Translation problems.
Most texts dealing with Special Relativity dare to write that a moving train appears shorter, and worse: seems shorter. As if the shortening is an optical illusion. Ridiculous. You seldom read that the moving train 'is' shorter. Why? Let me show you the verbs in the original 1905 version, and the english translation.
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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 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.
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Es könnte scheinen, daß alle die Definition der ,,Zeit“ be-
treffenden Schwierigkeiten dadurch überwunden werden könnten,...
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.”
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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
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 ...
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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
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...
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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.
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.
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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: 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. The word for word translation of the 1905 paper misses context. Prove is that in thousands of texts dealing with Special Relativity 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). Hence there is no reason at all to use 'apparent' (apparent time, apparent length) (= seeming, not proven real, illusive, illusory, ...).
(The same mistake occurs in other translations, because a lot of them are translations of the 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 Special Relativity: moving trains relative to an observer ARE shorter, events ARE not simultaneous for one observer and ARE simultaneous for the other, meaning both observers ARE in different 3D spaces (worlds). etc. I think that many authors are stuck in a type of Lorentz Ether Theory interpretation of the Lorentz Transformations with fictitious primed time and space coordinates, 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.
Scrap all those ambiguous words. Moving trains are shorter, not 'appear' shorter, and definitely not 'seems' to get shorter. Time of a moving clock runs slower (and doesn't appear to run slower) in 3D space of an observer that doesn't move with the clock. Is that so difficult? I know why people write 'appear'. Or they do not understand the relativity of simultaneity, or they do it ... simply because everybody does! People copy from everybody, even if what they copy is wrong. And if enough people copy it, after a while (100 years!) it becomes 'politically correct' and considered as the only thruth. That's dangerous for scientific evolution.
Face what Einstein found out and accept the consequences: the future exists, even if you feel uncomfortable with the consequences (such as free will). I know that most people refuse to take that step. So they look for clumsy interpretations of Special Relativity or stick to an ether theory with only fictitious primed time and space coordinates of Lorentz Tranformations. In Special Relativity the primed time and space coordinates are as real as the unprimed coordinates. (See my section 'Relativity for Experts.)
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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 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.
-------
Es könnte scheinen, daß alle die Definition der ,,Zeit“ be-
treffenden Schwierigkeiten dadurch überwunden werden könnten,...
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.”
-------
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
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 ...
--------
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
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...
-------
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.
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.
-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
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: 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. The word for word translation of the 1905 paper misses context. Prove is that in thousands of texts dealing with Special Relativity 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). Hence there is no reason at all to use 'apparent' (apparent time, apparent length) (= seeming, not proven real, illusive, illusory, ...).
(The same mistake occurs in other translations, because a lot of them are translations of the 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 Special Relativity: moving trains relative to an observer ARE shorter, events ARE not simultaneous for one observer and ARE simultaneous for the other, meaning both observers ARE in different 3D spaces (worlds). etc. I think that many authors are stuck in a type of Lorentz Ether Theory interpretation of the Lorentz Transformations with fictitious primed time and space coordinates, 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.
Scrap all those ambiguous words. Moving trains are shorter, not 'appear' shorter, and definitely not 'seems' to get shorter. Time of a moving clock runs slower (and doesn't appear to run slower) in 3D space of an observer that doesn't move with the clock. Is that so difficult? I know why people write 'appear'. Or they do not understand the relativity of simultaneity, or they do it ... simply because everybody does! People copy from everybody, even if what they copy is wrong. And if enough people copy it, after a while (100 years!) it becomes 'politically correct' and considered as the only thruth. That's dangerous for scientific evolution.
Face what Einstein found out and accept the consequences: the future exists, even if you feel uncomfortable with the consequences (such as free will). I know that most people refuse to take that step. So they look for clumsy interpretations of Special Relativity or stick to an ether theory with only fictitious primed time and space coordinates of Lorentz Tranformations. In Special Relativity the primed time and space coordinates are as real as the unprimed coordinates. (See my section 'Relativity for Experts.)