How far away is the nearest lightning bolt?
Imagine a hot, summer day. You’re sitting at home, feeling the stuffy air. You start to wonder whether today is going to be a stormy day. You could check your favourite website to see on the map where the lightning bolts are. But no — instead, you want to know how far away the most recent lightning strike was. And you want to know it precisely, instantly, and without lifting a finger. ...