Light years-I just dont understand how something as subjective as visibilty, is used as a major indicator of distance. Isnt that subjective. What if some species had a million times the eye power than us humans, wouldnt they view the distance of lets say stars very differently because it wouldnt be as many 'light years' away from them. Maybe I'm confused about how light years are actually measured, it just seems like using somethings visiblity to us, is a poor way to try to figure out actual distance. Thoughts?