So, first of all I'll repeat what I finished my last post with: I don't see any discussion on this thread of the lights-and-boards experiment. I'm a little confused as to why not?
I've read the account linked to by the flat earth main page, of someone who claims to have been there (it's here:
https://www.reddit.com/r/flatearth/comments/7sc4w5/about_the_cringiest_thing_youll_see_today/dt5gzyr/ ). I’ll note that this account is, as far I know, uncorroborated – but it describes ten attempts made where the experimenters were unable to find the light either through the hole in the centre of the board at the 3 mile point or over the top of it, and only one attempt where the light was seen - when held above the board , the position indicating a positive result for curvature. The producers of behind the curve didn’t show this (allegedly), and I don’t dismiss that this might be so without more evidence, having had dealings with the media myself.
The article on the flat Earth society front page claims that this must be due to 'curved rays' – atmospheric refraction unless I misunderstand that. The only atmospheric refraction effect I’m aware of that could account for this on a perfectly flat surface is an inferior mirage, which makes a higher object appear lower in the observers field of vision. But it would need a much steeper than normal temperature gradient over the surface: You need at least a 2.5 degree celcius/meter drop in temperature from the surface upwards, and more like a 4.0 degree change to get a clear mirage image - perfectly possible over asphalt on a sunny morning, much more unlikely at night. What’s more, inferior mirages usually produce a doubling effect, so the light would be visible at two heights at once - this would have been visible to the guys at the middle board and has not been reported. Inferior mirages are also (contrary to what the article on the main page says) inherently unstable, short lived, and produce other distortions as they fall apart - nothing like which was reported about the lights used, either those visible from the first board’s position or the second board’s position(a description of inferior mirages here:
http://www.islandnet.com/~see/weather/elements/infmrge.htm). Inferior mirages also usually happen within a meter of the ground and the experiments light path seemed to be safely above this.
It also seems like it would have been very bad luck for the area to be hit by that mirage just then, and anyway this explanation
isn't needed: The experimenters suspected themselves that there was a problem with the alignment, and given that they were aiming torch beams through 6 inch holes over a distance of kilometres (and the laser they'd wanted to use had failed, and the experiment as-performed was ad-hoc) I think that a problem with the alignment is the simplest explanation for the ten or so attempts where no light could be seen.
I bet there are FE guys already looking to do a repeat? I'd be interested to see evidence of what they find - I hope it will be reported, and some non-FE guys will be asked along to observe and corroborate.
…..I'll have to try a bigger configuration which I can tilt up to match my latitude. Have you ever done this experiment?
I've worked on a university undergraduate project to build a ring laser interferometer, as well as spectrometers, lasers, and other optical instruments in industry and research. The interferometer was over ten years ago (our supervisor was the only man in the Manchester hoping for an earthquake), but from what I (somewhat dimly) recall you will need a longish beam path - of tens of meters or more - to detect the Earth's rotation with an acceptable signal-to-noise ratio, using an interferometer (as mentioned before, ring laser gyros are more sensitive but more complex). IIRC sensitivity is proportional to the area enclosed by the ring. Apologies, I don’t know exactly how long off the top of my head. That's no disrespect meant btw, I admire your empiricism, just that I have built a few summer projects myself and I know one guy on a hobby budget faces practical limitations. Don't let me put you off though, it's a fascinating technical project and I totally see why it's one of the most interesting aspects of this for you. I'd be very interested to see an image of your set up? For what it's worth a few thoughts off the top of my head, based on twelve years working on optical instruments and scientific instrumentation generally, are:
- How far away is the nearest road? I spent most of my undergraduate project trying to find ways of screening out vibrations from the nearby A-road. Floating the base in a water or oil bath is an option, but carries its own difficulties.
- How stiff is the base? From working on spectrometers I know that it's possible to put a thumb heavily on one corner of the base and, without causing any visible misalignment, totally throw the alignment off.
- How good is the mirror stability? I'd recommend, if you can, glueing it into a metal mount and bolting the mount down hard.
