Why isn the sky bright at night if the universe has so many stars?
I would like to know why the night sky isn’t bright all the time. The stars in the universe give off heat and this heat has to go somewhere, right? Usually light accompanies heat, and this heat that doesn’t escape the universe must be heating it up and thus the night sky should be bright as day. (I am assuming that 10+ billion years is good enough to heat up the universe.) You’ve stumbled across a famous problem referred to as Olbers’ Paradox, the solution of which you will probably find quite surprising. To respond to the question the way you phrased it, I guess I would simply say “no, 10+ billion years is not enough time to heat up the universe.” More specifically, the fact that the universe is only around 13 billion years old means that an individual star can only heat up a region of space within a distance of about 13 billion light-years from it. Anything farther, and the light just wouldn’t have had enough time to get there yet. Therefore, when we look at the night sky, we only se
