From: helbig@asclothestro.multivax.de   
      
   In article <1pbx48j.1xmowyy1fnnxmfN%nospam@de-ster.demon.nl>,   
   nospam@de-ster.demon.nl (J. J. Lodder) writes:   
      
   > Thomas Koenig  wrote:   
   >   
   > > Nicolaas Vroom  schrieb:   
   > >   
   > > > Ofcourse you could claim that the speed of light is constant.   
   > >   
   > > The way that the SI units are defined now, the speed of light   
   > > in vacuum is indeed constant.  If you measure anything else than   
   > > 299792458 m/s, recalibrate your measurement devices.   
   >   
   > Nonsense.   
   > In the SI as it stands it is impossible in principle   
   > to measure the speed of light,   
      
   Because, for practical reasons, the metre is now defined as the   
   distance light travels in a certain time.  That is our definition, which   
   Nature doesn't know about.  We cannot magically influence Nature by   
   changing definitions.   
      
   With time, more and more SI units have been defined via fiat values of   
   constants of Nature.  This is a purely practical matter, because we   
   ASSUME that they do not change with time.  The definitions are also   
   coupled with experiments which are relatively easy to reproduce.   
      
   Back when the metre was defined as 1/10,000,000 of the distance from   
   north pole to equator along the meridian through Paris, that did not   
   somehow make it impossible to measure the change in the size of the   
   Earth with time.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)