There are lots of scientific paradoxes, but most of them are complicated and require a lot of background information. Not so with the Dark Night Sky Paradox. If you have ever looked at the sky, you have gathered all the data you need.
Here’s the thing: in the 19th century, the best math, science, and theories of the time figured that the Universe was infinite in size, and that it had existed forever. This sounds nice and plausible. It certainly is easier to comprehend than the idea of a universe coming out of nothing, called the Big Bang Theory. But here’s where the paradox comes from: look at the sky. Are you blinded, burned to a crisp, and completely annihilated by the heat of infinite suns? No? Well, that’s weird. Because if there were infinite stars, arranged regularly, then no matter how far away they were from Earth, they would all contribute a teeny tiny bit of light. And infinity, in case you haven’t noticed, is very big. All those stars would add up to an infinitely bright night sky- and an infinitely bright day sky, as well. For decades, astronomers struggled to make the math work. Then, they figured out how to measure redshift. Long story short, they discovered that all the stars in the universe are moving away from one another, zooming off into space as though searching for privacy. The Universe is expanding. So, working backwards, one realizes that the Universe was once very, very small. A few discoveries later (Cosmic background radiation, quantum theories, yadda yadda yadda,) they finally figured out why the night sky is dark: the Universe has a finite size, and it had a beginning. Turns out, there are not infinite stars- just a whole lot.
So, next time you step outside- or just, you know, exist- be thankful that the Universe isn’t infinite, and that there is a limit to the number of stars we can see.