ok, second question today: if we shine a laser (ideal laser; no spreading out whatsoever of the ray) in earth's atmosphere, at some distance the intensity of the laser will die out due to it hitting air particles. what if we shine it in a vacuum? e.g outer space My guess is that it will continue forever without dying out (as long as its path is constantly vacuum). This is why Hubble can detect galaxies far far away... Is my argument correct? Thank you!