“The question as to whether length contraction really exists or not is misleading. It doesn’t ‘really’ exist, in so far as it doesn’t exist for a co-moving observer; though it ‘really’ exists, i.e. in such a way that it could be demonstrated in principle by physical means by a non-co-moving observer.” – Einstein, 1911
To figure out what Stacy sees, you have to consider both the relative motion (classical mechanics; Galilean relativity) and the length contraction (special relativity) of Moe’s clocks to her. Special relativity doesn’t replace classical mechanics; it’s conceptually a small tweak to make our observations more accurate. (That tweak being that c is constant.)
Furthermore, the post that you replied to does take both relative motion and length contraction into account; sorry if there was any confusion. Fuller explanation of the math in the spoiler tag:
[SPOILER]Time for light to go between fore/aft mirrors = (contracted distance between mirrors) / (difference in velocity between light and the mirror it’s moving toward)
contracted distance between mirrors = 300 m / gamma (at speeds of 0.8c, gamma = 1.6666…) = 180 m
As I said before, though I find it’s state of existence and non-existence as a reality for Stacy’s view of Moe like a dodge, I would put this aside for no as there is no point.
There is a different in the length even without length contraction existing in any sense at all.
Well I would disagree that it makes anything more accurate, but that is beside the point.
You are wrong about up/down mirrors.
Though you are correct for Moe’s view of them, Stacy sees the light take a longer zigzag /////\ path between the mirrors which is further than: |
This:/ against |
Clearly the diagonal is longer. That is the point of me posting the Wikipedia page, the same one you pasted too!
The numbers are right, but I did screw up the explanation. The slowed light would be what Stacy saw if she kept her gaze on Moe’s up/down clock only, but the light would really be moving at c.
Trying again:
Time for Stacy to see light go between up/down mirrors = (time it takes for Moe to see light do so) * gamma
time it takes for Moe to see light do so = 300 m / c = 1.0 µs
gamma = 1.667
Time for Stacy to see light go between up/down mirrors = 1.667 µs
I wanted to have an explanation of the up/down mirror “formula” that didn’t directly reference gamma, but I wouldn’t be able to get it any simpler than it is on the WIkipedia page. It’s very similar to the Pythagorean theorem, if you can handle that.
Time dilation is necessary to explain how the moving observer, Moe experiences light moving at c, despite Stacy as a stationary observer seeing the light moving in a longer zig-zag path in a light clock at 90 degrees to the path of travel. The fact that the Moe could say with confidence he’s the stationary one (we drug both Stacy and Moe and wake them up after all acceleration is done somewhere far from other objects) is what makes this the theory of relativity.
As Kimble has explained, simple classical mechanics means the light in a light clock with light travelling along the path of travel has different path lengths depending on whether it’s the forward path or backward path. To explain this we have to acknowledge that simultaneity is frame dependent. Moe sees the bouncing as synchronised, while Stacy sees the clocks as synchronised, but the half measure of one clock being off.
If we do the math for the second light clock, we find that the path has to be shortened to keep our observation of light speed constant. That’s what length contraction is all about.
All this is experimentally verified and accepted and understood by professional physicists all over the world. The fact that you can find contrarian “evidence” online is completely meaningless, you can also find discussion on any number of nonsense ideas. Anyone with the ability to follow in Einstein’s footsteps (quite a few now that the footprints are there) can work this out for themselves from first principles.
No one has come up with an alternative that also matches the observations of actual experiments. It doesn’t matter that hundreds of people feel they intuitively know that their new way of looking at the subject is correct and that relativity, to them, is intuitively flawed, in the real world, and in the mind of thousands of more qualified physicists, relativity works.
For the record I beat him to it, but yes, agreed, the full cycle time is the same as if it were not moving, provided we ignore the length contraction expected.
I am not sure what you mean by “but the half measure of one clock being off”, but to me it sounds like you agree the full cycle path lengths for the 2 clocks are different and (assuming C) would be running at different time rates as far as Stacy is concerned, but not as far as Moe can see. This is a very clear paradox, and if a digital panel in Moe’s ship shows the totals for each it requires different readings, what Stacy would insist on never occurred in Moe’s log, that mix of totals would never have read on his panel.
