->  PR> Well there must be SOME explanation for radiometers. 
 
-> Well, radiometers are explained by gas molecules recoiling off the 
-> black vanes (gas expansion). 
  
Right. Radiometers turn with the shiny sides of the vanes leading. If 
the cause of the motion were radiation pressure, the shiny sides would 
trail, since more pressure would be exerted by photons reflecting off 
them than by photons being absorbed by the black sides. Also, in real 
radiometers, the vanes have to be made of some material that conducts 
heat poorly, so the black sides of the vanes can be warmer than the 
shiny sides. If the vanes are made of metal, the radiometer works 
badly if at all. Radiation pressure would work irrespective of the 
temperatures of the sides. 
  
-> However, when photon interaction is talked about it is always the 
-> electron that is the recipient of energy transfer. Why can't a proton 
-> or neutron also be a recipient? 
  
Having no charge, neutrons aren't affected by electromagnetic 
radiation. 
  
It isn't really an electron that is affected, but a combination of 
electrons and protons. Their separation is increased, or whatever. But 
since protons are so much more massive than electrons, the electrons 
are moved far more than the protons. 
  
-> Say if I had a vacuum tube free floating in space would it exhibit a 
-> net acceleration when an electron current flowed through it? 
 
->  M*i*k*e 
  
Why should it? 
  
                      dow 
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