[ELi5]If the universe is full of stars why is it so dark?
In: Physics
There are a few lines throughout the Hitchhiker’s Guide to the Galaxy that put some poetry to this. Many references to the idea that there is a LOT of stuff in the universe, but there is also A LOT of not stuff in the universe. Cubic light years with an average density of a single atom of hydrogen per cubic meter. The space is dark because that light gets more spread out the farther it travels and most of it, no mater where you are, has traveled a VERY long way.
Or if you aren’t into that and you want to get a bit more sciency and technical. Any light source is producing little bits of light. There are a lot of them but not infinitely many of them, and they aren’t all traveling in EXACTLY the same direction. No matter how tightly focused (which most light isn’t anyway) they spread out. The father away you get from that star or neon sign, the light has had more room to spread out. Go get a piece of paper and hold it REALLY CLOSE to a light. Now back it off a bit. Again, same distance as before. Again.
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