle of view which we consider perpendicular is actually at 30 degrees and contracted. Lets look at the Lorentz contraction for half the speed of light. The value you can look up and confirm it to be 0.866025. Sq. Rt. 1-1^2/2^2 is the Lorentz formula. Now cos 30 = 0.866025 a little trig. Or sq. rt. A^2=C^2-B^2 = [1^2 = 1^2 - 0.5^2]. [Sq. rt. 1 = 1- 0.25.] [Sq. rt. 1 = 0.75]. Since the square root of 1 is 1 and the square root of 0.75 is 0.866025 anyway you want to measure, we have a contraction of view due to the angle of view. Our clock slows down because the tick rate is based on the hypotenuse distance and not the perpendicular distance. The tick rate is only 86.6025% as fast as at relative rest. The view was 13.3075% visually shorter and distance light traveled was 13.3075% longer. Both used the same angle (the hypotenuse). Relativity is always correct while your understanding could be wrong.
Say you are sitting on the moon and were able to watch light from New York to San Francisco and back. Light being independent of the source. The photon leaves NY while SF is raveling towards the photon. You measure the distance. Now on the return trip to NY you once again measure the distance. NY to SF was a shorter distance for the photon to travel than SF to NY. NY moved away from SF while SF moved towards NY. If you used an atomic clock the different amount of clicks would correspond to the different distances for light speed. They auto correct in any direction with the two way speed of light measurement.
Say there is a kid on a moving truck bouncing a ball up and down. From the kids perspective the ball is straight up and down. If an observer at rest could only see the ball it would appear to be creating a triangle through space.
The point is we have to be careful in our rush to judgment. I find relativity a beautiful instrument to play with physics. Quantum mechanics is the construct for relativity.
A and C were both the speed of light being constant
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You are right. What they got is seems to be a speed difference that is measured from an orbiting station frame not from a station fixed to earth. The orbiting station sees the Earth surface moving at v and obviously will measure a speed difference between the Earth surface and c but a station on Earth will not notice the difference according to SR.
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There is one more image I need to transfer to you for a better understanding. Say we have a satellite in geosynchronous motion. There is a GR difference in tick rate that is a physical size difference in their respective clocks (ever so small, tiny to the point of insignificant except for accumulative display differences over days). Lets not consider that part and focus on the SR portion. We visually measure the satellite as being perpendicular with the observer to the center of the Earth. While an observer on earth would view the satellite perpendicular, the satellite is physically forward of its viewed position from the observer on Earth. The signal output and the photon reflection ride the spectrum at c independent of the satellite's forward movement. The observer on Earth has also moved forward to intercept the signal and visual reflection from the satellites previous position. So you can recognize with speed even using geosynchronous positions there is no perpendicular view possible if you understand relativity properly.
Main stream mathematically contracts space to allow a perpendicular view. This violates relativity to fudge the correct answer. The Lorentz contraction is the geometry of view. Mathematics can not be the cause of physical contraction. That's just silly.
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Apparently My model that uses absolute space and time also seems to show the same thing. After all perhaps they really did the correct measurement.
Notice that acording to my model there is no space contraction but instead objects extend their size with speed.
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Apparently My model that uses absolute space and time also seems to show the same thing. After all perhaps they really did the correct measurement.
Notice that acording to my model there is no space contraction but instead objects extend their size with speed.
Your missing the point of the kid on the truck bouncing a ball. The photon Velocity between mirrors cause the bouncing ball affect through space. Your math adds the fudge factor of the Lorentz contraction in the equation without understanding from where it came. Your trying to make everything observed a fixed frame. That is not possible with relativity.
Math is never the cause of physical change. Math can only follow physical change. You are trying to change the bouncing ball with velocity known as the gamma term and lengthen the straight leg to the length of the hypotenuse for your theory. That is as bad as main steam trying the shorten the distance from the hypotenuse to the perpendicular distance. Both violate the postulates of relativity. There is no perpendicular view with velocity. There is no fixed frame for mass. All mass travels through space removing energy from c. That is why there is no fixed measurement using time period.
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if you look at how the electron looks like it becomes clear how particles that compose objects like that box, extend their size in the direction of motion. When electron travels faster the helix unfolds until it becomes a high frequency photon. The length expansion of matter must be real.
In SR the length contraction is caused by space up scaling. Objects in the moving frame are smaller because the new gridlines are less dense.
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In order to follow relativity GR grid expansion also increases the electron travel distance for dilation to follow SR equivalence of tick rate. The grid expands for GR but not for SR. The hypotenuse increase is equivalent to the dilation increase for distance in comparing tick rates.
Here is how that works. At the surface of the Earth the attraction is 32 ft/s/s. Acceleration has very little to do with tick rate only velocity. So for an equivalent tick rate to the center of the Earth GR an instantaneous acceleration of 32 ft/s/s down to inertial velocity in ~8,000 miles linear deceleration. That is the equivalence in tick rate for SR to GR at the center of the Earth. There the increase in the hypotenuse of SR photon travel equals the grid dilation for increased electron travel distance for GR dilation.
As you can observe dilation also increases the travel distance for the electron, grid points and photon in GR. So in creation your theory on mechanical relativity has to follow relativity observations.
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Just recently I came up with a new idea to measure one way speed of light and/or synchronize distant clocks:
Let’s have two light sources at points A and B separated by distance d and sending constantly (perpendicular to AB) signals to clocks at A’ and B’
Let’s have an opaque rigid rod of the length d (it can be measured against AB while at rest with AB, so accuracy can be high) traveling with constant speed v (non-relativistic) parallel (and very close to) the line AB from B towards A. Initially the light from B to B’ will be blocked and the light from A to A’ will be allowed to be transmitted. When front end of the rod will start cutting off the light from A to A’ the light from B will start to be transmitted to B’ . At this moment, we will have both clock at A’ and B’ synchronized.
Alternatively when front end of the rod will start cutting off the light from A to A’ we can start the clock at A and when the light from B will start to be transmitted to B’ we can also send the light from B to A .When the light from B arrives at A the clock at A will measure one way speed of light.
In this method only one clock is needed.
We can improve the accuracy of the measurement sending the rod from A to B with the same speed v and measure one way speed of light from A to B. The average 2 way speed of light from A to B and from B to A has to be c.
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Just recently I came up with a new idea to measure one way speed of light and/or synchronize distant clocks:
Let’s have two light sources at points A and B separated by distance d and sending constantly (perpendicular to AB) signals to clocks at A’ and B’
Let’s have an opaque rigid rod of the length d (it can be measured against AB while at rest with AB, so accuracy can be high) traveling with constant speed v (non-relativistic) parallel (and very close to) the line AB from B towards A. Initially the light from B to B’ will be blocked and the light from A to A’ will be allowed to be transmitted. When front end of the rod will start cutting off the light from A to A’ the light from B will start to be transmitted to B’ . At this moment, we will have both clock at A’ and B’ synchronized.
We can improve the accuracy of the measurement sending the rod from A to B with the same speed v and measure one way speed of light from A to B. The average 2 way speed of light from A to B and from B to A has to be c.
What is a rigid rod? Do you mean a rod that breaks the rules of physics? If you push one end of a rod, the other end moves after a delay as the force is transferred to it, and that delay is tied to the speed of sound in the material used to make the rod. You would need to have a way to accelerate the whole rod at the same instant for your experiment to get round that problem, perhaps by using a rail gun, but you then come up against the problem of how you synchronise things so that all parts of the rod are accelerated at the same moment. You need to pick a frame of reference for your synchronisation, and having done that, you will have ensured that the speed of light your experiment measures will be c. If you synchronise for some other frame of reference, the speed of light you measure can be values very different from c.
[There is no known experiment that can measure the one-way speed of light, despite what has been claimed in this thread. Another incorrect claim here is that length-contraction is merely a visual effect, but actual length-contraction is essential to account for the results of experiments.]
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http://cdn.intechopen.com/pdfs-wm/39778.pdf
Thanks for the link Nilak. :0)
Gift concludes that it is the postulate about the speed of light that is wrong, but his conclusion also means that, as far as light is concerned, the one about the inertial frame principle is also wrong. It works for massive bodies, but not for light. If we exchange a ball while walking together, the ball can be aimed to our actual positions to reach us because it has mass so it can add our speed to its own speed, but light has to be aimed to our future position otherwise it will miss us, and that's unfortunately what the relativity principle means.The laws of physics may thus be the same for any inertial frame only if we add to those laws an absolute reference frame for light.
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"What is a rigid rod? Do you mean a rod that breaks the rules of physics? If you push one end of a rod, the other end moves after a delay as the force is transferred to it, and that delay is tied to the speed of sound in the material used to make the rod. You would need to have a way to accelerate the whole rod at the same instant for your experiment to get round that problem, perhaps by using a rail gun, but you then come up against the problem of how you synchronise things so that all parts of the rod are accelerated at the same moment. You need to pick a frame of reference for your synchronisation, and having done that, you will have ensured that the speed of light your experiment measures will be c. If you synchronise for some other frame of reference, the speed of light you measure can be values very different from c.
[There is no known experiment that can measure the one-way speed of light, despite what has been claimed in this thread. Another incorrect claim here is that length-contraction is merely a visual effect, but actual length-contraction is essential to account for the results of experiments.]"
The lasers at A and B are positioned that the rod's ends coincide with the lasers. This is done when rod is at rest in regards to the lasers. Then the rod is then moved out , then accelerated to constant speed v <<c (e.g. 100m/s), which will cause length contraction (if the rod is 10m long) around 3x10^-13m , way below our measurement accuracy. The rod will glide past lasers without acceleration (on magnetic cushion?) so there will be no stress on the rod.
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The lasers at A and B are positioned that the rod's ends coincide with the lasers. This is done when rod is at rest in regards to the lasers. Then the rod is then moved out , then accelerated to constant speed v <<c (e.g. 100m/s), which will cause length contraction (if the rod is 10m long) around 3x10^-13m , way below our measurement accuracy. The rod will glide past lasers without acceleration (on magnetic cushion?) so there will be no stress on the rod.
Your rod cannot be as rigid as you imagine it to be - if you push it from one end, there will be a delay before the other end starts moving, and the same applies if you pull it from the other end. If you try to avoid delays by accelerating the whole rod evenly at the same moment in time, you run into synchronisation issues. Whichever frame of reference you use to synchronise your moment of time along the rod will determine the number your experiment produces for the speed of light - all it does is give you a speed that relates to the frame you use for synchronisation, thereby rendering the experiment useless.
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"Your rod cannot be as rigid as you imagine it to be - if you push it from one end, there will be a delay before the other end starts moving, and the same applies if you pull it from the other end. If you try to avoid delays by accelerating the whole rod evenly at the same moment in time, you run into synchronisation issues. Whichever frame of reference you use to synchronise your moment of time along the rod will determine the number your experiment produces for the speed of light - all it does is give you a speed that relates to the frame you use for synchronisation, thereby rendering the experiment useless."
The rigidity of the rod should be enough to withstand the wind caused by the rod travelling through the air with the speed of ~10m/s. I think the Styrofoam would be sufficient, but of course we can find slightly better materials. Because the distance between the lasers A and B is EXACTLY (to the limit of our ability to mark it - not measure; just mark it) equal to the length of the rod, if the end of the rod at B will start allowing the light from laser at B to travel perpendicularly to B' we will know that the light from laser at A will start to be blocked by front end of the rod BECAUSE THE LENGHT OF THE ROD is exactly the same (disregard length contraction; at that speed it is really insignificant) as the distance d between the lasers.
The speed of the rod is not important either; the limited precision in positioning the lasers in regards to the length of the rod d would be compensated if we repeat the experiment from the other direction since 2 way speed of light has to be c.