This now requires quantum-Schroedinger-light-clocks-multiple contradictory states to explain, which should not be taken seriously as a solution!
I don’t agree with that as needed in this case to explain the speed of light since the frequency of the light clock could just be seen to change to keep light at C, but if length contraction does exist all the better. So no real objections if length contraction is used or not as the paradox exists regardless, it is just more dramatic with it (and expected).
Yup, but so far I agree with mostly everything you have said.
So it seems you agree that the ‘orthogonal’ clock has a longer round trip path right?
And the ‘aligned’ clock has a shorter round trip length due to length contraction and the fact that the motion merely imbalances the 2 phases but doesn’t increase anything.
To what are you referring to?
From reading your post (except for the opinion part at the bottom) I find we agree on every point seemingly, but you don’t seem to see the anomaly.
**So a few questions.
#1. Would you agree that the normally oriented (orthogonal) light-clock makes a zigzag length and hence has a longer path with relative motion than at rest? #2. Would you agree that while in one direction the aligned light clock has a longer path (than at rest) in one direction, the return phase is shorter to make no difference in round trip time than if it was at rest without length contraction which would raise the frequency observed if light is to be C? #3. Would you agree that if 1 and 2 are true, that the frequency of the aligned light clock would be higher than the orthogonal one according to Stacy (if light is assumed to be C)?
Please clarify, thanks.**
I guess there is an important point to make here, for an honest discussion we must both go into it at least being reluctantly willing to accept the other is actually right even if the odds we put on that being very very small.
Now I have admitted to being entirely certain about my main assertion, but I am willing to accept that either I might be unable to defend my position but choose not to change my mind (no contest), or fully concede the other person is right. If either of these things were to occur I would say so, and did with the red/blue experiment as it was becoming unwieldy.
I am not terribly interested in a discussion with someone who cannot accept that as obviously it would lead to deceptive arguments and a stalemate if they are unable make valid points but unwilling to bow out.
Indeed I will no longer respond to anyone I do not believe is genuine, no points can be won, but it will just degenerate.
I think experimentally there are some conditions that differ (according to a Wikipedia page).
But since SR is built on Lorentz, and if Lorentz turned out either not to explain the constance of the speed or light, or possibly only able/meant to explain the constancy of the measured speed of light in 2-way interferometry measurements but not to make C explainable in all directions, then SR would have no basis to claim it’s axiom. SR would only be supported on faith at that point as it could not support it’s contradictory axioms. At the very least the search for an explanation for the constancy would be needed.
note: I wanted to reply to this previously, but I had promised Pasta I wouldn’t participate is the noise and it would be 1 on 1.
I have now broken that promise but I hope he forgives me since the posts are all reasonable (not noise) and this isn’t getting in the way of he and I having a rapid fire convo at this time…
No, I mean that 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.
The full cycle path lengths are not different to either observer. Moe of course considers them stationary and thus equal, and Stacey, seeing both moving and one length contracted, will measure the paths to be longer, but equal. Anyone able to do the math or draw the geometry, will find it to be so.
I have just tried to test this to see if my assertion is correct that the aligned light clock has a shorter path, well I drew an image to graph out the various components and firstly I surprisingly found that motion does lengthen the aligned clocks net path!
And more than that it had a longer path than even the vertical one!
Very counter-intuitive.
A nice example off something that in counter-intuitive, but obviously not impossible.
Actually if my analysis was correct, with length contraction (thanks to a calculator) applied they are even length!
Firstly I’d like to point something out, I have managed to disprove my own thought experiment that I thought of earlier today and expressed initial reservations about.
But as I promised I am able to admit that.
Also it is the first experiment with anything tricky like this, my other thought experiments are all sound, the only other exception is the device with the 2 CD like sensors described in the first post of this thread which only produces a problem for SR if GR time dilation is used. Otherwise mutual (but paradoxical) time dilation will occur and while these can break SR with rotation the rest of the setup isn’t needed.
Incidentally I would like to note that IMO Kimble was reaching and wasn’t intellectually honest in saying length contraction wouldn’t occur/count, according to my drawn model (.5 c) the 2 clocks can only be in sync if the length contraction occurs.
So while this one isn’t right, it is not reflective of my other thought experiments, nothing so tricks in them as this.
