Can anyone see the problem with the below? Multiple Light Emission Points under SR Assume two rods of rest length d. Also, assume the two rods are in relative motion v. One rod names its endpoints O and R and the other names its endpoints O’ and R’. O’ has a light source. When O and O’ are co-located, O’ emits light up the positive x-axis toward R and R’. When O is viewed as stationary and R is met with the light, t = d/c from the light emission time. Therefore, O' will be located along the position x-axis a distance of vt = vd/c from O when R is struck. Likewise, When O' is viewed as stationary and R' is met with the light, t = d/c from the light emission time. Also, O will be located along the negative x-axis a distance of vt = vd/c from O' when R' is struck. Hence, both frames agree O and O' are separated by a distance of vd/c when each of the targets R and R' are hit by the light and there is only one such point for each where both can agree they are separated by vd/c. Einstein’s proclaimed the clock synchronization method is “free from contradictions”. www fourmilab.ch/etexts/einstein/specrel/www/ This clock synchronization method makes the following assertions. 1. The light path is precisely the path from the stationary light emitter to the stationary mirror. 2. The light path is precisely the path from the mirror back to the light emitter. 3. Light takes the same amount of time to travel each way. In order for the clock synchronization method to be “free from contradictions”, all three of the conditions above must be free from contradictions. Hence, in particular it must be a logical truth that the light path is precisely measured from the light emission point in the frame to the light receiver. Therefore, is must be a logical truth that the light emission point in the frame must be the absolute origination point for the light ray. If it is not the correct absolute light origination point, then it cannot be the case that condition 1 is a logical truth free from contradictions because the correct light path is not known. If condition one is not free from contradictions, then the clock synchronization method is not free from contradictions. Since the clock sync method lays the foundations for the Lorentzian transformation, then LT is not free from contradictions. In the above thought experiment, taking O as stationary, when O and O’ are separated by a distance vd/c, O claims the light path for the one light source is precisely the path from O to R. On the other hand, taking O’ as stationary, when O and O’ are separated by a distance vd/c, O ‘claims the light path for the one light source is precisely the path from O’ to R’. Each are supported by condition a above that their claims for the precise origination point of light is free from contradictions or that it is a logical truth. However, each claim a different origination point in space for the light beam when they are separated by a distance vd/c. Hence, both cannot express a logical truth for the actual light path. However, if either is wrong, then clock synchronization cannot be free from contradictions.
Is it a logical truth that, given a known length of fiber-optic cable, a light pulse will have a precisely measured distance to travel along the fiber? If no other sources of radiation are present in the fiber, is it a logical truth that sending a pulse of light from one end (a point of emission) will mean it is free from interference, so if a mirror is located at the receiving end, it should travel both ways in the same amount of time? This point is rather a fine one--for instance modern navigation would be a lot more difficult, and we would not have a GPS system broadcasting a global timebase. So the objections you have raised, are countered by fiber-optics and modern navigation systems, avionics, satellite positioning, actually quite a lot of things.
Yea, first you did not address the theoretical aspects of the argument. Next, you address fiber optic cables as some form of logic. At one mile, given the speed of the earth any cable would need to operate in the 10-12 second range. Do you have said experiments with one way light transfer with clock timing? Finally, you cite GPS as a resolution. GPS uses triangulation. I assume you can prove how this refutes the above. Show me.
Fiber-optics is a form of logic, absolutely. The logical form here, is communication at precise intervals of time, using precise wavelengths of light. Do you have any experience of interferometry? Do you know about the Michelson-Morley experiment?