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In SR there is a convention which says no mater what direction you are traveling speed of light is the same. However the one way speed of light can't be measured.
That's incorrect. First of all if that were true then it would violate the conservation of energy law. Second, all one has to do is pick up and read a good SR text like Ohanian's to see that statement to be in error. The one way speed of light has been measured.
If you don't wish to read an SR text then see the MIT Technology Review at
https://www.technologyreview.com/s/421603/the-one-way-speed-of-light-conundrum/
Specifically
One interesting question immediately arises: how do you measure the one way speed of light? It turns out there are various methods. One idea involves the emission and absorption of gamma rays by certain kinds of atoms in a solid. The process of absorption is very sensitive to the energy of the gamma rays. So if the speed of light (and therefore its energy) varies with direction, then the rate of absorption ought to change too.
In the 1960s and 70s, various physicists looked for a directional dependence by placing a gamma ray emitter at the edge of a rotating disc and an absorber at the centre. They then looked for any difference in the rate of absorption as the disc rotates but found none.
Neither have physicists using other techniques found any variation either. (The controversial Bulgarian Stefan Marinov claimed to have found evidence of a variation in the one way speed of light but his claims are not considered valid by most mainstream physicists.)
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You can calculate the one-way speed of light from Maxwell's equations. Then, remarkably, however you measure the propagation velocity of electromagnetic radiation in vacuo, it turns out to be exactly the calculated value, so either there is a selfcorrecting error in the calculation, or the two-way speed is the same as the one-way speed.
An everyday example is the average ground speed of an airplane flying a distance d with a tailwind w and returning against the same wind. The constant airspeed is a
Outbound time = d/(a + w). Return time = d/(a - w).
Total journey time = d((a - w) + (a +w)) / ((a + w) (a - w)) = 2da/(a2 - w2) > 2 d/a if w > 0. In other words, any difference between the "coming" and "going" speeds will result in a measured speed different from the calculated value.
Since the observed value of c is exactly the calculated value, it therefore must be the case that the two-way speed is exactly the same as the one-way speed.
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The rigidity of the rod should be enough to withstand the wind caused by the rod travelling through the air with the speed of ~10m/s.
Why do I have to explain this a third time? Your rod can never be rigid (and the air is irrelevant). When you move one end of the rod, there is a delay before the other end moves unless you try to move both ends of the rod simultaneously by accelerating them both individually, but if you do that you run straight into the issue of what is simultaneous, so you have to pick a frame of reference in which the two events are simultaneous, at which point you've already selected a speed of light for your experiment to "confirm".
...if the end of the rod at B will start allowing the light from laser at B to travel perpendicularly to B' we will know that the light from laser at A will start to be blocked by front end of the rod BECAUSE THE LENGHT OF THE ROD is exactly the same
Not so - you'd need the movement of the rod to be transmitted from one end to the other faster than the speed of light for such instantaneous coordination. A rod will actually communicate the movement at the speed of sound, so it's worse than using a light pulse. What you need to understand is that when you push or pull one end of your rod, the other end doesn't respond immediately, and the delay in the reaction of the other end is magnitudes worse than the delay from sending a light signal.
(disregard length contraction; at that speed it is really insignificant) as the distance d between the lasers.
Length contraction can indeed be ignored as the rod can move at very low speed, but that's not the issue - it's the delay between one end moving and the other end reacting to it that renders your experiment worthless.
The speed of the rod is not important either; the limited precision in positioning the lasers in regards to the length of the rod d would be compensated if we repeat the experiment from the other direction since 2 way speed of light has to be c.
As I've told you in two previous posts, you're up against a synchronisation issue. If you choose to synchronise events at the two ends of the rod by using the frame of reference in which the apparatus is stationary, you will measure the speed of light as c in both directions. If you choose a different frame of reference, you will measure a higher speed of light one way and a lower speed of light the other. If you do this with a hundred different frames of reference, you will get a hundred sets of different results and you'll be no closer to knowing which of them might be closest to being true.
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The one way speed of light has been measured.
That's incorrect. There are experiments which are often presented as having measured the one-way speed of light, but none have actually done so.
One interesting question immediately arises: how do you measure the one way speed of light? It turns out there are various methods. One idea involves the emission and absorption of gamma rays by certain kinds of atoms in a solid. The process of absorption is very sensitive to the energy of the gamma rays. So if the speed of light (and therefore its energy) varies with direction, then the rate of absorption ought to change too.
In the 1960s and 70s, various physicists looked for a directional dependence by placing a gamma ray emitter at the edge of a rotating disc and an absorber at the centre. They then looked for any difference in the rate of absorption as the disc rotates but found none.
The experiment fails to work because of the Doppler shift. The idea with the experiment is that the frequency of the radiation has a fixed value and the detector can only detect it if it remains constant at the absorber end. If the centre of the turntable is stationary in space, the absorber will be moving at a constant speed relative to it as it goes round, but it has to be tuned precisely to that speed of movement if it is to detect the radiation, so if you slow down the turntable or speed it up just a little (or a lot), the detector won't detect anything.
The idea of the experiment is that if the centre of the turntable is moving through space, the speed of the absorber will continually change (while the speed of the emitter is constant), so the idea was that it should stop detecting the radiation most of the time. The movement of the emitter causes the frequency of the radiation to fall due to its "clock" being slowed by that movement - it runs slightly in slow motion. The frequency the absorber is tuned to will likewise fall due to its extra movement through space. However, if you work through the maths properly, you find that as the "clock" of the absorber speeds up and slows down, the frequency of the radiation hitting it rises and falls to match due to the Doppler effect, and the match remains perfect at all times. There is no possible way for the experiment to show up any difference in the speed of light in different directions no matter how much that speed of light across it varies.
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Simple thought. How does a photon know whether it is coming or going? Obviously it can't know, so there can't be a difference between the propagation speeds.
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Simple thought. How does a photon know whether it is coming or going? Obviously it can't know, so there can't be a difference between the propagation speeds.
Sometimes the simple thoughts are the best.
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Simple thought. How does a photon know whether it is coming or going? Obviously it can't know, so there can't be a difference between the propagation speeds.
Hi Alan!
Two bonded protons that form a hydrogen molecule may not need to know which one of them is moving to follow precisely the direction and the speed they were given in the beginning, providing they kind of keep in mind the motion parameters of the information that allows them to stay bonded, because due to the limited speed of any information, one of them necessarily has to move before the other in the process, which necessarily produces doppler effect on the energy that carries the information, what should produce shifted steps between them, a step like motion that should necessarily follow the original acceleration if the exchanged energy has to stay constant. Here how this motion should look like at first glance.
(https://img4.hostingpics.net/pics/377553animationpetitspas.gif) (https://www.hostingpics.net/viewer.php?id=377553animationpetitspas.gif)
But if we give it a second thought, if we consider the problem of the one way speed of light for instance, a question arises: the left proton makes a full step before the information from that step reaches the right proton, and that right proton starts its step when the left one is close to it, so it doesn't have the time to make a full step before the information from that step starts to hit the left proton, and it should since I thought that those steps could represent what we call inertial motion. Of course the steps could be infinitely small for instance, but it seems to me that it would only postpone the issue, an issue that I did not yet succeed to imagine. Anybody can? Maybe Kris since he seems quite concerned by the limited speed of the information, or PmbPhy since he seems concerned by doppler effect?
Notice that this particular problem gives us a new tool to analyze the way light behaves, because if those steps really exist, light wouldn't just help us to measure motion, it would also participate to its production at the particles' level.
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Simple thought. How does a photon know whether it is coming or going? Obviously it can't know, so there can't be a difference between the propagation speeds.
There is no difference in the propagation speeds - the speed is imposed by the fabric of space, but there is a difference in the propagation speeds relative to the object the light came from if that object is moving through space. The light doesn't need to know anything, but simply sets off at the speed it's allowed to move at.
Let me remind you of my thought experiment with a fibre-optic cable running east-west right round the planet. If we send a pulse of light through it in both directions, we'll get a pulse returning from the west and another from the east, but they won't arrive at the same time because one of them has had to travel further due to the rotation of the Earth. The pulse moving west goes a shorter distance through space than the pulse moving east. If we try to measure the speed of those pulses of light at different points on their journey round the cable, we'll find that it is always c, and Einsteinists will assert that it is moving at c in both directions relative to each point at which they measure it rather than faster in one direction than the other. However, if it is really moving at c in both directions at each of an infinite number of points around the ring, it would be impossible for the pulses of light to arrive at the finish at different times - they would have to arrive simultaneously. The fact that the pulses do not return simultaneously proves that the speed of light at some of those points along the way cannot be the same in both directions relative to those points. This invalidates SR, but what Einsteinists do is what they always do - they tolerate contradictions and stick rigidly to a disproven theory.
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Hi David!
Unless a new theory on motion gets more useful than SR, there is no reason for physicists to reject it. We don't reject our old ideas just because they contain contradictions, otherwise we would never get the ground to build new ideas. I also think SR is wrong, and I am also pointing at its contradictions to discuss it, but I know it is not sufficient to convince anybody that my own theory is promising. To convince people, I know I have to show the benefits.
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Unless a new theory on motion gets more useful than SR, there is no reason for physicists to reject it.
Not so - if another theory does so much as produce the exact same numbers while making better sense (as with LET), they should switch to it instead of carrying on regardless while continuing to assert superiority of the irrational theory over the rational one. At the very least, they should drop all the irrational dogma and recognise that it cannot be the case that light moves at the same speed in opposite directions relative to all objects, but they persist in asserting that it does even though their position has been shown to be wrong on that score.
We don't reject our old ideas just because they contain contradictions, otherwise we would never get the ground to build new ideas.
Where theories produce contradictions, we should accept that they must be wrong instead of asserting that they are right, and then we should put more effort into finding out ways of correcting or replacing the faulty theory so that we have something that doesn't generate contradictions. The establishment's insistence in sticking with a disproven theory while rejecting one that does the same job while making better sense is actively holding back progress.
I also think SR is wrong, and I am also pointing at its contradictions to discuss it, but I know it is not sufficient to convince anybody that my own theory is promising. To convince people, I know I have to show the benefits.
The benefits are that you encourage more rational people to go into science instead of making it appeal to the irrational ones who are happy to tolerate contradictions and dig in to defend faulty models rather than working to correct them.
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"Why do I have to explain this a third time? Your rod can never be rigid (and the air is irrelevant). When you move one end of the rod, there is a delay before the other end moves unless you try to move both ends of the rod simultaneously by accelerating them both individually, but if you do that you run straight into the issue of what is simultaneous, so you have to pick a frame of reference in which the two events are simultaneous, at which point you've already selected a speed of light for your experiment to "confirm"
If the rod of length d=10m is moving with constant speed and its end is at point B, then its front must be at point A 10m forward. It has nothing to do with the speed of sound .
"Length contraction can indeed be ignored as the rod can move at very low speed, but that's not the issue - it's the delay between one end moving and the other end reacting to it that renders your experiment worthless."
If the rod has been moved out (let's say 10km away) and accelerated to the constant speed v and then let it glide (without any acceleration) past lasers at A and B, then if front end reaches point A, the rear end must be at point B; there is no delay between one end moving and the other reacting. They just both move with constant speed (or if you prefer, they are at rest and embankment is moving with constant speed -v)
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Not so - if another theory does so much as to produce the exact same numbers while making better sense (as with LET), they should switch to it instead of carrying on regardless while continuing to assert superiority of the irrational theory over the rational one. At the very least, they should drop all the irrational dogma and recognize that it cannot be the case that light moves at the same speed in opposite directions relative to all objects, but they persist in asserting that it does even though their position has been shown to be wrong on that score.
