Ask any elementary schooler reared on YouTube and they will tell you that the edge of the observable universe is 46.5 billion light years away. But have you ever wondered how we know this?
Come to think of it, how do we even know the distance to our nearest galaxy Andromeda (2.5 million lightyears)? Or for that matter how far out the stars in our own Milky Way are. After all, no human probe has travelled much beyond the Solar System.
There is a set of special tape measures that astronomers use to judge the extent of the sky. To make sense of them, we first need to get the hang of the scales involved.
