From: helbig@asclothestro.multivax.de   
      
   In article <0013b48a-26fc-4b7c-ade4-a70929efa9a7@googlegroups.com>,   
    writes:   
      
   > Why then can we not determine what % of the speed of light   
   > the particles where traveling at and with some algebra as usual   
   > determine their masses as well?   
      
   Note that neutrinos from the supernova 1987A in the Large Magellanic   
   Cloud emitted neutrinos which were detected on Earth.  Since the   
   difference in emission times of light and neutrinos is only about 3   
   hours, this is negligible for the travel time of 157,000 years and thus   
   provides a good lower limit on the speed of neutrinos (i.e. very close   
   to the speed of light).  This gives an upper limit on the mass of the   
   electron neutrino of about 26 eV.  Current limits are about 0.11 eV.   
   However, because of neutrino oscillations, we know that it is non-zero.   
      
   [[Mod. note -- To amplify one point Phillip made: measurements of neutrino   
   oscillations tell us the *difference* between the *squares* of the masses   
   of different types of neutrinos, i.e., they tell us something like   
      m1**2 - m2**2  .  But if my dim recollection is correct, they don't   
   easily tell us which of the 3 types of neutrinos  m1  and  m2  refer to.   
   -- jt]]   
      
   --- SoupGate-Win32 v1.05   
    * Origin: you cannot sedate... all the things you hate (1:229/2)