This might be a stupid question but, taking a shower yesterday, I was wondering how is light propagating through the air molecules. For example, take the light coming from a distant star entering our atmosphere. Between my eyes and the star there are billions of air molecules. How do the photons pass through all these molecules and be able to excite my eyes retina. Are the photons exciting each electron of the individual atom and thus propagate from atom to atom, molecule to molecule? How does this exactly work I'd like to know.