I agree that they should try to understand, and I noticed that some do, but can they change their mind? Take someone who believes in god for instance, can he change his mind just because it is more logical to think the contrary? Moreover, what would happen if everyone would change his mind every day just because another idea looks better? We have to resist to change otherwise things would not have the time to exist at all. That's probably why bodies resist to acceleration, and also why species stay the same while their mutations offer new possibilities to the natural selection. It's by hazard and coincidence that we change, otherwise we must stay the same.
Where theories produce contradictions, we should accept that they must be wrong instead of asserting that they are right, and then we should put more effort into finding out ways of correcting or replacing the faulty theory so that we have something that doesn't generate contradictions. The establishment's insistence in sticking with a disproved theory while rejecting one that does the same job while making better sense is actively holding back progress.
That would be true if developing new ideas did not depend on chance, but if it does, then it might be wrong, because trying to develop new ideas would not mean that one of them will work for sure, so that putting a lot of energy on that one could lead to disaster. The evolution of species doesn't work like that: it produces mutations everywhere at random, and it kind of hopes that one of them will do the job. We may have the feeling that we know how to control our evolution, but I think it's just an illusion due to the fact that changing is always uncertain, so that we kind of need that good feeling to help us jump off the cliff.
The benefits are that you encourage more rational people to go into science instead of making it appeal to the irrational ones who are happy to tolerate contradictions and dig in to defend faulty models rather than working to correct them.
Unless somebody suddenly suffers a mutation in his ideas, I'm afraid nobody changes ideas only while discussing with others. Even if I am aware of the phenomenon, I can't avoid the feeling that, at first sight, others' ideas do not work as well as mine, and I realize that I can't study them as well as I would like because of that feeling. It's like trying to study the bible while being atheist: you almost need to be masochist. I can easily observe my own resistance and I am alone to think the way I do, so I can imagine how resistant I would be if I had the whole scientific community behind me. :0)
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If the rod of length d=10m is moving with constant speed and its end is at point B, then its front must be at point A 10m forward. It has nothing to do with the speed of sound .
I thought the rod was stationary relative to the rest of the apparatus to begin with, but having looked back at what you originally said, I got that wrong because I was distracted by the word "rigid" and the bit about measuring it "at rest" - that set me off on the wrong track. So, I apologise for wasting your time with my previous comments on your thought experiment, and I'll attempt to deal with it correctly this time. I've looked at this kind of thought experiment more than once in the past and thought it was the same old thing coming round again in another form, but it's fully possible that on each occasion it involved a rod starting from stationary such that communication speed issues are involved in getting it moving. You've already got it moving though, and because the speed can be very low relative to the rest of the apparatus, length-contraction may not be be a factor (although it might be too soon to rule it out). Is it really possible that we've all missed a trick? I was sure I'd looked at this myself (a version with the rod already moving), but maybe I was diverted off into looking at a version with a stationary rod being accelerated and never got back to looking at the original idea. Whatever the case, your thought experiment is definitely worth looking at carefully, so lets test it to destruction. I'll quote it again as it's a long way up the page:-
Let’s have two light sources at points A and B separated by distance d and sending constantly (perpendicular to AB) signals to clocks at A’ and B’
Let’s have an opaque rigid rod of the length d (it can be measured against AB while at rest with AB, so accuracy can be high) traveling with constant speed v (non-relativistic) parallel (and very close to) the line AB from B towards A. Initially the light from B to B’ will be blocked and the light from A to A’ will be allowed to be transmitted. When front end of the rod will start cutting off the light from A to A’ the light from B will start to be transmitted to B’ . At this moment, we will have both clock at A’ and B’ synchronized.
We can improve the accuracy of the measurement sending the rod from A to B with the same speed v and measure one way speed of light from A to B. The average 2 way speed of light from A to B and from B to A has to be c.
What you're really doing is using your rod to start two clocks, the leading end of the rod starting one clock and the trailing end starting the other, and the clocks simply start as these ends run past them. You then send light from one clock to the other (or a radio signal) and note the time at which it is sent out on one clock, then the other clock records the time at which it is received. If the apparatus is stationary in space, the delay will be the same in both directions and will show the speed of light in both directions to be c, but if the apparatus is moving in the AB direction, the two timings will be different and different values for the speed of light will be generated for the two directions.
Has this really synchronised the clocks in an absolute way? A conventional method of synchronising the clocks might be to send a radio signal from half way between the two clocks and for the two clocks to start when they receive that signal, which means that if the apparatus is moving through space in the AB direction, clock A could start up long before clock B. If your system of synchronisation synchronises them differently, then you might have found something big. Let's add another rod going in the opposite direction. We can arrange things such that the leading end of the new rod passes clock A at the same time as the trailing end of your original rod passes clock A. If we do this, the trailing end of the new rod will pass clock B at the same time as the leading end of the original rod passes clock B. That locks things down very tightly. We can check the rods before doing the experiment, placing them with their ends at A and B to confirm that they are the right length. Then we take them away and set them moving towards the clocks from opposite directions.
Any compression or stretch from how we accelerate them will be lost as they rearrange themselves and settle down, and we can prove this by using two rods for each direction, one of each pair pushed up to speed while the one next to it is pulled. We now have two pairs of two rods with the two rods in each pair moving side by side, their front ends directly side by side and their trailing ends directly side by side too, thereby proving that any compression and stretch from the accelerations has been lost. Having dealt with this issue, lets simplify it back to two rods moving in opposite directions for the rest of the discussion.
Let's assume the clocks are not moving through space. The rods approach, and the ends pass clocks simultaneously, synchronising the clocks. We can also send a radio signal from half way between the clocks and have it arrive at both clocks at the same moment. We have perfect synchronisation with both synchronisation systems agreeing with each other.
Now let's assume the clocks are moving through space at high speed such as 0.867c. Our length AB is length-contracted to half its rest length, but so are the rods because they're moving at 0.867c plus or minus a tiny amount. We run our experiment again (well, it's your experiment, so if this works, it's your Nobel prize), and this time when we send out our radio signal from half way between the clocks it will reach clock A long before it gets to clock B. But what are the two rods doing? Let's look at the one moving in the AB direction first, then do the BA direction afterwards. For the two synchronisation methods to match up, the trailing end of this rod must reach clock A at the same time as the radio signal gets there. We know that the leading end of the other rod should be there at the same time too, so let's assume it's there. What's happening at clock B?
If there's any length-contraction issue with the rods, one will be infinitesimally shorter than the length AB and the other will be infinitesimally longer, so that means the leading end of our first rod might not have reached clock B yet. and although the leading end of our second rod has reached clock A, its trailing end may not have reached clock B. That leaves room for a delay, and given the slow movement of the rods relative to the clocks, it's just possible that our radio signal will still be able to reach clock B at the same time as those ends of the rods pass that clock, because even a tiny amount of length-contraction could add up to a significant difference. If it can, then the thought experiment will be defeated, and I have a nasty feeling that that's what's going to happen.
How can we check? Let's try moving the rods faster relative to the clocks so that we can get a decent value for the length-contractions acting on them and work out what the delays actually are. We can then repeat it with slower speed differences, but avoiding values which take us into places where calculators introduce significant rounding errors. We only need to do this with one rod from now on, so let's move the clocks through space at 0.867c and the rod at 0.968c. That's a high speed for the rod, but it's convenient because it gives us length-contractions to 1/2 for the distance between the clocks and 1/4 for the the rod. We now have a rod that's only half the length required to span the distance between the clocks. The radio signal is sent out from half way between A and B, then when it arrives at clock A, the trailing end of the rod passes clock A. At that moment, the leading end of the rod is now at the place where the radio signal was sent out from, so there is no way it can reach clock B at the same time as the radio signal which is already far ahead of it. Of course, we could use a rod that's twice as long so that the other end would be at clock B at that moment, but if we did that, we'd be assuming that our clocks are moving at 0.867c through space. If we assume that they are stationary instead, a double-length rod would need to be moving at 0.867c to be length-contracted to half the length AB, and the problem with that is that the relationship is wrong - to match up with this, the relative speed difference between clocks and rod would mean that if the clocks were moving at 0.867c, the rod would be moving through space at 0.99c rather than 0.968c.
[Edit: it wouldn't need to be double the length though as there's a delay before the radio signal reaches clock B, so we'd only need to lengthen the rod to get the end of the rod far enough ahead of the radio signal to reach clock B at the same time.]
My suspicion is that length-contraction is going to wreck the ability of the experiment to synchronise the clocks in the way it initially looked as if it could, but I'm going to post this now and take a break before getting back to it later (if someone else doesn't finish it off first).
[Edit 2: I'll get back to this tomorrow.]
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The experiment has been designed in such a way that it should be possible to carry it out in even modest lab. Most crucial part is positioning the lasers against the rod (the experiment could be modified with 2 narrow slots cut in the rod so both lasers could shine through only if they are perfectly aligned) and the clocks which should measure the time to at least 100ps precision.( As I have mentioned before, we could modify the experiment that only one clock would be required) The length of the rod doesn't need to be measured extremely precise; accuracy to 1mm will do. Now let's do some calculations:
time for the light to cover 10m is d/c=10m/3x10^8=~33ns.
The length contraction of the rod of length d=10 for v=100m/s will be dx((v^2)/(c^2)=10mx((10^4)/9x10^16)=~(10^-12)m.
If we can position the lasers against the rod with 1nm accuracy, the length contraction will be 1000 time smaller then our uncertainity in positioning the lasers..
For 1nm accuracy in positioning the lasers there will be uncertainty in synchronizing the clocks:
delta t= 1nm/100m/s=~10^-11s, which still will allow us to measure one way speed of light with 0.5% accuracy.
I think it could be possible to carry out such experiment without spending exuberant amount of money on necessary equipment.
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That's incorrect. There are experiments which are often presented as having measured the one-way speed of light, but none have actually done so.
If you know me at all I then you know that I never accept mere claims like that. You'd have to demonstrate that all the published papers which demonstrate that its been measured area all wrong or state why you're making that claim.
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That's incorrect. There are experiments which are often presented as having measured the one-way speed of light, but none have actually done so.
If you know me at all I then you know that I never accept mere claims like that. You'd have to demonstrate that all the published papers which demonstrate that its been measured area all wrong or state why you're making that claim.
The example you provided was one that was debunked long ago. I'm in contact with other people in the LET camp who've spent years going through all the experiments that supposedly measure the speed of light in a single direction who have found fatal flaws in every single experiment of that kind that they've been able to find. The best one they'd found involved a rotating rod with a fan-like device on each end (slits to let light through), but it failed to account for twist in the rod due to communication delays - when they tested me on it, I immediately realised that if you had two separate fans and coordinated them using radio communications, they'd move out of alignment due to delays and that the exact same delays would operate within the rod.
The reason you believe that experiments exist which have measured the one-way speed of light is that the people who put out these experiments rarely admit that they've got flaws in them once they've been debunked, so documentation is left in place asserting that they have succeeded in doing the job originally claimed of them. There's also a reason why you pointed to a particular example that's been debunked, because that's about as good as they get - if there was an experiment that actually did what they claim of it, it would be up there as the supreme example with a Nobel prize tied to it. The hard reality is that you have no experiment to point to that can measure the one-way speed of light because no such experiment has been found, and my thought experiment with the fibre-optic cable round the Earth should be a clue as to the fact that no such experiment has been found, because if such an experiment was known it would have demonstrated that light moves at different speeds in different directions across it.
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Hi Kris,
I'm not sure your way of analysing it is right, so I'll continue to blunder along with mine to see what happens. I made a mistake in what I said before:-
The radio signal is sent out from half way between A and B, then when it arrives at clock A, the trailing end of the rod passes clock A. At that moment, the leading end of the rod is now at the place where the radio signal was sent out from, so there is no way it can reach clock B at the same time as the radio signal which is already far ahead of it.