-Have you got all the mirrors silvered sides facing the beam? I know that doing that seems silly obvious, but I've mucked that up on a mirror and spent days looking for more serious errors to explain the weird results, so I know it's easily missed.
-I suggest setting it up and calibrating it in a basement, on a hard floor with no airspace underneath.
- How well can you control the temperature, pressure, and humidity? If you cant you should be able to at least monitor them while working.
-Bear in mind that all the electronics heats up, so I'd switch everything on and wait ten to fifteen minute to make sure it's warmed up whatever it's going to warm up and any thermal changes of dimensions are levelled off. Once you've got it set up don't use it until it's had a warm up period.
Of course I might be being a bit of pedant - I'm assuming you want to go for max sensitivity, and these were just points that were impressed on me when working with optical instruments for that.
WRT Sandokhan:
So I take from those quotes you're a skeptic of special relativity? I'm not an expert, but I’ve studied it and still have notes and the resources of the internet to work with, and I’m more than happy to discuss it with you. I will point out that the Sagnac effect is a first a classical effect, experimentally verified to hell and back (both in existence and degree) out with the context of SR, so getting into detail might mean we leave the topic of the thread quite a bit. I can't promise prompt replies on this topic, but I promise I will reply and to the best of my ability.
That's a bit of a misunderstanding, and I'm a pedant for definitions and measurements: The speed of light is the same for all observers in inertial (non-accelerating and non-rotating) frames, regardless of their apparent motion - the time for the light to go around the ring in one direction is measured as being out of synch with the time taken for it to go around in the other direction due the Sagnac effect, a counter intuitive effect encountered in rotating frames of reference (but not linearly accelerating ones).
You are following the lines of thought expounded long ago by Paul Langevin, who was proven wrong by the experiments carried out by Dufour and Prunier (in France, 1937) and by Herbert Ives in 1938.
https://www.theflatearthsociety.org/forum/index.php?topic=30499.msg1978311#msg1978311 (Dufour-Prunier experiment)
A. Dufour and F. Prunier created Sagnac interferometers that were composites of moving and stationary paths, including stationary sources and stationary detectors. This was essentially to test if the relativistic approach could be distinguished from the classical approach.
"In all cases of this experimental test, the Sagnac effect was the same. This overturned Langevin’s analysis, and in 1937, he had to revise his explanation, as pointed out by Kelly:
“In his final essay on the subject in 1937, Langevin proposed that the results published that year by Dufour and Prunier showed that one had to assume either (a) the light speed varied to c + wr in one direction and c – wr in the other direction, or (b) the time aboard the spinning apparatus had to change by a factor of +/-2wA/c2 in either direction. Indeed, Langevin went as far as to say that assuming (a), “we find, by a very simple and very general reasoning, the formula for the difference of the times of the path of the two light beams in the Sagnac experiment.” .
The proposition (b) though is untenable because if this were true then when the light beam passed back to the moving detector, the local time from each direction would be out of synchronization, meaning that the clocks cannot be counting real time and that the effective time dilation is meaningless. This was also pointed out by Herbert Ives in his 1938 paper criticizing Langevin. Ives says about the absurdity of Langevin’s proposition (b):
” There are of course not merely two clocks, but an infinity of clocks, where we include those that could be transported at finite speeds, and around other paths. As emphasized previously, the idea of “local time” is untenable, what we have are clock readings. Any number of clock readings at the same place are physically possible, depending on the behaviour and history of the clocks used. More than one “time” at one place is a physical absurdity. “
The only explanation left, is Langevin’s proposition a) that the light speed varies by C+/-wr in one or the other direction around the disk, consistent with Dufour and Prunier’s experimental results."
(but not linearly accelerating ones)
https://arxiv.org/ftp/physics/papers/0609/0609222.pdf (first experiment conducted by R. Wang)
https://arxiv.org/ftp/physics/papers/0609/0609202.pdf (second experiment carried out by R. Wang)
.....
