From: nospam@de-ster.demon.nl   
      
   Phillip Helbig (undress to reply)    
   wrote:   
      
   > In article , Jos   
   > Bergervoet  writes:=20   
   >   
   > > > First you must measure the speed of light. Or better, you have to des=   
   > cribe   
   > > > a general accepted way, how the speed of light is measured.   
   > >=20   
   > > But we have that! Observing the propagation of light using length and   
   > > time units based on the propagation of light. The outcome is fixed.   
   > >=20   
   > > > If you have such a recipe, you can measure and decide if the speed of=   
   >  light   
   > > > is everywhere the same and if this speeed is the same in -time- at a   
   > > > specific location   
   > >=20   
   > > The only way to change it is to abandon the accepted definition (which   
   > > always keeps the speed fixed). And perhaps this could happen, if   
   > > for instance all speeds in physics suddenly became 10% higher, except   
   > > light. Then most physicists would be open to the idea that actually we   
   > > should change this definition.   
   >   
   > Indeed.  It could happen.  It has happened.  The metre used to be=20   
   > defined as 1/10,000,000 of the quadrant of the meridian through Paris. =20   
   > The second used to be defined as a certain fraction of a year.  These=20   
   > definitions were changed.  Why?  In part because other definitions can=20   
   > be reproduced with greater accuracy, but also because they can change. =20   
   > Of course, it would have been silly to say that since the definition of=20   
   > the metre is fixed, the size of the Earth, or the length of the year,=20   
   > could not change, even in principle.   
   >   
   > > > The same type of problems exists between: what is mass and how is thi=   
   > s   
   > > > directictly measured or calculated based on different measurements.   
   >   
   > Like some other units, the kilogramme has recently been redefined.  Why?=20   
   > In part because the standard kilogramme in Paris was losing mass.  So,=20   
   > it was possible to detect it, even though it was the standard.   
   >   
   > The Universe does not care how we define our units.  Certain quantities=20   
   > either vary or they don't.  We cannot prevent them from varying by using=20   
   > them to define a unit.  When we are REASONABLY SURE that something does=20   
   > not vary (at least not detectably over interesting timescales), as a=20   
   > purely PRACTICAL matter one can define units in terms of constants of=20   
   > nature such as the speed of light.   
      
   The problem with your position is that you postulate   
   that what has to be shown,   
   namely that there is such a thing as the speed of light,   
   and that it is a constant of nature.   
      
   As far as we know now there is no such a thing.   
   We can formulate all known laws of nature in such a way   
   that the speed of light doesn't occur in any of them.   
      
   What remains is that the 'speed of light' is an artefact   
   caused by maladroit choices in the definition of our unit systems.   
   It has no more physical reality than Boltzmann's constant,   
   or the impedance of the vacuum.   
      
   If you want to have a 'speed of light' as a constant of nature   
   you must invent new, and fundamentally different laws of physics   
   in which there is such a thing,   
      
   Jan   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)