I was forgetting that the apparatus has moved past the midpoint, so the leading edge of the rod is still ahead of the radio signal heading for clock B. That makes sense, because for the two synchronisation methods to clash so badly would have shown that the experiment could indeed measure the one-way speed of light. For the experiment to fail to do so, the synchronisation methods should have matching results no matter how fast the apparatus is moving through space.
The method I'm using to test this is as follows.
(1) Pick a speed for the clocks A and B to move through space.
(2) Pick a distance of separation between A and B and adjust it for the length-contraction required for the speed in (1)
(3) Put a radio transmitter at point M, half way between A and B. Work out how long light (or the radio ping) will take to get from M to A and from M to B. Remember that A and B are moving, so the signal will reach A first (if they're moving in the AB direction rather than BA).
(4) Calculate how close to B the radio signal has got to at the point in time when it has reached A.
(5) Pick a speed for the rod to move through space and work out the length-contraction on it.
(6) Calculate how close to B the leading end of the rod will be at the point in time when its trailing end has reached A.
(7) Compare how long it will take for the radio signal and the leading end of the rod to catch clock B (from the starting points calculated in steps 4 and 6). Remember that clock B is racing away from them, so it's a moving target.
If we do this for a range of speeds for clocks and rods, I suspect we'll see an interesting pattern that will show that they both reach clock B simultaneously in every case. I don't have time to fiddle around with a calculator to do all that, but I might write a program to do it instead. I'll do that when I've got a bit more time free, unless you (or someone else) get in first. I expect there are more elegant ways to check it that a mathematician would apply straight away, but this one should do the job.
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Hi David,
I think it would be possible to carry out the experiment. Would you be (or would you know somebody ) interested in helping to set it up?
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Let's try again.
A photon has no idea whether it is travelling towards or away from you. Until it reaches you, it doesn't even know if you exist. Therefore its speed in vacuo is independent of direction.
Now suppose that the vacuum is in fact filled with aether, which is in some way essential for the propagation of light, and we are travelling through it in some direction. The measured two-way speed will depend on whether we are measuring "into wind" or "across wind", and the Michelson-Morley experiment (and its descendants) have clearly and consistently shown no difference.
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Hi David,
I think it would be possible to carry out the experiment. Would you be (or would you know somebody ) interested in helping to set it up?
I'd certainly like to be involved in setting it up if once the numbers have been properly crunched it looks as if it would work, but I don't think the right crunching has been done yet. I've thought of a simpler way to do that crunching, so here's the new approach. We need to crunch the numbers twice: the first time with the assumption that the clocks are stationary and that the rod is length contracted, and the second time with the assumption that the rod is stationary and that the clocks are moving past it instead, which means the clocks are closer together instead. When ends of the rod pass clocks, light is sent out towards the other clock, but on the first run, clock A starts running before clock B because the rod is shorter than the distance AB, and on the second run, clock B starts running before clock A because the rod is longer than the contracted distance AB.
So, what we need to know is this: what does clock A read when light reaches it from clock B, and what does clock B read when light reaches it from clock A. If the numbers match up for the first and second run, then the experiment cannot detect the one-way speed of light, but if they don't match, it is likely that you will get a Nobel prize. I'm sure this will have been explored a hundred years ago though, so I think they'll match.
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Let's try again.
A photon has no idea whether it is travelling towards or away from you. Until it reaches you, it doesn't even know if you exist. Therefore its speed in vacuo is independent of direction.
Now suppose that the vacuum is in fact filled with aether, which is in some way essential for the propagation of light, and we are travelling through it in some direction. The measured two-way speed will depend on whether we are measuring "into wind" or "across wind", and the Michelson-Morley experiment (and its descendants) have clearly and consistently shown no difference.
Correct: they measure the two-way speed of light and always show that to be c. That doesn't get us any further on as everyone appears to agree on that point already.
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The point is that if the one-way speed was c + x and c - x in the other direction,
(a) the measured two way speed would always be less than c
(b) the measured two-way speed would vary with the initial direction of propagation
(c) Maxwell's equations would not give the measured value of c
(d) indeed Maxwell's equations would not describe a selfpropagating electrromagnetic wave at all
(e) you would have to invent some means by which a photon would know whether it was travelling towards or away from you (and explain why "you" were of cosmic significance)
(f) the energy of the photons emitted from pair production and annihiliation would depend on the direction of travel of the initiating photon that produced the pair
and so forth. In a few words, if c depended on the direction of propagation, a whole lot of what we know from experiment would not be true. If c does not depend on the direction of propagation, the one-way speed must be the same as the two-way speed.
But if you want a single defining experiment, measure radiation pressure.
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The point is that if the one-way speed was c + x and c - x in the other direction,
(a) the measured two way speed would always be less than c
Not when your clock runs slow - your movement through space cancels out the difference.
(b) the measured two-way speed would vary with the initial direction of propagation
You need to elaborate on that to spell out where there's a problem.
(c) Maxwell's equations would not give the measured value of c
(d) indeed Maxwell's equations would not describe a selfpropagating electrromagnetic wave at all
Are you sure there isn't a distance term being smuggled in somewhere which is calculated based on the assumption that you aren't moving through space? And if there's no distance involved, how would the equations have any relation to relative position or to movement through space?
(e) you would have to invent some means by which a photon would know whether it was travelling towards or away from you (and explain why "you" were of cosmic significance)
Why would it need to know anything? If a photon's moving away from you, you simply won't encounter it.
(f) the energy of the photons emitted from pair production and annihiliation would depend on the direction of travel of the initiating photon that produced the pair
Again you need to elaborate. Where's the problem?
and so forth. In a few words, if c depended on the direction of propagation, a whole lot of what we know from experiment would not be true. If c does not depend on the direction of propagation, the one-way speed must be the same as the two-way speed.
All the experiments run into the same issue - movement through space is hidden and none of those experiments are capable of revealing that movement. Anyone who thinks they should be able to identify movement through space does not understand relativity adequately.
But if you want a single defining experiment, measure radiation pressure.
What use is that? Again you're being light on detail in the hope that your assertions will be left standing purely because there's not enough substance to them to attack. The faster you run into radiation, the higher its energy appears to be, so that would be measured as a higher pressure.
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If light signals moving at c, in opposite directions around the earth at the equator, return to their starting positions at different times, then with a rotation speed of o mph, 1 circuit requires .1333 sec. With a rotation speed of 1000 mph, the westbound signal arrives 200 ns earlier, the eastbound signal arrives 200 ns later. Knowing the time and distance should allow comparison of 1-way speeds. This experiment involves an absolute frame whereas in SR there is none.My statement in #4 was within the SR environment.
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If light signals moving at c, in opposite directions around the earth at the equator, return to their starting positions at different times, then with a rotation speed of o mph, 1 circuit requires .1333 sec. With a rotation speed of 1000 mph, the westbound signal arrives 200 ns earlier, the eastbound signal arrives 200 ns later. Knowing the time and distance should allow comparison of 1-way speeds. This experiment involves an absolute frame whereas in SR there is none.My statement in #4 was within the SR environment.
SR depends on tolerating contradictions. You pick the frame of reference in which you're stationary and assert that the speed of light is the same relative to you in all directions, but you ignore the fact that it can't then be the same in all directions relative to anything else that's moving relative to you. When you deal with something moving relative to you, you then switch to the frame in which it is stationary, and then you repeat the same assertion about light moving at the same speed in all directions relative to it while ignoring the fact that it then won't be the same in all directions relative to you any more. That is the ridiculous, irrational game SR people play time and time again. The fibre-optic-cable-round-the-earth thought experiment helps to show up the stunt they're trying to pull - it takes up the assertion that the speed of light is the same in all directions at any point (relative to that point) and applies that at all points on the circuit, then shows that if the assertions were all true, the light pulses would have to return to the timer simultaneously even though the path is longer one way than the other. But irrational people generally believe they are rational and appear to be incurable, so they blunder on with a disproven theory regardless.
[Edited to tighten up the wording.]
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Hi David,
I'm going for short holidays tomorrow. When I'm back, I'll do some further thinking how we can approach practical aspect of carrying out the experiment.
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Hi Kris,
If we run the experiment with the clocks stationary and the rod moving, the clocks will count how long it takes for light to reach them from the other clock after the rod starts them running. If we view this from a different frame of reference, we must see the clocks count up the same number of ticks. All frames of reference are believed to act exactly as if they are the one that represents an absolute frame, so no matter how fast the experiment runs through space, the clocks should count up the same values every time you run the experiment and make it impossible to measure the speed of the apparatus through space. Everything happening in the experiment must conform to the normal rules, so it cannot possibly work. And yet somehow, it still sounds as if it should work. There's something really weird going on that needs to be understood. Why does the thought experiment's argument sound so convincing? That's what I'm trying to explore, and I'll keep working on it until I can explain it.
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The SR clock synch method is to send an em signal from the center of the spacing of two clocks with a selected time for the center clock. This method synchronizes two clocks in the same frame and establishes a relative axis of simultaneity (red) for that frame at its current speed. It does not synchronize clocks from different frames.
The first graphic should represent the proposal in Kris #15.
https://app.box.com/s/79xzoqaefscp0meiuq1hlhi2ddvqw3n7
https://app.box.com/s/mun2wugdjlos0hqh7wxubmfcitjub04b
The second graphic shows synchronized clocks for A moving at .3c and B moving at .6c, relative to earth. It also shows the reciprocal observations of slow clocks. With both assuming equal path lengths for light transit times, the clock reading of 1.00 occurs at 1.075 on their local clock.
Speed of B as calculated by A = .366.
1/gamma = .931.
1.075(.931) = 1.00 (removing effect of td)
To establish synchronization between frames, each clock must respond to a signal from the other by sending the current time and one clock adjusted. Here is an example using the second graphic, but advancing the A-clock .32. All times are local.
A send 1.00 to B
B send 1.00 to A
A receive at 1.79
1.00/.931 = 1.074 (adjust B-time for td)
(1.79+1.00)/2 = 1.395 (calc mid point)
1.074 -1.395=- .32 (amount A must adjust its clock)
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david cooper #45
https://app.box.com/s/zlhkh5g3fv56n2t0rd1obd576prd95kg
graphics describe much better than words.
The graphic is a speed plot, thus c is constant at the same angle, and relative speed results in different distances traveled.
Calculations used 186000 mps.
Rotation speed is exggerated to show the tiny differences.
Why would someone be so hostile toward a theory?
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Imagine a solid cylinder, 30 cm in diameter and 30 cm long. Drill hole parallel to the axis, near the circumference. Spin the cylinder on its axis. Light can pass through the hole but will be attenuated as you increase the rate of rotation, unless you skew the hole slightly.
Assume you can spin the cylinder at 12,000 rpm (not difficult). It is left as an exercise to the reader to determine the skew angle required to maximise the amount of light that can pass through the hole. Make the experiment easy by drilling lots of holes. Now measure the one-way speed of light from the skew angle and rotation speed that produces the maximum transmitted intensity.
This "skewed hole" method is routinely used for analysing neutron beams and selecting neutrons of a desired speed, but needs a bit of engineering revision to cope with photons moving at c. Fortunately visible photons can be stopped by very thin sheets of metal, so we can replace the solid cylinder by an axle, maybe 1 km long, with thin discs at each end. perforated by circumferential holes. Put the whole thing inside an evacuated tube and use a laser source. You now have a feasible, updated and unidirectional version of Fizeau's classic 1848 experiment.
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Fortunately visible photons can be stopped by very thin sheets of metal, so we can replace the solid cylinder by an axle, maybe 1 km long, with thin discs at each end. perforated by circumferential holes. Put the whole thing inside an evacuated tube and use a laser source. You now have a feasible, updated and unidirectional version of Fizeau's classic 1848 experiment.
