# How to have light move faster than C **URL:** \ **Category:** The BBQ Pit\ **Created:** [February 24, 2014, 9:53pm UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160 "2014-02-24T21:53:29Z")\ **Posts on this page:** 20\ **Page:** 18
**Author:** ![mythoughts](https://avatars.discourse-cdn.com/v4/letter/m/7993a0/32.png) [@mythoughts](https://boards.straightdope.com/u/mythoughts)\ **Post date:** [March 3, 2014, 12:31am UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/342 "2014-03-03T00:31:54Z")
To quote Wikipedia: The relativistic explanation is very similar to the classical one however, and in both theories aberration may be understood as a case of velocity addition. So the differences are minor and without considering an entrained aether which gives results very close to SR, closer than the ‘classical one’ they probably considered. Then I suspect an entrained aether and possibly length contraction that could be involved potentially could explain the noticed aberration. But doing that degree of detailed analysis of a substance with a wide range of potential qualities would be beyond probably any human, and the only way would be to throw all the data into a computer and work out what the properties would need to be to fit all the data, assuming any possibility exists within the parameters of variation the computer could work with. And now it would be fit to the data so there would be little value in the result (it would be curve fit, a subject I am familiar with) until new data was found and it fit that too. ---
**Author:** ![mythoughts](https://avatars.discourse-cdn.com/v4/letter/m/7993a0/32.png) [@mythoughts](https://boards.straightdope.com/u/mythoughts)\ **Post date:** [March 3, 2014, 12:59am UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/343 "2014-03-03T00:59:38Z")
Furthermore regarding Stellar aberration, I found this: _It was already known in the 19th century, that partial aether dragging requires the relative velocity of aether and matter to be different for light of different colours – which is evidently not the case._ At first I was unclear what this was refereeing to then realized it probably refers to some degree of refraction? But if so, can we think of something that bends light regardless of frequency? Gravity! So to me it is easier to consider that maybe there is a perfectly reasonable alternative than throwing the baby out with the bathwater. And simpler than to accept all the paradoxes that I have mentioned (minus 1). ---
**Author:** ![Kimble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kimble/32/19185_2.png) [@Kimble](https://boards.straightdope.com/u/Kimble)\ **Post date:** [March 3, 2014, 3:36am UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/344 "2014-03-03T03:36:24Z")
> [@mythoughts](#): > > My reply is that firstly Einstein did not say that there IS no preferred reference frame, rather he presented a theory where IF there was one it could not be established where it was due to the distortions of length and clock speed which are proposed as distortions of space and time. Fair enough. > [@](#): > > My argument is that it should still be able to explain the constance of the speed of light if we assume that space is not ACTUALLY distorting, and the speed of light is not “REALLY” constant but merely measured that way because of distortions of matter. > > While both present the same essential results, we can more easily analyse the concept that matter is changing not reality, what I am supposing here that the mind bending nature of trying to imagine space and time distorted is that it makes us accept things because we fail to fully render such a paradoxical view. Disagree – that’s an argument from incredulity. Plenty of people can imagine spacetime distorted. Several of them have posted here. > [@](#): > > So if we shoot a photon from the rare of our spaceship and then immediately **accelerate** to the speed of light so that it will impact the the front of our spaceship at a further location, you could reason that the speed of light would appear slowed, less than C, but if we assume our clock is slow and our ship contracts in length, then this would make light speed seem to regain velocity as we see it. > > That makes sense. > > So if we now do the opposite, shoot a photon from the front of the ship to the rear, and then **accelerate** so that the rear of the ship is now closer to the photon we should see the speed of the photon increased, and if we have the length of the ship contract it now has less distance to go and we measure less time, thus the speed of light should be very much faster than C. (bolding mine) That example has to take GR into consideration. That’s beyond my pay grade. Short answer: Going back, the speed of light is still c. Instead of breaking c, the light is gravitationally redshifted. > [@](#): > > Now I am aware that there are implications of accelerating a ship with respect to non-simultaneity, but