7 Puzzles And Paradoxes To Twist Your Brain

4. Olbers’ Paradox

What is it?

If you think that this is all just philosophical mucking around, then think again, because Olber's Paradox helped us to understand one of the most fundamental principles in modern cosmology (as well as giving us a name for possibly one of the worst sitcoms on TV): The Big Bang Theory.

Olber's paradox, or the "Dark Night Sky" paradox, was the observation that the fact that the sky was dark at night must mean the the universe must have had a beginning (and presumably and end) and that it must be finite. In an infinite and eternal universe, the night's sky should not be black, but can you figure out why?

What's the solution?

In an infinite static universe, as it was thought to be for a great deal of history, the light from the infinite number of stars would have had an infinite amount of time to reach us, meaning that the sky should have been ablaze with the blinding light of an infinite number of fiercely burning suns.

As you're probably aware, it isn't, which must mean that the universe has a finite age and/or a finite number of stars. So, the simple observation that the night is dark led us to one of the most profound discoveries in astronomy - that the universe must have had a beginning.