How are you coordinating the two discs at the end of your axle to keep them aligned? No matter how rigid your axle is, it will twist due to delays in the communications of forces between atoms, so it adjusts for the speed it's moving through space. If you get rid of the axle and have a separate axle for each disc 1km apart and use radio signals to coordinate their rotation to try to stay aligned with each other, you should realise that they do not stay in sync, and the communication delays that cause them to deviate from the alignment you want them to have apply equally to the functionality of your 1km-long axle.
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david cooper #45
https://app.box.com/s/zlhkh5g3fv56n2t0rd1obd576prd95kg
graphics describe much better than words.
The graphic is a speed plot, thus c is constant at the same angle, and relative speed results in different distances traveled.
Calculations used 186000 mps.
Rotation speed is exggerated to show the tiny differences.
Why would someone be so hostile toward a theory?
Your diagram shows the speed of light being different in opposite directions relative to each point on the circuit. Why would anyone not be hostile towards the presentation of an irrational theory as a rational one?
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Here's a simple experiment.
Most airplanes carry a gadget called Distance Measuring Equipment (DME). It is a radio transceiver. About once per second it emits a coded radio pulse. If a DME ground station detects the pulse, it waits 50 microseconds then retransmits the code. The DME receiver subtracts 50 microseconds from the time between transmission and reception, and calculates the distance to the ground station, assuming c is independent of direction. It's a pretty old (1945) system that could be made a lot more accurate nowadays*.
Now suppose the discrepancy between out and return speeds is 2x in one direction, and 2y and 2z in the perpendicular directions. Set up a "precision DME" with three ground stations at known distances d (use a surveyor's chain) in the x, y and z directions, and measure their apparent distances d' with the DME
dx' = dxc2/(c2 - x2) and similarly for y and z.
If x, y and z are not all zero, there will be a discrepancy (d' - d) in at least two measurements.
*DME works over distances of up to 200 miles if you are lucky, and reads to +/- 0.1 mile even using thermionic valve technology. No point in making it more accurate for aviation use because the plane is moving at around 0.1mile/second anyway!
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How are you coordinating the two discs at the end of your axle to keep them aligned?
Drive the axle from its midpoint, so the discs have equal phase lag from the driving point, and wait as long as you like for any second-order phase lag to dissipate.
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How are you coordinating the two discs at the end of your axle to keep them aligned?
Drive the axle from its midpoint, so the discs have equal phase lag from the driving point, and wait as long as you like for any second-order phase lag to dissipate.
If the apparatus is not moving through space, the holes in the discs can be placed so that if light passes through one it will be able to pass through the other one too, but only in one direction - if it tries to go through in the opposite direction it will be blocked. We can use light from a laser so that we can use that light and avoid light travelling on other paths. If we now put the apparatus in a rocket and accelerate it to relativistic speed, the light from the laser will pass through it much more quickly, which makes it look as if the light should no longer be able to get through the second hole as that disc hasn't rotated into the right position in time for that to be possible, but movement through the fabric of space affects the coordination of the discs such that the lead one lags behind where you expect it to be and the rear one is ahead of your expectations in terms of its rotation, thus adjusting the apparatus to maintain the ability of the laser light to pass through both holes.
Keep the rocket moving fast but turn it around to move along backwards and what happens to the discs now? The experiment's rear disc now lags (because it is leading the way through space) while the experiment's front disc rotates ahead of schedule (because it's trailing the other disc on its way through space) and the result is that the light still passes through both holes even though it takes longer for it to travel from one hole to the other.
This auto-correction works well for low speeds of travel through space, but it looks as if it might break down at higher speeds, so perhaps this experiment could in theory identify the one-way speed of light if we could move the apparatus fast enough or improve its precision. However, it's really equivalent to a light clock with the mirrors at either end on rotating discs which always put the mirror in the right place just in time to hit the pulse of laser light on what for them is a tick of the clock (or half tick). The coordination of that should not go out of sync just from turning the clock round by 180 degrees - the rotations of the discs should automatically be adjusted to keep the mirrors hitting the light pulses because each rotating disc is directly equivalent to a clock. For that reason, I think the experiment cannot work no matter how quickly you move it through space, even though it feels as if it could work when you consider how long it could take light to travel through the apparatus in the same direction the apparatus is moving and compare that with how quickly light goes through it in the opposite direction. I can see now why the people I know who looked at this experiment last year spent seven months working on it before they decided it couldn't detect the one-way speed of light - there's something counter-intuitive going on with it.
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Set up a "precision DME" with three ground stations at known distances d (use a surveyor's chain) in the x, y and z directions, and measure their apparent distances d' with the DME
Are you taking into account length-contraction on your surveyor's chain, and how do you handle the variation in the actual distances as the Earth rotates and moves through space?
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Perhaps you would like to set out your definition of velocity? Or distance? Or time?
Anyway, if the earth's rotation or movement through space makes any difference to the propagation speed of light, you will find that dx', dy' and dz' vary with time and in relation to each other.
movement through the fabric of space affects the coordination of the discs such that the lead one lags behind where you expect it to be and the rear one is ahead of your expectations in terms of its rotation, thus adjusting the apparatus to maintain the ability of the laser light to pass through both holes.
Same argument applies: you should measure different rotation speeds for maximum illumination depending on the orientation of the axle relative to the direction of travel . No need for a rocket - with the dimensions I have suggested, the rotation of the earth will suffice.
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Perhaps you would like to set out your definition of velocity? Or distance? Or time?
Anyway, if the earth's rotation or movement through space makes any difference to the propagation speed of light, you will find that dx', dy' and dz' vary with time and in relation to each other.
There is no way that whatever it is you're doing there is going to show anything up, so this is a wild goose chase. But if you insist on following it through, I need to know what you're talking about and at the moment I can't make sense of it.
Now suppose the discrepancy between out and return speeds is 2x in one direction, and 2y and 2z in the perpendicular directions. Set up a "precision DME" with three ground stations at known distances d (use a surveyor's chain) in the x, y and z directions, and measure their apparent distances d' with the DME
What exactly are these 2x, 2y and 2z bits supposed to be? You've got radio signals moving on round trips there and back and a slowing of clocks due to movement which cancels out any delays caused by the whole system moving, so how are you going to pick up any discrepancy?
movement through the fabric of space affects the coordination of the discs such that the lead one lags behind where you expect it to be and the rear one is ahead of your expectations in terms of its rotation, thus adjusting the apparatus to maintain the ability of the laser light to pass through both holes.
Same argument applies: you should measure different rotation speeds for maximum illumination depending on the orientation of the axle relative to the direction of travel . No need for a rocket - with the dimensions I have suggested, the rotation of the earth will suffice.
Again there is no way this experiment can pick up its movement through space - it is directly equivalent to a pair of clocks bouncing light back and forth between each other. Imagine a clock with a hand that rotates like on an old clock. On the end of the hand is a mirror, but the clock is covered by a disc with a hole in it to allow the 12 position on the dial to be visible. The mirror appears in that hole once per rotation of the clock's hand, and it appears there every time the light pulse arrives from the other clock at the far end of the apparatus. We set it up with the apparatus at rest with both clocks putting their mirror behind the hole at the right time to intercept the light, and they bounce it back and forth continually. (We can boost it by having a laser shine through one of the mirrors which can be semi-silvered.) If we move the apparatus about, we can accelerate it this way and that, and twist and turn it, but nothing we do will stop those mirrors reaching the holes at the times when the light pulse arrives there - it all automatically corrects and keeps everything in sync, so long as the clocks are sufficiently accurate. If there's a need to maintain the synchronisation of the clocks by sending signals between them, this can be done with radio signals or by connecting them with a long axle - both will do the same job and keep them in sync with the light.
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Please follow the maths in my previous replies, which shows how any difference between out and return speeds always leads to a mean round-trip speed less than the maximum. Therefore any discrepancy, however caused, will be revealed by comparing the measured two-way speed in orthogonal directions. If there is no discrepancy, then the one-way speed must equal the two-way speed. No physics, no relativity, just algebra.
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Please follow the maths in my previous replies, which shows how any difference between out and return speeds always leads to a mean round-trip speed less than the maximum. Therefore any discrepancy, however caused, will be revealed by comparing the measured two-way speed in orthogonal directions. If there is no discrepancy, then the one-way speed must equal the two-way speed. No physics, no relativity, just algebra.
Please get up to speed with the maths - whenever a round trip involves a speed difference between the two directions, that always leads to a lower speed for the round trip which is cancelled out by the slowing of apparent time in the clock whose movement is causing that difference in speed for the two directions. You are cheating by using absolute time for your clock, and you aren't allowed to do that because you don't have an absolute-time clock on your plane (or at your ground stations).
I've worked out how to turn the counter-intuitive aspect of the other thought experiment into something that makes full sense. The best way to do it's to start with a long tube stationary in space and put a clock at either end with a mirror on the end of the second hand. We're going to play tennis with a photon. The clock at one end turns clockwise and the other anticlockwise (if we're looking at them from half way along the tube). Both clocks are covered by a screen with a hole in it, one clock having the hole in the 12 position and the other having its hole in the 6 position. The clocks are kept in sync by radio signals sent from half way along the tube. Our photon runs along the tube from the 12 of one clock as the tube rotates. By the time it reaches the other clock, the 6 position of that clock is in the right place for the photon to go through the hole and bounce off the mirror. When it gets back to the other clock, the tube has rotated 180 degrees again and the 12 position with the hole is back in place in time to bat the photon back again.
What happens when we move the tube lengthways at relativistic speed? Communication delays lead to the leading clock running behind time, which is good, because it takes light longer to reach it. If we replace the radio signals with an axle connecting to the hands of the clocks, it will twist (without stress) due to communication delays and provide the exact same lag of the leading clock. The trailing clock will run ahead of its expected schedule too for the same reason. If we turn the whole thing round so that the trailing clock becomes the lead clock (and the lead becomes the trailing), then the lag reverses and the photon continues to hit the holes every time and at the exact times when the mirrors are behind them (although we'll lose our photon while turning the tube round, so we'll need to introduce a new one - the same thing happens if the tube is not racing along through space, so the observed behaviour is identical for someone co-moving with the apparatus).
The tube rotates more slowly when it's moving through space at extreme speeds, so this enables the photon to travel from one mirror to the other with next to no rotation of the tube in one direction. The same photon making the return trip will take a very long time to cover the distance, but the tube will rotate nearly 360 degrees at a very slow rate of rotation and will have the hole and mirror in the exact place at the right time to hit the photon when it arrives. That is why it is counter-intuitive - you initially think it will need to twist more one way than the other and you know that it will actually twist the same amount in both directions, so when you think about light taking an extremely short time to pass through the apparatus in one direction and the extremely long time it will take to pass through it the other way, it feels as if it should be possible to detect the one-way speed of light with this experiment, but no - the twist moves the holes closer together for light moving one way through the apparatus while moving them further apart for the other direction, and the amount of rotation of the tube required to complete correct alignment varies in exactly the way required to hide the movement of the apparatus through space from the co-moving observer. This experiment illustrates beautifully the ability of relativity to keep the preferred frame hidden from us. The naive analysis leads to error and false belief systems - this experiment is promoted as a way to detect the one-way speed of light, but only by those who haven't thought it through properly or who deliberately seek to mislead.
[Edited to change 180 degrees to "nearly 360".]
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I haven't used "absolute time" for my clock. I have used the same clock to measure the time taken for a radio wave to transit in three different directions from the same point. Since none of the "ground" stations is moving with respect to the "air" station, any absolute movement of the entire system through the aether will result in a discrepancy between the measured speeds.