As I awoke, a second argument occurred to me about Moe’s light clocks that makes this not quite 100% dead (yet) just 99%, if the vertical axis (orthogonal) light clock were slightly shorter and if Stacy moved very quickly indeed then from Stacy’s view the counter for the vertical one would read 2 before the aligned axis (fore-aft) reads even 1.
Now the display would be half way between ends of the of the tubes on a diagonal, it would seem to me it could MAYBE read 2 and 0 for Stacy (signal delay only, instantaneous circuitry) while never reading that for Moe, but plotting this is really not easy and I confess I would not be surprised in the least if the order never disagreed.
I still think it is odd that there are 2 time rates in a sense, but I accept this is tiny and within the fudge-ability of non-simultaneity.
I also want to offer an apology to Kimble if I mistook his argument about length contraction nor raising the frequency.
While clearly it is real and does raise the frequency, it only does so to correct everything.
Initially the argument seemed to me to be a way to try and wriggle out of something, but now I confess I wonder if it was merely an attempt to explain something to me that was going over my head at that moment.
The circular case hasn’t entered our discussion yet (a quick search shows some previous discussion), and it introduces complexities that aren’t present in the straight line case, which we can analyze all the way through to observation if care is taken.
Given the work week I have coming up, I’ll have to pause here for many days. Fortunately Kimble is keeping things going. My path in this discussion has been to ensure that no subtle step is skipped over when drawing conclusions about what SR predicts. In SR thought experiments (linear, circular, or any set up), subtleties come about in full force when trying to figure exactly what each observer will measure and whether they disagree on things in a paradoxical way when they compare notes. It might be the case that the impossibilities of SR are not actually show-stoppers when all the observational subtleties are followed to completion. Hopefully the continuing discussion will shed light on this.
Well it is the first time anyone bothered to analyse my claims and put numbers to anything too.
So I genuinely do not believe the others have had any valid criticism against them besides the complexity of analysis of the red/blue photon test which does not invalidate the concept.
I will for now revert my arguments to rotation with time dilation and length contraction which IMO is pretty much bulletproof, but I will look for a better argument also as Pasta was not terribly happy looking at rotating frames under SR, and I don’t blame him!
It seems like a slam dunk on my side without starting, to have a 100 year time discrepancy between a rotating disk and the lab does not seem very tenable. If time dilation must happen both sides (Rim and lab) for light clocks in the lab to not be superluminal to the rim and if a video camera is mounted and synchronized by a laser/reed switch then we would expect a stable video that would show the lab in slow-mo from the time dilation.
And Special Relativity HAS placed it’s bet’s on this one! It has said the rotating frame ages less, except that would break the constancy of the speed of light if the time dilation wasn’t mutual (light clocks)!
And the video-camera could record every revolution, and the revolution counts would have to match between lab and rim.
So to have the rim see less time pass in the lab per revolution by it’s view you would end up with a very inexplicable paradox.
The rotating frame is accelerated so time dilation is not symmetric. It’s difficult to grasp which parts of your setup you consider important to prove the discrepancies you believe you’ve discovered, but here’s a different thread from this forum examining a different rotating setup that, to me at least, clarified a few things. Understanding rotating reference frames.
To hammer this in, the rim doesn’t see less time pass in the lab. The rim is in an accelerated reference frame and relativity used properly means it sees the lab slowed down.
I am still going to contribute, but I have been putting a bit too much time into this so I will probably reduce the time I give this for a bit, and I have no new argument that I have not already made.
At some point though I will probably try to summarize each major thought experiment into one post that I will try to compress as much as possible.
I am not opposed to also share evidence and interpretations of evidence that discounts the point of view that SR has been ‘proven’, but only in a separate thread as that really is an independent subject.
A thought experiment could prove that SR is wrong -as it is now- but SR could be saved by modification.
A thought experiment could prove SR wrong, and yet the solution could be a theory other than an entrained aether.
A thought experiment could prove SR wrong, and an entrained aether could be the truth as I assert.
So presentations of thought experiments to oppose SR stand weather or not the evidence for SR is almost unassailable (and true) or terrible and based on confirmation bias and slanted interpretation (and false).
