radiometer 2
the original explanation for how crookes' radiometer works was presented surprisingly enough by a guy named crookes who built the original device. he theorized the brand new theory of radiation pressure was the explanation. to get his paper published he had to get it past some guy named maxwell. as in maxwell's equations. incidentally it was maxwell's theory of radiation pressure. so maybe he didn't check the work as thoroughly as he should have. basically you have photons smashing into and imparting all of their energy and momentum to the dark side of the vanes. ergo we see sunlight push the black panes. right? wrong. photons bouncing off the shiny side of the vane deliver twice as much momentum. ergo the solar engine spins the wrong way.