Unfortunately I can’t remember where I read this. I think I followed a link through Twitter. But it was very thought provoking, so I wanted to share.
A question was posed, probably by a child because who else thinks like this: If the stars are so bright and there’s so many millions/billions of them, why don’t they light up the blackness? Why don’t those lights fill in all the spaces so it’s white up there at night and not dark?
And this was the answer given: It probably would be all light up there, except that the speed of light is 299,792,458 m/s, so there are some stars that are so far away that their light hasn’t been able to travel all this way yet. If the universe was compressing, then eventually the sky would be very bright at night, but since it is expanding, it’s actually going to get darker and darker out there. Over time (lots and lots of time) there won’t be as many stars to see up there.
Though I always wonder, if the universe is supposed to be mind-blowingly, infinitely big, then how can it expand. Where is it expanding to? What other place is there for it to expand into? But I think that’s a post for another day.