So – you are quite correct, the Sagnac effect has been shown and derived for a general case (That was little after I'd studied the subject.), which includes a straight line acceleration....From a starting point in general relativity, just as the circular sagnac effect can be derived from special relativity. But as for the rest of it....
if I understand aright, you're saying (or rather your image-quote is) that you've proved the hammer doesn't work because you cannot cut logs with it: Maybe this is more for other readers but...Special Relativity is, in the first instance, a theory that deals with inertial frames of reference: Frames, or Cartesian co-ordinate systems, that move in a straight line at a constant speed. In any one such frame every observer agrees on the current passage of time, even if they came from a different frame and have a different passage of time in their history.
It can be ‘fudged’ to analyse some non-inertial frames up to a point - linearly accelerating frames - by treating them as a series of instantaneous snapshots which can be treated as inertial frames – i.e. the accelerating frame is being considered over such a tiny time increment that the acceleration can be treated as zero. that works as longas the acceleration is not too large. It is not really meant for the analysis of rotating frames – in rotating frames, where every observer has a different acceleration, each observer observes a different passage of time, and analysing things with SR gets impossible.
That’s ok – SR is supposed to be a limited theory (the special means ‘special case’ relativity, literally).
So it’s not at all clear to me that the work of Dufour et all deals any blow to special relativity – there's no invalidation of the theory, which has correctly predicted a lot of otherwise very mystifying phenomena, from what they found: The rotating frame of the interferometer isn’t part of SR’s domain, so while its inability to resolve the apparent paradox without violating it's postulates might be disappointing, it hardly disproves the theory – you can’t prove a hammer doesn’t work by failing to cut logs with it! And there's no suggestion that there should be diffrence between the SR case and the classical case: Any special relativistic effects the Sagnac interferometer feels would apply equally along both directions of the beam, and so cancel.
Langevin succeeded in deriving the Sagnac effect from general relativity - general relativity predicts it, as can SR and classical mechanics. Again, there's maybe a mystery but no disproof there - at most you could say that maybe GR needs extending or modifying. More recent, successful, analysis of the Sagnac effect involve treating the rotating frame as having non-orthogonal co-ordinates and/or a non-Euclidian geometry – an idea that started with the Ehrenfest paradox - something that is much more part of general relativity (the ‘general case’ relativity which is more complete, but still with some acknowledged limits), in which such co-ordinate systems have been used to tackle rotating systems within the frame work of relativity a lot (they have also been used to solve problems in quantum mechanics and string theory too). These derivations usually show that, contrary to intuition, even in the rotating frame the two beams follwo paths through spacetime of different lengths - and the more recent ones are general case derivations (so includingthe linearly accelerating case).
And, yes, there are researchers who think that the Sagnac effect is better explained by the speed of light following a loop being non-invariant (like this one
https://link.springer.com/article/10.1023/A:1022548914291) but even these don’t claim to have disproved SR – they treat the non-inertial frame case as one which a modified but related version of relativity should be applied to. In fact they
rely on SR being valid for inertial frames. They found a bit of prominence when the OPERA experiment though they’d found evidence of neutrinos travelling faster than light.
So, let's say that the researchers who want to modify general relativity to make a rotating frame a special case where C can be varied are correct, which I'm
definitely not qualified to judge. Would that disprove special relativity? No, no more than SR 'disproved' Newtonian mechanics or Galilean relativity. Just as those things were a special case (but valid within their limits) of Einstien's theories so SR is already known and acknowledged to be a special case of general relativity. If it were shown true that general relativity needed modifying to include variable C under some circumstances, via the sagnac effect or an freaking FTL alien starship appearing over New York one day, it simply shows that both general and special relativity are part of some larger theory - which, since neither are claimed to be a theroy of everything, we already know must be true.
