Why Is the Night Sky Black?

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…

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Why Is the Night Sky Black?