And why muck about with a perfectly good experiment that doesn't require the complicated "synchronisation" of anything?
And what on earth do you mean by "moving the tube lengthways at relativistic speed"? Moving it with respect to what? It's already travelling at a relativistic speed away from distant galaxies!
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I haven't used "absolute time" for my clock. I have used the same clock to measure the time taken for a radio wave to transit in three different directions from the same point. Since none of the "ground" stations is moving with respect to the "air" station, any absolute movement of the entire system through the aether will result in a discrepancy between the measured speeds.
Any movement of the system through the fabric of space will slow your clocks and completely cancel out the effect that you wrongly believe your clocks would pick up.
And why muck about with a perfectly good experiment that doesn't require the complicated "synchronisation" of anything?
You claim the experiment can pick up the one-way speed of light, but I've explained why it can't by showing it to be directly equivalent to a pair of clocks, and we know very well how clocks behave in that kind of scenario - they do not allow you to detect the one-way speed of light because they run at different rates as you move them around and in a synchronised pair the lead one will lag behind the trailing one to the exact right extent to hide the system's movement through the fabric of space. Your analysis of the experiment is therefore incompetent.
And what on earth do you mean by "moving the tube lengthways at relativistic speed"? Moving it with respect to what? It's already travelling at a relativistic speed away from distant galaxies!
Moving it relative to the fabric of space. The distant galaxies are moving away due to expansion of the fabric - the preferred frame shifts for different locations because of that expansion.
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n the around the world light path, the frame is the earth N-S pole. The initial position of the emitter-detector moves eastward at v. Light moves at c east and west.
Since the rotation speed is so small compared to c, a graphic proof is not possible, but we can use the coordinate transforms to prove
measured light speed is c for E and W, and all inertial frames.
With g=gamma:
x'=g(x-vt)
t'=g(t-xv/cc)
Substituting a=v/c, t=x=1/(1-a), c=1,
x'=g[1/(1-a)-a/(1-a)]=g
t'=g[1/(1-a)-a/(1-a)]=g
c'=x'/t'=1
The example in the graphic used a=.3, but all speeds yield the same result.
https://app.box.com/s/o84dfa03hu6e266toil3ccccvv3iffs5
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You claim the experiment can pick up the one-way speed of light, but I've explained why it can't by showing it to be directly equivalent to a pair of clocks,
I cannot see how one clock is equivalent to a pair of clocks, or why (a+b)(a-b) is not equal to a2-b2 in your universe.
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Speed up the rotation. You can have a ring of fibre-optic cable rotate at close to c and make the light in it do multiple circuits too (because it'll do many laps in one direction for every lap in the other relative to the start-finish line). You can then attach tags to the cable in as many places as you like and assert that the speed of the light in the cable passes each of those tags at the same speed relative to it in both directions, but you can't make that work for a single frame of reference.
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You claim the experiment can pick up the one-way speed of light, but I've explained why it can't by showing it to be directly equivalent to a pair of clocks,
I cannot see how one clock is equivalent to a pair of clocks,
You have a pair of discs with holes in them separated by 1km on either end of a long rotating axle. The rotation of the axle is a kind of clock, and because the two ends of it get out of phase with each other, each disc will behaves like an independent clock, and indeed the axle itself becomes an infinite series of independent clocks as it twists.
...or why (a+b)(a-b) is not equal to a2-b2 in your universe.
If you move a light clock through space, it ticks more slowly, but if you measure its tick rate against another clock that's co-moving with it, you won't notice that it's ticking more slowly as that other clock will be slowed equally. It's only if you have a magic absolute-time clock that you'll be able to show up the slowing of the moving light clock. The result is that no matter how fast you move a system through the fabric of space, you'll never be able to detect that movement by looking at the clocks that are part of that system unless they records absolute time, but we don't have access to any clocks that can do that.
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For Kris,
I've had a bit of time to look at Kris's proposed experiment properly and can see why it feels as if the experiment should work (meaning detect the one-way speed of light) as well as why it doesn't actually work.
To start with, let's look at a range of speeds of movement for the rod past the clocks. I've done my calculations based on the clocks being one metre apart instead of ten metres, and the rod too is one metre long. I'm also going to move the rod much faster than Kris would want to do so, but I'm doing this solely to make the numbers easier to work with and easier to understand - the pattern they reveal tells you all you need to know about what would happen with slower speeds. So, the speeds I'm using are 0.1c, 0.01c, 0.001c and 0.0001c, the slowest of these being apx 30km/s. In the four lines below, we have those speeds followed by the length of the 1m rod when length-contracted by moving at each speed, then the approximate amount of shortening of the rod in mm:-
0.1c, 0.9949874371m, 5mm
0.01c, 0.9999499987m, 0.05mm
0.001c, 0.9999995m, 0.0005mm (= 0.5 microns)
0.0001c, 0.999999995m, 0.000005mm (= 0.005 microns)
You can see form this that the length contraction figures are settling into a pattern of going down ten times more quickly than the speed, so by the time you get to speeds like one mm/s, there's almost no delay at all between the ends of the rods passing first and second clocks.
What happens though if we move the whole system at 0.866c through space? We need to convert the speeds for the rod carefully because it isn't a simple matter of adding each one to 0.866c - you do have to add them to 0.866, but you then have to adjust the result by dividing it by 1 plus 0.866 times the speed being added. So, the four new speeds for the rod passing the clocks are listed at the start of the four lines below. As before, they are followed by their contracted lengths in metres, then the amount of shortening of the rod in mm:-
0.8890328965c, 0.4578433236m, 42.5667637mm
0.868503939c, 0.495682265m, 4.317734962mm
0.8662751875c, 0.4995671122m, 0.4328878101mm
0.8660504016c, 0.4999567m, 0.04330002031mm (= 43.3 microns)
[Be aware that the contracted clock separation at 0.866c is to 0.5m, so you can see the lengths tending towards that.] The actual relative speeds of the rod to the clocks (as measured by someone stationary while the clocks move relative to him at 0.866c) are as follows:-
0.02300749272c
0.002478535216c
0.0002497837156c
0.00002499781557c
Let's name our two frames of reference to make it easier to refer to them when switching between them. The original frame is frame R (rest) and the other frame is frame M (moving). The numbers given in all the blocks of numbers above are of measurements made from frame R. For someone moving along with the clocks in the later four examples (someone who is at rest in frame M), the rod appears to be moving at 0.1c, 0.01c, 0.001c and 0.0001c in those same four cases, so these are frame M numbers. Notice that the actual relative speeds (the frame R ones for the moving system) are tending towards being a quarter of the perceived speeds (the frame M ones), and the reason for that is simple: length contraction means that the rod will move forward half as far though space in frame R to appear to have moved any given distance in frame M, but the functionality of the moving system has also been slowed to half speed, so the relative movement is doubly reduced, and that's why it's reduced to a quarter.
What we now need to do is calculate how long it will take for the leading end of the rod to reach clock B after the trailing end has reached clock A, so you'll see the numbers for that below. The first four lines are for the system stationary in frame R, while the second four lines are for the system moving at 0.866c in frame R. The speeds are in mm per nanosecond, and in each line they are followed by the gap to be closed (in mm), and then the time required to close them (in nanoseconds):-
30mm/ns, 5mm, 1/6ns
3mm/ns, 0.05mm, 1/60ns
0.3mm/ns, 0.0005mm, 1/600ns
0.03mm/ns, 0.000005mm, 1/6000ns
6.9mm/ns, 42.5667637mm, 6.109663242ns
0.74356mm/ns, 4.317734962mm, 5.806841361ns
0.074935mm/ns, 0.4328878101mm, 5.776844066ns
0.007499mm/ns, 0.04330002031mm, 5.774105922ns
So, you can see in the case of the first four (where the clocks are stationary in frame R), the times taken to close the gap tend towards zero, but in the other four cases (where the clocks are moving at 0.866c in frame R), they are tending to a different value somewhere around 5.77ns. What significance does this number have?
Light goes 1m in 3.3333333...ns, but the system is contracted to half its rest length, so we only need to cover half a metre. Light passes the rod more quickly in one direction than the other though. Why does this matter? Well, we want to compare our timings with the synchronisation of the clocks based on sending out a signal from the midpoint between them and how long the delay is between that signal reaching clock A and reaching clock B. That signal only has to cover a gap of quarter of a metre, though the clocks are moving at 0.866c, so it will take longer to close that gap in one direction than the other. Are you thinking what I'm thinking yet? Might that delay be somewhere in the region of our 5.77ns?
We need to work out how long the synchronisation signal takes to travel from half way between the clocks to clock B (which is moving away from the light or radio signal) and then subtract the time that it takes to travel from half way between the clocks to clock A (which is moving towards the light or radio signal) as this will let us put a figure on how much the clocks are out of sync due to their high speed of movement through space. It takes 6.220084679ns for light to travel from half way between the clocks to clock B [and we get that number by multiplying a quarter of 3.333333333... by 1/(1-sin(60))], and it takes 0.4465819874ns for it to travel from half way between the clocks to clock A [which we get by multiplying a quarter of 3.3333333333... by 1/(1+sin(60))], so the clocks are out of sync. by 5.773502692ns.
So, the reason the experiment sounded as if it should work was that the stationary system has a moving rod with length-contraction acting on it which tends towards zero contraction as the speed of the rod is reduced, leading to simultaneous starting of the two clocks, but when the system is moving, the length-contraction of the rod follows a different pattern (even though it doesn't appear that way to a co-moving observer). Look at the figures for the stationary system with the shortening going from 5mm to a hundredth of that, then a ten thousandth, then a millionth. Then look at the figures for the moving system where it starts at 42mm (already a much greater gap, and this despite the clock separation distance being halved), then going to a tenth of 43, then a hundredth, and then a thousandth - the gap is reducing at a much gentler rate which keeps pace with the change in speed of the rod such that any slower speed you use will simply have the gap reduce in proportion, thereby needing the same length of time for the movement of the rod to close it and start the second clock. To a frame M observer, the clocks at rest in frame M will appear to be started just as simultaneously as the clocks at rest in frame R appear to a frame R observer. This means that if you build your experiment, it is guaranteed to produce a null result.
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Hi Kris,
If we run the experiment with the clocks stationary and the rod moving, the clocks will count how long it takes for light to reach them from the other clock after the rod starts them running. If we view this from a different frame of reference, we must see the clocks count up the same number of ticks. All frames of reference are believed to act exactly as if they are the one that represents an absolute frame, so no matter how fast the experiment runs through space, the clocks should count up the same values every time you run the experiment and make it impossible to measure the speed of the apparatus through space. Everything happening in the experiment must conform to the normal rules, so it cannot possibly work. And yet somehow, it still sounds as if it should work. There's something really weird going on that needs to be understood. Why does the thought experiment's argument sound so convincing? That's what I'm trying to explore, and I'll keep working on it until I can explain it.
Hi David,
Using this experiment, we do not even need synchronized clocks. Instead we can reflect the light from A' and B' to the photo sensor somewhere in front and using digital oscilloscope measure the difference in arrival time of the two signals.
I think it can be done with 2 lasers, 2 mirrors and one 10ghz digital oscilloscope
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Hi Kris,
I know that we don't need synchronised clocks, but when you move the rod, it does length-contract a little and leads to a tiny delay in starting clock B after clock A has started running. If the whole system is moving (i.e. the clocks as well as the rod) then the length contraction on the rod will be greater relative to the length-contraction on whatever it is that maintains the separation distance between the clocks, and that means there's a greater delay before clock B is started - a delay which guarantees that the clocks will always produce the same numbers when you run your experiment regardless of how fast the system is moving through space. The faster the system moves, the greater the delay there will be before clock B is started, but if you're co-moving with the clocks, you will not detect any increase in that delay at all because you will have a very different view of which events are simultaneous, and that happens because of the way your clocks are synchronised in that frame and the delays in getting signals from one place to another. The calculations show that the experiment will produce a null result, and that doesn't make it an attractive experiment to put a lot of time and money into.
