OLBERS' PARADOX: WHY IS THE SKY DARK AT NIGHT?

If the universe of stars is large enough your line of sight should be blocked in every direction by a "solid wall of stars." The entire sky would be as bright, and as hot as the surface of the Sun. The immense distance to the stars making up the "wall of light" would have no effect on the total amount of energy reaching us. We should be surrounded by a blazing oven of light. Instead the sky is practically black. This is because the universe is not old enough to fill the sky with light. The universe may be infinite in size but there hasn't been enough time since the universe began for starlight traveling at the speed of light to reach us from the farthest reaches of space. We can only see the part of the universe that lies between 12 to 15 billion years ago since the Big Bang. There may be an infinite number of stars beyond that cosmic horizon but we can't see them because their light has not yet arrived. And the observable part contains too few stars to fill up the sky with light. Dying stars spew gas and dirt back into space and this material gives birth to new generations of stars. But after enough generations, all the nuclear fuel in the universe is eventually exhausted and the formation of luminous stars must come to an end. So even if the universe were infintely old as well as infintely large, it would not contain enough fuel to keep the stars shining forever and to fill up all of space with starlight. And so the night sky is dark.