I am trying to force the conclusion that unless something is done, if a photon is in one agreed location at any instant in all frames, then something must surely be used to explain how it can be C in this case as it is in the light clock time dilation thought experiments, it seems odd to have an explanation sometimes and to take it on faith in one instance of moving head on into light. You get non-simultaneity without acceleration. For example, in the original version of the Moe and Stacy experiment we just discussed: > [@naita](#): > > …if we synchronise the clocks for Moe, so that he always sees the pulses hitting the left and farthest mirror simultaneously, then they also hit the right and nearest mirror simultaneously. (Assuming he’s the same distance from all the mirrors.) > > If we synchronise the clocks for Stacey in the same manner, the pulses will always hit the nearest mirror “early”. Note that we can’t do this for both observers at the same time as they won’t agree on what “simultaneous” entails. > [@mythoughts](#): > > Let’s not just say the speed of light is C “because it is”. We have theoretical (c = (ε[sub]0[/sub]µ[sub]0[/sub])[sup]-1/2[/sup]) and experimental evidence that it is. Barring a statement of intent from a relevant deity, I don’t see what further evidence is necessary. > [@mythoughts](#): > > To quote Wikipedia: The relativistic explanation [of stellar aberration – Kimble] is very similar to the classical one however, and in both theories aberration may be understood as a case of velocity addition. > > So the differences are minor and without considering an entrained aether which gives results very close to SR, closer than the ‘classical one’ they probably considered. > > Then I suspect an entrained aether and possibly length contraction that could be involved potentially could explain the noticed aberration. I’ll believe it when I see it. Do you understand how entrained aether and length contraction interact? Do you have any kind of idea how this aether would work, other than “very well”? If not, is there any point in trying to disprove it? Or any _way_ to do so? > [@](#): > > But doing that degree of detailed analysis of a substance with a wide range of potential qualities would be beyond probably any human, and the only way would be to throw all the data into a computer and work out what the properties would need to be to fit all the data, assuming any possibility exists within the parameters of variation the computer could work with. > > And now it would be fit to the data so there would be little value in the result (it would be curve fit, a subject I am familiar with) until new data was found and it fit that too. Here are some numbers that work: Aether drag = 0; aether wind = 0; length contraction = gamma. How would any of your paradoxes support differences in those values? ---
**Author:** ![simster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/simster/32/1047_2.png) [@simster](https://boards.straightdope.com/u/simster)\ **Post date:** [March 3, 2014, 3:58am UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/345 "2014-03-03T03:58:15Z")
> [@Kimble](#): > > [QUOTE=mythoughts] > Let’s not just say the speed of light is C “because it is”. We have theoretical (c = (ε[sub]0[/sub]µ[sub]0[/sub])[sup]-1/2[/sup]) and experimental evidence that it is.\*\* Barring a statement of intent from a relevant deity, I don’t see what further evidence is necessary.\*\* [/QUOTE] (bolding mine) - almost sprayed the monitor on that one. I’m going to remember this quote - thanks. ---
**Author:** ![mythoughts](https://avatars.discourse-cdn.com/v4/letter/m/7993a0/32.png) [@mythoughts](https://boards.straightdope.com/u/mythoughts)\ **Post date:** [March 3, 2014, 5:57am UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/346 "2014-03-03T05:57:17Z")
While replying, an experiment came to me… Take a fibre optic loop, at zero degrees have a light source that sends a blue photon one way and a red photon the other way till they meet in the middle at 180 degrees. Now we can put a detector that will trigger only if both photons pass in precisely that location, they must both be there at the same instant, and we test it, it works. Now we will rotate it at high speed with the light source being triggered by something in the stationary frame, actually it could be the light is provided by the stationary frame and is let in as a window in the disk intercepts the light and funnels it into the fibre optic. Now these 2 frames have 2 different expectations of where the light will meet (pass), both agree it’s 180 degrees away, but that differs for both, if the lab frame can detect where both it expects to find it and where the disk does, then it must disagree with the disk! Now yes you CAN just say non-simultaneity is OK, but it means that the exact instant the disk measures it, the lab wouldn’t see that photon in that space, or either photon at that moment. the lab and disk detectors are in almost the exact same location of space (arbitrarily close) and are looking at the exact same moment and they completely disagree with what is there. Special Relativity really only works if photons are allowed to be in different locations at once depending on the frame, but if this were so you could meet the same photon twice (without it reflection, just change your frame). ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [March 3, 2014, 6:12am UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/347 "2014-03-03T06:12:30Z")
