rayleigh scattering there is a citation needed at the claim that rayleigh scattering can be seen i just did some research on rayleigh scattering in air i added some content to rayleigh scattering the bottom line is that at atmospheric pressure rayleigh scattering at nm is about per meter a mw green laser has a luminous power of lumen and hence rayleigh scattering is e lumen per meter over a mm beam a m surface the beam will hence appear roughly as if it were illuminated at e millilux which is comparable to a moonless clear night sky i should actually correct the number to deal with the angular distribution a dark adapted eye should be able to see this especially when you look along the beam which multiplies the apparent brightness by sin theta where theta deg means you look paralell to the beam now i'm not sure how to turn this original research into verifiable encyclopedic content t