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Hi David,
1.The experiment could be done with lasers moving at half speed (-v/2) towards the rod which will move with the speed v/2.
Any length contraction of the rod should be the same as contraction of the lasers mounting.
2. the experiment can be run using different speeds of the rod and separation of the signals can be compared. If the separation of the signals indeed increases with the speed, the length contraction should be taken into account. If not, we can ignore it.
3. We do not (and we can't) measure the length of the rod in some absolute rest frame. If we are moving at 0.866c through the space, we can't really know it, so our measurement is valid in our inertial frame (for example, the if we measure 1m,in our inertial frame 0.66c, in some inertial frame at absolute rest it would be 2m) Any length contraction should be also calculated in regard to our inertial frame.
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Hi Kris,
1.The experiment could be done with lasers moving at half speed (-v/2) towards the rod which will move with the speed v/2.
Any length contraction of the rod should be the same as contraction of the lasers mounting.
I'm assuming these lasers are attached to the clocks and are used for sending light pulses from one clock to the other. We really have two rods, one with a clock at each end while the other is just a rod. Both rods are the same length as each other when they're stationary relative to each other. If by luck they are both stationary in space before we do the experiment, we can move one in one direction and the other in the opposite direction at the same speed, with the result that both will contract to the same extent. However, if they were both moving through space at high speed when they were stationary relative to each other, when we move them past each other to do the experiment, one of them will contract a bit more while the other will lengthen a bit (because they were both contracted already). We won't know which rod is extending and which is contracting, but whichever way round it is, we will get a null result. If the rod with the clocks is the one that contracts while the other rod extends (or uncontracts a bit), clock B will start running before clock A, but the light signal from clock B will take much longer to reach clock A and the light from clock A will get to clock B more quickly such that both clocks always stop with the same two times recorded on them.
You can test this for yourself by crunching the numbers in the way that I did in post #67. Pick speeds for the two rods and work out the length-contraction on them, first on the basis that the system is at rest, then on the basis that it's moving at high speed to the right, and then on the basis that it's moving at high speed to the left. Then work out how long light will take to reach one clock from the other. If you can't produce numbers that show that the experiment could produce anything other than a null result, I don't think anyone sane will want to put any time or money into building it, so you're going to have to do some maths to test your idea and look to see if you can find any circumstance in which a different result could somehow emerge from it. I looked at a stationary system and a system moving at 0.866c, but I didn't test -0.866c, so that might be a good place for you to start. When doing the calculations, make sure you don't type in approximate values when you reuse results of one part of a calculation in the next - store them in memory and use them again from there as you'll need to maintain their high precision. It helps if your calculator has multiple memories available on it.
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Hi David,
I was thinking about your analysis in #67.
I think your calculations are right but your reasoning is incorrect. If you were to measure length contraction of the moving rod in the inertial frame of the lasers, you have to do the calculation in relation to this frame. Regardless how fast the whole setup would be travelling through the space, you can only make your measurements from the point of view of your inertial frame. Even if you travelling at .999c you perceive the rod travelling at say 3m/s and length contraction will be d(sqrt(1-(3m/s)^2)/c^2) ; your calculations would be only valid if you were to make the measurement from within the rest frame if you believe you were moving at 0.86c (or the frame which is moving with the speed of 0.86c relative to you).This would require you to establish an absolute rest frame, which according to current knowledge, is impossible.
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Hi David,
I was thinking about your analysis in #67.
I think your calculations are right but your reasoning is incorrect. If you were to measure length contraction of the moving rod in the inertial frame of the lasers, you have to do the calculation in relation to this frame. Regardless how fast the whole setup would be travelling through the space, you can only make your measurements from the point of view of your inertial frame. Even if you travelling at .999c you perceive the rod travelling at say 3m/s and length contraction will be d(sqrt(1-(3m/s)^2)/c^2) ; your calculations would be only valid if you were to make the measurement from within the rest frame if you believe you were moving at 0.86c (or the frame which is moving with the speed of 0.86c relative to you).This would require you to establish an absolute rest frame, which according to current knowledge, is impossible.
A signal from the midpoint of A-B when aligned to the midpoint of A'-B', synchs each pair of clocks dirrently depending on speed. The only time the axis of simultaneiy for each align is when they have the same speed, i.e. at rest relative to the other, a trivial problem.
If you have ever tried to square a circle, you should see the futility.
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Hi David,
I was thinking about your analysis in #67.
I think your calculations are right but your reasoning is incorrect. If you were to measure length contraction of the moving rod in the inertial frame of the lasers, you have to do the calculation in relation to this frame.
Which means that if you assume the lasers and clocks are stationary, you will measure the rod to be length-contracted to such a small extent that the clocks would start practically simultaneously and will record the same time as each other by the time the light from the other clock reaches them, although clock A may record a tiny amount of extra time than clock B if the clocks are sufficiently accurate for the tiny amount of length-contraction acting on the rod to show up. However, if the clocks and lasers are actually moving at 0.866c, there will be a lot more length-contraction acting on the rod relative to the length-contraction acting on the clock separation and a big delay between the clock A starting to count up from zero and clock B starting to do the same. Crucially though, it won't look like that at all to an observer co-moving with the clocks because his measurements of the rod will not reveal to him the true length, and he will see both clocks start counting simultaneously, making it appear to him as if the system is stationary.
This would require you to establish an absolute rest frame, which according to current knowledge, is impossible.
You don't need to identify an absolute rest frame because all frames behave as if they are that absolute rest frame to anyone doing experiments based on that frame. If you happen to be moving at 0.866c and observe a system which is stationary in the absolute rest frame, it would look to you as if it was moving at 0.866c and you would measure the same length-contraction on system and amplified length-contraction on the rod as someone stationary in the absolute frame who measures the behaviour of an identical set of apparatus moving at 0.866c. That's what relativity does - it hides all the differences from us and does so in such a systematic way that all attempts to find an asymmetry have ended in failure. I've been caught out by it several times, on each occasion thinking I'd identified something that would enable an experiment to show up a difference in the behaviour of different frames in some way, but each time it evaporated away as I found I'd made incorrect assumptions about some key part of it. The maths of relativity is astonishing, and so far it has had an answer to every challenge anyone has thrown at it - it simply refuses to let us measure the one-way speed of light.
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Which means that if you assume the lasers and clocks are stationary, you will measure the rod to be length-contracted to such a small extent that the clocks would start practically simultaneously and will record the same time as each other by the time the light from the other clock reaches them, although clock A may record a tiny amount of extra time than clock B if the clocks are sufficiently accurate for the tiny amount of length-contraction acting on the rod to show up. However, if the clocks and lasers are actually moving at 0.866c, there will be a lot more length-contraction acting on the rod relative to the length-contraction acting on the clock separation and a big delay between the clock A starting to count up from zero and clock B starting to do the same. Crucially though, it won't look like that at all to an observer co-moving with the clocks because his measurements of the rod will not reveal to him the true length, and he will see both clocks start counting simultaneously, making it appear to him as if the system is stationary.
So how you can calculate any length contraction? Let's say 2 spaceships passing each other at relative speed of 0.1c. How would you know they are not moving at 0.99c in relation to some distant galaxy?
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So how you can calculate any length contraction? Let's say 2 spaceships passing each other at relative speed of 0.1c. How would you know they are not moving at 0.99c in relation to some distant galaxy?
You need to calculate the length contraction for them more than once using a range of different frames as the absolute frame for the base of the calculations, but it will only take a few different frames to show you that no frame can possibly give you a different end result when observers co-moving with the rockets make their measurements.
If your spaceships are passing each other at 0.1c and both are moving at the same speed relative to an absolute frame, you would use the speed 0.05c for both ships (perhaps calling one -0.05c) and calculate that they are both contracted to 0.9987492178 of their rest length.
When you take into account the fact that the chosen frame almost certainly isn't the absolute frame and decide to see what happens if that frame is actually moving at 0.99c through the real absolute frame (which will again be a guess as to which frame is the absolute frame), you then need to work out the speeds for the rockets by adding 0.05c to 0.99c (for the rocket moving faster through space) and then dividing the result by 1 + 0.05 x 0.99, so that rocket's actual speed through the new "absolute" frame will be 0.9909480705 (giving it a length of 0.134257506 times its rest length), while the other rocket's speed is found by subtracting 0.05 from 0.99 before dividing by 1 - 0.05 x 0.99, so that rocket's actual speed would be 0.9889531825 (giving it a length of 0.1482282117 times its rest length).
The rest length of anything moving at 0.99c is 0.1410673598 its rest length, so we can now look at the percentage changes in lengths, but to make it easier to describe this, I'll introduce a rod which has the same rest length as the two rockets, and the two rockets are passing it in opposite directions at what the rod measures as the same speed. In the original case where the system was stationary, the length contraction on both ships was to about 99.87% of the length of the rod. In the later case where the rod is moving at 0.99c and the rockets are passing it in opposite directions at what the rod again measures as the same speed, the rockets moving faster than the rod through space is contracted to about 95.17% of the length of the rod (which is itself severely contracted), while the rocket moving slower through space is contracted to about 105.1% of the length of the more-severely contracted rod. Those percentages are a lot further away from 100% than the 99.87% in the original case, but an observer co-moving with the rod wouldn't be able to measure that severity of extra contraction - he would measure both rockets as being 99.87% of the rod's length.
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Hi David,
Try to analyze the scenario at 0.86c when the rod is moving from opposite direction: according to your reasoning it will be expanded not contracted, by the same amount (very nearly)as contraction in the other direction. This would give you opportunity to measure your absolute frame as well as the contraction/expansion (which so far never been directly measured)
But to be absolutely sure there is no tricks relativity is playing on you, you could devise an experiment with 2 rod moving in opposite directions. The difficulty would be to adjust the speeds and timings of the rods passing the lasers so the lasers would get through the slits on both rods simultaneously.(the light would either pass through both pair of slits or neither). It could be challenging but not impossible.
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Hi Kris,
In the case with the system moving at 0.866c, if the rod's moving a little faster than that and the clocks are moving a little slower, the rod will be shorter than the separation gap between the clocks, leading to clock A being started before clock B, whereas if the rod's moving a little slower than that and the clocks are moving a little faster, the rod will be longer than the separation gap between the clocks, leading to clock B being started before clock A. That delay will in both cases give a head start to whichever light signal has to move further through space to reach the other clock, and it will always be a big enough delay to ensure that the two clocks stop with the same times on them as if the system was stationary. You can check that by working out what the delay is and how long it will take the signals to go from each clock to the other - that's what I did at the end of post #67, so you need to learn how to do the same thing for any set of speeds that you want to work with for the parts of the apparatus. If you need help understanding how to apply the maths, I'll be happy to spell it out in more detail so that you can make sense of it, but you will have to crunch your own numbers from now on.
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In the case with the system moving at 0.866c, if the rod's moving a little faster than that and the clocks are moving a little slower, the rod will be shorter than the separation gap between the clocks, leading to clock A being started before clock B, whereas if the rod's moving a little slower than that and the clocks are moving a little faster, the rod will be longer than the separation gap between the clocks, leading to clock B being started before clock A. That delay will in both cases give a head start to whichever light signal has to move further through space to reach the other clock, and it will always be a big enough delay to ensure that the two clocks stop with the same times on them as if the system was stationary. You can check that by working out what the delay is and how long it will take the signals to go from each clock to the other - that's what I did at the end of post #67, so you need to learn how to do the same thing for any set of speeds that you want to work with for the parts of the apparatus. If you need help understanding how to apply the maths, I'll be happy to spell it out in more detail so that you can make sense of it, but you will have to crunch your own numbers from now on.