> [@mythoughts](#): > > . . . Now these 2 frames have 2 different expectations of where the light will meet (pass), both agree it’s 180 degrees away . . . I’m not totally sure, but I think that’s not true. We, in the non-rotating frame, expect to see the two photons arrive at 180 at slightly different times. If I’m at all correct here, it’s the [Sagnac effect.](http://en.wikipedia.org/wiki/Sagnac_effect) Light travelling around a closed rotating loop takes different times to arrive at a target, depending on the direction of travel. (The classic Sagnac experiment uses a square path, not a circular one, but the same effect is seen.) The rotating circle is an accelerating frame of reference, so the predictions of a non-rotating model won’t work. ---
**Author:** ![mythoughts](https://avatars.discourse-cdn.com/v4/letter/m/7993a0/32.png) [@mythoughts](https://boards.straightdope.com/u/mythoughts)\ **Post date:** [March 3, 2014, 6:50am UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/348 "2014-03-03T06:50:50Z")
> [@Kimble](#): > > Disagree – that’s an argument from incredulity. Plenty of people can imagine spacetime distorted. Several of them have posted here. True, I misspoke. It is not the distortions as such that I can’t imagine (except for in these paradoxical thought experiments), what I really wanted was to free the mind from the view that the speed of light can be C without any explanation. I thought that if I said “how can the speed of light be measured to be C when it shouldn’t be” would get objections. > [@](#): > > We have theoretical (c = (ε[sub]0[/sub]µ[sub]0[/sub])[sup]-1/2[/sup]) and experimental evidence that it is. Barring a statement of intent from a relevant deity, I don’t see what further evidence is necessary. I don’t understand the math obviously, but I was saying that as scientists or people interested in it, knowing it is, is not enough. We don’t just accept that matter is, we investigate till we find atoms, and we don’t just accept that, we find electrons and protons, and we don’t just accept that we go deeper into the structure of matter. Saying it is because it is sounds like a religious person saying God IS because he IS, no explanation necessary. But since light is the only thing that has this special and seemingly impossible state to it, then we should investigate HOW something that is normally not even conceivable now is. Additionally I disagree that there isn’t evidence to the contrary, Silvertooth and a modern replication of Silvertooth as well as most interferometry experiments see a drift, just less than a static aether without length contraction. > [@](#): > > I’ll believe it when I see it. Do you understand how entrained aether and length contraction interact? On a basic level, if the aether is entrained by matter it would be expected not to undergo length contraction but with partial entrainment and possibility of differently moving aether’s dragging through each other things may get more complex, I am uncertain. Length contraction existing for the atmosphere due to partial drag (imperfect entrainment) sound probable, and reasonable to explain aberration. > [@](#): > > Do you have any kind of idea how this aether would work, other than “very well”? Yes, but what I do know is not hugely relevant to how it would act on a planetary scale. > [@](#): > > If not, is there any point in trying to disprove it? Or any _way_ to do so? I **do** know enough to prove or disprove it, but a ‘messy’ partially entrained aether with probable fluid properties is very complex, it is not as pure. Anyway I have an opposite assertion, I am not currently aware of a single light speed measure that would go in SR’s favour. It is a very perfect and mathematical theory but most results I have seen it is a bit off in it’s prediction, close enough for it to claim victory, but an aether that is mostly stationary will read C also. Experiments that can pick between them requires moving the measuring instrument relative to large earth mass that should entrain the aether better than the equipment. I have never heard of such a test. It would be difficult since the device could not be enclosed without risking entrainment which probably means a high velocity in a rock tunnel holding a vacuum high speed interferometry experiment. > [@](#): > > Here are some numbers that work: Aether drag = 0; aether wind = 0; length contraction = gamma. How would any of your paradoxes support differences in those values? If you are asking me how would these thought experiments work with an aether, my answer would be non-paradoxically, each object would find the aether it holds to support C as the value for light and the only difference would be when 2 frames are mixed. There would be no length contraction or time dilation unless the matter was moving through the aether as opposed to entraining it. I suspect your question was sarcastic. Please don’t get exasperated. ---
