-> Yes, but there are two types of "light mills". Most mills
you see turn into  
-> direction of the reflecting side of their wings (as if a force would be 
-> pressing against the dark side), which clearly shows that they're not moving 
-> because of the momentum transferred by impact of photons.  Those serving as 
-> radiometers turn the other way round (and their built-up is thus 
different). 
  
Personally, I have never seen a "light mill" that literally uses the 
pressure of the radiation falling on it. The pressure would be 
extremely small. Let's see... Suppose the light intensity is one 
kilowatt per square metre, which is about that of full sunlight on the 
Earth. So the "mass" of the light falling on one square metre in a 
second is 10^3/C^2. So the momentum is 10^3/C, or 1e3 / 3e8, which 
comes to about 3 micronewtons per square metre, i.e. a pressure of 
three micropascals. On a radiometer vane with an area of 1 cm^2, the 
force would be about 3e-10 newtons, or about 3e-11 kilograms-weight, or 
300 nanograms-weight. So the force on the vane would be equivalent to 
the weight of a tiny (almost certainly invisible) speck of dust with a 
mass of 0.3 micrograms. 
  
Making the mill capable of being turned by such a tiny force would be a 
major challenge! 
  
                      dow 
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