Hi David,
The math is quite simple; the problem is that you are using bits and pieces from one theory and another bits from the reality which the same theory is explicitly excluding. The length contraction was a postulate in SR (never confirmed experimentally; some people still argue that it is not physical phenomenon) which is applicable to a moving body relative to another body which is "at rest". It is not possible to determine which body is in motion and which one is at rest. And there is no possibility of discovering if the whole system is in motion, so the only possibility to determine length contraction is to make arbitrary one frame at rest relative to another which is constant motion.
Your idea that both the rod and the lasers may travel at some constant speed (0.86c) should not be detectable by any theoretical or practical means. However the fact the rod traveling in one direction is shortened and lengthened in opposite direction can be detected by measuring by one clock the time it takes for both edges of the rod to pass the laser .
Let's say the rod is traveling in the direction of the system (which is moving with 0.86c). First front edge is passing A, then trailing edge. Because the rod is lengthened, it should take a bit more time in comparison to the rod of original length. Now we transport the rod in opposite direction. The rod is shortened, so the time it takes for both ends to pass point A will be a bit shorter. Carefully measuring the time difference (while monitoring rigorously the speed of the rod) we could calculate the absolute speed of the system. This is definitely invalidated by the theory which introduced length contraction in first place.
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Hi Kris,
The math is quite simple; the problem is that you are using bits and pieces from one theory and another bits from the reality which the same theory is explicitly excluding. The length contraction was a postulate in SR (never confirmed experimentally; some people still argue that it is not physical phenomenon) which is applicable to a moving body relative to another body which is "at rest". It is not possible to determine which body is in motion and which one is at rest.
The idea of length contraction came about as a result of the Michelson Morley experiment and was needed in order to account for the unexpected null result. All theories have to account for the result of that experiment. I have never seen any viable explanation of it other than physical length contraction, and although SR allows it to be a kind of illusion (because the object is not physically changed, but merely presented with a different orientation within a 4D geometry), it is no illusion within a 3D frame of reference where it is measured as contracted - you must be allowed to fit more objects into a given amount of space when they're contracted. The physical need for length contraction is also understood - we can measure the amount of relativistic mass added to particles in particle accelerators and see how at higher speeds the energy put in progressively adds more to the relativistic mass and less to the speed of the particle, thereby ensuring that it can never reach the speed of light. When you take relativistic mass into account, you'll find that orbits must length-contract as the system (e.g. planets going round a star) moves faster through space. The same length contraction must also occur within small objects - if a rod rotates about its centre such that one end is periodically moving faster through space than the other, the end that moves faster through space will lag behind where you might expect it to be, leading to the rod bending, but that bend will be undetectable to anyone co-moving with the rod - they will continue to measure it as straight at all times. This lagging of the forward movement automatically requires length-contraction as the material bunches up, but there is no compression force on it because the communication distances for forces between the particles of the rod are lengthened by the higher speed of movement. If you want to deny length-contraction, read through this thread https://www.thenakedscientists.com/forum/index.php?topic=70299.0 and join the conversation there - I will be happy to show you that without length-contraction you would need to have light move at superluminal speed to account for the null result of MMX - some photons would need to move faster than others which are going in the same direction, and some of them would even run into direct contradiction by requiring the same photon to overtake itself.
And there is no possibility of discovering if the whole system is in motion, so the only possibility to determine length contraction is to make arbitrary one frame at rest relative to another which is constant motion.
Why do you think you need to be able to discover whether the whole system's in motion? Obviously it would be nice to know that, but it is not necessary to find out in order to determine that a system will appear to behave the same way to any observers co-moving with it regardless of what speed it is moving at through space (and to determine that no observer moving at any other speed will be able to tell either).
Your idea that both the rod and the lasers may travel at some constant speed (0.86c) should not be detectable by any theoretical or practical means. However the fact the rod traveling in one direction is shortened and lengthened in opposite direction can be detected by measuring by one clock the time it takes for both edges of the rod to pass the laser .
The fact that the rod might be uncontracted or contracted, or that it might be contracted more when moving in one direction and contracted less when moving in the other direction, does not lead to it being possible to measure these contractions unless you can already identify an absolute frame of reference to use as the base for your measurements. You don't have that to use as a base though, so you can only make conditional measurements, and the conditional measurements that you make will be the same no matter what speed the system is actually moving at through space.
Let's say the rod is traveling in the direction of the system (which is moving with 0.86c). First front edge is passing A, then trailing edge. Because the rod is lengthened, it should take a bit more time in comparison to the rod of original length. Now we transport the rod in opposite direction. The rod is shortened, so the time it takes for both ends to pass point A will be a bit shorter. Carefully measuring the time difference (while monitoring rigorously the speed of the rod) we could calculate the absolute speed of the system.
If the rod has less contraction on it than the clocks, the leading end will start clock B before the trailing end starts clock A. If the rod has more contraction on it than the clocks, the trailing end will start clock A before the leading end starts clock B. In both cases, the trailing clock is started first, giving it extra time to tick up a high score before light from the other clock can reach it. The clocks will count up the same number of ticks as if the system was stationary and you will generate a null result from the experiment just like the MMX.
This is definitely invalidated by the theory which introduced length contraction in first place.
Your only hope of your experiment not producing a null result is if the MMX doesn't produce a null result.
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If the rod has less contraction on it than the clocks, the leading end will start clock B before the trailing end starts clock A. If the rod has more contraction on it than the clocks, the trailing end will start clock A before the leading end starts clock B. In both cases, the trailing clock is started first, giving it extra time to tick up a high score before light from the other clock can reach it. The clocks will count up the same number of ticks as if the system was stationary and you will generate a null result from the experiment just like the MMX.
That is not what I have said. Please read again. Or look at this example:
Let's have a pipe 1m diameter at 45 degrees to your 0.68c moving frame. The ball of 1m diameter is just moving through it . Any increase in physical dimension of the ball would stop the movement of the ball. If the ball is moving at 10(sqrt2)m/s, there will be 10m/s speed component parallel (or antiparallel) to your 0.68c frame. Following your reasoning the movement of the ball will be possible in only one direction through the pipe (with the component 10m/s antiparallel to the speed of your 0.68c frame)
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That is not what I have said. Please read again.
Let's say the rod is traveling in the direction of the system (which is moving with 0.86c). First front edge is passing A, then trailing edge. Because the rod is lengthened, it should take a bit more time in comparison to the rod of original length. Now we transport the rod in opposite direction. The rod is shortened, so the time it takes for both ends to pass point A will be a bit shorter. Carefully measuring the time difference (while monitoring rigorously the speed of the rod) we could calculate the absolute speed of the system. This is definitely invalidated by the theory which introduced length contraction in first place.
Sorry - I thought you'd got muddled when you referred to the two ends of the rod passing clock A, so I didn't realise you were exploring a new aspect of this. Remember that with the three rod system moving at 0.99c, the true speeds of travel of a moving rod in opposite directions relative to the middle rod (which is moving at 0.99c) were not 0.05c each way relative to the clocks, but 0.0009480705 and 0.001046817, so when the rod is less contracted (by moving less quickly through space) it is moving faster relative to the middle rod, while when more contracted (by faster movement through space) it is moving more slowly relative to the middle rod, and that means the timings that you measure for it passing one point on the middle rod will be identical to a local clock on the middle rod.
Or look at this example:
Let's have a pipe 1m diameter at 45 degrees to your 0.68c moving frame. The ball of 1m diameter is just moving through it . Any increase in physical dimension of the ball would stop the movement of the ball. If the ball is moving at 10(sqrt2)m/s, there will be 10m/s speed component parallel (or antiparallel) to your 0.68c frame. Following your reasoning the movement of the ball will be possible in only one direction through the pipe (with the component 10m/s antiparallel to the speed of your 0.68c frame)
I'm not sure I can make full sense of your description (does antiparallel mean perpendicular?), but what I can do is show you a program (which runs using JavaScript on a webpage) that should help you understand this kind of scenario, and you can then program in your own objects if you want to test your own numbers. Use a proper computer rather than a tablet or phone because it works best if you control it using a keyboard. Open http://www.magicschoolbook.com/science/ref-frame-camera.htm in another tab, then program in the following series of objects (copy these numbers onto a piece of paper first to make this easier, and be careful not to make any mistakes as you can't correct them afterwards - take your time and tick them on the piece of paper as you go so that you don't lose your place, and don't click the "reset" button unless you want to delete the objects to start again):-
0, 0, 180, 220, 220, 180, -180, -220, -220, -180, 0, 0, 0
0, 0, 80, 120, 120, 80, -80, -120, -120, -80, 0, 0, 0
That gives you eight white dots to indicate the pipe at 45 degrees. Now you need to add three square "balls" (you can imagine each square to contain a ball, and the way the square distorts should enable you to visualise how the ball distorts, or alternatively you can simply regard them as cubes of ice sliding through a square-section tube). You would be wise to highlight and copy the value 0.6123724357 first so that you can paste it into the dialogue box the four times when you need it (but be aware that the second two times you also need to make it negative):-
0, 0, 40, 0, 0, 40, -40. 0, 0, -40, 0, 0, 1
0, 0, 30, -10, 10, -30, -30, 10, -10, 30, 0.6123724357, 0.6123724357, 2
0, 0, 30, -10, 10, -30, -30, 10, -10, 30, -0.6123724357, -0.6123724357, 4
You now have three squares, one stationary and two moving at 0.866c in opposite directions (which is the speed that the vectors -0.6124... combine to give you). The moving squares are shown contracted to half their rest length. When you click the "start/stop" button on the screen (or press the "S" key on the keyboard), you'll see the two length-contracted squares move in opposite directions along the pipe. (You can click the "direction" button or press the "D" key to run them backwards if you want to get them back into the pipe once they've left it.)
What you should do next though is change the frame of reference you're viewing them from, and some frames are already tied to the number keys for you, so if you press "3", for example, you'll get to a frame that's moving at 0.866c on the Y axis direction, although the display remains centred on the pipe at all times to stop it moving down and off the bottom of the screen. If you click on "Set Frame velocity" you can choose a frame of reference of your own by typing in the required vectors for its speed, so using 0.6123724357 for both vectors will show you the green "ball" as it would appear to someone co-moving with it, thereby removing all the contraction from it, while anything that isn't co-moving with that "ball" will show the amount of length-contraction that it should be seen to have from that frame.
The pipe isn't moving, of course, but with relativity, when you observe it from a different frame it will look and behave exactly as if it is moving. To check that this is the case, you can move the "balls" back to where they started, select a frame such as X = 0, Y = -0.866 and then note down the numbers displayed below the action (just above the main text on the page) for each of the five objects (the first two of which are the pipe). You can use these values to type in the objects from scratch such that the pipe will move at 0.866c upwards through the absolute frame. When you then switch to displaying the frame X = 0, Y = 0.866 you'll see it look identical to what you originally programmed in with the system stationary in the absolute frame, showing you the symmetry of the behaviour of different frames, all of them looking just like that absolute frame if you make the system stationary in it and then switch away from that frame to see how it warps, and all the warping will look just the same as it did before. There are never any differences that could enable any observer co-moving with any object to measure different values for the system moving at different speeds through space. Importantly, this program was written specifically for Lorentz Ether Theory using an absolute frame - all the maths that runs it is designed to make all the moves within that absolute frame before converting to how things would appear from other frames of reference, and it's using radically different maths from any program of this kind that someone in the SR camp might write, but what it displays on the screen at the end of the process is identical.