This post is a continuation of my post https://www.physicsforums.com/showpost.php?p=4041285&postcount=10 and https://www.physicsforums.com/showthread.php?t=629655&page=2 PeterDonis and Harrylin are correct I better start a new thread for this. I repeat my post here. Thanks for the link to Einstein's 1905 paper. The english translation. I hope you ever read the original german paper: http://nausikaa2.mpiwg-berlin.mpg.de/cgi-bin/toc/toc.x.cgi?dir=Einst_Zurel_de_1905&step=thumb I did it for you. I speak flemish which is close to german. That helps a lot. Let me first show you the verbs in the english and german versions: >>>>>>>>>>>>>>>>>>> It is known that Maxwell's electrodynamics—as usually understood at the present time—when applied to moving bodies, leads to asymmetries which do not appear to be inherent in the phenomena. Daß die Elektrodynamik Maxwells -- wie dieselbe gengen- wärtig aufgefaßt zu werden pflegt -- in ihrer Anwendung auf bewegte Körper zu Asymmetrien führt, welche den Phänomenen nicht anzuhaften scheinen, ist bekannt. ------- It might appear possible to overcome all the difficulties attending the definition of “time” by substituting “the position of the small hand of my watch” for “time.” Es könnte scheinen, daß alle die Definition der ,,Zeit“ be- treffenden Schwierigkeiten dadurch überwunden werden könnten, ------ Thus, whereas the Y and Z dimensions of the sphere (and therefore of every rigid body of no matter what form) do not appear modified by the motion, the X dimension appears shortened in the ratio Während also die Y - und Z-Dimension der Kugel (also auch jedes starren Körpers von beliebiger Gestalt) durch die Be- wegung nicht modifiziert erscheinen, erscheint die X-Dimension im Verhältnis ------ We still have to find the amplitude of the waves, as it appears in the moving system. If we call the amplitude of the electric or magnetic force A or A' respectively, accordingly as it is measured in the stationary system or in the moving system, we obtain Wir haben nun noch die Amplitude der Wellen, wie dieselbe im bewegten System erscheint, zu suchen. Nennt man A bez. A' die Amplitude der elektrischen oder magne- tischen Kraft im ruhenden bez. im bewegten System gemessen, so erhält man ----- It follows from these results that to an observer approaching a source of light with the velocity c, this source of light must appear of infinite intensity. Es folgt aus den entwickelten Gleichungen, daß für einen Beobachter, der sich mit der Geschwindigkeit V einer Licht- quelle näherte, diese Lichtquelle unendlich intensiv erscheinen müßte. <<<<<<<<<<<<<<<<<<<<<<<<<< You noticed that Einstein used two different verbs: 'scheinen' and 'erscheinen'. He doesn't mix these at random. They have different meanings: 'Sheinen' means: illusion - an appearance that does not correspond to reality - it appears so, but it may not be true - what you see is mere appearance - only outward show, things are not what they seem to be, etc. (Anschein= farce, sham, make-believe, pretence etc...) 'Erscheinen' is more: as it shows, come to light, as it is, etc. In the english version 'sheinen' and 'erscheinen' are translated by one verb only: 'appear'. Strictly speaking the translation is not wrong (ask google to translate the english words and somehow you will find 'appear'), but the very important difference in meaning in german disappears in the english translation. Or at least 'might very well' get lost. I suppose that in english one can use the verb 'appear' in both meanings as long as the context makes clear what the semantics are. In the english 1905 paper translation that's not so obvious as in the original german text. Prove is that in thousands of texts dealing with SR the english 'appears' is often replaced by 'seems', which is a synonym of 'appears', but not the correct one to match the german significance. 'Seems' refers to 'scheins' (= illusion). [STRIKE]Dalespam's[/STRIKE] [edit: PeterDonis'] use of 'apparent' (= seeming, not proven real, illusive, illusory, likely, ostensible) is also prove of this, otherwise there would be no need to add that adjective. And his 'sense' of simultaneity is superb poetry, but no physics. (The same mistake occurs in other translations, because a lot of them are translations of the/an english text. I will not go into that.) Worse is that authors of those ambiguous texts (because of the use of 'appear' without proper explanation, or the word 'seem'), are probably not aware of the real significance of SR: trains ARE shorter, events ARE not simultaneous for one observer and ARE simultaneous for the other, meaning both observers ARE in different 3D worlds. etc. Those authors (not unlike many PF members) hide themselves in a type of Lorentz Ether Theory interpretation of the Lorentz Transformations as illusionary abstract calculations, because it matches perfectly the incorrect 'seems' interpretation of the german 'erscheins'. Unfortunately all those hundreds of thousands of people over the last 100 years are wrong. That's the most dreadfull and horrible scenario Einstein could ever imagine. I hope I made my point clear why I get extremely nervous, with a sense of (to say the least) acute desperation, when I am confronted with a text using 'appear' vocabulary. (There is a tree in front of you. Nobody says that a tree appears in front of you. And for me a moving train is shorter, not appear shorter. A blitz of 10.000 volt shivers through my body. And make it a 20.000 volt when I read that the train 'seems' shorter. And over the last 20 years it was (and still is) flabbergasting to read how people try to defend that false, erroneous approach of SR.