From: nospam@de-ster.demon.nl   
      
   Phillip Helbig (undress to reply)    
   wrote:   
      
   > In article <1p3rzqg.11e6pqz12s5pn3N%nospam@de-ster.demon.nl>,   
   > nospam@de-ster.demon.nl (J. J. Lodder) writes:   
   >   
   > >> Discussing the CMB is a bit of a red herring, because if one saw   
   > >> departures from the black-body spectrum, one would suspect some   
   > >> astrophysical cause.  So think of lab measurements of black bodies: over   
   > >> what range in frequency have they been made and to what precision?   
   > >   
   > > The fact that they can measure deviations of the CMB   
   > > from the ideal black body spectrum implies   
   > > that they can verifiy the black body spectrum   
   > > for a laboratory black black body to greater accuracy.   
   > > (they use one for calibration, iirc)   
   >   
   > I'm pretty sure that any deviations are from the theoretical curve, not   
   > from a lab measurement.  Certainly the theoretical curve and the lab   
   > measurements agree over the range in which they have been compared.  But   
   > at really high frequencies, the CMB signal isn't strong enough to   
   > detect, and, as far as I know, no-one has measured at really high   
   > frequencies in the lab either.   
   >   
   > > Asking about the high end tail is not very useful,   
   > > for there will always be a higher point   
   > > where it is not verified, so you can go on asking forever,   
   >   
   > That is true.  But the original question was to what multiple of the   
   > peak has it been measured in the lab?   
      
   That is also not a very useful question,   
   for there is no such thing as a 'black body' in the lab.   
   A black body is an idealisation.   
   So any observed deviations are going to be ascribed   
   to the laboratory 'black body' not being ideal,   
   rather than to errors in the theoretical black body formula,   
      
   Jan   
      
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