From: ram@zedat.fu-berlin.de   
      
   PengKuan Em  writes:   
   >Relativistic length contraction is theoretically predicted but not directly   
   >tested   
      
     In fact, it has not been observed directly. But there are   
     two indirect observations: "the behavior of colliding heavy   
     ions can only be explained if their increased density due to   
     Lorentz contraction is considered. Contraction also leads to   
     an increase of the intensity of the Coulomb field   
     perpendicular to the direction of motion, whose effects   
     already have been observed" (Wikipedia).   
      
     The length contraction derives from the whole worldview of   
     special relativity (SR) which has been confirmed many times   
     (e.g., confirmations of time dilation) and therefore it would   
     be strange if all other predictions of the SR were true,   
     but only Lorentz contraction would be false.   
      
     If one would use the same effort to directly confirm Lorentz   
     contraction as was used to observe gravitational waves,   
     it should be possible to observe it (more) "directly". But   
     people possibly think that it is not worth the effort since   
     nobody expects it to be a false prediction, given that we   
     already have two indirect confirmations of Lorentz contraction   
     and many other confirmations of predictions of the SRT.   
      
     I also remember this line of thought: some particles of the   
     cosmic radiation created in the upper atmosphere have a   
     certain lifespan which would be too short to allow them to   
     reach the ground. But they do arrive here since time dilation   
     allows them to live longer. But from their own point of view   
     they have the speed 0, and so they can not have a dilated time   
     from their own point of view. How do they than explain that   
     they reach the ground from their own point of view? Well, for   
     them, the Earth is moving towards them and so the height of   
     the atmosphere is Lorentz-contracted, and therefore they can   
     travel trough it within their lifespan.   
      
     So this means that one man's time dilation is another man's   
     Lorentz contraction, so that, by this, all confirmations of   
     time dilation also indirectly confirm Lorentz contraction.   
      
   [[Mod. note -- There are lots of references to experimental tests of   
   various apsects of special relativity (including time dialation) at   
   Tom Roberts' & Siegman Schleif's excellent web page   
     http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments.html   
   So far the tests (very) strongly support special relativity.   
   -- jt]]   
      
   --- SoupGate-Win32 v1.05   
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