No. Wrong. You shouldn’t take “seen to be moving at almost 2 times the speed of light” to mean that it’s moving at 2c.
The answer is simple and non-relativistic. From my link that you cite:
Basically it’s as if two people were are standing, watching a merry go round but not on it. They decide to run around the merry go round and set the brown horse that’s directly opposite them as the finish point. As they start running, the merry go round is turning. The one that’s running against the rotation is going to reach the horse first. He’s not running any faster than the guy running the other way. It’s that the finish line is moving to meet him.
I got up early this morning for a drink of water, and when I flicked on the light switch, I got pissed off at how long it took the photons to reach my eyes.
Proof light has a speed limit. Checkmate, Mythoughts!
From my skimming of your past Sagnac effect posts, I gather that you would like to defeat relativity by looking at a beam of light… traveling not in a straight line but in a closed loop… but not by itself but with another beam… and with two detectors… but not located at the same position… and (thus necessarily) with displaced clocks that need to be synchronized… using a clock synchronization approach that you constructed… all while working in a rotating frame… which necessarily means no global inertial reference frame exists for the system.
Is that right? Do you not think that that Rube Goldbergian setup could possibly… just maybe… be complicated enough that simply intuiting oneself through it might lead to a subtle mistake? Is that a possibility?
You’ve claimed that there’s all sorts of evidence that relativity is broken. Why would you want to use this cumbersome and complicated example to prove your point if simpler, more direct evidence exists?
Grin! Sympathies, to be sure; the few creationists who wander into the SDMB are usually stupid as dirt, and not particularly amusing.
Where I get astonished is when there are math cranks! Math is one of the very few fields where the conclusions are proven. Real, solid, meaningful proof. The physical sciences would love to have the kind of certainty that we have in, say, the Intermediate Value Theorem.
And yet…we have no shortage of goofwads who pop up and think they can overturn calculus, redefine infinity, or produce a whole new definition of “number” that changes the entire philosophic underpinnings of our industrialized civilization.
Garden variety creationists, alas, tend to be mean-spirited. They consign their opponents to hell with an astonishing lack of human empathy.
And the same is true if a light speed test is done with observers in different inertial frames, there are different distances because one finishing line is moving, but in this case that is not considered a relivant under SR.
My point is you can’t have it both ways, if the view of the rotating frame is not respected and the rotating observer sees light finish faster around one way than the other, then from his definitively moving perspective the photons must be moving at different velocities, and one faster that he would expect light to be.
Additionally if a clock sync method capable of giving an honest one way speed of light answer is used, he could see this speed on light difference over even a short length.
And if this were grown to astronomical proportions he would barely notice the deviation from straight line motion despite the fact that he is in a rotating frame at near C.
Yes, this is indeed it, and if the merry go round had somehow 2 horses counter rotating, he would see different speeds for these 2 horses, one almost stopped and one at twice the speed.
And if the merry go round was so large it almost looked straight, then you would have a situation where almost but not actually straight line motion would find the speed of light to be different in different directions.
There is no need for the rest of the Sagnac loop to exist, and indeed given the limitation of C you would not know for a long time if it did or did not exist at that moment.
Because the experimental evidence is not in question, this is a though experiment expanding on not just an experiment tried a hundred years ago, but actually used in technology.
Additionally Special Relativity has a known position regarding this, and that position is at odds with the normal predictions that SR makes with respect to motion effecting the speed of light.
All that needs to be done is to firstly point out that if the time around the total loop is far from equal, with light in the rotating frame seeming to move above and below C depending on direction, then if a synch scheme that isn’t totally rigged is used we can prove it in a section of the loop too.
It really is nonsense to have one photon making many complete cycles from the rotating frame while the other is struggling to complete one cycle and then pretend that somehow the speed of light in each section could be equal both ways genuinely, the results for the portion can’t dispute the results for the whole loop.
Next all that is needed to grow the loop, this changes nothing important except for lowering the RPM needed to get the Sagnac loop moving near light speed.
Now we have transitioned from a rotating frame that on a human scale looks like rotation, to a rotating frame that without zooming way way out looks very much like an inertial frame.
Except it MUST still find the same results of a smaller loop.
I can dispute SR in many ways, if you want experiments that show it, I listed several and then I also posed superluminal jets and instantaneous near fields also. If you want more I can give you claims of a gravity impulse at 64 times C.