Interesting things to read on the subject
Ehrenfest paradox:
https://en.wikipedia.org/wiki/Ehrenfest_paradox (yes, wikipaedia, it's agood place to start)
An introduction to / examination of relativistic rotating frames:
https://www.amherst.edu/media/view/10267/original/reden05.pdfA comparison of theories of relativistic rotation:
https://arxiv.org/pdf/gr-qc/0604118.pdfUCR relativity and rotating frames:
http://math.ucr.edu/home/baez/physics/Relativity/SR/rotatingCoordinates.htmlAn intro to the use of non-orthogonal co-ordinate systems in relativity:
https://arxiv.org/pdf/gr-qc/0105071.pdf An Intro to the Sagnac effect:
https://www.mathpages.com/rr/s2-07/2-07.htmAn intro to Langevins first derivation of the Sagnac effect from general relativity:
https://www.sciencedirect.com/science/article/pii/S1631070517300907Derivation of the General Case SagnacExperimental Result from the Rotating Frame:
http://cds.cern.ch/record/559222/files/0206033.pdfSagnac Effect, Ring Lasers and Terrestrial Tests of Gravity:
https://www.mdpi.com/2075-4434/3/2/84/htm#B48-galaxies-03-00084The Sagnac Phase Shift Suggested by the Aharonov-Bohm Effect for Relativistic Matter Beams:
https://link.springer.com/article/10.1023/A:1026053828421Rotation in relativity and the propagation of light:
https://arxiv.org/pdf/0905.0765.pdfNon-time-orthogonal reference frames in the theory of relativity:
https://arxiv.org/pdf/gr-qc/0005121.pdfP.S:
One general point, more for other readers: “More than one “time” at one place is a physical absurdity “ …that’s been proven to be untrue since Ives etc by experiments investigating the predicted effects of SR: ‘Clocks’ whose ticks are fundamental to the nature of waves and matter (the vibrations of atoms, or periodic signals emitted by subatomic particles for example) have been sent on different paths (typically one high speed and one not) and measured the predicted differences in the passage of local time. When these clocks are brought back together in the same place, and velocity, they both show the length of time that has passed for one is not the same as that which has passed for the other - they have followed different paths through space time, experienced different inertial frames, and though they are eventually back in the same place and inertial frame each has gone through a different value of time to get there. So we legitimately have two different times in one place. That these ticks are so fundamental means that there is little doubt that macroscopic systems experience the same time dilation, by any meaningful measure – hence an absolute, ‘real time’, is consigned to being at most a philosophical concept. Time, basically, is the clock measuring it and has been shown to be so, even when it seems absurd to us – the universe is under no obligation to match our common sense, intuition, or instincts. The might not apply directly to the Sagnac effect – but it isn’t a theoretical concept, it is a well tested, actual effect in line with SR - one of relativity's innumerable successes.
EDIT: Sorry, a couple of other points that i feel like I should mention for discussions sake:
1: General relativity only requires that the speed of light be preserved locally - so in GR you can see light rays travelling faster than C, as long as nothing in their vicinity can overtake them. That brings us onto...
2: A rotating system in GR doesn't just allow for things to apparently travel FTL without breaking any fundamental postulates (as long as they are still slower than the light in their vicinity) it insists on it! Imagine being on a merrygo round, and measuring the apparent tangental velocity of an object a very large distance away: It only has to get so far away before it's tangental velocty exceeds C. That's fine within GR as long as the light flying past that distant object is still the fastest thing in the vicinity.
3: A rotating system in GR has a preffered/special frame: Only the frame of the axis of rotation (IIRC - I will check) is inertial, so I would assume that it's only in that frame the C must be an absolute limit for all observers, and SR's postulates left intact. it's the only frame in which an observer wouldn't feel coriolosis force. In the case of the Sagnac interferomenter that would mean that only in the frame of the lab must C be constant.
4: The rotational Sagnac effect cannot be putting the propogation of light onto a simple ballistic C + emitter speed basis. Look at the experiment: The pro-rotational beam, which would be the faster if a simple ballisitc explanation could apply, is the one that takes longer to complete the loop. That is one of the things it originally proved infact.
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