From: eric@flesch.org   
      
   On 01 Sep 2021, nospam@de-ster.demon.nl (J. J. Lodder) wrote:   
   >The assertion was that you can at least in principle use laboratory   
   >measurements of the speed of light to see if it varies.   
   >To see that you can't you need to have at least a vague idea   
   >of how such measurements are done.   ...   
      
   I just wanted to thank the OP for his excellent precis.  It has   
   bothered me for a long time that with defining our length scale in   
   reference to c-dependent physical outputs, that we've given up an   
   absolute length scale as a basis of measurement.  That is, we've   
   assumed c to be ever unchanging WRT a physical rod.  If that   
   assumption is wrong, we've disabled our ability to find out.  We have   
   put blinkers on ourselves.  It can't be right to do that.   
      
   In all the sciences, only astronomy looks directly backwards into   
   time.  We assume that there is no overhead in doing so.  And yet there   
   is the redshift which we interpret as physical recession.  But who can   
   say what exactly separates the present from the past?  The redshift   
   may be a symptom of something else as yet unmodelled.   
      
   Normally if we set up an apparatus or a software system and switch it   
   on, then if its particles/data are seen to be expanding and   
   accelerating all around, we adjudge that the system is mis-calibrated.   
   So we look for how to calibrate it.  Our "accelerating expansion"   
   universe may simply be uncalibrated, and a new parameter needed to   
   calibrate it.  I greatly hope that we haven't already blinkered   
   ourselves in such a way as to make that calibration impossible.   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)