**Author:** ![mythoughts](https://avatars.discourse-cdn.com/v4/letter/m/7993a0/32.png) [@mythoughts](https://boards.straightdope.com/u/mythoughts)\ **Post date:** [March 3, 2014, 7:01am UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/349 "2014-03-03T07:01:03Z")
> [@Trinopus](#): > > I’m not totally sure, but I think that’s not true. We, in the non-rotating frame, expect to see the two photons arrive at 180 at slightly different times. If I’m at all correct here, it’s the [Sagnac effect.](http://en.wikipedia.org/wiki/Sagnac_effect) Light travelling around a closed rotating loop takes different times to arrive at a target, depending on the direction of travel. > > (The classic Sagnac experiment uses a square path, not a circular one, but the same effect is seen.) > > The rotating circle is an accelerating frame of reference, so the predictions of a non-rotating model won’t work. If the speed of light wasn’t C in acceleration, then it could be measured to be higher or lower than C depending on the direction of acceleration. ---
**Author:** ![mythoughts](https://avatars.discourse-cdn.com/v4/letter/m/7993a0/32.png) [@mythoughts](https://boards.straightdope.com/u/mythoughts)\ **Post date:** [March 3, 2014, 8:21am UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/350 "2014-03-03T08:21:55Z")
It seems Sagnac effect is clearly evidence of an aether, the speed does change and that must mean greater than C. Here is a page that talks about it: [Anti-Relativity: Experiments Prove Special Relativity Wrong](http://www.anti-relativity.com/sagnac.htm) ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [March 3, 2014, 10:44am UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/351 "2014-03-03T10:44:08Z")
It’s irrelevant to disputing the claims of relativity that your way of calculating the speed of light from an accelerated frame of reference gives a speed of light faster than c. Relativity says that the speed of light in vacuum will be observed to be c in any inertial reference frame. Time dilation and length contraction in inertial reference frames are symmetric. In accelerated frames time dilation is **not** symmetric, so you can create set-ups where, using your way of seeing things, light speed is higher than c. But your faster than c light is still moving at c in **all inertial reference frames** , which is what relativity predicts. And the way physicists calculate things is to acknowledge that accelerated frames give asymmetric time dilation, and calculate what speed the observed light will have in an inertial frame. ---
**Author:** ![mythoughts](https://avatars.discourse-cdn.com/v4/letter/m/7993a0/32.png) [@mythoughts](https://boards.straightdope.com/u/mythoughts)\ **Post date:** [March 3, 2014, 11:10am UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/352 "2014-03-03T11:10:25Z")
Ok, the Sagnac effect if I am reading things correctly says that light will take different times around an optical loop if there is some rotation. And fibre optic Sagnac loops work fine, so let’s take one and rotate it until the linear velocity of the fibre loop approaches C. Now since light apparently moves independently of the rotation of the fibre path, then now the light takes just over half the time it should take to go around in one direction, and in the other direction the light will take a much longer time, to the point where it rotates say 20-40 times in one direction sooner than once the other direction! Since this is so it should be possible to establish the velocity of the slow light progress by having signals sent around the fast way, and we can easily account for the different path length by wasting some length. But another thing occurs to me, this effect only applies to light! You see I do not believe that an optically clear things entrain the aether (or the spectrum of aetheric substance that light for light). You see I can find no record of an electrical Sagnac effect! This would be easy to notice, if the Sagnac effect slowed the electrical transmission around a coil, why use fibre optic if you don’t have to? And how could this have gone unnoticed? Ok, I will admit that for an electrical version we must use 2 parallel conductors like speaker wire and apply positive and negative simultaneously so we have no self induction in the loop. The fact that no mention of an electrical Sagnac effect exists makes me think that it doesn’t occur, which means we could still send electrical signals that would be faster than the speed of light! Either that or I have got a viable alternative to the optical version. Another thought, since light moves so slowly the long way, you could end up with the optical version of a sonic boom almost. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [March 3, 2014, 11:45am UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/353 "2014-03-03T11:45:59Z")