There is one argument I will make freshly and see if Kimble (who I apologise as I suspect I misinterpreted the length contraction point) can maybe he or naita could give an answer…
As seen in the failed thought experiment with Stacy and Moe, the light in Moe’s ship is seen to move in very different velocities in each direction, this makes the observation for her, but how can we explain why Moe’s movement relative to these photons can explain in his perspective why the light is C also?
This is a point I tried to make that Pasta didn’t grasp, so I will try again.
If Moe’s ship is moving relative to the light (in the view of normal space) then what effects can correct these 2 photons very uneven relative velocities?
I would assert that length contraction and a slowed clock so far as I can imagine only serves to cause light speed measurements to return higher speeds as the clock will register less time passing over an decreased distance in either direction, light that was too fast would now be measured as faster.
So my current suspicion is that Lorentz contraction was possibly never meant to explain the constancy of light speed in all direction, but the measured constancy of light speed in an interferometry experiment with different path elements.
But I admit my knowledge of Lorentz is at present insufficient as I have expressed.
But If Lorentz does not try explain the actual constancy of the speed of light then SR only survives on faith that some explanation could exist but has not yet been found.
Here is a video showing the effects of travelling at relativistic velocities, but at low speed with slow light:
This is worth watching too:12 year old kid with 170 IQ and very intense math skills, he is challenging Einstein, but not on SR (yet).
Here he makes an important point:
Forget what you know, question assumptions.
He says stop learning (or at least being taught), and start thinking in your own creative way!
Science should be about truth not compliance.
He is autistic, failed finger painting, failed special ed., but he is undeniably brilliant.
It reminds me of why I did poorly in a physics class I took at an institute of technology, I was more interested in my concept of an impractical perpetual motion machine based on Relativity, where spinning mass becomes more massive with velocity, hence pulls down to earth on an otherwise balanced wheel, then somehow losslessly transfers it’s kinetic energy to another mass that is in position to continue the motion if it’s mass (gravitational attraction) were to increase.
I am not confident that the mass an object gains from nearing light speed should be taken that literally (though it should if equivalence is to be maintained) , but I agree with him, it is thinking independent thoughts and creativity that is the source of true genius.
Considering the increasing energy beyond the classical as an increase in relativistic mass is considered less than useful by many these days: Mass in special relativity - Wikipedia
I have experience tutoring people in math. I took enough math classes in college to get a double major in it (alongside computer science). On the other hand, my last physics classes were in 1990. I’ve kept up with astronomy, so I know the basic ideas and the consequences of GR and SR. However, I haven’t really tried to explain relativity to people. (Until now.)
So, when I see comments like:
all I can say is "There is no normal space. There’s what Stacy sees and there’s what Moe sees. " My followup would be “There is no normal space. There’s what Stacy sees and there’s what Moe sees.” Further replies would simply add all-caps, more bolding, more italicizing, larger font size, etc. I don’t know how to teach that information.
I also don’t know the history of physics, so I can’t answer general questions very well. But, I did remember this:
… is false. Lorentz contraction was also designed to account for stellar aberration – the fact that in order to look at a very distant star, you have to point your telescope very slightly in the direction the earth is currently moving (no more than 20.5 arcseconds = 0.0057 degrees). This was first observed back in 1725.
Short version: Because Moe isn’t moving with respect to the clock.
Long version: The math’s hard – too hard for me to bother with, I think – but I think it’d be easier if I understood simultaneity better.
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.
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.
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.
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.
Let’s not just say the speed of light is C “because it is”.
I am not asserting that it is false, I am asserting that SR’s flavour of contradictory contraction is. Length contraction is an aether based concept that can also apply to an entrained aether potentially.
I am even willing to accept the possibility that the aether I am certain is real may possibly not be the luminiferous aether.
Indeed it would be absurd to deny the existence of an aether of some kind with all the evidence in modern physics, the only question is what type,
I think I will look into stellar aberration further, obviously you point a telescope where you see a star so I don’t automatically understand it, unless the argument is that our view of space distorts the sky differently as we move?
Short version: Because Moe isn’t moving with respect to the clock.
Long version: The math’s hard – too hard for me to bother with, I think – but I think it’d be easier if I understood simultaneity better.
[/QUOTE]
Ok, so you believe the corrective factor might be simultaneity?
But if so it must still overcome the motion, the shortening, the slow clock which seems like a lot to answer to normalize the speed of light.