Delta4Embassy
Gold Member
http://phys.org/news/2015-12-night-sky-black.html
"It sounds obvious. That's what night is. The sun has set and when you look up at the sky, it's black. Except where there's a star, of course. The stars are bright and shiny.
But wait. Imagine you are deep in a forest. All around you there are trees. Wherever you look, you are looking at a tree. Maybe a big tree close up or a bunch of small trees further away. Surely it should be the same with stars. We're deep in the universe and whatever direction we look in, there ought to be stars there – billions and billions and billions of them. You would have thought that they'd fill the whole night sky, with the more distant ones fainter but more numerous.
Olbers' Paradox
This is called "Olbers' Paradox" after a 19th-century astronomer, although the conundrum was around for a couple of centuries before him. And the answer – at least, now – is fairly clear.
The reason the night sky isn't just a blaze of light is because the universe isn't infinite and static. If it were, if the stars went on forever, and if they had been there forever in time, we would see a bright night sky. The fact that we don't tells us something very fundamental about the universe we live in."
rest at link
"It sounds obvious. That's what night is. The sun has set and when you look up at the sky, it's black. Except where there's a star, of course. The stars are bright and shiny.
But wait. Imagine you are deep in a forest. All around you there are trees. Wherever you look, you are looking at a tree. Maybe a big tree close up or a bunch of small trees further away. Surely it should be the same with stars. We're deep in the universe and whatever direction we look in, there ought to be stars there – billions and billions and billions of them. You would have thought that they'd fill the whole night sky, with the more distant ones fainter but more numerous.
Olbers' Paradox
This is called "Olbers' Paradox" after a 19th-century astronomer, although the conundrum was around for a couple of centuries before him. And the answer – at least, now – is fairly clear.
The reason the night sky isn't just a blaze of light is because the universe isn't infinite and static. If it were, if the stars went on forever, and if they had been there forever in time, we would see a bright night sky. The fact that we don't tells us something very fundamental about the universe we live in."
rest at link