I did the Sagnac effect to death with a previous relativity doubter. If you’re going to absorb ill conceived relativity criticism from random internet armchair physicists like it was water and you were a sponge I’m going to leave this train while I can. If you, as you appear to think you have, have insights that will overturn relativity, then you need to first learn what relativity means to actual physicists today. You will not learn that by accepting relativity-doubters as truthful or representing actual scientific doubt, and you will not be taken seriously, or even understood unless you manage to use technical terminology in the way it’s understood by everyone else, instead of your own personal idea of what the words mean. And just for fun, here’s an animation I made durning the previous Sagnac discussion: [http://www.geogebratube.org/student/m9696](http://www.geogebratube.org/student/m9696) ---
**Author:** ![mythoughts](https://avatars.discourse-cdn.com/v4/letter/m/7993a0/32.png) [@mythoughts](https://boards.straightdope.com/u/mythoughts)\ **Post date:** [March 3, 2014, 12:02pm UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/354 "2014-03-03T12:02:32Z")
My argument in the previous message was slightly incomplete… According to a webpage trying to explain why the Sagnac effect does not dispute SR despite the signal times differing between the 2 directions… It is claimed that an observer rotating with the fibre optic will see the speed of light in a segment of the fibre path to be C both ways, but SOMEHOW the total trip times are different… So he is trying to say that it is both C AND isn’t C! But that only C is found as a direct measurement of a portion… Well that certainly sounds suspicious… How can we disprove him that the speed of light in a segment isn’t C? What if we have the fibre rotating near the speed of light again and then the same photon could complete many laps while the other photon is still making it’s way through the first quarter. This allows us to look at this first quarter and what has been seen? Well one photon has completed many laps while the other has only almost finished this segment. So we ask again, is the speed of light measured in just this segment C? NO! Obviously this is not even vaguely possible. [http://www.physicsinsights.org/sagnac\_1.html#observer-on-disk](http://www.physicsinsights.org/sagnac_1.html#observer-on-disk) See there, it is claimed that the observer on a short length will see the speed of light to be (almost) C, because to have it be otherwise SR would be false. So this is absolute proof that the speed of light CAN NOT be C in both directions while one gets lapped several times! And yet everything on the Sagnac effect would back up that this should be possible! ---
**Author:** ![Trinopus](https://avatars.discourse-cdn.com/v4/letter/t/2bfe46/32.png) [@Trinopus](https://boards.straightdope.com/u/Trinopus)\ **Post date:** [March 3, 2014, 7:22pm UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/355 "2014-03-03T19:22:51Z")
> [@naita](#): > > I did the Sagnac effect to death with a previous relativity doubter. . . . FWIW, thank you for having done that, as it educated me to the effect, which I’d never learned in class. I would have naively thought that the light would arrive at the opposite side of the spinning loop at the same time – that there would be no interference fringes. I’d have been wrong! This is the danger of using intuition to argue relativity. It doesn’t work! Our previous (and possibly current) correspondents were uninterested in learning, but I was (and am.) So…thanks! ---
**Author:** ![mythoughts](https://avatars.discourse-cdn.com/v4/letter/m/7993a0/32.png) [@mythoughts](https://boards.straightdope.com/u/mythoughts)\ **Post date:** [March 3, 2014, 7:57pm UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/356 "2014-03-03T19:57:58Z")
Richard Feynmann — ‘Study hard what interests you the most in the most undisciplined, irreverent and original manner possible’. Trinopus, if the total trip time is relative to the rotation of the observer around the light path, and this is taken to the point that the trip time is almost halved in one direction and almost crawling in the other due to relativistic velocities, then the speed of light in one portion (one quarter) CAN NOT be measured to be C in either direction since one photon laps the other an arbitrary number of times while the other is struggling to pass that portion of the loop. And carry this out it would apply to any motion with a subtle enough of a bend to describe a portion of a circle of ANY size, so not just rotation but essentially all motion in practice. Special Relativity is a model that comes kinda close to the truth (partial entrainment of an aether = close to C, length contraction and time dilation effects with movement through the aether) so it gets most stuff right enough, and interprets the rest with such a stilted view with so much confirmation bias to toe the party line that it becomes accepted as true. And unquestionable to anyone who holds it is too much respect to be irreverent towards it. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [March 3, 2014, 8:35pm UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/357 "2014-03-03T20:35:06Z")
> [@mythoughts](#): > > Special Relativity is a model that comes kinda close to the truth (partial entrainment of an aether = close to C, length contraction and time dilation effects with movement through the aether) so it gets most stuff right enough, and interprets the rest with such a stilted view with so much confirmation bias to toe the party line that it becomes accepted as true. > > And unquestionable to anyone who holds it is too much respect to be irreverent towards it. Why is physicists accepting SR and GR, many of them after examining the nitty gritty of it for years, “toeing the party line”, while you calling your pet aether theory “truth” is being an independent thinker? You discovery that your intuition about light clocks perpendicular to each other was wrong, and that the flaws were only discoverable by examining the situation methodically and completely should have taught you something. Instead you keep trusting your intuition and cherry picked cook websites over people who’ve actually examined these situations in depth. Your beef with relativity is strawmen, misunderstandings and your unshakable anti-relativity bias. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [March 3, 2014, 8:36pm UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/358 "2014-03-03T20:36:50Z")
> [@Trinopus](#): > > FWIW, thank you for having done that, as it educated me to the effect, which I’d never learned in class. I would have naively thought that the light would arrive at the opposite side of the spinning loop at the same time – that there would be no interference fringes. I’d have been wrong! > > This is the danger of using intuition to argue relativity. It doesn’t work! > > Our previous (and possibly current) correspondents were uninterested in learning, but I was (and am.) So…thanks! You’re welcome. I hadn’t heard of the Sagnac effect myself before that thread, but as I was already knee deep in the discussion I couldn’t not educate myself and keep soldiering on, even if educating the instigator was futile in the end. ---
**Author:** ![mythoughts](https://avatars.discourse-cdn.com/v4/letter/m/7993a0/32.png) [@mythoughts](https://boards.straightdope.com/u/mythoughts)\ **Post date:** [March 3, 2014, 9:04pm UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/359 "2014-03-03T21:04:43Z")
> [@naita](#): > > You discovery that your intuition about light clocks perpendicular to each other was wrong, Yes, but that flaw in intuition is unrelated to SR (just a result of changing positions of mirrors), it was something I said I was not totally certain of initially and was able to disprove myself inside of a day without using any math, besides a length contraction calculator to see if they would be in sync with length contraction. Additionally nothing related to that error has any impact on this. But you are bringing up a previous example because despite your knowledge of the Sagnac effect you are unable to explain away this issue, so you are the one using killing strawmen. > [@](#): > > and that the flaws were only discoverable by examining the situation methodically and completely should have taught you something. Instead you keep trusting your intuition and cherry picked cook websites over people who’ve actually examined these situations in depth. > > Your beef with relativity is strawmen, misunderstandings and your unshakable anti-relativity bias. Ok, so then enlighten me, how would it work considering that the trip around the loop is relative to the absolute rotation of the loop/observer? ---