I have shown that the interpretation on many interferometer experiments has been stilted to fit SR.
And I have given many examples of problems with time dilation, length contraction and the like, no one has successfully addressed them, though two at least gave some effort to do so but failed.
If you are ACTUALLY interested, I am willing to go back and make these ones, but IMO the Sagnac effect is as solid as it gets as SR basically admits that it does not follow he constancy of C since rotating frames are absolute motion.
But as no inertial frames exist in reality, SR is out of luck.
Like the light clocks perpendicular to and aligned with the direction of travel, this is a rare pearl of a well described thought experiment, even if your conclusion is premature.
Try this follow-up on for size.
We’ve been placed in a distant spaceship by whatever means, look out at the universe with the port side sensor array and see a pulsar we pick as reference point. In the interest of science we name it P1. We do the necessary measurements with the pulsar as our clock, and determine that according to mythoughtian physics, we have an absolute speed of v, with light speed registering as c+v in one direction and c-v in the other.
As you pointed out and I rashly tried to refute by intuition (dangerous stuff for any user), if we make the distance arbitrarily large, we can make other effects of our possible orbit around P1 arbitrarily small. In mythoughtian physics this means we might as well be moving in a straight line, things should still work out the same, while in an Einsteinian universe simultaneity and synchronisation would rear its ugly head, and tell us synching by pulsar isn’t as good as it intuitively seems.
Anyway, we’re not Einsteinians, we subscribe fully to mythoughtian physics, and go to sleep happily knowing that we’re travelling at v. Yeah, we’re easily to please like that. Next morning we wake up and the computer tells us that the instruments in the port side sensor array have all malfunctioned during ship-night, but that the starboard array is now available again. Oh, and our synchronised clocks all stopped during the night as well. Bummer.
Luckily there’s a pulsar to our right as well, so we start up our clocks, measure light speed in both directions, and are mildly surprised to discover that we’ve stopped during the night. Light speed is c in both directions. Then the computer tells us the port side sensors are back up, and that it’s puzzled about our log entry on a change of speed since the accelerometers have not malfunctioned and show no change in velocity.
Now given the additional knowledge that we were moving at v at a right angle with respect to to the direction of P1, at a distance where determining if we’re on a circular path by geometric means is not an option, (and possibly doesn’t matter,) and that we’re right on a line drawn through P1 and P2, with a distance to either so large and a velocity so low that our travel during the night makes no practical change in that situation. And given that we’re co-moving with P2 with the same velocity with respect to P1. How do you reconcile the differences in velocity measurements? What do you expect will be the result when we compare the clocks synchronized to P2 with the signals from P1?
Do the thought experiment from scratch yourself if you want to. Draw up P1, the space ship S and P2 on a straight line. Cover P2 and think about what you’ll be observing regarding P1, cover up P1 and think about what you’ll be observing regarding P2.
Can we resolve this by stating the co-moving S and P2 must both actually be moving in an absolute sense.? What then if we’d observed P2 first? Why should one pulsar P1 orbiting the center of the Milky Way, be a better reference than another pulsar P2, also orbiting the center of the Milky Way?
Can we resolve this by stating that S and P2 are the stationary objects, and P1 is the one moving? Then what observations would we expect to make regarding a hypothetical super-pulsar at the center of the galaxy that both S and P2 are orbiting at the same velocity?
That’s because there are no objective ways of telling one inertial frame from another, and if c wasn’t invariant, the differences in distances would vary depending on the frame we chose as preferred. Try it for yourself. It’s a bit tricky to do the necessary math-by-drawing that you used successfully earlier, but not impossible.
Rotating frames on the other hand have been shown to be rotating and rotating at a specific speed no matter how you look at it. That’s what the Sagnac-effect shows.
Now you believe that you can use the Sagnac-effect to show something profound about flaws in SR, but as I showed in my expanded thought experiment above, that idea is fundamentally flawed.
And yes, everything in the universe is influence by gravity, so perfectly inertial reference frames don’t exist, but SR is only the initial idea upon which GR builds, and GR takes gravity into consideration. And where gravitational influences are negligible SR predicts the experimental results we get in reality, just as GR predicts the result we get where gravity is important.
Why don’t you go off and rethink this for a while, and come back when your theory at least correctly predicts the precession of Mercury.