Sure, do you understand that frequency based experiments cannot decide the speed of light? They are consistent with the ballistic theory of light. One such attempt is known as the Emission Hypothesis (or the ballistic theory of light), and was developed partly by Walther Ritz (C&N p.353). According to this theory, light behaves like bullets shot from a gun, its speed with respect to the source being a universal constant and independent of any ether. This idea is consistent with the null results of the Michelson-Morley experiment and many others.laser.phys.ualberta.ca /~egerton/specrel3.htm Walter Ritz's emitter theory (or ballistic theory), was also consistent with the results of the experiment en wikibooks.org/wiki/Modern_Physics:Michelson-Morley_Experiment This rules out any conceptually coherent ballistic theory of light propagation, according to which the speed of light is the vector sum of the velocity of the source plus a vector of magnitude c. Ironically, the original Michelson-Morley experiment was consistent with the ballistic theory, but inconsistent with the naïve ether theory, whereas the Sagnac effect is consistent with the naïve ether theory but inconsistent with the ballistic theory. Of course, both results are consistent with fully relativistic theories of Lorentz and Einstein, since according to both theories light is propagated at a speed independent of the state of motion of the source.www mathpages.com/rr/s2-07/2-07.htm Now what? Note here. The Kennedy-Thorndike Experiment R.J. Kennedy and E.M. Thorndike, “Experimental Establishment of the Relativity of Time”, Phys. Rev. 42 400–418 (1932). This uses an interferometer similar to Michelson's, except that its arms are of different length, and are not at right angles to each other. They used a spectacular technique to keep the apparatus temperature constant to 0.001°C, which gave them sufficient stability to permit observations during several seasons. They also used photographs of their fringes (rather than observing them in real time as in most other interferometer experiments). Their apparatus was fixed to the Earth and could only rotate with it. Their null result is consistent with SR. This experiment uses different armature lengths. Speed calculations require the same lengths. Therefore, in a simple way based on the above, frequency does not decide a constant speed of light.
Ok, but light isn't just frequency. Perhaps you will need to explain optics and refraction all over again (/giggle)? Remember, in the end there is only logic, all else is folly, my son.
Yes. You made many mistakes. For a start, 1. You ignored that length is different in different frames of reference. 2. You ignored that time is different in different frames of reference. 3. You mixed frames. 4. You ignored that simultaneity is relative.
I think I know what you're getting at Jack, I've had a thread like this before. Imagine that this fiber optics cable is enormous and that you can hitch a ride on it through space. It is extended and has a mirror on its end, so it is a lot like one of your rods. Putting much of the discussion aside- this is what you will have going on inside the cable. If you are riding the cable (assuming that the cable is moving at a relativistic speed), light will travel back and forth through the cable in the same amount of time. But if you are observing this cable from a stationary frame, light will take less time to travel in one direction than another. To someone in a stationary frame light may take only 1/10 of a second to travel in one direction through the cable and then 10 seconds to travel back. However, to the person travelling alongside the cable it will still take the same amount of time going in both directions. It doesn't make any sense to me either.. Its as if time was dilated differently between two different intervals - this is at least what it seems like intuitively. DH is right, simultaneity is relative (it depends on your reference frame).
Perhaps if we just stay with the communications logical framework, since it does really demonstrate that light travels according to special relativity. There are three ways to modulate light in a fiber optic cable. The Sagnac effect is a beam of continuous light interfering with itself. In fiber optics there is TDM, WDM and FDM available in modern networks. Since there are three ways to modulate the signal, light must use the remaining "signal energy" to carry itself. That's all four of the available spacetime degrees of freedom we know about. Then of course, there are entangled photons. Here communication isn't in the frame as such.
I did not ignore anything. I connected frames using distance. Now, let's take O as stationary. The following are indisputable conculsions under SR. 1) Light will strike the stationary target R at t = d/c 2) When light strikes R, O' has moved down the positive x-axis of O a distance vd/c. Now, let's take O' as stationary. The following are indisputable conculsions under SR. 1) Light will strike the stationary target R' at t' = d/c 2) When light strikes R', O has moved down the negative x-axis of O' a distance vd/c. Note how I am not crossing into the other frame and carefully avoiding length contraction. Now, I establish a logical connection by using the distance between the observers O and O'. So, both frames agree when they are separated by a distance of d/c, using their own frame's metrics, they each conclude individually their stationary targets are hit. Then, a simple logical conjunction is used. This is legitimate since each is in control of its own metrics. So, when O looks right and see O' at a distance , R is hit and in agreement, O' is concurrently seeing that same distance between the two by looking left and conclude O' is hit. Hence, there are two different light paths. Now certainly, normal LT usage would have O claim R' is hit at t_R' = d/(λ (c-v)) and O' would conclude R is hit when t_R = d/(λ (c+v)) But, a theory needs to be consistent from every possible angle.
DH is right, simultaneity is relative (it depends on your reference frame Agreed, but that is not what I am doing. I connect the two frames together using a measured constant speed of light between the emission point in the frame and more important on an agreement of the distance O and O' are from each other when their stationary targets are hit.
OK, but I am not contesting a constant speed of light. Tests from moving light sources are sufficient to prove light moves through the vacuum of space at only one speed, c. I am questioning and showing a problem with the SR light speed measurement technique. It is claimed the light path is precisely from the light emission point in the frame to the light receiver. I am showing that is inconsistent.