**Author:** ![Ronald\_Raygun](https://avatars.discourse-cdn.com/v4/letter/r/c67d28/32.png) [@Ronald\_Raygun](https://boards.straightdope.com/u/Ronald_Raygun)\ **Post date:** [March 3, 2014, 9:12pm UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/360 "2014-03-03T21:12:45Z")
> [@mythoughts](#): > > My argument in the previous message was slightly incomplete… > > According to a webpage trying to explain why the Sagnac effect does not dispute SR despite the signal times differing between the 2 directions… > > It is claimed that an observer rotating with the fibre optic will see the speed of light in a segment of the fibre path to be C both ways, but SOMEHOW the total trip times are different… > > So he is trying to say that it is both C AND isn’t C! > > But that only C is found as a direct measurement of a portion… Well that certainly sounds suspicious… > > How can we disprove him that the speed of light in a segment isn’t C? > > What if we have the fibre rotating near the speed of light again and then the same photon could complete many laps while the other photon is still making it’s way through the first quarter. > > This allows us to look at this first quarter and what has been seen? Well one photon has completed many laps while the other has only almost finished this segment. > > So we ask again, is the speed of light measured in just this segment C? > > NO! > > Obviously this is not even vaguely possible. > > [Sagnac Effect: A Simple Description](http://www.physicsinsights.org/sagnac_1.html#observer-on-disk) > > See there, it is claimed that the observer on a short length will see the speed of light to be (almost) C, because to have it be otherwise SR would be false. > > So this is absolute proof that the speed of light CAN NOT be C in both directions while one gets lapped several times! > > And yet everything on the Sagnac effect would back up that this should be possible! The classical explanation of the Sagnac effect does try to explain it with anisotropic speeds of light around the disc, and you’re just making the same argument. What’s going on here is that you’re misunderstanding the word “short”. The author means to say “infinitesimal” in a mathematical sense, but there isn’t a direct analog for the word in common, non-jargony English. Any sort of measurement around the circumference of the disk involves summing up all of these infinitesimals, and the interpretation of such a sum is questionable. The reason is because the rotating disk does not admit a proper frame. Rather, the “frame” is a gluing together of an infinite number of local frames at different points and different times according to some convention – but no such convention exists which allows for a self-consistent synchronization scheme! This is why I’ve brought up simultaneity and synchronization in the past. I’ll note that you tried to handwave these objections away with arguments about how these things hold for really short (infinitesimal) distances – but the point has always been that you have to add these distances up to get anywhere! In order to experimentally account for desynchronized clocks, you have to introduce a time lag, as mentioned in the website you linked to, which – by the way – is probably the clearest Gedankenexperiment I’ve seen of this effect. I had answered your argument regarding a rotating hexagonal disk in a previous thread, but you ignored it. The author of the website you linked to gives a brief comment in the bottom about length contraction of the circumference. My response was that, regardless of whether or not the circumference is length-contracted, the radius does not change, and the hexagon never fits inside the cylinder. Now, as I had mentioned, it’s common for people to claim that a shrinking circumference and a constant radius implies curvature of some sort. You can find some arguments for and against this line of thought in a review of relativistic rotation here: [http://arxiv.org/pdf/gr-qc/0604118.pdf](http://arxiv.org/pdf/gr-qc/0604118.pdf) It assumes some mathematical familiarity – that’s the way it goes – but there are plenty of references as well as plenty of non-mathematical interludes. ---
**Author:** ![mythoughts](https://avatars.discourse-cdn.com/v4/letter/m/7993a0/32.png) [@mythoughts](https://boards.straightdope.com/u/mythoughts)\ **Post date:** [March 3, 2014, 9:23pm UTC](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160/361 "2014-03-03T21:23:22Z")
naita, are you a defender of the noble and unquestionable truth of Special Relativity with unwavering confidence in it? Because if you are and I make sense you will have to turn to personal attacks, appeals of authority, writing incomprehensible answers (including equations I can’t tackle), strawmen, intellectual dishonesty and various other techniques for winning an argument when in the wrong. I don’t need someone who is going to say that I am right even if they can’t see any way I couldn’t be correct, they could just admit it is beyond them to see the flaw. If you can’t accept that I might POSSIBLY be right (however slim odds) or at least concede I have you stumped, then I would request kindly you don’t contribute to this thread as it would not lead to you fighting dirty. I am willing to change my view always if the weight of evidence shifts under unbiased interpretation. I hope you are also. [Previous page](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160.md?page=17) [Next page](https://boards.straightdope.com/t/how-to-have-light-move-faster-than-c/682160.md?page=19)