: Where to find Einstein's Paper of 1918? Preferably in german language? And, where to find any document concerning Langevins presentation?   

 :: I don't know where Langevins's paper can be found; but Einstein's 1918 paper I have (in German), in PDF for who wants it.   

 ::: ErNa received it from me, but I guess that he could not follow Einstein's arguments. In any case, the paragraph starting with "It is sometimes claimed that the twin paradox cannot be resolved without the use of general relativity [...] This is false" obviously needs to be corrected, as it's POV based on a particular interpretation of what the paradox is about, contrary to what Einstein and many others mean with it. I didn't correct that yet, for it requires quite some work.   

 ::::I hope I could follow;-). But I still try to understand, why so many people misunderstand RT (and why I didn't care for it for so many years). A key point seems to be: LT doesn't say anything about the the appearance of anything in the fixed frame. A fixed observer doesn't see anything changed, except: timescale in/of the moving object is slowed down -> spectra are shifted (doppler-compensated!) and live-time is expanded. But dimensions are not changed. And: it becomes more and more difficult to increase speed of such an object. In terms of mass it means: mass is increased. But today, people obviously switch to relativistic momentum. OK, we will see!  

 :::: Why so many people misunderstand SRT, usually has to do with either the counterintuitive reciprocity (paradoxical for those who don't understand how the LT work, and often confused with the twin paradox), or with the apparent conflict between claims that "only relative motion matters" and the fact that the theory predicts absolute effects which intuitively should result from an absolute cause  the Twin Paradox. Thus, when such clarifications are included in this article, it would certainly contribute to understanding of SRT. In contrast, at the moment this article likely just helps to increase the confusion. BTW, a "fixed observer" determines that also the length dimension of moving objects is changed.   

 :::::A very simple question: A "fixed observer", that is, a man, drifting in space, no gravitational field or force, fires an object. The only fact, he can observe, which is non-newtonian is: the energy to accelerate the object to a speed of v is not 1/2 mv², but higher. Where from can we have an information about the variation of distances? I do not no about LT, I do not use a different inertial frame. If I want, -there is no must- i can acquire some information about "timespeed" of the moving object by measuring some characteristic spectral lines. The observes redshift is not explained by the doppler effect, but a combination of dopplershift and dilated time in the moving object. Now, if I suppose, that time is dilated for the moving object and -that is an postulat of RT, all systems measure same speed of light, than the moving object that measures the same speed of movement, as the fixes observer does, must measure distances shorter. But measure means: compare the distance do a meter, he carrys with himself. Therefore: the fixed object sees himself and the moving object without deformation. the moving object sees itself without distortion, but the fixes observer is distored.  

 Your story became incomplete and possibly already with implied error at the point "if I suppose, that time is dilated for the moving object" - one has to add: "according to measurements using the observer's coordinate system" (for example with two calibrated fixed clocks, or by laser bouncing, both with the conventional assumption that light speed is isotropically  c relative to the observer). Next, the last part is erroneous, as one cannot but measure/calculate the other (moving) object as contracted, thus with deformation.   

 :The whole thing becomes more complicated, if on adds! We have to remove. "Time is dilated" should be clear enough. Them You say "calibrated fixed clocks", what is it? I say: "Spectral lines of hydrogen atom". Were is the difference?