So basically I'm wondering if gravity can effect the rate that light dissipates and if their is less gravity in between galaxies. If two rays of light start on a horizontal plane, one ray inside a galaxy and one outside. Both rays having no other variables in their path, dust particles, molecules, etc. Will one ray dissipate faster than the other? Could gravity be less concentrated in between galaxies? I know this is a rather silly question but I'm only in high school, have pondered on it and can not find any answers.