Once upon a time there were some sums which we could not do. No matter how hard we tried, we could not work them out
The reason was because in order to find the answer we had to get the square root of -1. But there is no such number in our world. It is indeed a very strange thing that we can have minus numbers, but not one of them has a square root
One day however a visitor came from another world. His name was i
He stayed with us while we did our sums, sitting in the place where the square root of -1 should go. And something magic happened. We could keep on going till we got an answer to our sum, an answer which was a perfectly ordinary number from our own real world
So then i could go home