If the rotating observer actually measures the speed of the photons, he will find that they are traveling at c, relative to his frame of reference. If some non-rotating observer measures photons coming off the rotation, he will find that they too are moving at c relative to his frame of reference. If one set of photons is traveling a longer distance, it will take them longer, but that does not affect their speed, which will be measured as c.
So no one is having it both ways. All observers are having it exactly the same way - anyone who measures the speed will find it to be c. If they change their point of view and measure it from a different frame, it will be c again.
No matter how you change your frame of reference, you will always find the speed of light to be c. If you want to compare the results of measuring the speed of light from two different points of view, it will always turn out that the speed is c. So there will never be a different measurement.
I am not really saying that straight and from our scale very slightly curved lines are the same.
I am saying that SR tries to make different predictions for them, and SR is based on perfectly straight lines, but in reality these do not exist.
Now there is a potential part 2 where if the other truths are accepted as such, then additional ‘impossible’ perfectly straight motion is added which for an arbitrary period looks indistinguishable from the crve, but SR would make different predictions about it’s observations of the speed of light.
Your questions are good ones, you are going ahead me.
But note that you made only one mistake, you said that this is mythoughtian physics, really this is SR you are describing.
Mythoughtian physics would have the ship entrain the aether with it and the speed of light would always be C in each direction within provided the object entrained it’s aether sufficiently which I believe an opaque metal space ship would primarily.
The complications you detail are SR’s issues with making different predictions for perfectly straight and imperceptibly curved motion.
The only ‘Mythoughtian’ component is using a synch scheme that does not defeat any attempt to measure a real difference in the one was speed of light, horses, sound, bunny rabbits, baseballs…
That the speed of light will be measured differently with a sane synch scheme is already established by a Relativity supporter, and since the rigged nature of the Einsteinian scheme is even noted by Wikipedia.
Then the case is clear that this substitution is not only reasonable, it is necessary and inescapable.
Thank you, I appreciate your response being both thoughtful (intelligent) and respectful, it is very welcome.
a) Going around in a circle is not the same as going in ‘almost but not quite’ a straight line (whatever the hell that means) that would have items on it that could counter rotate in such a manner that they were observable to ‘all’.
b) the perception of the moving person (or standing still observer) of the 2 other differently moving objects is due to their perception only - it has no direct impact on the actual speed the items are, in fact, moving.
In other words - in your merry go round scenario - there is no evidence that the little ponies are moving at a rate other than the same rate - them moving in different directions in relation to each other and even in relation to the observers speed of travel may influence the ‘percieved’ speed by the observer, but has no direct implication on the items ACTUAL speed.
It might not be mythoughtian, but it’s not SR. In SR light speed would be measured the same either way because one would know using a pulsar as a synchronising device would lead to inconsistent results.
I think what makes math a bit luckier than other subjects (though not completely immune, unfortunately) about crackpots is the fact that it’s so abstract. People experience Newtonian physics everyday, and lots of people are electronics hobbyists. They have a rough understanding of classical mechanics and E&M, and therefore assume that their familiarity intuition works perfectly well with relativity and quantum. Math is less accessible, though. You may have some crackpots blathering on about, say, Goedel’s theorem or calculus (which are nontrivial, but don’t require much background to understand the basics); you really don’t have any random people on the Internet claiming to have a shorter proof of the Kervaire invariant problem or any proof for the Novikov conjecture. You do get attempts to prove Fermat’s Last Theorem, because most people understand how to add and multiply integers. For that matter, you see far fewer crackpots attack GR than SR, because the background needed to even state the basic results of GR are more complicated than those for SR. mythoughts has no idea what, say, the stress-energy tensor is; he hasn’t even figured out how SR claims velocities add, which is high-school algebra at most.
But do you think crackpots like mythoughts would be stopped by something as weak as logic? They have special, magical insights that only they are smart, open-minded, and intuitive (details are for unenlightened suckers) to understand; yet, paradoxically, they’re compelled to preach about those insights on the Internet. People like mythoughts just want to feel special: They want to be reassured that even though they have no training, or education, or understanding of the problem, they don’t need any of that. In fact, they’re better for it, because they have a deep, intuitive understanding that transcends petty details like math or logic or experimental evidence. They grok the subject; actual experts in it are just caught up in irrelevant minutiae.