From: nospam@de-ster.demon.nl   
      
   Thomas Koenig  wrote:   
      
   > J. J. Lodder  schrieb:   
   >   
   > > For example, is a centimeter compatible with a nanosecond?   
   > > No, of course not, well indoctrinated kiddies will tell you   
   > > with the wisdom of 1793.   
   > > However, these days the nanosecond equals 29.9792458 cm (exactly)   
   >   
   > Time certainly doesn't equal length, and trying to use definitions   
   > of units in such a way is misleading at best.   
      
   To you perhaps, but not to all.   
   High energy physicists, and all others using natural units   
   have no problem with it.   
      
   > Otherwise, tell me what reasonable result you get if you add a   
   > second to a meter.   
      
   That equals one second, for all practical purposes.   
   OTOH, if you add a nanosecond to a meter the result is 1.299792458   
   meter, or about 4.335641 nanoseconds.   
      
   > > This is what your little GPS unit is doing for you:   
   > > it counts, adds, and multiplies with all those nanoseconds,   
   > > and presents the results of it all in meters or miles.   
   >   
   > It converts the results.   
      
   The point was that interally it treats time and space   
   on the same footing. (solving 4 eqns with 4 unknowns)   
   (as it must, for relativistic corrections *are* important   
   in getting your calculted position right) [1]   
      
   > > In a very real sense the metric system came too early.   
   > > (before the relevant physics was well enough understood)   
   > > If we could start all over again   
   > > there wouldn't be a separate length unit at all.   
   >   
   > It is certainly useful to have both; if only to avoid the mistake   
   > of adding a length to a time.   
      
   You don't believe what your GPS is telling you?   
      
   So a thought experiment for you:   
   suppose we do meet those intelligent LGM,   
   and suppose that they do physics just like us,   
   except for measuring length and time in the same unit.   
   Where would they go wrong?   
   What *physical* result would be impossible for them   
   to compute correctly?   
      
   Jan   
      
   [1] There is a yet another 'Einstein is always right'   
   experiment in progress.   
   As you may know a launch failure put two of the Galileo sats   
   in an incorrect, because very elliptical orbit.   
   ESA has decided that these sats will be put to use   
   in a science experiment while they do what they can   
   to rectify the situation.   
   .   
   Because of the ellipticity of the orbit the relativistic corrections   
   for height and speed will depend quite noticably   
   on the instanteneous position in orbit. (and not just on average)   
   They will measure and confirm this.   
   You get three guesses...   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)