You are ignoring that the length of rod O'R' from the rest frame of rod OR is not d. You are ignoring that spacetime is not Newtonian in special relativity. Learn to apply the Lorentz transformations.
Look up above. I did apply LT. I know how to apply it. However, these measurements are made with the stationary system of coordinates. Einstein: Let us take a system of co-ordinates in which the equations of Newtonian mechanics hold good.2 In order to render our presentation more precise and to distinguish this system of co-ordinates verbally from others which will be introduced hereafter, we call it the ``stationary system.'' www .fourmilab.ch/etexts/einstein/specrel/www/ So, I measure the location of the observer of the moving frame in the metrics of the stationary system. I do this both ways. Einstein: Now to the origin of one of the two systems (k) let a constant velocity v be imparted in the direction of the increasing x of the other stationary system (K), and let this velocity be communicated to the axes of the co-ordinates, www .fourmilab.ch/etexts/einstein/specrel/www/ Everything I did is legal.
No it's not. In the O frame, the distances O->O' and O->R are measured at the same time by the observer at O. In the O' frame, these measurements occur at different times. You assumed simultaneity is the same for both frames, in violation of the Lorentz transformations.
Nope. If is true, LT is one way to view this problem. But, LT should be able to handle scrutiny Each frame interprets reality and measurements separate in its own frame. Then, they are brought together under one light beam and also the distance from each other. It is quite simple. The metrics of a frame, when viewed stationary, must be consistent since t =d/c is universal. Now, that means if you are in relative motion to me and you believe in your own metrics you are 100 meters from me, I must believe I am 100 meters to you in my metrics. I am circumventing SR. If this relationsip does not hold, then t = d/c is not universal within each frame. Since this is not about clocks, but about consistent distances, the lack of simultaneity argument does not apply. Besides, I have a simpler approach I will post.
No, you aren't getting it. Your distance to another observer is NOT a matter of belief, but measurement. Measurement tells you things about distant frames in two ways, time and space. That's all there is, if you think about it. So the distance from you to another observer is a question of space and time. You can imagine a rigidly fixed distance exists between you, but you have to test this if you assume it has to be true at some point (of imaginary time). The only way to test it is to send and receive signals to and from the remote observer, and the only reliable method. all other methods considered, is with light at the speed of light. Then any errors in measurement will be small, and you can assume that communication is reliable, and synchronous. There really isn't anything more to it, because there really isn't anything more than space and time, as Einstein carefully points out, several times.
No, you aren't getting it. Your distance to another observer is NOT a matter of belief, but measurement. I am getting it. The distance between the two observers is not a matter of believe, I guess. I said it is vd/c in the measurements between the two emission points using the stationary system of coordinates. I am sure you will recognize this kind of logic. Instead of using d, use x. Frame to frame conversion of time. Distance light traveled is ct. Now, expand by λ to go from unprimed to primed to compensate for length contraction. ct' = ctλ. What is the distance between the two light emission points as I said when light travels a distance x? The distance between the origins of the frames is vx/c. Now, switch to the emission point of the primed frame to the unprimed frame and confess SR is a theory of multiple light emission points. Expand this distance between the two emission points for length contraction removal. (vx/c)λ Switch to the primed emission point and call that one valid and adjust the distance of the light traveled from this switch. ct' = ctλ - (vx/c)λ Derive primed frame time by dividing by the across the frame universal constant c, t' = tλ - (vx/c²)λ t' = ( t - vx/c² )λ Now, for the other way, assume the same rest distance x, so x' = x t = ( t' + vx/c² )λ As we can see, the distance between the two emission points within the stationary frame's coordinates is used routinly and compatible logic under LT. Hence, my logic holds since I use the coordinates of the stationary frame for this measurement of vx/c just like LT. Since LT goes both ways for the same rest distance, then LT concludes if O is vx/c from O' then O' is vx/c for the same rest x from O in the measurements of the stationary coordinates.
You continue to make the false assumption that simultaneous measurements in one frame correspond to simultaneous measurements in all other frames. Observer O sees a light beam reach point R at time t, and records the arrival of O' at -vd/c also at time t. According to frame O', these events and associated measurements occur at different times. Your analysis simply doesn't work, because if you want to find a contradiction in Relativity then you have to play by the rules.
